NSRRC, Hsinchu
An in-vacuum undulator with a room-temperature permanent magnet and a superconducting wiggler has become a mature technology and is widely used; it can adopt a short-period length in a medium-energy facility to provide an enhanced photon flux in the hard x-ray region. A cryogenic permanent magnet is applicable for an in-vacuum undulator to enhance the remanence field (Br) and the coercivity force. In future, a cryogenic permanent-magnet undulator and a superconducting wiggler will become mainstream to fulfill a user's requirement of a discrete and a continuous spectrum, respectively, but superconducting technology with HTS wires will have the best potential for the development of insertion devices after the next decade. HTS bulk magnets with magnet flux density 17 T are applicable even for a superconducting undulator; such an undulator can decrease the period length to about 10 mm. A small magnet gap with an extremely- short-period length (about 5 mm) has been studied with a stacked-layer of thin HTS tapes for a superconducting undulator. This report is a review to describe the current and future developments of insertion devices for a medium-energy storage ring and FEL facility.
JAEA, Ibaraki-ken
We report the demonstrated irradiation effect of laser-accelerated protons on human cancer cells. In-vitro (living) A549 cells are irradiated with a proton beam having a single bunch duration of 20 ns and a beam flux of ~1014cm−2s−1*. The dynamics differ by seven orders of magnitude to the case of a typical Ion Beam Therapy (IBT) operation with a synchrotron: 0.4 s in bunch duration and ~107cm−2s−1 in beam flux. We have measured the yield of DNA double-strand break with phosphorylated histone H2AX immunostaining method and estimated Relative Biological Effectiveness (RBE) of the laser-accelerated protons.
* A. Yogo et al., Appl. Phys. Lett. 94, 181502 (2009).
TUB, Beijing
In this paper, the design of a C-band SW accelerating tube is presented and its high power test set is shown. The tube can accelerate electrons to 9 MeV or 6 MeV. Its length is about 620mm, and a Pierce electron gun is used. A 2.5MW pulsed magnetron at 5712 MHz is served as the tube's RF power source. Two energy modes are performed by changing the input RF power and the injecting voltage of electron gun.
Kyoto University, Photonics and Electronics Science and Engineering Center, Kyoto
A liquid cluster ion beam irradiation system has been developed for surface processing and modification of solid materials used in the semiconductor industry. The liquid clusters are produced by the adiabatic expansion method. The vapor pressure of the source materials such as water or ethanol is increased by heating, and ejected to a vacuum chamber through a supersonic nozzle. The ionized clusters by the electron impact ionization are accelerated to typically 3-9 kV after the elimination of monomers by the retarding voltage method, and irradiated on the solid surfaces. The sputtering yield of silicon by the ethanol cluster ion beam irradiation was more than 100 times larger than that by an argon monomer ion beam. On the other hand, the radiation damage and surface roughness caused by the ethanol cluster ion beam irradiation decreased when the mean cluster size was increased by increasing the retarding voltage. Irradiation effects of liquid cluster ion beams on polymers are also discussed.
RLNR, Tokyo
AIST, Tsukuba, Ibaraki
WERC, Tsuruga , Fukui
Positron that is the antiparticle of the electron, by the specific character, can evaluate vacant spaces in microstructure from atomic level to nanometer level, which is difficult in other measurement methods. In the case of high functional material, this structure often relates directly to the performance, and the evaluation method that uses the positron beam is expected as a useful measurement tool to develop a new material. If it is able to produce more high-intense and low-energy positron beam with an accelerator, the microstructure evaluation is carried out in prompt and high accuracy for various demands of the material analysis. We have studied a positron production system using a superconducting electron linac instead of normal conducting one. Electron beam accelerated with the superconducting linac is irradiated on tantalum and converted to bremstrahlung photons, and positron beam is produced by pair creation of them. The designed acceleration energy of the superconducting electron linac is 15-40 MeV and the maximum beam power is 10 kW. The system configuration and the progress status will be presented.
Università di Brescia, Brescia
I.N.F.N., Pavia
CERN, Geneva
The AEGIS experiment is expected to be installed at the CERN Antiproton Decelerator in a very close future, since the main goal of the AEGIS experiment is the measurement of gravity impact on antihydrogen, which will be produced on the purpose. Antihydrogen production implies very challenging environmental conditions: at the heart of the AEGIS facility 50 mK temperature, 10-12 mbar pressure and a 1 T magnetic field are required. Interfacing extreme cryogenics with ultra high vacuum will affect very strongly the design of the whole facility, requiring a very careful mechanical design. This paper presents an overview of the actual design of the AEGIS experimental facility, paying special care to mechanical aspects. Each subsystem of the facility - ranging from the positron source to the recombination region and the measurement region - will be shortly described. The ultra cold region, which is the most critical with respect to the antihydrogen formation, will be dealt in detail. The assembly procedures will be considered too, as they are expected to be critical to make the set-up phase easier, as well as to make possible any future improvement of the facility itself.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
The charge exchange device for 3GeV RCS in J-PARC, which require that a broken foil is exchanged for a new foil by remote control and automatically in vacuum. The control system's important task will be to control under the unified management of the vacuum system and foil driving system and to support EPICS. This device consists of the vacuum system using PLC (Programmable Logic Controller) and the foil driving system using MCU (Multi Control Unit). A workstation (WS) was required, and we developed control system which control under the unified management of 2 different type of system. The uniform management control system became complex system. In fact, therefore control system was unfinished system, it did not protect trouble such as the vacuum gate valve closed while transfer rod insert in the ring. Each algorithm of PLC, MCU and WS was reviewed, and the control system that was able to do the unified management was restructured. Each algorithm of PLC, MCU and WS was debugged so that this control system is made remote control using EPICS. We introduce the reconstruction of the control system for the charge exchange system at the RCS in J-PARC.
KAERI, Daejon
The solid target of the RFT-30 30 MeV cyclotron in KAERI was designed to produce the metalic radioisotopes, such as Zn-62, Cu-67, Ge-68, Pd-103, and In-111. The target control system should provide high reliability to prevent any kind of failure. Moreover, the operating procedures and maintenance cycle should be optimized and well organized to cover the unexpected situations. In this study, a simulation of the control system for the solid target in KAERI was carried out to confirm the operability of the solid target transport system. The receiving and irradiation stations are connected each other through square tube, and the control software was also checked. The developed solid target control system controls vacuum, cooling, and the whole procedures before, during, and after the irradiation.
National Chiao Tung University, Hsinchu
NTHU, Hsinchu
NSRRC, Hsinchu
Resonant transition radiation (RTR) driven by a femtosecond electron beam is being studied. An aluminum foil stack with vacuum spacers is used as the radiator. With a 27 MeV electron bunch with pulse duration at ~ 100 fsec incident normally on the aluminum foil stack, high photon yields in hard X-ray regime can be obtained. Characteristics of the radiation such as emission spectrum, spatial distribution are calculated. The dependence of RTR photon yields on beam size and bunch length are also studied.
KEK, Ibaraki
Injection into the J-PARC main ring is implemented by 4 kickers and 2 pulsed septa at 3 GeV in a long straight section. To accommodate the injection beam of 54 pmm.mrad, both septa have large physical acceptance of 81 pmm.mrad. However, large aperture leads to large end fringe field interfereing the circulating beam and causing beam loss, which has been observed even at low beam intensity during the beam commissioning. To provide users a proton beam with high beam power, the injection beam intensity will increase greatly in future, which creates difficulties for the present injection system. To accommodate these high intensity beams with low beam loss, the injection system needs to be upgraded. Taking account the strong space charge effects, even larger physical is needed to reduce the localized beam loss, which creates severer end fringe leakage field. This paper will discuss the problems encountered in operating the present septa, and give an optimized design for the new septa.
NSRRC, Hsinchu
The free space between magnets of TPS storage ring is very tight, especially the space between quadrupole and sextupole magnets. The minimum space between the yoke of quadrupole and sextupole is about 150mm, and the space between coils is only 10mm. In this case, the significant magnetic field distortions could have an impact on the performance of machine. Two magnets simulation compare to the individual magnet were performed in TOSCA 3D model. The crosstalk effect shows that the sextupole component increases from 0.0004% to 0.04% in the quadrupole magnet and the quadrupole component increases from 0.0008% to 0.06% in the sextupole magnet. We discuss this crosstalk effect and how to decrease the effect with appropriate shielding.
GSI, Darmstadt
The FAIR SIS100 accelerator at GSI Darmstadt will be equipped with fast ramped superconducting magnets. The high current Uranium beam modes with intermediate charge states, require ultra low vacuum pressures that can be achieved in long term operation only by cold beam pipes acting as a cryopump with stable temperatures well below 12 K for all operating cycles. The straightforward layout for reliable cooling usually conflicts with an efficient design for fast ramped superconducting accelerator magnets, strongly affected by AC loss generation, field distortion and mechanical stability problems. A full functional vacuum chamber design for SIS 100 has to take into account all these conflicting boundary conditions and trade off between mechanical stability, acceptable field distortions, AC loss minimisation and achievable temperatures. We discuss the cooling conditions for the dipoles and for the beam pipe including first test results. The analysis of the principal design aspects for the vacuum chamber with respect to the magnets operation parameters and an integral design approach are given. We present a technological feasible solution for model testing and full scale manufacturing.
GSI, Darmstadt
JINR, Dubna, Moscow Region
TEMF, TU Darmstadt, Darmstadt
Superconducting magnets are planned to be installed at the SIS100 accelerator ring for FAIR. The error compensation multipole corrector and the steerer are built as nested magnets to save longitudinal space in the ring, the chromaticity sextupole is a superferric magnet. We present the dynamic field quality of the SIS100 dipole and the vacuum chamber deterioration next to the 2D and 3D field quality of the multipole corrector and of the chromaticity corrector. The quality of the injection field of the SIS100 dipole is mainly dominated by eddy currents as soon as the field ramp starts. We show its AC losses concerning the hydraulic limits for cooling the magnet with forced two phase helium flow and conclude on the maximum chromaticity correction which is feasible for the foreseen magnet design. The results are discussed in respect of recent beam dynamic calculations on the ramp.
Hitachi Ltd., Ibaraki-ken
Hitachi, Ltd., Power & Industrial Systems R&D Laboratory, Ibaraki-ken
SAGA, Tosu
A 4T superconducting wiggler for 1.4GeV synchrotron radiation facility Saga Light Source (SAGA-LS) was developed and manufactured. The wiggler consists of one superconducting magnet as main-pole and two normal conducting magnets as side-poles. The superconducting coils are wound with NbTi wires on iron poles, which are directly cooled by a 2-stage GM cryocooler. The structure of the wiggler is made for compactness and cryogen-free operation. This paper describes its magnet design and manufacturing processes.
CERN, Geneva
On 19th September 2008 the Large Hadron Collider (LHC) experienced a serious incident, caused by a bad electrical joint, which stopped beam operation just a few days after its beginning. During the following 14 months the damage was repaired, additional protection systems were installed and the measures to avoid a similar incident were taken (i.e. new layer of the Magnet Quench Protection System [nQPS], more efficient He release valves). As a consequence, a large number of powering tests had to be repeated or carried out for the first time. The re-commissioning of the already existing systems as well as the commissioning of the new ones has been carefully studied, then performed taking into account the history of each of the eight LHC sectors (warm-up, left at floating temperature,'). Moreover, a campaign of measurements of the bus-bar splice resistances has been carried out with the nQPS in order to spot out non conformities, thus assessing the risk of the LHC operation for the initial energy level. This paper discusses how the guidelines for the LHC 2009 re-commissioning were defined, providing a general principle to be used for the future re-commissioning.
Muons, Inc, Batavia
North Carolina State University, Raleigh, North Carolina
YBCO superconductors originally developed for high temperature operation carry significant critical current even in the presence of extremely high magnetic field when operated at low temperature. The final stage of phase space cooling for a muon collider uses a solenoid magnet with fields approaching 50 T. As part of an R&D effort we present measurements of mechanical and electromechanical properties of the YBCO conductor. We examine the critical current verses magnet field angle at 4.2 K in a magnetic field. Quench properties of the conductor such as minimum quench energy threshold and quench propagation velocity will be measured to establish safe operational conductions for the muon cooling magnets. In this paper we describe a conceptual picture for a high field solenoid to be used for muon phase space cooling that incorporates these low temperature properties of YBCO.
LBNL, Berkeley, California
The Muon Ionization Cooling Experiment (MICE), an international collaboration sited at Rutherford Appleton Laboratory (RAL) in the UK, will demonstrate ionization cooling in a section of a realistic cooling channel using a muon beam. A five-coil superconducting spectrometer solenoid magnet will provide a 4 tesla uniform field region at each end of the cooling channel. Scintillating fiber trackers within the 400 mm diameter magnet bore tubes measure the emittance of the beam as it enters and exits the cooling channel. Each of the identical 3 meter long magnets incorporates a three-coil spectrometer magnet section and a two-coil section that matches the solenoid uniform field into the MICE cooling channel. The cold mass, radiation shield and leads are kept cold by means of three two-stage cryocoolers and one single-stage cryocooler. After incorporating several design changes to improve the magnet cooling and reliability, the fabrication and acceptance testing of the spectrometer solenoids has been completed. The key features of the spectrometer solenoid magnets are presented along with the details of a finite element model used to predict the thermal performance of the magnets.
KEK, Ibaraki
LBNL, Berkeley, California
Osaka University, Osaka
OXFORDphysics, Oxford, Oxon
Liquid hydrogen absorbers for the Muon Ionization Cooling Experiment (MICE) have been developed, and the first absorber has been tested at KEK. In the preliminary test at KEK we have successfully filled the absorber with ~2 liters of liquid hydrogen. The measured hydrogen condensation speed was 2.5 liters/day at 1.0 bar. No hydrogen leakage to vacuum was found between 300 K and 20 K. The MICE experiment includes three AFC (absorber focusing coil) modules, each containing a 21 liter liquid hydrogen absorber made of aluminum. The AFC module has safety windows to separate its vacuum from that of neighboring modules. Liquid hydrogen is supplied from a cryocooler with cooling power 1.5 W at 4.2 K. The first absorber will be assembled in the AFC module and installed in MICE at RAL.
CERN, Geneva
RAYSCAN, Meersburg
For the inspection of certain critical elements of the LHC machine a mobile computed tomography system has been developed and built. This instrument has to satisfy stringent space, volume and weight requirements in order to be usable and transportable to any interconnection location in the LHC tunnel. Particular regions of interest in the interconnection zones between adjacent magnets are the plug in modules (PIM), the soldered splices in the superconducting bus-bars and the interior of the quench diode container. This system permits detailed inspection of these regions without needing to break the cryo vacuum. Limited access for the x-ray tube and the detector required the development of a special type of partial tomography, together with suitable reconstruction techniques for 3 D volume generation from radiographic projections. We present the layout of the complete machine and the limited angle tomography as well as a number of radiographic and tomographic inspection results.
CERN, Geneva
The first LHC shut-down started in fall 2008, just after the incident on the 19th of September 2008. In addition to the typical work of a shut-down, a large number of interventions, related to the 'consolidation after the incident' were performed in the LHC loop. Moreover the amount of work increased during the shut-down, following the recommendations and conclusions of the different working groups in charge of the safety of the personnel and of the machine. This paper will give an overview of the work performed, the organization of the coordination, emphasizing the new safety risks (electrical and cryogenic), and how the interventions were implemented in order to ensure both the safety of personnel and a minimized time window.
CERN, Geneva
National Technical University of Athens, Athens
We study the interaction of macro-particles residing inside the LHC vacuum chamber, e.g. soot or thermal-insulation fragments, with the circulating LHC proton beam. The coupled equations governing the motion and charging rate of metallic or dielectric micron-size macro-particles are solved numerically to determine the time spent by such "dust" particles close to the path of the beam as well as the resulting proton-beam losses, which could lead to a quench of superconducting magnets and, thereby, to a premature beam abort.
KEK, Ibaraki
Nagaoka University of Technology, Nagaoka, Niigata
New acceleration system using an induction cell has been developed at KEK by using KEK 12-GeV PS*. We call an accelerator using the induction acceleration system "Digital Accelerator". The PS-Booster is now being renovated as the first Digital Accelerator (DA) by introducing the induction acceleration instead of rf**. Argon ion beam from the ECR ion source is injected to the DA by an electrostatic beam kicker. Another electrostatic device with the same structure is used for chopping the beam before injection. The accelerated beam is extracted by the existing extraction system, which comprises bump, septum and kicker magnets. Since these magnets are installed in a vacuum chamber, vacuum pressure deteriorates due to outgas from them. In order to reduce a beam loss in the DA ring, the pressure level is crucial especially for an ion beam. Therefore, we decided to put the septum magnet outside the vacuum chamber and insert a vacuum duct in the gap, since it dominantly contributes to the vacuum pressure more than the other magnets. This paper describes the electrostatic beam chopper, injection kicker and septum magnet containing the vacuum duct for the KEK DA and beam dynamics.
*K. Takayama, Phys. Rev. Lett. 98, 054801 (2007)
**K. Takayama, "KEK Digital Accelerator for Material and Biological Sciences", T. Iwashita, "Induction Acceleration System", in this conference
KEK, Ibaraki
Nagaoka University of Technology, Nagaoka, Niigata
Sokendai, Ibaraki
Tokyo City University, Tokyo
RBRC, Upton, Long Island, New York
Nippon Advanced Technology Co. Ltd., Ibaraki-prefecture
Iwate university, Morioka, Iwate
A novel circular accelerator capable of accelerating any ions from an extremely low energy to relativistic energy is discussed. A digital accelerator (DA)* is based on the induction synchrotron concept, which had been demonstrated in 2006. All ions are captured and accelerated with pulse voltages generated by induction acceleration cell (IAC). The IAC is energized by the switching power supply, in which power solid-state conductors are employed as switching elements and their tuning on/off is maneuvered by gate signals digitally manipulated from the circulating signal of an ion beam. Acceleration synchronized with the revolution of the ion beam is always guaranteed. The concept is realized by renovating the KEK 500 MeV booster into the DA, introducing a laser ablation ion source. Ion energy of 85-140 MeV/au and intensity of 10+9 - 10+10 /sec are estimated and these ions will be delivered without any large-scale injector. Companion papers** will discuss more details of instruments of DA. Applications for innovative material sciences and life sciences will be briefly introduced as well as the outline of DA.
*K. Takayam, J. of Appl. Phys. 101 (2007) 063304.
**K.Takayama "Ion source and LEBT", T.Adachi "Injection and extraction system", T.Iwashita "Induction acceleration system" in this conference.
CEA, Gif-sur-Yvette
CIEMAT, Madrid
FZJ, Jülich
The IFMIF project aims to build a high intensity material irradiation facility which one of the main components is a high intensity deuteron accelerator. A prototype of this accelerator will be built in Rokkasho in Japan. It includes a cryomodule composed of 8 superconducting cavities (HWR) powered by 200 kW couplers to accelerate the deuteron beam from 5 MeV to 9 MeV. The beam is focused inside the cryomodule by 8 superconducting solenoids. The cryomodule design has to respect some severe beam dynamics requirements, in particular a restricted space for the component interfaces and an accurate alignment to be kept during cooling down. A double cryogenic system has been designed as it is necessary to control the cavity cooling independently from the solenoid one. The cryomodule design should also be compatible with its environment in the Rokkasho building. This paper gives then a general overview of the 1rst cryomodule current design and its interfaces. It defines the concept chosen for the Cryogenic System, explains the method foreseen for the assembly and alignment and describes the integration study in Rokkasho.
CEA, Gif-sur-Yvette
CIEMAT, Madrid
TTI, Santander
FZJ, Jülich
The driver of the International Fusion Material Irradiation Facility (IFMIF) consists of two 125 mA, 40 MeV CW deuteron accelerators. A superconducting option for the 5 to 40 MeV linac based on Half-Wave Resonators (HWR) has been chosen. The first cryomodule houses 8 HWR's supplied by high power RF couplers; each of them should be able to operate at 200 kW in CW. This paper will give an overview of the RF design of the 175 MHz CW power coupler. The detailled mechanical studies and the realization will be performed by the Industry. Global approach of the contract with the Industry and the organization of the intermediate validation tests will be discussed. In a second part, the choices and the last advances concerning the couplers RF power test stand will be described.
IAP, Frankfurt am Main
TU Darmstadt, Darmstadt
GSI, Darmstadt
StrahlSim is a unique code for the simulation of charge exchange driven beam loss and dynamic vacuum effects in heavy ion synchrotrons. Dynamic vacuum effects are one of the most challenging problems for accelerators using intermediate charge state, high intensity heavy ion beams (e.g. AGS Booster, LEIR, SIS18). StrahlSim can be used as a design tool for synchrotrons, e.g. for the estimation of pumping power needed to stabilize the dynamic vacuum. Recently, StrahlSim has been extended to simulate time dependent longitudinal pressure profiles. The new code calculates a self-consistent static pressure distribution along the accelerator and simulates local pressure rises caused by dynamic and systematic beam losses. StrahlSim determines the loss distribution of charge exchanged beam ions and respects the beam energy dependence of the charge exchange cross sections. The beam loss calculated by means of the new time dependent longitudinal pressure profiles has been benchmarked with measured data from the latest SIS18 machine experiments.
INFN- Sez. di Padova, Padova
INFN/LNL, Legnaro (PD)
INFN-Torino, Torino
In the framework of the IFMIF/EVEDA project, the RFQ is a 9.8 m long cavity, with very challenging mechanicals specification. In the base line design, the accelerator tank is composed of 18 modules that are flanged together. The construction procedure of each module foresees the horizontal brazing of the four electrodes and then the vertical brazing of the flanges. A RFQ prototype, composed of 2 modules, aimed at testing all the mechanical construction procedure is under construction. In this article, the progress of the prototype construction and the progresses in the design and engineering phase, as well the description of all the fabrication phases is reported.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
KEK, Ibaraki
The J-PARC RFQ (length 3.1m, 4-vane type, 324 MHz) accelerates a beam from the ion source to the DTL. The beam test of the linac was started in November 2006 and 181 MeV beam was successfully accelerated in January 2007. Since then, the linac has been delivered beams for commissioning of the linac itself, downstream accelerators and facilities. Trip rates of the RFQ, however, unexpectedly increased in Autumn 2008, and we have been suffering from this issue for user run operation since then. We tried to recover by tender conditioning, modification of RF control, improvement of vacuum properties and so on. By taking these measures, we manage to have 2 to 3 days continuous beam operation. In this report, we describe the status of the RFQ.
University of Warwick, Coventry
Fundación Tekniker, Elbr (Guipuzkoa)
Bilbao, Faculty of Science and Technology, Bilbao
Fundación TEKNIKER, Eibar (Gipuzkoa)
STFC/RAL, Chilton, Didcot, Oxon
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
STFC/RAL/ISIS, Chilton, Didcot, Oxon
Elytt Energy, Madrid
Imperial College of Science and Technology, Department of Physics, London
The Front End Test Stand (FETS) at the Rutherford Appleton Laboratory is intended to demonstrate the early stages of acceleration (0-3 MeV) and beam chopping required for high power proton accelerators, including proton drivers for pulsed neutron spallation sources and neutrino factories. A Low Energy Beam Transport (LEBT), consisting of three solenoids and four drift sections, is used to transport the H- beam from the ion source to the FETS Radio Frequency Quadrupole. We present the status of the installation and commissioning of the LEBT, and compare particle dynamics simulations with preliminary measurements of the H- beam transport through the LEBT.
GSI, Darmstadt
The engineering design, including the specifications for the accelerator components of the FAIR synchrotron SIS100 has been summarized in the Technical Design Report. The final stage of technical planning shall approach production readiness for the major technical systems in 2010. Significant progress has been achieved in the design of the cryomagnetic system with its main dipole and quadrupole modules, enabling the production of the first pre-series dipole magnet. Slight modifications of the lattice have been implemented to equalize most of the cryostat interconnections, leading to a simplified design and installation effort, and a reduced variety of components and spar parts. The new parallel tunnel allows optimal short interconnections between the supply units and power converters and the accelerator components. The status of the engineering design of SIS100 will be reported.
JINR, Dubna, Moscow Region
BINP SB RAS, Protvino, Moscow Region
JINR/LHE, Moscow
The 'Nuclotron-M' project started in 2007 is considered as the key point of the first stage of the NICA/MPD project. General goal of the 'Nuclotron-M' project is to prepare all the systems of the Nuclotron for its long and reliable operation as a part of the NICA collider injection chain. Additionally the project realization will increase the Nuclotron ability for realization of its current experimental program. Results of the last runs of the Nuclotron operation are presented.
SLAC, Menlo Park, California
CERN, Geneva
In order for the LHC to reach an ultimate luminosity goal of 1035, CERN is considering upgrade options for the LHC injector chain, including a new 50 GeV synchrotron of about 1.3 km length for protons and heavy ions, to be called the PS2. In this ring the proton energy is ramped from 4 GeV in 1.2 s, and the design (proton) current is 2.7 A. The present baseline of the vacuum system considers elliptical stainless steel chambers bakeable up to 300°C, various coatings to mitigate electron cloud are under study. For a bare stainless steel or Inconel chamber, the resistive wall wake alone will lead to multi-bunch instability, whereas for transverse mode coupling (TMCI), the threshold is above the design beam current, though this instability may become an issue once other impedance contributions are taken into account. A copper layer of varying thickness is shown to raise the TMCI threshold but to have relatively little effect on the multi-bunch resistive-wall growth rate unless the coating is very thick. We are also studying the effect of the copper coating on the penetration of the guide field during the energy ramp, which sets an upper limit on the allowable thickness.
Siemens AG, Healthcare Technology and Concepts, Erlangen
Air insulated Cockcroft-Walton (Grienacher) cascades have been historically used to generate high voltages for accelerating particles. This paper explores how this technology can be utilised through a system level approach to develop more compact accelerator configurations with much higher voltages and gradients. One such concept is presented that realises a 20MeV, 1mA tandem accelerator that has a footprint ~2m^2
BINP SB RAS, Novosibirsk
An electrostatic tandem accelerator with 1.25 MV at the high voltage terminal was designed, assembled and successfully commissioned at BINP. The accelerator of ELV-type will be used as injector for cancer therapy facility by carbon ions beams. The 10 keV beam of negative carbon ions with current up to 100 mkA is injected into the tandem and charge exchange in the vacuum heat insulation magnesium vapor target. The results of commissioning tests and beam parameters measurements are presented.
GANIL, Caen
CEA, Gif-sur-Yvette
LPSC, Grenoble Cedex
IPN, Orsay
SPIRAL2 is a radioactive beams facility, composed of a superconducting linac driver, delivering deuterons with an energy up to 40 MeV (up to 5 mA) and heavy ions with an energy up to 14.5 MeV/u (up to 1 mA). The superconducting linac is composed of two families of quarter wave resonators: type A (optimized for beta=0.07, 1 per cryomodule) and B (beta=0.12, 2 per cryomodule). The accelerator is scheduled to be commissioned from mid-2011 onwards. The project is therefore in production phase. This paper summarizes the latest results and the status of the superconducting linac. All 16 type B cavities have been tested. Cryomodules from both families are presently being assembled in series. Installation of the cryomodules in the new building in GANIL shall begin in August 2011.
GSI, Darmstadt
IAP, Frankfurt am Main
The super heavy element research is one of the outstanding projects at GSI. At SHIP* six new elements have been discovered; moreover, nuclear chemical experiments with transactinides were recently performed at TASCA**. This experimental program strongly benefits from high average beam intensities. In the past beam currents were raised significantly by a number of improvements. The present upgrade program comprises the installation of a superconducting (sc) 28 GHz ECR ion source, a new frontend (low energy beam transport and RFQ), and, in the long term, an sc cw Linac. For the short term, the new RFQ will raise the duty factor by a factor of two (50%), limited by the following accelerator only. This bottleneck will be resolved by the applied cw Linac. Beam tests with a newly developed sc CH cavity are scheduled for 2012. The setup of the RFQ as the major upgrade of the 20 year old HLI*** is in progress, the commissioning will be finished in March 2010. Besides a higher duty factor, improved longitudinal beam quality and transmission are expected. This paper reports on the challenging rf and beam commissioning.
* Separator for Heavy Ion Reaction Products
** TransActinide Separator and Chemistry Apparatus
*** High charge state injector, a part the UNILAC
IAP, Frankfurt am Main
Abstract A short RFQ prototype was built for tests of high power RFQ structures. We will study thermal effects and determine critical points of the design. HF-Simulations with CST Microwave Studio and measurements were done. Conditioning of the facility with 20 kW/m and simulations of thermal effects with ALGOR are on focus now. First results and the status of the project will be presented.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
KEK, Ibaraki
The J-PARC RFQ (length 3.1m, 4-vane type, 324 MHz) accelerates a negative hydrogen beam from 0.05MeV to 3MeV toward the following DTL. As the trip rates of the practically using RFQ increased in autumn 2008, we started the preparation of a new RFQ as a backup machine. The beam dynamics design of the new RFQ is the same as the current cavity, however, the engineering and RF designs are changed. The processes of the vane machining and the surface treatments have been carefully considered to reduce the discharge problem. The vacuum brazing technique has been chosen for vane integration. In this report, the detailed design will be described with the progress of the fabrication of the new RFQ.
CERN, Geneva
The Linac4 RFQ will accelerate the H- beam from the ion source to the energy of 3 MeV. The RFQ is composed of three sections of 1 meter each, assembled by means of ultra high vacuum flanges and an adjustable centering ring. The complete 3-m long RFQ will be supported isostatically over 3 points like a simple beam in order to minimise the maximum deflection. The ridge line, used to feed the RF power into the RFQ, will be supported via springs and its position adjusted in such way that no strain is introduced into the RFQ at the moment of its connection. The mechanical design has been done at CERN where the modules are completely manufactured, heat treated and brazed also. In that way, all of the processes are carefully controlled and the influence, notably of the heat treatments, has been understood in a better way. Since 2002 several four vanes RFQ modules have been brazed at CERN for the TRASCO and IPHI projects. A two-step brazing procedure has been tested. This technique is actually used for the assembly of the CERN Linac4 RFQ. This paper describes the design, the mechanical procedures adopted for machining and assembly and the first results obtained.
Imperial College of Science and Technology, Department of Physics, London
STFC/RAL/ISIS, Chilton, Didcot, Oxon
STFC/RAL, Chilton, Didcot, Oxon
This paper will present the mechanical engineering design for a 324 MHz 4-vane RFQ, which has been developed for the Front End Test Stand (FETS) project based at the Rutherford Appleton Laboratory (RAL) in the UK. The design criteria will be discussed along with particular design features of the RFQ including the tuners, vacuum ports, main body cooling pocket design and the support / alignment structure. Different techniques for creating the RF and vacuum seal between major and minor vanes are also discussed.
STFC/RAL/ISIS, Chilton, Didcot, Oxon
Imperial College of Science and Technology, Department of Physics, London
The front end test stand (FETS) [1] being constructed at the Rutherford Appleton Laboratory is entering the next stage of commissioning, with the three-solenoid magnetic low energy beam transport (LEBT) now installed and undergoing commissioning. The next major component to be manufactured is the 3 MeV, 324 MHz, four metre radio frequency quadrupole (RFQ). The mechanical design is almost complete so a comprehensive finite element model of the entire RFQ has been made in ANSYS to ensure the electromagnetic, thermal and structural properties are sound. An analysis of the cooling strategy and expected resonant frequency shift due to thermal expansion are presented.
FZJ, Jülich
BINP SB RAS, Novosibirsk
The 2 MeV electron cooling system for COSY-Jülich was proposed to further boost the luminosity even in presence of strong heating effects of high-density internal targets. The project is funded since mid 2009. Manufacturing of the cooler components has already begun. The space required for the 2 MeV cooler is being made available in the COSY ring. The design and construction of the cooler is accomplished in cooperation with the Budker Institute of Nuclear Physics in Novosibirsk, Russia. The 2 MeV cooler is also well suited in the start up phase of the High Energy Storage Ring (HESR) at FAIR in Darmstadt. It can be used for beam cooling at injection energy and is intended to test new features of the high energy electron cooler for HESR. Two new prototypes of the modular high voltage system were developed, one consisting of gas turbines the other based on inductance-coupled cascade generators. The new 2 MeV electron cooler is described in detail and tests of components are reported.
Kyoto ICR, Uji, Kyoto
NIRS, Chiba-shi
S-LSR is a compact ion storage and cooler ring to inject beam of the 7MeV proton and the 40MeV Mg+. The average vacuum pressure measured by the vacuum gauges without beam was achieved up to about 4x10-9 Pa in 2007. Many experiments have been carried out using the proton and Mg beam, for example the one-dimensional beam ordering of protons utilizing the electron cooler, the extraction tests of the short bunched beam and the laser cooling for the Mg beam had been performed. The beam lifetime can be estimated with the vacuum pressure or the loss-rate of the beam energy. The values of the estimated lifetime are nearly equal to the measured lifetime values. The present status of the proton beam lifetime and the vacuum pressure is reported.
YerPhI, Yerevan
The Vibrating Wire Monitor (VWM) with aperture 20 mm was developed for scan of electron beam with large transversal sizes. Test experiments with VWM placed in air were done on the 20 MeV electron beam of Yerevan Synchrotron Injector with 4-7 uA at outlet. A new design of VWM is proposed for scan of the beam with even greater transversal sizes.
DESY, Hamburg
BNL, Upton, Long Island, New York
TUD, Dresden
DESY Zeuthen, Zeuthen
PETRA III is the new 3rd generation hard X-ray synchrotron light source at DESY, operating at a beam energy of 6 GeV. Machine commissioning began in April 2009 and user operation starts in 2010. In order to achieve a high brilliance, damping wigglers with a total length of 80 m are installed to reduce the horizontal emittance down to an extremely low value of 1 nm rad. For a precise emittance online control, a dedicated diagnostics beamline was built up to image the beam profile with synchrotron radiation from a bending magnet in the X-ray region. The beamline is equipped with two interchangeable X-ray optical systems, a pinhole optic for standard operation and a high resolution compound refractive lens optic. In addition, the synchrotron radiation angular distribution can be exploited at high photon energies. In this presentation, first experience with the system will be reported.
FZJ, Jülich
UniDo/IBS, Dortmund
GSI, Darmstadt
JINR, Dubna, Moscow Region
To study electron cooling in a synchrotron nondestructive methods only are suitable. The ionization profile monitor (IPM) delivers real-time data in both transverse planes allowing detailed analysis of beam profile evolution in COSY. First attempts to use scintillation of residual gas (SPM) to measure beam profiles were very promising. Beam diagnostics based on recombination is usually used to optimize electron cooling of protons (H0-diagnostics). However, it is not available when cooling antiprotons. So the IPM and possibly the SPM are vital for electron cooling optimization in the HESR ring. The new beam instrumentation at COSY is introduced and its relevance for the new 2 MeV electron cooler project and the HESR are discussed. Results of beam studies performed during electron cooling beam times at COSY are presented.
ELETTRA, Basovizza
DEEI, Trieste
FERMI@Elettra is a soft X-ray fourth generation light source under construction at the ELETTRA laboratory. To characterize the beam phase space by means of measurements of the bunch length and of the transverse slice emittance two deflecting cavities will be positioned at two points in the linac. One will be placed at 250 MeV (low energy), after the first bunch compressor (BC1); the second at 1.2 GeV (high energy), just before the FEL process starts. The Low-Energy RF Deflector consists in a 5 cells, standing wave, normal conducting, RF copper cavity. A single ANSYS model has been developed to perform all of the calculations in a multi-step process. In this paper we discuss and report on results of electromagnetic, thermal, and structural analysis.
Hiroshima University, Graduate School of Science, Higashi-Hiroshima
KEK, Ibaraki
Energy Recovery Linac (ERL) as synchrotron light source is planned to construct in KEK. Before the construction of full-set of ERL, compact ERL to study the accelerator technologies will be constructed. For the injector, a high voltage photoemission gun with DC operation and measurement systems for the low emittance beam will be developed. In order to observe bunch length and longitudinal beam profile, we have designed a single-cell deflecting cavity with 2.6 GHz dipole mode. We describe the optimization of the cavity, mechanical design and the measurements results with simulation.
KEK, Ibaraki
Sudden decrease in the beam lifetime is sometimes observed in many electron storage rings. Such an event has been commonly attributed to dust trapping, but its mechanism has not been entirely elucidated yet. Our recent research at PF-AR has shown that trapped dust with certain conditions can be visually observed by video cameras, and the recorded movies revealed that the trapped dust moved longitudinally. In addition, the light emission from the dust indicated that its temperature reached 1000 K or more. Thus, direct observation of trapped dust has been proved to be an effective way to investigate the dust trapping mechanism. We have carried on this research with advanced cameras, such as high-sensitivity or high-speed cameras, and the results will be presented.
KEK, Ibaraki
MELCO SC, Tsukuba
J-PARC, KEK & JAEA, Ibaraki-ken
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
Experiences of operating BPM's during beam commissioning at the J-PARC MR are reported. The subjects are: (1) bug report, statistics and especially the effect of a beam duct step, (2) position resolution estimation (<30 micrometers with 1 sec averaging), (3) beam based alignment.
Saint-Petersburg State University, Saint-Petersburg
LETI, Saint-Petersburg
We describe both analytically and numerically beams radiation in presence of media which can be realized as modern metamaterials. In particular, effects of reversed Cherenkov radiation (RCR)* and reversed Cherenkov-transition radiation (RCTR)** are considered. These phenomena can be used for detection of charged particles and diagnostics of beams. Earlier we noted some useful properties of radiation in the case of the boundary between an ordinary medium and an isotropic left-handed metamaterial (LHM)*. Now we continue to analyze prospects of use of LHM for beam diagnostics. Moreover, we investigate RCR and RCTR in the case of certain anisotropic materials with properties being similar to properties of LHM. The useful features are reversed character of radiation and, particularly, existence of two thresholds for RCTR (lower threshold and upper one). This fact allows selection of particles (or beams) with energy in some predetermined range. The specific radiation patterns (having two or three lobes in anisotropic metamaterial) can be useful for particle energy measurement as well.
* Z.Y. Duan, B.-I. Wu, S. Xi, H.S. Chen., M. Chen, Progress in Electromagn. Research, v.90, p.75 (2009).
** S.N. Galyamin, A.V. Tyukhtin, A. Kanareykin, P. Schoessow, PRL, v.103, p.194802 (2009).
TPU, Tomsk
Tomsk Polytechnic University, Nuclear Physics Institute, Tomsk
A noninvasive technique to determine a sub-mm length of electron bunches (rms < 100 um) based on a measurement of the coherent Cherenkov radiation (CChR) spectrum in THz range is proposed. CChR is generated when electron bunch moves in a vacuum near dielectric target. If the optical properties and geometry of a target are chosen in order to achieve a low absorption with a dispersion allowing expanding the Cherenkov cone, such target may be considered as the «natural Cherenkov prism». We demonstrated a feasibility of using of CsI prism for measurement of a bunch length in the range 50-200 um for Lorentz factor = 100. We also measured CChR power from Teflon target generated by the 6.1 MeV bunched electron beam with bunch rms length 1.2 mm and compared it with coherent diffraction radiation one for identical conditions. CChR seems to be a promising radiation mechanism for a new beam diagnostics technique.
Fundación TEKNIKER, Eibar (Gipuzkoa)
Bilbao, Faculty of Science and Technology, Bilbao
STFC/RAL/ISIS, Chilton, Didcot, Oxon
A Front End Test Stand is being built at the Rutherford Appleton Laboratory in the UK to demonstrate a chopped H− beam of sufficiently high beam quality for future high-power proton accelerators (HPPA). The test stand consists on a negative Hydrogen ion source, a solenoid LEBT, a 324 MHz four vane RFQ, a MEBT composed of rebunching cavities and choppers and a set of diagnostics ending with a beam stop. The beam stop, which has to accept a 3 MeV, 60 mA, 2 ms, 50 Hz (10% duty factor) H− beam, consists of a coaxial double cone configuration where the inner cone's inner surface is hit by the beam and the inter-cone gap is cooled by high-speed water. The cones are situated inside a water tank and mounted at one end only to allow thermal expansion. In order to minimize both prompt and induced radiation pure aluminium is used, but the poor mechanical properties of pure aluminium are overcome by employing a metal spinning process that increases the yield strength to several times the original value of the non-deformed material. CFD and FEM codes have been used to avoid high temperature gradients, to minimize thermal stresses, and to minimize fatigue caused by the pulsed beam.
CERN, Geneva
SMI, Vienna
The hyperfine transition frequency of hydrogen is known to a very high precision and therefore the measurement of this transition frequency in antihydrogen is offering one of the most accurate tests of CPT symmetry. The ASACUSA collaboration will run an experiment designed to produce ground state antihydrogen atoms in a CUSP trap. These antihydrogen atoms will pass with a low rate in the order of 1 per second through a spin-flip cavity where they get excited depending on their polarization by a 1.42 GHz magnetic field. Due to the small amount of antihydrogen atoms that will be available the requirement of good field homogeneity is imposed in order to obtain an interaction with as many antihydrogen atoms as possible. This leads to a requirement of an RF field deviation of less than ± 10 % transverse to the beam direction over a beam aperture with 100 mm diameter. All design aspects of this new spin-flip cavity, including the required field homogeneity and vacuum aspects, are discussed.
EPFL, Lausanne
CERN, Geneva
To improve the quality of the CLIC Test Facility 3 drive beam, it has been proposed that a photo injector replaces the actual thermionic gun. This would produce a lower emittance beam and minimize beam losses in the injector since the RF bunching and sub‐harmonic bunching systems would not be needed anymore. Such a photo injector, named PHIN, is currently being developed at CERN. One of the difficulties is to provide a high intensity beam (3.5A) with a stable (0.1%) beam energy over 1.5us as well as a relative energy spread less than 1%. A 90° spectrometer line featuring a segmented dump and an Optical Transition Radiation screen has been constructed and commissioned in order to study the time evolution of the beam energy along the pulse duration. In the following paper, we present the design as well as the results from the previous two PHIN runs.
LBNL, Berkeley, California
CLASSE, Ithaca, New York
Grove City College, Grove City, Pennsylvania
The CESR Damping Ring Test Accelerator collaboration (Cesr-TA) utilizes the CESR e+/e- storage ring at Cornell University for carrying out R&D activities critical for the ILC damping rings. In particular, various locations have been instrumented for the study of the electron cloud effects and their amelioration. In this paper we present the results obtained using the TE wave propagation method to study the electron cloud evolution and its dependence on several beam and machine parameters. Whenever possible, we have also compared our measurements with those obtained by using retarding field analyzers (RFA) with good agreement. Amongst the results obtained, we were able to detect a strong resonance of the electron cloud with the TE wave in regions of the beampipe where a dipole-like magnetic field is also present. Besides the standard transmission method, we are also developing an alternative procedure, the so-called resonant BPM, which can be used for a more localized measurement of the electron cloud density, which has already yielded promising results.
CLASSE, Ithaca, New York
CalPoly, San Luis Obispo, CA
During the last several years CESR has been studying the effects of electron clouds on stored beams in order to understand their impact on future linear-collider damping ring designs. One of the important issues is the way that the electron cloud alters the dynamics of bunches within the train. Techniques for observing the dynamical effects of beams interacting with the electron clouds have been developed. These methods will be discussed and examples of measurements will be presented.
INFN/LNF, Frascati (Roma)
Istituto Nazionale di Fisica Nucleare, Milano
Università di Roma I La Sapienza, Roma
INFN-Roma II, Roma
Università di Roma II Tor Vergata, Roma
University of Rome La Sapienza, Rome
Rome University La Sapienza, Roma
ENEA C.R. Frascati, Frascati (Roma)
The region of the spectrum from 0.3 to 5 THz is of great interest for several experiments in different areas of research. A THz radiation source can be produced at SPARC as coherent transition radiation emitted by either a compressed or longitudinally modulated beam intercepting a metal foil placed at 45° with respect to the beam propagation. Results on the characterization of the THz source at SPARC are described in the paper.
ORNL, Oak Ridge, Tennessee
ORNL RAD, Oak Ridge, Tennessee
The use of a beam stop to absorb full or partial beam at various points along a particle accelerator is commonplace. The design of accelerator components such as magnets, linacs and beam instruments tends to be a fairly focused and collective effort within the particle accelerator community with well established performance and reliability criteria. Beam stop design by contrast has been relatively isolated and unconstrained historically with much more general goals. This combination of conditions has lead to a variety of facility implementations with virtually no standardization and minimal concensus on approach to development within the particle accelerator community. At the Spallation Neutron Source (SNS), for example, there are four high power beam stops in use, three of which have significantly different design solutions. This paper describes the design of a new off-momentum beam stop for the SNS. Content will be balanced between hardware description, analyses performed and the methodology used during the development effort. Particular attention will be paid to the approach of the design process with respect to future efforts to meet beam stop performance metrics.
SINAP, Shanghai
Shanghai KEY Laboratory of Cryogenics & Superconducting RF Technology, Shanghai
The digital low level radio frequency (DLLRF) system and the beam trip diagnostic system in the storage ring of Shanghai Synchrotron Radiation Facility (SSRF) have been operational for more than one year. The DLLRF has successfully maintained the amplitude and phase stability of the cavity field in the superconducting cavity even when the beam current in the storage ring reached 300mA at 3.5GeV, and the beam trip diagnostic system has been realized and is helpful for improving the reliability of the RF system.
CERN, Geneva
EPFL, Lausanne
Chalmers University of Technology, Chalmers Tekniska Högskola, Gothenburg
Electron cloud is a limitation to increasing the beam current in the CERN SPS in the frame of an intensity upgrade of the LHC complex. Coating the vacuum chamber with a thin amorphous carbon layer is expected to reduce the electron cloud build-up. Three SPS straight sections have been coated to study the performance of this carbon coating. The microwave transmission method is one possible way to monitor electron cloud and hence to test the effect of the coating. In this paper the evolution of the experimental setup for measurements of the electron cloud using LHC type beams with different bunch spacing will be described. Due to the low revolution frequency of about 43 kHz serious electromagnetic compatibility problems and intermodulation have been found. These effects and their mitigation are described. Finally we present the measurement results illustrating the possible reduction due to the carbon coating.
CSIC, Madrid
CERN, Geneva
UAM, Madrid
ESA-ESTEC, NOORDWIJK
We are presenting first results of direct measurements of the secondary electron emission yield (SEY) for several magnetic materials like ferrites at energies of primary electrons from 5 to 1000 eV. In order to minimize the impact of surface charging, the primary electron beam had a short pulse modulation of 400ns with a very low repetition rate. This paper discusses a method of developing a secondary-electron-suppressing highly textured ferrite surface with low SEY by depositing a layer of very fine ferrite particles onto a substrate. The experimental results indicate that the SEY of the particulate ferrite surfaces is much lower than that of flat ferrites. In comparison we have confirmed that ordinary carbon coating with rather large grain size returns SEY value close to unity. However, a surface with very finely powdered carbon has a much smaller secondary emission yield of about 0.5, but the adhesion of these carbon powders to the surface is often not reliable enough for many applications. As a remarkable fact it has been found that gold- and also carbon-coated ferrites have SEY peak values lower than unity up to 1000eV.
NSRRC, Hsinchu
The Taiwan Photon Source (TPS) is a third generation synchrotron accelerator which the designed energy will be 3 GeV whereas the current is 500mA. The role of crotch absorber is designed to protect downstream UHV vacuum chamber. It is is the only mask component to absorb large amount of synchrotron radiation (bending magnet) in the storage ring. Crotch absorber is installed from transverse direction of the bending chamber to intercept the power. Two bent OFHC copper tubes are vacuum brazed on the copper mask. A 30 degree groove is machined to face bending magnet fan. The reason is not only to dissipate the heat but also to limit back scattering to the rest of chambers. Top and bottom of the absorber are bolted with beryllium copper springs; they will provide extra support for the absorber after it is installed in the Aluminum chamber. Three thermocouples will be embedded inside of the mask to monitor the temperature gradient. Final prototype of the crotch absorber with thermal analysis, design and machined parts are also presented in this paper.
BNL, Upton, Long Island, New York
PVI, Oxnard
Institute of High Current Electronics, Tomsk
Electron clouds, which can limit machine performance, have been observed in many accelerators including RHIC at BNL. They can be suppressed by low secondary electron yield beam pipe surfaces. Additional concern for the RHIC machine, whose vacuum chamber is made from relatively high resistivity 316LN stainless steel, is high wall resistivity that can result in unacceptably high ohmic heating for superconducting magnets. The high resistivity can be addressed with a copper (Cu) coating; a reduction in the secondary electron yield can be achieved with a TiN or amorphous carbon (a-C) coating. Applying such coatings in an already constructed machine is rather challenging. We started developing a robotic plasma deposition technique for in-situ coating of long, small diameter tubes. The technique entails fabricating a device comprising of staged magnetrons mounted on a mobile mole for deposition of about 5 μm (a few skin depths) of Cu followed by about 0.1 μm of a-C. As a first step, a 15-cm Cu cathode magnetron is being designed and fabricated, after which, 30-cm long sample of the RHIC pipe are to be Cu coated. Deposition rates and affects on RF resistivity are to be measured.
INFN/LNF, Frascati (Roma)
Metallic clearing electrodes have been designed to absorb the photo-electrons in the DAΦNE positron ring. They have been inserted in the wigglers and dipoles vacuum chambers and have been connected to external high voltage generators. In the paper we present the design of the devices and the results of the electromagnetic simulations related to both the transfer and longitudinal beam coupling impedances. We also present the results of the RF measurements and the first results with the DAΦNE circulating positron beam.
KEK, Ibaraki
SLAC, Menlo Park, California
Coherent synchrotron radiation (CSR) is generated when a bunched beam traverses a dipole magnet or a wiggler/undulator. It can degrade the beam quality in both storage rings and linacs through enhancing the beam energy spread and lengthening the bunch length, even cause single-bunch microwave instabilities. Using several methods, CSR impedances in the positron damping ring (DR) of the SuperKEKB which is under design were calculated. From the impedances due to CSR, resistive wall and various vacuum components, quasi-Green function wake potentials were constructed and used in simulations of Particle-In-Cell (PIC) tracking. We present the CSR related results in this paper.
KEK, Ibaraki
University of Tokyo, Tokyo
Tohoku University, Graduate School of Science, Sendai
SuperKEKB is the upgrade plan of the current B-factory experiment with the KEKB accelerator at KEK. Its luminosity is designed to be 8x1035 /cm2/s (40 times higher than KEKB) and the integrated luminosity is expected to be 50 ab-1. In SuperKEKB, it is important to evaluate the beam induced BG and design the interaction region (IR) to assure the stable detector operation. To estimate the beam induced BG, we construct the beam-line simulation based on the GEANT4 simulation. In this paper, we report the BG evaluation and the IR design for SuperKEKB.
SLAC, Menlo Park, California
We discuss the feasibility of an application of an implicit finite-difference approximation to calculate the fields of a bunch moving with no restriction inside the vacuum chamber.
BNL, Upton, Long Island, New York
In this paper we present the design and prototype measurement of small gap (5mm to 10 mm aperture) dipole and quadrupole for the future high energy ERL (Energy Recovery Linac). The small gap magnets have the potential of largely reducing the cost of the future electron-ion collider project, eRHIC, which requires a 10GeV to 30 GeV ERL with up to 6 energy recovery passes (3.8 km each pass). We also studied the sensitivity of the energy recovery pass and the alignment error in this small magnets structure and countermeasure methods.
CERN, Geneva
The commissioning of the beam transfer systems for LHC included detailed aperture measurements in the injection regions and for the beam dump systems. The measurements, mainly single pass, were made using systematic scans of different oscillation phases and amplitudes, and the results compared with the expectations from the physical aperture model of the LHC. In this paper the measurements and results are presented and compared with the specified apertures in these critical areas.
CERN, Geneva
The UA9 experiment was installed in the CERN-SPS in March '09 in view of investigating crystal assisted collimation in coasting mode. Inside a vacuum vessel, two 2 mm long silicon crystals, bent by about 150 microradians are mounted on accurate goniometers, and a small 10mm long tungsten target is used to compare the effect of crystals with that of a standard scatterer. A moveable 60 cm long block of tungsten is located downstream at about 90 degrees phase advance to intercept the deflected beam. Scintillators, gas GEMs and beam loss monitors measure nuclear loss rates induced by the interaction of the halo beam in the crystal itself. A Roman pot is installed in the path of the deflected particles in between the crystal and the collimator, equipped with a Medipix detector to reconstruct the transverse spot of the impinging beam. Finally UA9 takes advantage of an LHC-collimator prototype installed close to the Roman pot to help in setting the beam conditions and to reveal in a destructive manner the deflected beam shape. This paper describes in details the hardware installed, and the procedures developed to set-up and detect the channeling conditions.
SLAC, Menlo Park, California
The Phase II upgrade to the LHC collimation system calls for complementing the 30 high robust Phase I graphite secondary collimators with 30 high Z Phase II collimators. The Phase II collimators must be robust in various operating conditions and accident scenarios. This paper reports on the final construction and testing of the prototype collimator to be installed in the SPS (Super Proton Synchrotron) at CERN. Bench-top measurements have demonstrated the device is fully operational and has the mechanical and vacuum characteristics acceptable for installation in the SPS.
UMAN, Manchester
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
Gallium Arsenide (GaAs) photocathodes have in recent year been widely used and have become the focus for use in modern accelerators and light sources such as the Accelerators and Lasers in Combined Experiments (ALICE) and the International Linear Collider (ILC). Once activated to a Negative Electron Affinity (NEA) state and illuminated by a laser, these materials can be used as a high-brightness source of both polarised and un-polarised electrons. This work presents an effective preparation procedure including heat cleaning, atomic hydrogen cleaning and the activation process for NEA GaAs photocathode. The stability of quantum efficiency (QE) and lifetime of NEA GaAs photocathode have been studied in the load-lock and photocathode preparation system for the ALICE photo- electron gun which has a base pressure in the order of 10-11 mbar. These studies are also supported with experimental evidence from surface science techniques such as Photoelectron Spectroscopy (XPS) and Low Energy Electron Diffraction (LEED) to demonstrate the processes at the atomic level.
Muons, Inc, Batavia
JLAB, Newport News, Virginia
Many user facilities such as synchrotron radiation light sources and free electron lasers require accelerating structures that support electric fields of 10-100 MV/m, especially at the start of the accelerator chain where ceramic insulators are used for very high gradient DC guns. These insulators are difficult to manufacture, require long commissioning times, and often exhibit poor reliability. Two technical approaches to solving this problem will be investigated. Firstly, inverted ceramics offer solutions for reduced gradients between the electrodes and ground. An inverted design will be presented for 350 kV, with maximum gradients in the range of 5-10 MV/m. Secondly, novel ceramic manufacturing processes will be studied, in order to protect triple junction locations from emission, by applying a coating with a bulk resistivity. The processes for creating this coating will be optimized to provide protection as well as be used to coat a ceramic with an appropriate gradient in bulk resistivity from the vacuum side to the air side of an HV standoff ceramic cylinder. Example insulator designs are being computer modelled, and insulator samples are being manufactured and tested
SINAP, Shanghai
The injection system composed of four kickers and two septa in the SSRF have been built and operated. The commissioning shows that fine injecting efficiency and smaller disturbance are carried out. The septum magnets are eddy current designs with a sheet of magnetic screening material around the stored electron beam to reduce the leakage field. The beam tube with RF finger flanges at each end is added to keep the continuity of impedance for the circulating beam. The pulser excite the septum with 60μsecond waveform of half sine-wave and 8kA peak current. Four identical kicker magnets provide the symmetric bump in 10 meter long straight sections. The excitation waveform is a 3.8μsecond half sine pulse up to 7 kA peak. The emphasis was on achieving the best possible tracking in time of the magnet field waveforms so that the residual closed orbit disturbance is minimized for top-up injection. The performance of the injection system with these pulsed magnets are described.
SLAC, Menlo Park, California
SLAC is proposing a rotatable collimator design for the LHC phase II collimation upgrade. This design has 20 facet faces on each cylindrical jaw surface and the two jaws, which will move in and out during operation, are rotatable in order to introduce a clean surface in case of a beam hitting a jaw in operation. When the beam crosses the collimator, it will excite broadband and narrowband modes that can contribute to the beam energy loss and power dissipation on the vacuum chamber wall and jaw surface. In this paper, the parallel eigensolver code Omega3P is used to search for all the trapped modes in the SLAC collimator design. The power dissipation generated by the beam in different vacuum chamber designs with different jaw end geometries is simulated. It is found that the longitudinal trapped modes in the circular vacuum chamber design with larger separation of the two jaws may cause excessive heating. Adding ferrite tiles on the vacuum chamber wall can strongly damp these trapped modes. The short-range wakefields will also be calculated to determine the broadband beam heating and transverse kick on the beam. We will present and discuss the simulation results.
CLASSE, Ithaca, New York
Cornell University, Ithaca, New York
LBNL, Berkeley, California
ANL, Argonne
Retarding field analyzers (RFAs) provide an effective measure of the local electron cloud density and energy distribution. Proper interpretation of RFA data can yield information about the behavior of the cloud, as well as the surface properties of the instrumented vacuum chamber. However, due to the complex interaction of the cloud with the RFA, particularly in regions of high magnetic field, understanding these measurements can be nontrivial. This paper will examine different methods for interpreting RFA data via cloud simulation programs. Possible techniques include postprocessing the output of a simulation code to predict the RFA response, and incorporating an RFA model into the program itself.
SOLEIL, Gif-sur-Yvette
Ever since the commissioning times, transverse instabilities, which now have been identified as the so called Fast Beam-Ion Instability (FBII), have existed in the SOLEIL storage ring. Though along with the improvement of the vacuum level with increasing beam dose its relative importance has decreased to a large extent as compared to the classical instabilities due to the coupling impedance, the FBII still exists persistently at high current, making it difficult to attain a stable beam at the final goal of 500 mA. In particular, sudden beam losses are frequently encountered after keeping the beam stable over a certain time with transverse feedback at the final current, which raised a question as to whether the observed phenomena are compatible with the saturating effect of the FBII. Experimental analysis using the bunch by bunch feedback diagnostics as well as theoretical and numerical analysis using multibunch tracking have been carried out to understand the instability quantitatively and to elucidate the mechanism of the beam losses.
Technion, Haifa
Electron cloud confined to move in the vertical direction by either the wiggler field or a dipole field has been investigated extensively. We present results of an analysis demonstrating that electrons may be trapped in the region of zero vertical field of a wiggler. Their characteristic frequency and life-time are established and some of the implications are discussed.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
J-PARC, KEK & JAEA, Ibaraki-ken
There is the famous formula of the horizontal impedance for the matched-traveling wave kicker. However, the real and the imaginary parts of the impedance do not satisfy the Hilbert transformations. On the other hand, the impedance measured by a loop method does not directly give the beam impedance. In this paper we theoretically derive the beam impedance and reproduce the impedance by using the estimated inductances of the kicker by the loop measurement.
CERN, Geneva
Amorphous carbon coatings with low secondary electron yield have been applied to the liners in the electron cloud monitors and to vacuum chambers of three dipole magnets in the SPS. The electron cloud is completely suppressed for LHC type beams in these monitors even after 3 months air venting and no performance deterioration is observed after more than one year of SPS operation. Upon variation of the magnetic field in the monitors the electron cloud current maintains its intensity down to weak fields of some 40 Gauss, where fast conditioning is observed. This is in agreement with dark traces observed on the RF shields between dipoles. The dynamic pressure rise has been used to monitor the behavior of the magnets. It is found to be about the same for coated and uncoated magnets, apart from a weak improvement in the carbon coated ones under conditions of intense electron cloud. Inspection of the coated magnet is foreseen in order to detect potential differences with respect to the coated monitors. Measurements of the stray fields outside the dipoles show that they are sufficiently strong to induce electron cloud in these regions.
EPFL, Lausanne
CERN, Geneva
Using B. Zotter's formalism, we present here a novel, efficient and exact matrix method for the field matching determination of the electromagnetic field components created by an offset point charge travelling at any speed in an infinitely long circular multilayer beam pipe. This method improves by a factor of more than one hundred the computational time with three layers and allows the computation for more layers than three. We also generalize our analysis to any azimuthal mode and finally perform the summation on all such modes in the impedance formulae. In particular the exact multimode direct space-charge impedances (both longitudinal and transverse) are given, as well as the wall impedances to any order of precision.
EPFL, Lausanne
CERN, Geneva
The exact formalism from B. Zotter to compute beam coupling impedances has been fully developed only in the case of an infinitely long circular beam pipe. For other two dimensional geometries, some form factors are known only in the ultrarelativistic case and under certain assumptions of conductivity and frequency of the pipe material. We present here a new and exact formalism to compute the beam coupling impedances in the case of a collimator-like geometry where the jaws are made of two infinite plates of any linear material. It is shown that the impedances can be computed theoretically without any assumptions on the beam speed, material conductivity or frequency range. The final formula involves coefficients in the form of integrals that can be calculated numerically. This way we obtain new generalized form factors between the circular and the flat chamber cases, which eventually reduce to the so-called Yokoya factors under certain conditions.
EPFL, Lausanne
CERN, Geneva
In this study B. Zotter's formalism is applied to a circular infinitely long beam pipe made of a conductor of infinite thickness where an offset point-charge travels at any given speed. Simple formulae are found for the impedances and electromagnetic fields both at intermediate frequencies (recovering Chao's results) and in the low frequency regime where the usual classic thick wall impedance formula does not apply anymore due to the large skin depth compared to the pipe radius.
EPFL, Lausanne
CERN, Geneva
The SPS kickers are major contributors to the SPS transverse beam coupling impedance. The current "flat chamber" impedance model for a kicker is obtained by applying form factors to the theoretical impedance of an axisymmetric ferrite beam pipe. This model was believed to be acceptable for the vertical dipolar impedance, as two-wire measurements on SPS kickers revealed a satisfactory agreement. However, one-wire measurements on PS kickers suggested that this model underestimates the kickers' transverse quadrupolar (detuning) impedance. The longitudinal and transverse dipolar impedances of another kicker model that accounts for the metallic plates on each side of the ferrite were derived in the past by H. Tsutsui. The same formalism is used in this paper to derive the quadrupolar impedance. These formulae were then successfully benchmarked to electromagnetic simulations. Finally, simulating the interaction of an SPS bunch with the improved kickers' model results in a positive horizontal tune shift, which is very close to the tune shift measured with the SPS beam.
IUCF, Bloomington, Indiana
ORNL, Oak Ridge, Tennessee
The instability caused by the electron cloud effect (ECE) may set an upper limit to beam intensity in proton storage rings. This instability is potentially a major obstacle to the full intensity operation, at 1.5·1014 protons per pulse, of the Spallation Neutron Source (SNS). High intensity experiments have been done with different sets of parameters that affect the electron-proton (e-p) instability, of which bunch intensity and bunch shape are considered as two main factors. In the experiment, the phase and amplitude of the second harmonic RF cavity are used to modify the bunch shape. Simulation with the beam dynamics code ORBIT has been carried out to compare with experimental results and to understand the impact of bunch shape on electron cloud build-up and beam stability. We have also attempted to benchmark the e-p model to predict the frequency spectrum and the RF buncher voltage threshold values against experimental results. Details and discussion will be reported in this conference.
* M.T.F. Pivi and M.A. Furman, PRSTAB 6, 034201 (2003)
** V. Danilov et. al, 39th ICFA Advanced Beam Dynamics Workshop, 2006
*** B. Macek et. al, PAC 2003
SLAC, Menlo Park, California
BNL, Upton, Long Island, New York
Collimators and other similar accelerator structures usually include small-angle tapering to lower the wakefields generated by the beam. While the low-frequency impedance is well described by Yokoya's formula (for axisymmetric geometry), much less is known about the behavior of the impedance in the high frequency limit. In this paper we develop an analytical approach to the high-frequency regime for round collimators and tapers. Our analytical results are compared with computer simulations using the code ECHO.
BNL, Upton, Long Island, New York
Case Western Reserve University, Center for Synchrotron Biosciences, Upton, New York
Stony Brook University, Stony Brook
The diamond amplified photocathode has the potential to dramatically increase the average current available from photoinjectors, perhaps to the amphere-class performance necessary for flux-competitive fourth-generation light sources. Electron emission from a diamond amplifier has been observed from hydrogen-terminated diamond, using both photons and electrons to generate carriers. The diamond electron amplifier has been demonstrated, with an emission gain of 40. Very high average current densities (>10 A/cm2) have been transported through the diamond using x-ray generated carriers. The device relies on high-purity intrinsic diamond with low crystalline defect density, as well as a negative electron affinity achieved by hydrogen termination. The effects of diamond purity and crystalline defects on charge transport in the material, and emission from the diamond surface have been studied using a number of techniques and the process is now well understood. The electron affinity of diamond has been measured to be -1.1 eV; the fraction of the electrons produced in the material which are emitted from the surface has also been measured.
YerPhI, Yerevan
We consider generation of diffusive radiation by a charged particle passing through a random stack of plates in the infrared region. Diffusive radiation originates due to multiple scattering of pseudophotons on the plates. To enhance the radiation intensity one needs to make the scattering more effective. For this goal we suggest to use materials with negative dielectric constant .
DESY, Hamburg
INFN/LASA, Segrate (MI)
Caesium telluride photocathodes are used as laser driven electron sources at the Free-Electron-Laser Hamburg, FLASH, and will be used at the European XFEL. One concern of the operation of photocathodes in these user facilities is the degradation of the quantum efficiency during operation. After improving vacuum conditions and removing contaminants, the cathode life time increased from a couple of weeks to several months. In this contribution we report on long time operation of Cs2Te cathodes in terms of QE measurements and investigations on the homogeneity of the electron emission. Another concern of electron guns operated with long RF-pulses (0.8 ms at FLASH) is the generation of dark current either from the cathode or from the gun body. During the last years a constant high amount of dark current, emitted from the gun body itself, was observed at FLASH. Caused by that during the shut-down 2009/2010 the RF-gun at FLASH, operated more than five years, was replaced. The improved dark current situation with the new RF-gun is presented in terms of dark current measurements under different operational conditions.
Sokendai - Okazaki, Okazaki, Aichi
UVSOR, Okazaki
Nagoya University, Nagoya
Light source technologies based on laser seeding are under development at the UVSOR-II electron storage ring. In the past experiments, we have succeeded in generating coherent DUV (Deep Ultra-Violet) harmonics with various polarizations. A spectrum measurement experiment of CHG (Coherent Harmonic Generation) was carried out by using a spectrometer of from visible to DUV range. In order to diagnose spectra of shorter-wavelength CHG, a spectrometer for VUV (Vacuum Ultra-Violet) has been constructed and the VUV CHG was measured. In addition, we try to use a seeding light source based on not only fundamental of Ti: Sapphire laser and the harmonics generated from non-linear crystals but also HHG (High Harmonic Generation) in a gas for the CHG experiment. Now the HHG system is under development. In this presentation, we introduce the VUV spectral measurement system and the HHG system and also report about comparison between the results of the current CHG experiments and design studies of numerical calculation for them.
AIST, Tsukuba, Ibaraki
Recently, an FEL in the near-infrared (IR) region was oscillated at a compact storage ring NIJI-IV whose circumference was 29.6 m. We have been developed a device for the storage ring FEL in the IR region with a 3.6-m optical klystron ETLOK-III, and the first lasing at a wavelength of around 1450 nm was achieved at February 2009. The maximum power of the FEL was 0.3 mW per vacuum window and the relative linewidth was 3·10-4.* Moreover, gamma-ray beam was also produced in the long straight section of NIJI-IV by Compton backscattering of the intra-cavity IR FEL and the stored electron beam with an energy of 310MeV. After the first lasing experiment, we have successfully performed to extend the lasing wavelength region and increase FEL power, and this recent progress will be presented.
* N. Sei, H. Ogawa, K.Yamada, Opt. Lett. 34 (2009) 1843.
HU/AdSM, Higashi-Hiroshima
We report that a lifetime of GaAs photocathode activated the surface to negative electron affinity (NEA) at various temperatures. An electron source with the NEA-GaAs photocathode is an important device for high-average-current electron accelerators, such as a next-generation light source based on an energy recovery linac, in which a high power laser is illuminated to the photocathode for generation of the electron beam of 100mA. For example, the laser power of 15W should be needed for the quantum efficiency of 1% and the wavelength of 800nm. Consequently the high power laser causes to rise the GaAs temperature. The degradation of photo emission from the cathode is enhanced by a thermal desorption of Cs due to the temperature rise, even if the beam is not extracted. We have measured the cathode lifetime at various temperatures between room temperature and 100 C.
HU/AdSM, Higashi-Hiroshima
JAEA/ERL, Ibaraki
KEK, Ibaraki
A NEA-GaAs photocathode is an important component for the next generation light source based on the ERL. Although the NEA-GaAs cathode has high quantum efficiency, deterioration of the NEA surface becomes serious with a high current operation. Therefore improvement of a vacuum in the cathode chamber is essential to get a long lifetime of the NEA-GaAs cathode. We are developing a photocathode test bench consisting of titanium (TP340) chamber, whose outgas rate is 1/1000 smaller than one of a SUS chamber, a cryo-pump (4000l/s) and a NEG pump (1900l/s). We report mainly the vacuum performance of the system.
KEK, Ibaraki
Hiroshima University, Graduate School of Science, Higashi-Hiroshima
Tohoku University, School of Scinece, Sendai
Compact ERL (cERL) is a test accelerator to establish accelerator technologies for GeV-class synchrotron light source based on ERL (Energy Recovery Linac), and will be constructed in KEK. It consists of an injector with photo cathode 500 kV DC gun, a merger section, super conducting RF cavities for acceleration and energy recovery, return loops, and a beam dump. To operate and test the photo cathode gun before installing it in the cERL injector, Gun Test Facility is constructing in KEK, AR south experimental hall. The Gun Test Facility has two photo cathode guns, 200 kV gun developed by Nagoya University and new 500 kV gun which is being developed, laser system to be emitted electrons from photo cathode surface, beam transport lines, and a beam diagnostics system. The diagnostics system consists of a double slit emittance measurement system, beam position monitors, transverse profile monitors, and a deflecting cavity to measure the bunch length and the longitudinal profile. In this presentation, the progress in the construction of the Gun Test Facility and the beam dynamics simulation will be presented.
JAEA/ERL, Ibaraki
KEK, Ibaraki
HU/AdSM, Higashi-Hiroshima
Nagoya University, Nagoya
A 500-kV, 10-mA photocathode DC gun has been designed and is now under fabrication by the collaboration efforts of JAEA, KEK, Hiroshima Univ. and Nagoya Univ. The Cockcroft-Walton generator and the ceramic insulator are installed upright in the SF6 tank. We have adopted a multiple-stacked cylindrical ceramic insulator, because this type of ceramic insulator has shown good stability and robustness at the 200-kV Nagoya polarized gun and the 250-kV JAEA FEL gun. The vacuum chamber, the guard-rings and the support-rod electrode are made of titanium alloy with very low out-gassing and robustness to high voltage performances. The Cockcroft-Walton generator, the ceramic insulator, the vacuum chamber and the guard-rings have been assembled and a high-voltage test has been successfully done with up to 550kV. The high-voltage test and up-to-date status of the gun development will be presented in detail.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
STFC/DL, Daresbury, Warrington, Cheshire
ISP, Novosibirsk
ALICE is an Energy Recovery Linac built at STFC Daresbury Laboratory to investigate the process of energy recovery. The project is an accelerator research facility intended to develop the technology and expertise required to build a New Light Source (NLS) in the UK based on a suite of Free-Electron Lasers. Currently the ALICE gun accommodates only a single photocathode at any one time, and the system must be vented to atmospheric pressure for photocathode replacement. To meet the stringent vacuum demands for good photocathode lifetime, the system then requires baking for up to three weeks. A new load-lock cathode preparation system has been designed as an upgrade to the ALICE gun. The load-lock can accommodate up to six photocathodes, and permits rapid transfer of photocathodes between the load-lock activation chamber and the gun, thus maintaining the vacuum. The photocathode preparation facility was successfully commissioned in spring 2009, and has since permitted a quantum yield of 15% to be achieved at a wavelength of 635 nm. Presently, a new gun vessel and photocathode transport system is under manufacture, with a view to this being fully-installed on ALICE in Spring 2012.
CERN, Geneva
Electron-cloud is one of the main limitations for particle accelerators with positively charged beams of high intensity and short bunch spacing, as SPS at CERN. The Secondary Electron Yield (SEY) of the inner surface of the vacuum chamber is the main parameter governing the phenomenon. The effect could be eliminated by coating the magnets vacuum chambers with a material of low SEY, which does not require bake-out and is robust against air exposure. For such a purpose amorphous carbon coatings were produced by magnetron sputtering of graphite targets. They exhibit maximum SEY between 0.9 and 1.1 after air transfer to the measuring instrument. After 1 month air exposure the SEY rises to values between 1.1 and 1.4. Storage under nitrogen or by packaging in Al foil makes this increase negligible. The coatings have a similar XPS C1s spectrum for a large set of deposition parameters and exhibit an enlarged line-width compared to pure graphite. The static outgassing without bake-out depends on deposition parameters and is in a range from 1 to 10 times higher than that of stainless steel. Instead, electron stimulated outgassing is lower than for stainless steel and is dominated by CO.
SESAME, Amman
The construction of SESAME, a 2.5 GeV, and 3rd generation synchrotron-light source is under progress. The first electron beam from the Microtron at low energy (less than 10 MeV) could be obtained on July, 14th, 2009 and reproduced several times. The tests of the injection and extraction system as well as the hydraulically and electrical tests of the main magnets of the Booster are complete and the vacuum chambers tests are underway. The Booster RF cavity and its plunger have been conditioned successfully by 1.7 kW CW RF power. The installation of the Booster is expected to start after the completion of the shielding. The design of the completely new storage ring is finalised and the Phase 1 beamlines is updated.
ASCo, Clayton, Victoria
The Australian Synchrotron has been open to users since April 2007. Beam availability is now consistently above 98%, with a Mean Time Between Failures (MTBF) of approximately 50 hours and a Mean Down Time (MDT) of approximately 1 hour. This paper discusses the program of activities that has been undertaken to improve beam availability, and to maximize the MTBF and reduce the MDT.
LNLS, Campinas
Karlsruhe Institute of Technology (KIT), Karlsruhe
In the beginning of 2008 an upgrade of the beam position monitors (BPMs) of the Brazilian Synchrotron Light Source (LNLS) electron storage ring was decided and scheduled as part of the continuous effort to improve the electron beam orbit stability. The objective was to replace most of the 24 BPMs installed in the storage ring and install new radiation absorbers inside the vacuum chamber. The original stripline BPMs were sensitive to temperature changes in the vacuum chamber. Heat, which induced mechanical stress in the striplines, could lead to fluctuations in the position readings thereby disturbing the orbit stability. The problem affected differently the BPMs. Although not a great issue during a typical user shift, the perturbations could pose some problems for the most sensitive experiments. One third of the BPMs were replaced in October 2008 and the remaining in October 2009. Thus, this large vacuum intervention aimed at improving the thermal and mechanical stability of the electron beam orbit measurement system. Finally, it will be presented the main changes made in the vacuum chambers and a survey of the evolution of the vacuum system after both interventions.
LNLS, Campinas
The main facility of the Brazilian Synchrotron Light Laboratory is a 93 meters circumference, 1.37 GeV storage ring. Recently, the first superconducting insertion device was installed in the machine. This 4 T ID produces powerful beams that can damage the non-cooled parts of the accelerator vessel in the case of a miss-steered beam, even with a relatively large vacuum chamber cross section. In this paper we present the design details and the first operational results of the electronic beam position interlock system. Topics about redundancy engineering will be discussed as well.
SOLEIL, Gif-sur-Yvette
The SOLEIL synchrotron light source is now delivering photons to 20 beamlines with a current of 400 mA in top-up mode. The long and short term H and V beam position stabilities are in the range of one micron thanks to the efficient slow and fast orbit feedbacks, and to the improved tunnel temperature regulation. The bunch by bunch transverse feedback is running with two independent H and V loops. To enable canted undulator implementations, a 3 magnet chicane has been installed in a medium straight whereas an additional triplet of quadrupole was inserted in the middle of a long straight to create a double low vertical beta. 17 insertion devices are now installed in the storage ring, 2 will be added early 2010, 8 are under construction, including a cryogenic undulator. Following the significant progression of the vacuum conditioning, the lifetime is now mainly Touchek limited. An electron bunch slicing set-up is also being installed to provide 100 fs long X-rays pulses to two existing beamlines. ~4500 hours will have been delivered in 2009 to the Beamlines with an availability above 96 % thanks to the very reliable operation of the unique SOLEIL RF system.
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Elektronen-Speicherring BESSY II, Berlin
PTB, Berlin
The Metrology Light Source* is the first storage ring optimized for THz generation**. It applies a bunch shortening mode, based on a flexible momentum compaction factor 'alpha'. The emitted THz radiation is very sensitive to the machine tuning, its power could vary by many orders of magnitude. We report on coherent THz signal intensities as a function of different machine parameters, such as beam energy, beam current, rf voltage and alpha tuning.
* R. Klein et al., Phys. Rev. ST. Accel. Beams vol. 11, 110701 (2008). ** J. Feikes et al., The Metrology Light Source: The First Electron Storage Ring Optimized for Generating Coherent THz Radiation, submitted to Phys. Rev. ST. Accel. Beams (2009).
IPM, Tehran
The effect of surface roughness on the secondary electron emission from a sandblasted surface is investigated using a Monte-Carlo method. Sandblasted surfaces can significantly reduce the secondary emission yield and have a large sensitivity to the percentage of surface roughness.
KEK, Ibaraki
A hybrid fill mode has been tested at the Photon Factory storage ring (PF-ring). The hybrid fill mode consists of a train of low-current bunches and a high-current single bunch. Since a bunch-by-bunch feedback system was not available because of the high contrast of currents between the bunch train and the single bunch, we suppressed multibunch instabilities in the transverse and longitudinal planes by using the octupole magnets and RF phase modulation, respectively. We also suppressed single-bunch instabilities by controlling ring chromaticity. As a result, we successfully stored a 450 mA current with the hybrid fill mode: 1/2 filling (2.56 mA/bunch × 156) + 1 single bunch opposite to the bunch train (50 mA/bunch). The distribution of vacuum pressures along the ring was similar for the hybrid fill and the typical single-bunch mode. In this conference, we will present the results of this test experiment as well as some future subjects to be solved for the user operation.
CELLS-ALBA Synchrotron, Cerdanyola del Vallès
The Synchrotron Light source ALBA is entering the commissioning period and beam should be provided to the users by the end of 2010. The installation of the full energy 3 GeV booster is finished, with the commissioning taking place in January 2010. The installation of the storage ring is almost finished and the commissioning should take place in summer 2010. The detailed milestones of the project are presented.
CELLS-ALBA Synchrotron, Cerdanyola del Vallès
The new 3rd generation synchrotron radiation source ALBA built nearby Barcelona is planned to start operation in 2010 with several different insertion devices installed in the storage ring either from the beginning or within the first year of operation. The list of first insertion devices includes: 2 planar PPM SmCo in-vacuum undulators with the period of 21.6 mm; 2 Apple-II type PPM NdFeB undulators with the periods of 62.36 and 71.36 mm respectively; 1 superconducting planar wiggler with the period of 30 mm and a maximum field of 2.1 T, and a 1 conventional wiggler with the period of 80.0 mm and a maximum field of 1.74 T. The emitted light of these IDs covers wide spectral range extending from hard X-rays to UV. Pre-design of the IDs was done by ALBA, but manufacturing has been outsourced. Production is now finished and they have been tested with magnetic measurements. The paper will present the final as build magnetic designs as well as the main results of magnetic measurements performed on the manufactured devices.
NSC/KIPT, Kharkov
The status of X-ray generator NESTOR that is under construction in Kharkov Institute of Physics and Technology is described in the paper.
SINAP, Shanghai
SSRF control system is a hierarchical standard accelerator control system based on EPICS. The VME 64X system, special embedded controller and PLCs are used for low level devices control or interlocks system. Using a uniform 1000Base-T backbone redundancy control network instead of field bus for mostly device controller with VLAN technique adopted, and integrate with EPICS using soft IOC. Digital technology such as digital power supply control system, new event timing system and digital phase control system are used and also integrated with some embedded EPICS IOC. An uniform System development and run time environment of hardware and software is adopted at the whole process. The high level physical application environment using MatLab 2007a with Accelerator Toolbox (AT) & middle layer with MatLab CA (Channel Access) connected component MCA/LabCA. The high level physical application can be integrated with the control system easily and conveniently. With the SSRF centre database, an enhanced distributed archive engine based on RDBS with native XML data type is been testing.
KEK, Ibaraki
Akita University, Akita
Profile shape measurements detecting profile slope angle, which corresponds to the differential of the profile shape, have been used for evaluating profile shapes highly precisely. They are hardly affected by scanning error in measurement and considered to have advantages for long distance measurements. Here, profile measurement using a level was adopted for straightness alignment of the KEK e-/e+ injector linac, considering the straightness alignment as a profile shape measurement. The slope angles between the alignment base plates of the linac could be detected with reproducibility of 10 micro-rad (σ) by sequential measurement interval of 1 to 2 m. The reproducibility of the straightness derived from the angle measurements was 42 micrometer (σ) for 69 m of the measurement distance and agreed well with the estimated value based on our error propagation model. These results show that straightness reproducibility of better than 1 mm (2-σ) can be achieved for 500 m of the KEK e-/e+ injector linac by sampling interval of 2m, and for 10 km of the ILC linac by sampling interval of 20 cm.
KEK, Ibaraki
A new laser-based alignment system is under development in order to precisely align accelerator components along an ideal straight line at the KEKB injector linac. The new alignment system is strongly required in order to stably accelerate high-brightness electron and positron beams with high bunch charges and also to keep the beam stability with higher quality towards the next generation of B-factories. A new laser optics with Airy pattern (so-called Airy beam) has been developed and the laser propagation characteristics in vacuum has been systematically investigated at a 82-m-long straight section of a beam line of the injector linac. The laser-based alignment measurement based on the new laser optics has been carried out with a measurement resolution of ±0.1 mm level by using a previously-used laser detection system. The experimental results are reported along with the basic design of the new laser-based alignment system.
CERN, Geneva
A prerequisite for a successful nanometre level magnet stabilization and pointing system is a low background vibration level. This paper will summarize and compare the ground motion measurements made recently in different accelerator environments at e.g. CERN, CESRTA and PSI. Furthermore the paper will give the beginning of an inventory and characterization of some technical noise sources, and their propagation and influence in an accelerator environment. The importance of the magnet support is also mentioned. Finally, some advances in the characterization of the nanometre vibration measurement techniques will be given.
JASRI/SPring-8, Hyogo-ken
RIKEN/SPring-8, Hyogo
Fiber-based beam loss monitors (BLM) have attracted much attention in recent years. Among them, systems using the detection of the Cerenkov light generated by the secondary charged particles hitting an optical fiber set along the vacuum chamber, offer the possibility to detect beam losses with a very fast response time (less than a few ms) over long distances, good position accuracy and sensitivity at a reasonable cost. For the undulator section of the SPring-8 X-FEL, radiation safety considerations set the desirable detection limit at 1 pC (corresponding to a 0.1% beam loss of the initial 1 nC/pulse) over more than a hundred meter. We report on a the test operation of a fiber-based BLM carried out at the 250 MeV SPring-8 Compact SASE Source (SCSS), a 1/16th model of the future X-FEL. The expected detection limit of the BLM based on a large (400 μm) core multimode fiber is below 2 pC over 120 m (for a corresponding 10 mV signal) while the position accuracy is expected to be better than one meter.
RIKEN/SPring-8, Hyogo
JASRI/SPring-8, Hyogo-ken
A fiber-based beam loss monitors (BLM) is under development for the undulator section of the SPring-8 X-FEL: the system is based on the detection of the Cerenkov light generated by the secondary charged particles hitting an optical fiber set along the vacuum chamber. Various parameters come into account in the final performance of the system, such as the impact angle and energy of the lost electrons, the fiber position (angular and radial) with respect to the point of impact, fiber characteristics (numerical aperture, index, diameter), etc. Thorough numerical studies have been carried out to investigate the performances of the system. Comparison with the experimental results obtained at the SPring-8 Compact SASE Source (SCSS), a 1/16th model of the future X-FEL are also given.
JASRI/SPring-8, Hyogo-ken
Electricity generation from scattered secondary particles has been examined for a kind of energy-recovery by using a beam loss monitor at the SPring-8 storage ring, in which PIN photodiodes are utilized without a reversed bias voltage in similar to a solar cell. The system and results will be reported.
LAL, Orsay
DESY, Hamburg
INFN/LNL, Legnaro (PD)
CSIC, Madrid
LAL-Orsay is developing an important effort on R&D and technology studies on RF power couplers for superconductive cavities. One of the most critical components of those devices is the ceramic RF window that allows the power flux to be injected in the coaxial line. The presence of a dielectric window on a high power RF line has a strong influence on the multipactor phenomena. The most important method to reduce the multipactor is to decrease the secondary emission yield of the ceramic window. Due to its low Secondary electron Emission Yield (SEY), TiN thin film is used as a multipactor suppressor coating on RF ceramic coupler windows. In this frame work, TiN deposition was made by magnetron reactive sputtering. XPS and XRD analysis were performed to control the film composition and stoechiometry. Coating thickness was optimized so that the TiN coating effectively reduces the SEY but does not cause excessive heating, due to ohmic loss. For this purpose, SEY measurements on covered and uncovered TiN Alumina substrates, multipactor level breakdown on TiN coated Cupper substrates and RRR measurements were performed for different deposit thicknesses.
LAL, Orsay
Within the XFEL project Laboratoire d'Accélérateur Linéaire (LAL) is engaged to deliver 800 fundamental power couplers operating at 1.3 GHz at nominal power of 120 kW for the superconducting linac. This paper presents the strategies chosen for industrial production along with that of conditioning so as to deliver couplers at the rate of 8 per week.
KEK, Ibaraki
JAEA/ERL, Ibaraki
ISSP/SRL, Chiba
A prototype module including a couple of 1.3 GHz superconducting 9-cell cavities has been designed as the main linac of cERL which is the test facility to establish the basic ERL technology at KEK. The shape of 9-cell Nb structure has been optimized to accelerate a CW beam of 100 mA with sufficiently damped higher order modes (HOM) which is achieved by adopting an eccentric fluted beam pipe and a cylindrical beam pipe of a large diameter of 123 mm. Extracted HOMs are absorbed by the ferrite cylinders bonded on the copper beam pipes by HIP process. A power coupler with double disk-ceramics has been developed to transfer an RF of 20 kW CW to the cavity in full reflection. The test results of fabrication, cooling and RF performance for these components are integrated as the prototype module of the main linac for cERL facility.
KEK, Ibaraki
Cryomodule tests of four Tesla-like cavities is under preparation for S1-global project at KEK. An average maximum accelerating gradient (Eacc,max) of four cavities in the vertical tests at 2 K was reached to approximately 25 MV/m. Conditioning of four STF-2 input couplers was carried out at a high power test stand with a 5MW-pulsed klystron. Two types of frequency tuning system with a slide-jack tuner and a piezo tuner is installed at the center or end position of the He jacket. String asssembly of the four cavities will be started in March, and the first cool-down test of the cryomodule is scheduled in June, 2010.
KEK, Ibaraki
Hydrogen absorbed in niobium was measured using effect of hydrogen Q-degradation. A niobium cavity was designed and manufactured for this experiment. Hydrogen was introduced from outside of the cavity by electrolysis of diluted sulfuric acid on the outer surface of the cavity with an anode made by stainless steel. The Q-factor is one of the most unstable property of superconducting cavities. Especially, the reproducibility of Q-factor cannot be so expected after disassembled and reassembled it. In this experiment, the Q-factor was measured without disassembling, because hydrogen was introduced from outside of the cavity. The Q-degradation was observed successfully. And the Q-factor becomes worse and worse, when hydrogen was introduced more and more. To estimate the amount of hydrogen which is absorbed in niobium, small and thin niobium samples were prepared. They were warmed by the energizing heating in vacuum after having introduced hydrogen. The out-gas was analyzed by QMS, and the amount of hydrogen was estimated. This method can be applied to measure the absorbed hydrogen during electro or chemical polishing of cavities without some influence of changing the surface morphology.
KEK, Ibaraki
Crab cavities were installed in KEKB in 2007. The function of the cavity is to tilt the bunch of the beam in the longitudinal direction. But if the RF phase gets out of control, the cavity kicks the beam like a steering magnet. To avoid this unwanted kick, the RF phase must be controlled well. In beam operation, some disturbances may occur such as a discharge, a quench, etc. When such disturbances occur, it is very difficult to control the RF phase precisely. We can't trust measured RF phase at that time. In KEKB, beam is aborted quickly when a disturbance is detected. Beam behavior before detect the disturbances has been investigated. We discuss following items. (1)How fast should the beam be aborted after detecting disturbances? (2)How fast should RF be turned off after detecting disturbances? (3)What a kind of disturbance is harmful? (4)Is the beam abort necessary at all? (Is just to turn RF off OK?)
KEK, Ibaraki
ISSP/SRL, Chiba
JAEA/ERL, Ibaraki
We started to develop an input power coupler for a 1.3GHz ERL superconducting cavity for ERL main linac. Required input power is about 20kW for the cavity acceleration field of 20MV/m and the beam current of 100mA in energy recovery operation. The input coupler is designed based on the STF-BL input coupler, especially choke-mode type ceramic window was applied. After that some modifications are applied for the CW 20kW power operation. We fabricated input coupler components such as ceramic windows and bellows and carried out the high-power test of the components by using a 30kW IOT power source and a test stand constructed.
KEK, Ibaraki
JAEA/ERL, Ibaraki
ISSP/SRL, Chiba
In order to verify the technology needed for ERL main linac cavities, we fabricated a prototype of L-band 9-cell KEK-ERL superconducting cavity. For the ERL, along with high gradient and high Q-value, strong HOM damping is required. Its cell shape is optimized for the HOM damping. The cavity has large irises of 80 mm diameter, large beampipes of 120 mm and 100 mm diameter and the eccentric fluted beampipe. After a series of surface treatment, such as annealing, electro-polishing, high-pressure-rinsing and baking, several vertical tests have been performed. As for cavity diagnostics, a rotating X-ray and temperature mapping system was constructed. The cavity performance was limited to less than 20 MV/m by the field emissions. The X-ray distributions caused by field emission were clearly observed by X-ray mapping system. In this report, we summarize the recent results of the vertical tests.
Sokendai, Ibaraki
KEK, Ibaraki
Buffered chemical polishing (BCP) has been widely used as a final recipe of the surface treatment for niobium cavities and there is still much room to improve this technology since it is environment friendly, cheaper and simpler than electro-polishing. To examine BCPed surface in detail, we carried out BCP experiment followed by various rinsing methods on a series of niobium samples at KEK. As a result of the BCP process some contaminants like fluorine, carbon, etc. have been detected at the surfaces which may be the prominent cause of limiting the performance of SRF cavities. To remove these contaminants, various rinsing processes such as ultra pure water rinse, ultrasonic pure water rinse, alcoholic rinse, detergent rinse, high pressure water rinse (HPR) had been tested after the BCP. The preliminary results show that, only HPR had potential to mitigate these contaminants. In this article, we describe the surface analysis results using X-ray photo electron spectroscopy etc and a comparative study of niobium BCPed samples followed by above mentioned rinsing processes.
Kyoto ICR, Uji, Kyoto
KEK, Ibaraki
The vertical test is a performance trial done by cooling the superconducting cavity, and injecting the high-frequency electricity. The temperature mapping (T-map) system is developed for the vertical test. T-map system can find heat sources that may be caused by defects on inner surfaces of superconducting cavities. The purpose of our studies on T-map is to realize a high spacial resolution and easy installation of the sensors. CMOS analog multiplexers in the cryogenic temperature can manage about thousand sensors per 9 cells to send their signals with fewer lines. Inspection efficiencies to raise the production yield of the cavities would be improved by using such a high resolution T-map system. The preliminary test of the cryogenic temperature by the T-map system is reported.
PKU/IHIP, Beijing
Peking University is striving for constructing a superconducting radio-frequency accelerator test facility (PKU-SETF) to provide coherent radiations [1]. A cryomodule consisting of a China made 9-cell TESLA type cavity was designed and constructed for this purpose, which is expected to provide 15-20 MeV energy gain at an operating temperature of 2K. Some technical issues in the manufacturing progress are reported, including the tungsten inert gas (TIG) welding of the LHe vessel and the superconducting cavity, the demagnetization of the vacuum vessel made of pure iron, and the manufacturing of the main power coupler.
PKU/IHIP, Beijing
Peking University, School of Physics, Beijing
Spoke cavities have been developed and have apparent advantages for high current proton accelerator based on superconductivity at low and medium energy region. As the research and the technical reserve, Peking University has started the R&D program of single spoke cavity (SSC). The work is proposed to do beam load experiment on the HI-13 Tandem at CIAE. The maximum kinetic energy of proton beam is 26MeV, and the frequency of the chopper for superconducting is 150MHz. It leads us to the choice of a 450MHz and β=0.2 single spoke cavity. In this paper, the RF design, mechanical study, fabrication arts, tolerance analysis, and room temperature RF test is presented.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
CLASSE, Ithaca, New York
STFC/DL, Daresbury, Warrington, Cheshire
The Daresbury international Cryomodule Collaboration requires a suitable RF coupler that will fit into the footprint of the ALICE cryomodule, with the ability of transfering potentially up to 30 kW CW of RF power into the cavity whilst maximising the capability for adjusting the coupling. For this a modified Cornell Injector coupler has been used. Modifications to the cold section was carried out. These couplers have now been assembled into a test cavity and conditioned to 30 kW pulsed, 10 kW CW. This paper describes the modifications required to fit inside the cryomodule and details of the tests that were carried out.
Muons, Inc, Batavia
JLAB, Newport News, Virginia
A superconducting RF (SRF) power coupler capable of handling 500 kW CW RF power is required for present and future storage rings and linacs. There are over 35 coupler designs for SRF cavities ranging in frequency from 325 to 1500 MHz. Coupler windows vary from cylinders to cones to disks, and RF power couplers are limited by the ability of ceramic windows to withstand the stresses due to heating and mechanical flexure. We propose a novel robust co-axial SRF coupler design which uses compressed window technology. This technology will allow the use of highly thermally conductive materials for cryogenic windows. Using compressed window techniques on disk co-axial windows will make significant improvements in the power handling of SRF couplers. We present the bench test results of two window assemblies back to back, as well as individual window VSWR in EIA3.125 coax. A vacuum test assembly was made and the windows baked out at 155C. The processes used to build windows is scalable to larger diameter coax and to higher power levels.
Danfysik A/S, Jyllinge
Danfysik A/S has built a cryogenic in-vacuum undulator for Diamond Light Source, with a period length of 17.7 mm and an effective K of 1.7 at cryogenic temperatures. The undulator is hybrid-type, with Vanadium Permendur poles and NdFeB poles. In order to verify the performance of the device under cryogenic conditions, an in-vacuum measuring system is required. We present the magnetic measurements at room temperature and under cryogenic in-vacuum conditions. The magnet assembly cannot be baked, due to a choice of high-remanence, low coercivity magnet grade. We discuss the vacuum performance of the undulator.
SOLEIL, Gif-sur-Yvette
The production of hard X rays at SOLEIL, a 2.75 GeV, requires short period and small gap in-vacuum undulators. For shifting further the radiation toward higher energies, the peak magnetic field of the undulators can be further increased by cooling the permanent magnets at cryogenic temperature below 100 K. A R&D programme for the construction of a 2 m long 18 mm period CPMU is launched: the use of PrFeB enables to increase the peak magnetic field at a cryogenic temperature of 77 K. Praseodymium was chosen instead of Neodymium type magnets, because it prevents the appearance of the Spin Reorientation Transition. The magnetic characterisation of different permanent magnet grades at cryogenic temperatures (NdFeB and PrFeB), and the magnetic and thermal measurements on a small 4 period NdFeB cryogenic undulator are presented. The status on the progress of the CPMU conception is given. The magnetic and mechanical design, including the cooling of the girders at 77K, and the thermal budget are described. The designs of the dedicated magnetic measurement benches, which will be required to check the magnetic performance of the undulator at low temperature, are also reported.
SOLEIL, Gif-sur-Yvette
The production of high fluxes in the hard X-rays region is a major issue on medium energy storage rings. It requires the installation of Insertion Devices with high magnetic field and a large number of periods. The construction of a superconducting wiggler has been first envisaged but reveals to be maintenance constraining, much more complex and expensive than the permanent magnet technology. A small gap in vacuum wiggler composed of 38 periods of 50 mm has been preferred. The compact magnetic system allows to produce in a limited space a magnetic field of 2.1 T in a small gap of 5.5 mm, whereas an auxiliary counterforce system based on non-magnetic springs compensate the magnetic forces (up to 8.5 Tons) acting between magnet arrays. The gap between jaws and the mechanical deformations have been controlled and corrected. Magic fingers corrections have been also performed to reduce the integrated multipoles and to minimize the 2nd order integrals resulting from the tight width of the wiggler poles. This paper presents the design of the wiggler, the construction, and the results of the measurements after magnetic corrections.
ESRF, Grenoble
An important upgrade of the ESRF is planned from 2009 to 2016. It is mainly driven by the improvement of beamlines performances and capacity. On the storage ring side, the length of the straight sections will be increased from 5 m to 6 m with a possible further extension to 7 m. These long sections will provide a higher photon flux, and it will allow the installation of canted undulators. The length of the insertion devices (ID), such as revolver undulators and in-vacuum undulators, will be modified to fit the first upgraded beamline sections. The resulting implication on the length of new IDs will be presented. The concept of canted undulators is a proposed optional feature. It will rely on novel permanent magnet chicane providing a maximal separation angle of 5.4 mrad while keeping short distance between canted undulators. Magnetic chicane magnets with low fringe field and homogeneous longitudinal field integral have been designed. The developed magnets will be presented.
Uni HH, Hamburg
DESY, Hamburg
ANL, Argonne
A seeded free-electron laser (FEL) experiment at VUV wavelengths, called sFLASH, is being prepared at the existing SASE FEL user facility FLASH. Seed pulses at wavelengths around 35 nm from high harmonic generation (HHG) will interact with the electron beam in sFLASH undulators upstream of the existing SASE undulator section. In this paper the tuning results and performance of the sFLASH undulators are presented.
Karlsruhe Institute of Technology (KIT), Karlsruhe
BNG, Würzburg
A 1.5 m long superconducting undulator with a period length of 15 mm is planned to be installed in ANKA middle 2010 to be the light source of the new beamline NANO for high resolution X-ray diffraction. The key specifications of the system are an undulator parameter K higher than 2 (for a magnetic gap of 5mm) and a phase error smaller than 3.5 degrees. In order to characterize the magnetic field properties of the superconducting coils local field measurements have been performed by moving a set of Hall probes on a sledge in a liquid helium bath: the results are reported.
Karlsruhe Institute of Technology (KIT), Karlsruhe
CERN, Geneva
BNG, Würzburg
STFC/RAL, Chilton, Didcot, Oxon
INFN/LNF, Frascati (Roma)
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
Diamond, Oxfordshire
UMAN, Manchester
Rome University La Sapienza, Roma
MAX-lab, Lund
Max-Planck Institute for Metal Research, Stuttgart
One of the still open issues for the development of superconducting insertion devices is the understanding of the beam heat load. With the aim of measuring the beam heat load to a cold bore and the hope to gain a deeper understanding in the beam heat load mechanisms, a cold vacuum chamber for diagnostics is under construction. The following diagnostics will be implemented: i) retarding field analyzers to measure the electron flux, ii) temperature sensors to measure the total heat load, iii) pressure gauges, iv) and mass spectrometers to measure the gas content. The inner vacuum chamber will be removable in order to test different geometries and materials. This will allow the installation of the cryostat in different synchrotron light sources. COLDDIAG will be built to fit in a short straight section at ANKA. A first installation at the synchrotron light source DIAMOND is under discussion. Here we describe the technical design report of this device and the planned measurements with beam.
Karlsruhe Institute of Technology (KIT), Karlsruhe
Precise measurements of the magnetic properties of conventional, i.e., permanent magnet based insertion devices has undergone tremendous improvements over the past 10 to 15 years and initiated a new era in synchrotron light sources worldwide. A similar breakthrough is now necessary in the field of superconducting insertion devices. In this contribution we describe the planned instrumentation to perform magnetic measurements of the local field, the field integrals and the multipole components of superconducting undulator coils in a cold invacuum (cryogen free) environment.
ELETTRA, Basovizza
RIAL VACUUM S.p.A, Parma
The FERMI@Elettra project at the ELETTRA Laboratory of Sincrotrone Trieste (ST), currently under construction, will be comprised of a linear accelerator and two Free-Electron-Laser beamlines (FEL1, FEL2). In order to deliver high-intensity VUV and soft X-ray pulses, permanent magnet undulators with 9 mm minimum variable gap will be used. The adopted vacuum chambers will have a 7 by 25 mm2 elliptical internal cross-section. While manufacturing the vacuum chamber in aluminum helps reducing the resistive wall wakefield effects, the chamber inner wall surface quality is strongly correlated to the surface roughness wakefield component. We report on the results of the study to improve the wall surface finish and lower the roughness periodicity. The chamber manufacturing status and its alignment mechanism is also presented.
RIKEN/SPring-8, Hyogo
PSI, Villigen
JASRI/SPring-8, Hyogo-ken
The cryogenic permanent magnet undulator (CPMU) is an insertion device in which permanent magnets are cooled down to cryogenic temperature (CT) to improve the magnetic performances. Although CPMUs are realized by a slight modification of in-vacuum undulators (IVUs), we have several technical challenges to be overcome. Among them, the most important one is how to ensure the magnetic performance, in other words, how to measure the magnetic field at CT, and how to correct it if necessary. A new method of the phase-error correction has been proposed at SPring-8, in which the gap variation is corrected by adjusting mechanically the in-vacuum beam. What is important in this method is that the correction can be done at CT without breaking the vacuum, i.e., an 'in-situ' field correction is possible. The correction method has been tested to check the feasibility using the new CPMU with a magnetic period of 14 mm and a magnetic length of 1.7 m constructed for Swiss Light Source. In this paper, the principle and results are described together with the details of the new measurement system SAFALI (self aligned field analyzer with laser instrumentation) for the field measurement of CPMUs.
SINAP, Shanghai
The undulator controller based on Siemens S7-300 PLC is mainly consisted of controlling motion of two stepper motor, monitoring real-time gap position of upstream and downstream through position feedback derived from four linear absolute encoders (LAEs) with 0.1μm resolution, monitoring cooling water's temperature and flux (CWTF), monitoring magnet array temperature (MAT), providing remote access for EPICS via Ethernet, as well as MPS and PPS interlock interface to and from upper-level protection system. In addition, the controller is equipped with considerate motion safety protection tactics. As for the gap position protection, besides mechanical hard stop, software limit, photo-interrupter limit and kill switch are available to achieve it. As for the taper protection, software limit is available to achieve it.
MAX-lab, Lund
The MAX IV light source, presently under construction at MAX-lab in Lund, Sweden, will consist of two separate storage rings and a linac-driven short-pulse facility. The two storage rings are operated at different energies, 3 GeV and 1.5 GeV, to provide synchrotron radiation of high brightness over a broad spectral range. The 3 GeV linac serves as a full-energy injector for the storage rings as well as the driver of the short-pulse facility delivering intense x-ray pulses. The paper describes a selection of possible insertion devices to be installed at the MAX IV 3 GeV ring and the expected heat loads produced by the insertion devices.
Diamond, Oxfordshire
Diamond Light Source is currently operating with two multipole superconducting wigglers, one with 49 poles at 3.5 T and another with 49 poles at 4.2 T. The cryogenic arrangement is similar in both cases; each cryostat contains a liquid helium bath cooled by four cryocoolers. The design goal was to allow up to six months continuous operation in the storage ring between refilling the liquid helium bath. However, the helium boil-off is much higher than expected, necessitating much more frequent refills. As well as having a cost implication, this also currently poses a restriction on the operating beam current. In this report we present the results of measurements carried out under various beam conditions to try to understand the reason for the higher boil-off in terms of heat load seen by the cryostat and effective cryocooler performance. We also present our plans for dealing with the problem in the near and longer term.
BNL, Upton, Long Island, New York
Various magnet sorting strategies have been used to minimize trajectory and phase errors in undulators, ranging from intuitive pairing of stronger and weaker magnets, to full 3D FEM simulation with actual Helmholtz coil magnet data. We present a simpler approach, first deriving trajectory displacement, kick angle and phase error signatures of each component of magnetization error from a 3D Radia* undulator model. Then, for a given sequence of magnets, the trajectory and phase profiles are computed by cumulatively summing the scaled displacements and phase errors. The rms error is then minimized by swapping magnets according to one's favorite optimization method. A fast, simple magnet swapping algorithm, implemented in Mathematica, is described. 100,000 iterations take only minutes, so dozens of solutions can be compared. This approach was applied recently at NSLS to a short in-vacuum undulator, which required no trajectory or phase shimming. We also obtain trajectory and phase error signatures of some mechanical errors, to guide "virtual shimming" and specifying mechanical tolerances. Finally, multipole signatures of some simple inhomogeneities are modeled.
* O. Chubar, P. Elleaume, J. Chavanne, "A 3D Magnetostatics Computer Code for Insertion Devices", SRI97 Conference August 1997, J. Synchrotron Rad. (1998). 5, 481-484
NIRS, Chiba-shi
The development of the screen monitor system (SCN) at the Heavy Ion Medical Accelerator in Chiba (HIMAC) comprises the surveillance of the carbon beam. In the three-dimensional scanning system for the carbon therapy, the beam qualities, i.e., position, size and intensity of the beam, play a significant role for the patient's treatment. Therefore, we designed a semi-nondestructive monitoring system located on the the high-energy beam transport line to monitor the beam qualities by using a thin fluorescent screen and a high-speed charge-coupled device. The beam position and profile were obtained from the light emitting distribution of the screen. The SCN was checked on the prototype scanning system at HIMAC and succeeded to monitor the beam real-time in steps of about 10 msec, corresponding to a 100 Hz sampling rate. The developments steps will focus toward a operation at HIMAC's new therapy facility extension, recently. In the conference, we would like to report on details of the automatic beam tuning before starting the treatment and the interlock system during therapy using the SCN.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
J-PARC, KEK & JAEA, Ibaraki-ken
KEK, Ibaraki
At the J-PARC 3-GeV injection, the injection painting area is designed to be different for supplying the MLF (Material Life Science Facility) and MR (50GeV Main Ring) beams. Along with the injection system in the ring, pulsed switching magnets which are installed in the injection beam-line should also have a function to control the beam orbit at 25Hz. The deflection angle ranges from 3 to 38 mrad to meet the user operation as well as the beam physics run.
CIEMAT, Madrid
CERN, Geneva
The goal of the present CLIC Test Facility (CTF3) is to demonstrate the technical feasibility of specific key issues of the CLIC scheme. The extracted drive beam from the combiner ring (CR), a pulse of 35 A magnitude and 140 ns duration, is sent to the new CLic EXperimental area (CLEX). A Tail Clipper (TC) kicker is required, in the CR to CLEX transfer line, to allow the duration of the beam pulse to be adjusted: the unwanted bunches are kicked into a collimator. The TC must have a fast field rise-time, of not more than 5 ns, in order to minimize uncontrolled beam loss. Striplines are used for the TC: to establish the required fields, the applied pulse wave front must fully propagate along the striplines. To reduce the wave front propagation time, the overall length of the stripline assembly is sub-divided into 4 sections. The TC has been designed with the aid of detailed numerical modelling: the stripline cross-section and coaxial-to-stripline transitions were carefully optimized using a 3D code. The results of simulations and the measured behaviour of the striplines are presented; in addition measured current pulses are shown.
CERN, Geneva
A five-turn continuous extraction is currently used to transfer the proton beam from the CERN PS to the SPS. This extraction uses an electrostatic septum to cut the filament beam into five slices, causing losses of about 15 %. These losses would be an even greater drawback when the beam intensity is further increased for the CERN Neutrinos to Gran Sasso facility. To overcome this, a Multi-Turn Extraction (MTE) has been implemented, in which the beam is separated, prior to extraction, into a central beam core and four islands. Each beamlet is extracted using a set of kickers and a magnetic septum. For the kickers two new pulse generators have been built, each containing a lumped element Pulse Forming Network (PFN) of 12.5 Ohms, 80 kV and 10.5 μs. For cost reasons existing 15 Ω transmission line kicker magnets are reused. The PFN characteristic impedance deliberately mismatches that of the magnets to allow a higher maximum kick. The PFN design has been optimised such that undesirable side-effects of the impedance mismatch on kick rise-time and flat-top remain within acceptable limits. The kicker systems put in place for the current first phase of MTE are presented.
LLNL, Livermore, California
Vacuum insulators composed of alternating layers of metal and dielectric, known as high-gradient insulators (HGIs), have been shown to withstand higher electric fields than conventional insulators. Generally, vacuum insulator failure is due to surface flashover, initiated by electrons emitted from the triple junction. These electrons strike the insulator surface and produce secondary electrons, which also strike the insulator surface to create more secondary electrons and lead to avalanche. Magnetic field from the external sources, the high-current electron beam, the conduction current in the transmission line or the displacement current in the insulator can deflect primary and secondary electrons' trajectories either toward to or away from the insulator surface, and hence affect the performance of the high-voltage vacuum insulator. The displacement current effects are particularly interesting for short pulse applications. This paper presents the displacement current effects with various short applied voltage pulses on performance of high-gradient insulators. Optimal HGI configurations will also be discussed.
KEK, Ibaraki
Fermilab, Batavia
INFN/LASA, Segrate (MI)
DESY, Hamburg
In an attempt at demonstrating an average field gradient of 31.5 MV/m as per the design accelerating gradient for ILC, a program called S1-Global is in progress as an international research collaboration among KEK, INFN, FNAL, DESY and SLAC. The S1-Global cryomodule will contain eight superconducting cavities from FNAL, DESY and KEK. The cryomodule will be constructed by joining two half-size cryomodules, each 6 m in length. The module containing four cavities from FNAL and DESY has been constructed by INFN. The module for four KEK cavities is being modified at present. The assembly of the cryomodules is scheduled from January 2010, and the operation of the system is scheduled from June 2010 at the KEK-STF. In this paper, the construction of the S1-Global cryomodule will be presented.
KEK, Ibaraki
Dr. Matsumoto in KEK and his colleague have developed the MO flange for vacuum sealing of normal conducting high peak power RF wave-guide. This is impedance free sealing. We have applied this sealing to SRF cavity technology instead of indium sealing. We used pure aluminum gasket for the sealing material. We had a difficulty on the titanium flange but succeeded to establish leak tightness in super-fluid Helium by stainless flange. In this paper, we will report the R&D results.
Kyoto ICR, Uji, Kyoto
KEK, Ibaraki
A prototype of a permanent magnet quadrupole lens for ILC final focus doublet is fabricated. In order to demonstrate the feasibility, it will be tested in a real beam line. Such practical experiences include its shipping, storage, handling, installation, alignment technique, and so on. Because permanent magnets cannot be switched off in contradistinction to electromagnets, they should be evacuated from beam lines when no interference is desired and the process should be quick with enough reproducibility. The magnetic center and strength stability including reproducibility are also important issues during the beam test. In order to reduce interferences with current ongoing testing items at ATF2, the magnet will be installed at a further upstream position of the ATF2 beam line. The installation and test plan will be described.
CERN, Geneva
UMAN, Manchester
Uppsala University, Uppsala
The 1.5TeV CLIC beams, with a total power of 14MW per beam, are disrupted at the interaction point due to the very strong beam-beam effect. As a result, some 3.5MW reach the main dump in form of beamstrahlung photons. About 0.5MW of e+e- pairs with a very broad energy spectrum need to be disposed along the post-collision line. The conceptual design of this beam line will be presented. Emphasis will be on the optimization studies of the CLIC post-collision line design with respect to the energy deposition in windows, dumps and scrapers, on the design of the luminosity monitoring for a fast feedback to the beam steering and on the background conditions for the luminosity monitoring equipment.
CERN, Geneva
Fermilab, Batavia
High-energy accelerators are large projects funded by public money, developed over the years and constructed via major industrial contracts both in advanced technology and in more conventional domains such as civil engineering and infrastructure, for which they often constitute one-off markets. Assessing their cost, as well as the risk and uncertainty associated with this assessment is therefore an essential part of project preparation and a justified requirement by the funding agencies. Stemming from the experience with large circular colliders at CERN, LEP and LHC, as well as with the Main Injector, the Tevatron Collider Experiments and Accelerator Upgrades, and the NOvA Experiment at Fermilab, we discuss sources of cost variance and derive cost risk assessment methods applicable to the future linear collider, through its two technical approaches for ILC and CLIC. We also address disparities in cost risk assessment imposed by regional differences in regulations, procedures and practices.
CERN, Geneva
The maximum tolerable pressure value in the chamber of the CLIC electron Main Linac is determined by the threshold above which the fast ion instability sets in over a bunch train. Instability calculations must take into account that, since the accelerated beam becomes transversely very small, its macroscopic electric field can reach values above the field ionization threshold. In this paper we first discuss threshold values of the electric field for field ionization and the extent of the transverse region that gets fully ionized along the ML. Then, we show the results of the instability simulations from the FASTION code using the new model, and consequently review the pressure requirement in the ML.
Muons, Inc, Batavia
Fermilab, Batavia
Intense muon beams have many potential applications, including neutrino factories and muon colliders. However, muons are produced as tertiary beams, resulting in diffuse phase space distributions. To make useful beams, the muons must be rapidly cooled before they decay. An idea conceived recently for the collection and cooling of muon beams, namely, the use of a Quasi-Isochronous Helical Channel (QIHC) to facilitate capture of muons into RF buckets, has been developed further. The resulting distribution could be cooled quickly and coalesced into a single bunch to optimize the luminosity of a muon collider. After a brief elaboration of the QIHC concept, some recent developments are described.
LBNL, Berkeley, California
BNL, Upton, Long Island, New York
A Neutrino Factory requires an intense and highly cooled (in transverse phase space) muon beam. We discuss a hybrid approach for a linear 4D cooling channel consisting of high-pressure gas-filled RF cavities –potentially allowing high gradients without breakdowns– and discrete LiH absorbers to provide the necessary energy loss that results in the needed muon beam cooling. We report simulations of the channel performance and its comparison with the vacuum case; we also discuss the various technical and safety issues associated with cavities filled with high-pressure hydrogen gas. Even with additional windows that might be needed for safety reasons, the channel performance is comparable to that of the original, all-vacuum Feasibility Study 2a channel on which our design is based. If tests demonstrate that the gas-filled RF cavities can operate properly with an intense beam of ionizing particles passing through them, our approach would be an attractive way of avoiding possible breakdown problems with a vacuum RF channel.
CERN, Geneva
BINP SB RAS, Novosibirsk
The CLIC damping rings should produce the ultra-low emittance necessary for the high luminosity performance of the collider. This combined to the high bunch charge present a number of beam dynamics and technical challenges for the rings. Lattice studies have been focused on low emittance cells with optics that reduce the effect Intra-beam scattering. The final beam emittance is reached with the help of super-conducting damping wigglers. Results from recent simulations and prototype measurements are presented, including a detailed absorption scheme design. Collective effects such as electron cloud and fast ion instability can severely limit the performance and mitigation techniques have been identified and tested. Tolerances for alignment and technical system design such as kickers, RF cavities, magnets and vacuum have been finally established.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
STFC/DL, Daresbury, Warrington, Cheshire
The University of Liverpool, Liverpool
Cockcroft Institute, Warrington, Cheshire
BINP SB RAS, Novosibirsk
A vacuum vessel design of wiggler sections should meet a few challenging specification. The SR power of about 40 kW is generated in each wiggler. Expanding fan of SR radiation reaches the beam vacuum chamber walls in the following wiggler and may cause the following problem: massive power dissipation on vacuum chamber walls inside the cryogenic vessel, radiation damage of superconducting coil, high photo-electron production rate that cause an e-cloud build-up to unacceptable level. Therefore this power should be absorbed in the places where these effects are tolerable or manageable. A few possible solutions for tackling all SR related problems as well as vacuum design are discussed in the paper in details.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
Ion induced pressure instability is a potential problem for the ILC positron damping ring (DR)if the chosen pumping scheme does not provide sufficient pumping. The ion induced pressure instability effect results from ionisation of residual gas molecules by the beam particles, their acceleration in the field of the beam towards the vacuum chamber walls, causing ion induced gas desorption from vacuum chamber walls; these gas molecules in their turn can also be ionised, accelerated and cause further gas desorption. If the pumping is insufficient, this effect may cause a pressure instability, in which the pressure in the beam chamber grows rapidly to an unacceptable level. To analyse the ion induced pressure instability in the ILC positron DR the energy gained by ions was calculated for the appropriate beam parameters; it was found that the energy gain of ions will be about 300 eV. The ion induced gas desorption was estimated, and pumping solutions to avoid the ion induced pressure instability are suggested. The cheapest and most efficient solution is to use NEG coated vacuum chamber.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
STFC/DL, Daresbury, Warrington, Cheshire
The University of Liverpool, Liverpool
Cockcroft Institute, Warrington, Cheshire
BINP SB RAS, Novosibirsk
A 374-m long wiggler section is a key part of ILC damping ring that should alloy reaching a low beam emittance for the ILC experiment. Synchrotron radiation generated by the beam in the wigglers should be absorbed by different components of vacuum vessel, including specially designed absorbers. The optimisation of the mechanical design, vacuum system and anti-e-cloud mitigation requires accurate calculation of the SR power distribution. The angular power distribution from a single wiggler was calculated with in-house developed software. Then the superposition of SR from all wigglers allows calculating power distribution for all components along the wiggler section and the downstream straight section.
Cockcroft Institute, Warrington, Cheshire
STFC/DL, Daresbury, Warrington, Cheshire
The University of Liverpool, Liverpool
The longitudinal wake fields have been calculated by using 3D code, CST Particle Studio, for a number of different vacuum chamber components of the 6.4 km ILC damping ring design. Based on the results, studies of bunch lengthening and single-bunch instabilities have been carried out. Bunch lengthening from a particle tracking code are compared with results from numerical solution of the Haissinski equation. The tracking code is used to predict the threshold for single-bunch instabilities.
IHEP Beijing, Beijing
IHEP Beiing, Beijing
1.3 GHz superconducting radio-frequency (SRF) technology is one of the key technologies for the ILC and future XFEL / ERL projects of China. With the aim to develop this technology, IHEP has started a program to build an SRF Accelerating Unit in the frame of ILC collaboration. The SRF Accelerating Unit contains a 9-cell 1.3 GHz superconducting cavity, a short cryomodule, a high power input coupler, a tuner, a low level RF system and a high power RF source, etc. The unit can undergo beam test and used as the booster for any SRF linac based test facility. Recent progress of the components R&D is presented.
DAE/VECC, Calcutta
K500 Superconducting Cyclotron (SCC) is already commissioned successfully at VECC, Kolkata by accelerating Ne3+ internal beam with 70 nA beam current at 670 mm extraction radius. The Radio Frequency cavity of SCC is successfully operational since last two years. All these years were very challenging and worthy period from the point of view of gaining experience and knowledge by solving fabrication and assembly problems faced during construction of 10 m tall copper made coaxial RF cavities and tackling RF related commissioning problems. RF system operates within the frequency range of 9 to 27 MHz for generating maximum 100 kV DEE voltage. The construction of the RF system demands making of numerous critical soldering and brazing joints including joints between ceramic and copper along with maintaining close dimensional accuracies, assembly tolerances, mirror symmetricity, surface finish and utmost cleanliness. This paper presents the details of fabrication and installation procedures and their effects on the final performance of the cavities. It also highlights the problems faced during the commissioning process of the RF cavities.
RRCAT, Indore (M.P.)
BARC, Mumbai
Tuning of a photocathode gun for desired RF properties of the pi mode, such as FB ~1, fpi = 2856 MHz, and beta ~1, requires precise tuning of the resonant frequency and beta of its independent cells. In this paper, we present a parametric and analytical formulation to predict geometrical dimensions of independent cells and the coupling slot on the full cell to obtain the desired pi mode RF parameters during operation, taking into account the effect of brazing and vacuum. We also compare results obtained from low power RF measurements on a photocathode gun with those predicted by the above formulation.
KEK, Ibaraki
Under the CERN-SLAC-KEK collaboration, we have been developing the high gradient TW accelerator structures. One of the main focuses is the feasibility study of CLIC accelerator structure at X-band. A high power facility, Nextef*, was established at KEK in 2007. A few structures have been tested, including an un-damped disk-loaded structure successfully tested beyond 100 MV/m, a heavily damped structure to be tested from late 2009 and a structure made in a quadrant configuration. These structures follow the same accelerating-mode RF parameter profile, called CLIC-C**, but show different features at high gradient operation. Various observables, such as dark current, vacuum activities, light emission, breakdown rate, and so on, are measured. We discuss the high gradient phenomena related to these observables and the possible improvement for stable operation at a higher gradient.
* T. Higo et al., THP038, LINAC06,2006.
**A. Grudiev, http://indico.cern.ch/conferenceDisplay.py?confId=30911
KEK, Ibaraki
A waveguide vacuum valve for WR90 waveguide was designed, fabricated and tested. The valve consists of a modified commercial gate valve sandwitched with smooth tapers. The TE10 traveling wave in WR90 waveguide is "transmoded" into TE11+TM11 mode in the taper, going through the gate valve and is tapered back to the normal mode in WR90. The test has been successfully done. The valve stably trasmitted 40MW peak power with 500ns pulse width and this is limited by available RF power source.
KEK, Ibaraki
In order to improve the capture efficiency of the positron produced at the target in present KEKB Injector linac, a new project has just started to utilize L-band (1298MHz) RF. The present S-band (2856MHz) capture cavities and successive three RF units are to be replaced by those of L-band. The specifications of the L-Band system should fulfill the demands of a positron damping ring downstream which is also to be under study for super KEKB project. Besides the whole design work of the system, our present ongoing work is rather concentrated on establishing L-Band RF source and accelerating structures.
KEK, Ibaraki
BNL, Upton, Long Island, New York
An RF system using Magnetic Alloy is considered as an option to study the beam dynamics of a linear non-scaling FFAG. Such an FFAG may have many resonances, which affect the beam more when the beam crosses them slowly. The RF system aims at ordinary RF bucket acceleration with an RF frequency sweep of 3 % in 100 turns. The cavity has only 10 cm length to fit in a short straight section. The required RF voltage is 100 kV per turn and each of the three cavities is designed to generate 50 kV.
Toshiba, Yokohama
JASRI/SPring-8, Hyogo-ken
TOSHIBA is manufacturing the L-band acceleration system for the SPring-8 Joint Project for XFEL. We have developed a new type duct-shaped SiC dummy load for its power distribution system. The load terminates a WR650 waveguide and can absorb the maximum mean power of 10kW. In order to reduce VSWR less than 1.1 in the frequency range of 1.428GHz, we shaped the SiC absorber into a 35cm long tapered cylinder and mounted matching stubs in the waveguide near the inlet of the load. The SiC absorber was fit into a cylindrical copper with efficient water-cooling channels. The design and manufacture and the low-power tests of our original dummy load are described in this paper.
USTC/PMPI, Hefei, Anhui
USTC/NSRL, Hefei, Anhui
Collinear load, consisted of several coaxial cavities, is a substitute for traditional waveguide-type load to absorb the remnant power of the LINAC and makes the accelerating structure compact and small-size. The power loss on the cavities of collinear load brings thermal deformation which affects their resonant frequency deeply. In this paper, a new approach of 3D reconstruction of the thermal deformed cavities is utilized to evaluate the accurate influence on frequency change caused by non-uniform deformation and water cooling strategies of collinear absorbing load are studied. Then the thermal behavior of a six-cavity collinear load, which is coated with Kanthal alloy and FeSiAl alloy and used on a 2856MHz, 2π/3 mode respectively, is researched. The results show that the collinear load with Kanthal alloy can only absorb up to 10kW, while with FeSiAl alloy it can dissipate 15kW when the water flow controlled within 3.0kg/s for energy saving.
* Tian Z. etc., "Finite Element Analysis of RF Cavity", Parietti L. etc., "Thermal/Structural Analysis and Frequency Shift", Anthony, etc. "A NURBS-based Technique for Subject-specific Construction".
HUST, Wuhan
The design study of a 10MeV compact cyclotron CYCHU-10 has been developed at Huazhong University of Science and Technology (HUST). We developed the basic shapes and dimensions and carried out the simulations for the CYCHU-10 cavities with 3D numerical calculation softwares in this paper. The distributions of electromagnetic field are illustrated by means of the electromagnetic and structural analysis, and the wooden model test is preformed as well. In addition, this paper gives mechanical tolerance effects which deformed due to the limit of mechanical working of cavities under practical conditions. This work helps to evaluate the performances of capacitive frequency trimmer design.
BINP SB RAS, Novosibirsk
ICKC, Novosibirsk
ICKC SB RAS, Novosibirsk
The prototype of parallel coupled accelerating structure is developed. It consists of five accelerating cavities, common excitation cavity and RF power waveguide feeder. The excitation cavity is a segment of rectangular waveguide loaded by resonance copper pins. The excitation cavity operate mode is T 105. Connection between excitation cavity and accelerating cavities is performed by magnetic field. The theoretical model of the parallel coupled accelerating structure is developed. According to model the tuning and matching of the structure are performed. The electrodynamics characteristics are measured. In storage energy regime the accelerated electron beam is obtained.
CIEMAT, Madrid
CERN, Geneva
The goal of the present CLIC test facility (CTF3) is to demonstrate the technical feasibility of the CLIC scheme. The Test Beam Line (TBL) is used to study a CLIC decelerator focusing on 12 GHz power production and the stability of the decelerated beam. The extracted CTF3 drive beam from the combiner ring (CR) features a maximum intensity of 28 A and 140 ns pulse duration, where the Test Beam Line consists of 16 cells, each one including a BPM, a quadrupole on top of a micrometer-accuracy mover and a RF power extractor so-called PETS (Power Extraction and Transfer Structure). This paper describes the first prototype fabrication techniques, with particular attention to the production of the long copper rods which induce the RF generation. A special test bench for the characterization of the device with low RF power measurements has been developed. Performed mesurements of the scattering parameters and the electric field profile along the structure are carefully described. Finally, the prototype has been installed at CLEX, and first measurements with beam are also reported.
CERN, Geneva
PSI, Villigen
PSI-XFEL and Elettra-Fermi-require a X-band RF structure. As CLIC is pursuing a program for producing and testing x-band high-gradient RF structures, a collaboration between PSI, Elettra and CERN, has been established to build a multipurpose X-band accelerating structure. This paper focuses on its engineering design which is based on disk-shaped cells bonded together by different technologies (diffusion bonding, vacuum brazing and laser beam welding). The accelerating structure consists of 2 coupler subassemblies and 73 disks, and include wake field monitor waveguides. The engineering study also comprises the external cooling system, consisting of two parallel cooling circuits, and the tuning system, allowing for the fine-tuning by means of cell deformations. The engineering solution for installation and sealing of wake field monitor feed-through devices inside the accelerating structure RF-cavity is also proposed.
Fermilab, Batavia
Muons, Inc, Batavia
Alternative RF cavity fabrication techniques for accelerator applications at low frequencies are needed to improve manufacturability, reliability and cost. RF cavities below 800 MHz are large, take a lot of transverse space, increase the cost of installation, are difficult to manufacture, require significant lead times, and are expensive. Novel RF cavities partially loaded with a ceramic for accelerator applications will allow smaller diameter cavities to be designed and built. The manufacturing techniques for partially loaded cavities will be explored. A new 200MHz cavity will be built for the Fermilab Proton Source to improve the longitudinal emittance and energy stability of the linac beam at injection to the Booster. A cavity designed for 400 MHz with a ceramic cylinder will be tested at low power at cryogenic temperatures to test the change in Qo due to the alumina ceramic. Techniques will be explored to determine if it is feasible to change the cavity frequency by replacing an annular ceramic insert without adversely effecting high power cavity performance.
LBNL, Berkeley, California
Normal conducting RF cavities must be used for the cooling section of international Muon Ionization Cooling Experiment (MICE) which is currently under construction at Rutherford Appleton Laboratory (RAL) in UK. Eight 201-MHz cavities are needed for the MICE cooling section; fabrication of the first five cavities is nearly complete. This paper reports the cavity fabrication status that includes the cavity design, fabrication techniques and preliminary low power RF measurements of the first five cavities.
IUCF, Bloomington, Indiana
In this report, we present our design of a fast extraction kicker for ALPHA. Due to the fast rise time and high voltage requirement, we choose the traveling wave kicker. Both 2D Posisson and 3D Microwave Studio simulation are carried out. Uniformity of electric field, energy transmission through the stripline structure and time response of the kicker are studied carefully. A prototype kicker will be built and tested soon.
IIT, Chicago, Illinois
Fermilab, Batavia
ANL, Argonne
Muon cooling requires high-gradient normal conducting cavities operating in multi-Tesla magnetic fields for muon beam focusing in an ionization cooling channel. Recent experience with an 805-MHz pillbox cavity at the Fermilab MuCool Test Area has shown significant drop in accelerating field performance for the case of parallel electric and magnetic fields. It has been suggested that having the magnetic field perpendicular to the electric field should provide magnetic insulation and suppress breakdown. An 805-MHz Cu rectangular box cavity was built for testing with the fields perpendicular. It was mounted on an adjustable support to vary the angle between the rf electric and external magnetic field. We report on design and operation of the rectangular box cavity.
SLAC, Menlo Park, California
KEK, Ibaraki
INFN/LNF, Frascati (Roma)
We report results of ongoing high power tests of single cell standing wave structures. These tests are part of an experimental and theoretical study of rf breakdown in normal conducting structures at 11.4 GHz. The goal of this study is to determine the accelerating gradient capability of normal-conducting rf powered particle accelerators. The test setup consists of reusable mode-launchers and short test structures powered by SLAC's XL-4 klystron. We have tested structures of different geometries, cell joining techniques, and materials, including hard copper alloys and molybdenum. We found that the behavior of the breakdown rate is reproducible for different structures of the same geometry and material. The breakdown rate dependence on peak magnetic fields is stronger than on peak surface electric fields for structures of different geometries.
SLAC, Menlo Park, California
CERN, Geneva
KEK, Ibaraki
A CERN-SLAC-KEK collaboration on high gradient X-band structure research has been established in order to demonstrate the feasibility of the CLIC baseline design for the main linac stably operating at more than 100 MV/m loaded accelerating gradient. Several prototype CLIC structures were successfully fabricated and high power tested. They operated at 105 MV/m with a breakdown rate that meets the CLIC linear collider specifications of < 5·10-7/pulse/m. This paper summarizes the fabrication technologies including the mechanical design, precision machining, chemical cleaning, diffusion bonding as well as vacuum baking and all related assembly technologies. Also, the tolerances control, tuning and RF characterization will be discussed.
SLAC, Menlo Park, California
SLAC participates in the U.S. High Gradient collaboration whose charter includes basic studies of rf breakdown properties in accelerating structures. These studies include experiments with different materials and construction methods for single cell standing wave accelerating structures. The most commonly used method of joining cells of such structures is the high temperature bonding and/or brazing in hydrogen and/or vacuum. These high temperature processes may not be suitable for some of the new materials that are under consideration. We propose to build structures from cells with an rf choke, taking the cell-to-cell junction out of the electromagnetic field region. These cells will be clamped together in a vacuum enclosure, the choke joint ensuring continuity of rf currents. Next, we propose a structure with a choke joint in a high gradient cell and a view port which may allow us microscopic, in-situ observation of the metal surface during high power tests. And third, we describe the design of a TM01 choke flange for these structures.
FZD, Dresden
TU Dresden, Dresden
The superconducting linear accelerator ELBE at the Forschungszentrum Dresden/Rossendorf has two superconducting accelerator modules and a superconducting photo injector (SRF-Gun). They are operated by a cryogenic Helium plant with a cooling power of 200 W at 1.8 K. Since the commissioning of the plant in 1999 minor and major impurity problems have influenced the operation stability of the plant. The presentation will give an overview of the ELBE cryogenic system and will focus on the different sources of plant contamination and their effects on the plant operation which have been found during the nearly 10 years of plant lifetime. Especially the contamination with residues of oil brake up so as air and water from different sources have limited the run periods of the plant and effected special service and maintenance procedures.
IUAC, New Delhi
Superconducting Linac at Delhi was partly established and commissioned with one linac cryomodule to house 8 quarter wave niobium cavities along with buncher and rebuncher cryomodule. Two more linac cryomodules are designed, developed and integrated with beam line and cryo distribution line recently. Design of present modules are modified based on the feedback from earlier modules. Present paper will be highlighting the modified design along with thermal and vacuum performance of the present modules w.r.t earlier module.
NSRRC, Hsinchu
NEXANS Deutschland Industries AG & Co. KG, Moenchengladbach
The National Synchrotron Radiation Research Center is constructing the Taiwan Photon Source (TPS), a 3-GeV synchroton facility. The superconducting radio frequency (SRF) cavity modules are selected as the accelerating cavities in the electron storage ring. A test area for the SRF modules is established in the RF laboratory, which includes cryogenic environment, RF transmitter, low level RF control system, and radiation shielded space. The liquid helium is transferred from the cryogenic plant in the experimental area of the Taiwan Light Source (TLS), which is not only far from the RF laboratory but also characterized by a complicated route of 205 meters. The main concerns on the cryogenic transfer are the installation difficulty, heat loss, two-phase flow, and pressure loss. Instead of a multi-channel transfer line, which would request a long installation period on radiation-restrict area, flexible cryogenic transfer lines from Nexans were chosen. The installation period was dramatically reduced to one week. With a test Dewar in the RF lab and valve boxes on both ends of the transfer lines, a long distance cryogenic transfer system was completed and proved to work functional.
NSRRC, Hsinchu
The TPS is 3 GeV photon source under construction in Taiwan. The electron needs four superconducting RF cavities to maintain the energy. The construction of a new refrigeration/liquefaction helium plant is under way to supply the liquid helium for superconducting RF cavities. This is the third year of the seven years project and part of the design features and parameters is different from the prilimilary design. This paper presents the design of the cryogenic system, which is including the features of the new cryogenic plant, the pressure drop of warm helium pipeline, the distribution valve box and the multichannel line. The design of liquid nitrogen supply line and the phase separator will be also included.
KEK, Ibaraki
OHTSUKA, Tsukuba-shi
The MO (Matsumoto-Ohtsuka) -type flange is suitable for connection flanges of beam pipes for accelerators. The flange uses a metal gasket that exactly fits the aperture of the beam pipe, and has a small beam impedance. The flange can be applied to a complicated aperture. We developed a stainless-steel MO-type flange for a copper beam pipe with antechambers. Several beam pipes were installed in the KEKB B-factory positron ring and were tested using beams. No serious problem was observed up to a beam current of 1600 mA (~10 nC/bunch and ~6 ns bunch spacing). Based on experiences in the stain-less steel case, a possibility of employing copper-alloy and aluminum-alloy MO-type flange has been experimentally studied. They can mitigate the heating problems found in the case of stainless-steel flanges, and simplify the manufacturing procedure of beam pipes made of copper or aluminum alloy. Copper-alloy (CrZrCu) flanges show a comparable vacuum sealing property to the stainless-steel one, and several beam pipes with this flange has been successfully installed in the KEKB. The R&D on aluminum-alloy (A2219 and A2024) flanges has recently started, and a promising result was obtained.
KEK, Ibaraki
In J-PARC 50GeV synchrotron ring, large vacuum pressure rises above 10-3 Pa are found at 30GeV acceleration final stage of intensity over 1013 protons per pulse in the chambers of the in-vacuum electrostatic septum magnet for the slow-extraction(SX), magnetic septum for SX, and the kicker magnet for the fast-extraction. This pressure rise depends on beam intensity and peak-current, and can be reduced by continuous beam operations, such as scrubbing with proton beam, secondary emission electrons and other cations of remaining gasses or desorptions.
CELLS-ALBA Synchrotron, Cerdanyola del Vallès
The mechanical installation of the booster synchrotron of ALBA started in January 2009 and finished by having the system under vacuum in April 2009. The preparation of the booster vacuum system for the installation (partial assembly with the pumps and instrumentation, bakeout, etc) started already in September 2008. For the storage ring, the main mechanical installation was done from May to September 2009. The average pressure in the booster synchrotron is in the range of low 10-9 mbar and in the storage ring is in the low 10-10 mbar. The preparation of the installation, the installation and the present performance will be presented in this contribution. The first round of the booster commissioning took place at the end of 2009 and the beginning of 2010. The first data of the booster vacuum system commissioning are presented as well.
CERN, Geneva
At the start of the CERN Large Hadron Collider (LHC) 2008-2009 shutdown, all the LHC experimental vacuum chambers were vented to neon atmosphere. They were later pumped down shortly before beam circulation. In parallel, 2.3 km of vacuum beam pipes with NEG coatings were vented to air and re-activated to allow the installation or repair of several components such as roman pots, kickers, collimators, rupture disks and masks and re-activated thereafter. Beside these standard operations, "fast exchanges" of vacuum components and endoscopies inside cryogenic beam vacuum chambers were performed. This paper presents a summary of all the activities held during this period and the achieved vacuum performances.
CERN, Geneva
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
Pressure increases are observed with the first beams circulating in the CERN Large Hadron Collider (LHC) close to some collimators. This paper describes the vacuum performances of the collimators as measured in the laboratory and also the performances obtained in the machine. Based on these observations, estimations of some operational behavior such as pressure increase and NEG reactivation scenario are given.
CERN, Geneva
During the sector 3-4 incident, the two apertures of the 3 km long cryogenic vacuum sectors of the CERN Large Hadron Collider (LHC) were brutally vented to helium. A systematic visual inspection of the beam pipe revealed the presence of soot, metallic debris and super insulation debris. After four month of cleaning, the beam vacuum system was recovered. This paper describes the tools and methodologies developed during this period, the achieved performances and discusses possible upgrades.
NSRRC, Hsinchu
Aluminum alloy was chosen for vacuum chamber materials and oil-free manufacturing, ozone water cleaning processes were used to obtain ultrahigh vacuum in TPS vacuum system. The storage ring vacuum system is divided into 24 unit cells and there are 6 ionized gauges, 8 ion pumps and 6 gate valves in one cell. An interlock system is designed to monitor and control the vacuum devices to keep ultrahigh vacuum. Because the vacuum chamber is exposed to the high power synchrotron radiation directly, cooling water and temperature statuses on the vacuum chamber are also monitored. The hardware, software and their associated interlock logic will be described.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
KEK/JAEA, Ibaraki-Ken
KEK, Ibaraki
The hybrid type thick boron-doped carbon (HBC) stripping foils are installed and used for the beam injection at the 3GeV RCS (Rapid Cycling Synchrotron) in J-PARC (Japan Proton Accelerator Research Complex). The HBC foils are developed by Sugai group in KEK, which improved the lifetime drastically. Up to now, the performance deterioration of the stripping foils can not be seen after the long beam irradiation for the 120kW user operation and 300kW high power beam demonstration at the RCS. In order to examine the characteristic of the HBC foils, various beam studies were carried out. The beam-irradiated spot at the foil was measured by scanning the foil setting position, the charge exchange efficiency was evaluated with various thickness foils, and the effect of the SiC fibers supporting the foil mounting was checked with different mounting foils. Beam study results obtained with using the HBC foils will be presented. In addition, the trends of outgas from the stripping foils and the deformations of the foils during the beam irradiation will be reported.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
MHI, Nagoya
KEK, Ibaraki
At the 3GeV RCS (Rapid Cycling Synchrotron) in J-PARC (Japan Proton Accelerator Research Complex), the scheme of H- charge exchange injection using stripping foils is adopted. The charge exchange system is composed of three stripping foil devices. The first stripping foil device, which converts the H- beam from the 181MeV LINAC into the H+ beam, can replace the broken foil with new one in vacuum remotely and automatically. In September 2007, mechanical trouble with the first stripping foil device had occurred just before the RCS beam commissioning was started. The magnetic coupling of the transfer rod had been decoupled and the transfer rod had been broken which was caught in the vacuum gate valve. We studied the trouble cause, re-examined the structural design and the selection for the material, and then verified the specification from endurance tests with sample pieces. Then the improved device was installed in the ring in September 2008. In this presentation, we report the mechanical trouble and that countermeasure, including the improvements of the charge exchange system.
CERN, Geneva
The High Radiation to Materials facility - thereafter HiRadMat - is designed to allow testing of accelerator components, in particular those of the LHC and its injectors, with the impact of high-intensity pulsed beams. The facility is currently under construction, as an approved CERN project. The installation of the dedicated primary beam line and experimental area is planned during the 2010-2011 CERN accelerator technical shutdown. It will be ready for users after commissioning and some initial running in October 2011. A detailed proton beam line design has been performed in order to fulfill the beam parameter specification, in particular the demanding optics flexibility at the test stand location. The studies presented include trajectory correction and aperture studies as well as specifications of magnetic systems, power converters, beam instrumentation and vacuum systems.
ORNL, Oak Ridge, Tennessee
ORNL RAD, Oak Ridge, Tennessee
LANL, Los Alamos, New Mexico
BNL, Upton, Long Island, New York
The diamond stripper foils in use at the Spallation Neutron Source worked successfully with no failures until May 3, 2009, when we started experiencing a rash of foil failures after increasing the beam power to ~840 kW. The main contributions to foil failure are thought to be 1) convoy electrons, stripped from the incoming H− beam, that strike the foil bracket and may also reflect back from the electron catcher, and 2) vacuum breakdown from the charge developed on the foil by secondary electron emission. In this paper we will detail these and other failure mechanisms, and describe the improvements we have made to mitigate them.
LNLS, Campinas
Diffusion bonding is a welding process where the main mechanism responsible for the union of the materials is the interdiffusion of atoms across the joint surface, even in solid state. The objective of the present work is to produce bonded joints that could be used in vacuum components for particle accelerator. Is this work was produced a welding joint between two dissimilar materials: oxygen free copper and AISI 316 L stainless steel. Each sample was bonded in vacuum (10-5mbar) at a temperature range between 800 and 900°C, pressure of 12MPa and holding times between 30 and 60min. Optical microscopy, scanning electron microscopy, mechanical testing and helium leak test were used to study the bond quality. The images obtained by optical and electron microscopy revealed good quality interfaces without the presence of defects and pores. All samples are tested through the helium leak test and were approved. The results indicate great potential to use this process in the manufacturing of components suitable for ultra high vacuum, for application in the design of new LNLS storage ring.
KEK, Ibaraki
Mitsubishi Electric Corp., Communication Systems Center, Amagasaki City, Hyogo
The L-band inductive output tube (IOT) without trolly was developed to operate under higher applied voltage. The operation frequency of conventional IOTs is tuned using its trolly. This mechanism is based on the lower frequency IOT. However it causes less insulation voltage of the ceramics since the electric insulation oil is not available for its trolly and the length of the insulation ceramics is limited because it is a part of the resonant cavity. In case of IOTs, it is important to increase the applied voltage for higher output power since the grid gap is very narrow and its area cannot be increased to keep the gain. Thus we developed an IOT which has a longer insulating ceramic and the input cavity is filled with vacuum to use the electric insulation oil. Further the dielectric waveguide can solve to feed the input microwave to the cathode grid without trolly. These new features of the IOT is very effective for the fixed frequency application such as the accelerator, for example the energy recovery linac. The design and the experimental results will be presented in this report.
Euclid TechLabs, LLC, Solon, Ohio
KEK, Ibaraki
LETI, Saint-Petersburg
Ceramics Ltd., St. Petersburg
Fermilab, Batavia
The BST based ferroelectric-oxide compounds have been found as suitable materials for a fast electrically-controlled RF switches and phase shifters that are under development for accelerator applications in X, Ka and L - frequency bands. The BST(M) material (BST ferroelectric with Mg-based additives) allows fast switching and tuning in vacuum and in air both; switching time of material samples < 10 ns has been demonstrated*. One of the problems related to accelerator application of BST ferroelectric is its high dielectric constant. Decreasing the permittivity however is usually strongly correlated with a decrease in the tunability (k(E)=ε(0)/ε(E)) of ferroelectrics. The use of linear dielectric inclusions in BST ceramics could result in significant suppression of the mentioned k(E) dependence, with the best case being that the tunability vs. ε decrease could be unchanged. On the basis of our measurements we report here two unusual phenomena observed**: (i) the increase both the dc and the dynamic tunability with a decrease of the dielectric constant; (ii) the dynamic tunability was observed to exceed the static tunability at specific magnitudes of the applied field.
* A.Kanareykin et al, Proceedings PAC'09.
** A.Kozyrev et al Applied Physics Letters,v.95,p.012908,(2009).
Muons, Inc, Batavia
ANL, Argonne
An extremely low emittance RF gun is being designed for the X-ray Free Electron Laser Oscillator (XFEL-O), which is now being proposed by ANL. An adjustable coupling factor for this gun is very desirable for providing operational flexibility. What is required is a fundamental RF power coupler (FPC), adjustable in situ, that can operate at 100 MHz and 200 kW CW. If rotational motion is used in the adjustable coupler, it is usually necessary to break the vacuum between the coupler and the RF cavity, thereby risking prolonged down-times and the introduction of contaminants into the vacuum system. We propose a novel system for adjusting the coupling coefficient of coaxial couplers to allow for individual control and adjustments to the RF fields under different beam loading scenarios. The RF coupler has no movable parts and relies on a ferrite tuner assembly, coax TEE, and double windows to provide a VSWR of better than 1.05:1 and a bandwidth of at least 8 MHz at 1.15:1. The ferrite tuner assembly on the stub end of the coax TEE uses an applied DC magnetic field to change the Qext and the RF coupling coefficient, β, between the RF input and the cavity.
DESY, Hamburg
High frequency Higher Order Modes (HOM) propagating in the beam line of a superconducting linac can carry a substantial fraction of the energy deposited in accelerating structures by the beam. In this contribution, we report test results of the beam line absorber (BLA), which was designed and fabricated at DESY, and installed in the FLASH accelerator to absorb the HOM energy generated by high current beams. Two tests were carried out, in September 2008 and September 2009, during so called high current runs. The experiments confirmed the concept of the BLA design and showed remarkable agreement with computer modeling of the HOM energy absorption.
Cockcroft Institute, Warrington, Cheshire
Lancaster University, Lancaster
LLNL, Livermore, California
Imperial College of Science and Technology, Department of Physics, London
The University of Liverpool, Liverpool
The efficiency of future positron sources for the next generation of high-energy particle colliders (e.g. ILC, CLIC, LHeC) can be improved if the positron-production target is immersed in the magnetic field of adjacent capture optics. If the target is also rotating due to heat deposition considerations then eddy currents may be induced and lead to additional heating and stresses. In this paper we present data from a rotating target wheel prototype for the baseline ILC positron source. The wheel has been operated at revolution rates up to 1800rpm in fields of the order of 1 Tesla. Comparisons are made between torque data obtained from a transducer on the target drive shaft and the results of finite-element simulations. Rotordynamics issues are presented and future experiments on other aspects of the positron source target station are considered.
Fermilab, Batavia
The NOνA Experiment will construct a detector optimized for electron neutrino detection in the existing Neutrino at Main Injector (NuMI) beamline. The NuMI beamline is capable of operating at 400 kW of primary beam power and the upgrade will allow up to 700 kW. Ceramic beam tubes are utilized in numerous kicker magnets in different accelerator rings at Fermilab. Kovar flanges are brazed onto each beam tube end, since kovar and high alumina ceramic have similar expansion curves. The tube, kovar flange, end piece, and braze foil alloy brazing material are stacked in the furnace and then brazed. The most challenging aspect of fabricating kicker magnets in recent years have been making hermetic vacuum seals on the braze joints between the ceramic and flange. Numerous process variables can influence the robustness of conventional metal/ceramic brazing processes. The ceramic-filler metal interface is normally the weak layer when failure does not occur within the ceramic. Differences between active brazing filler metal and the moly-manganese process will be discussed along with the applicable results of these techniques used for Fermilab production kicker tubes.
Fermilab, Batavia
The NOνA Experiment will construct a detector optimized for electron neutrino detection in the existing Neutrino at Main Injector (NuMI) beamline. This beamline is capable of operating at 400 kW of primary beam power and the upgrade will allow up to 700 kW. The cavities will operate at 53 MHz and three of them will be installed in the Recycler beamline. Thermal stability of the cavities is crucial since this affects the tuning. Results of finite element thermal and structural analysis involving the copper RF cavity will be presented.
TU Darmstadt, Darmstadt
GSI, Darmstadt
The central accelerator SIS100 of the FAIR-facility will provide high intensity, intermediate charge state heavy ion beams. In order to assure a reliable operation with the intermediate charge states, a special synchrotron design, including ion catcher system had to be developed. Intermediate charge state heavy ions suffer from high cross sections for ionization. Due to the dedicated synchrotron layout, ions which have been further stripped by collisions with residual gas atoms are not lost uncontrolled onto the beam pipe but are caught by the ion catcher system in the cryogenic arcs. The construction and test of a cryo-catcher prototype at GSI is a workpackage of the EU-FP7 project COLMAT. A prototype catcher including cryostat will be set-up at GSI to perform measurements with heavy ion beams of the heavy ion synchrotron SIS18.
CERN, Geneva
Linac4 is the new H- linear accelerator under construction at CERN aiming to double the brightness of the beam injected to the CERN PS Booster (PSB) for delivering proton beams to experiments or further CERN accelerators, down to the LHC. The injection system in the PSB is based on the H- charge exchange where the 160 MeV H- beam is converted into an H+ beam by stripping the electrons with a carbon foil. A beam dump located inside a pulsed magnet for the injection bump will intercept the unstripped ions (H0 and H-) and measure the collected charge to detect the relative efficiency and degradation of the stripping foil. The challenge of the dump design is to meet the requirements of a beam dump providing a current measurement and at the same time minimizing the perturbation of the magnetic field of the surrounding pulsed magnet. This paper describes all phases of the dump design and the main issues related to its integration in the line.
Lancaster University, Lancaster
Cockcroft Institute, Lancaster University, Lancaster
In this paper we examine the effect of introducing an Electromagnetic metamaterial into a Travelling Wave structure to mediate inverse Cherenkov acceleration. Electromagnetic metamaterials are artificial materials that consist of macroscopic structures that yield an effective permittivity and permeability less than zero. The properties of metamaterials are highly frequency dependent and give rise to very novel dispersion relationships. We show that the introduction of a specifically designed metamaterial into the interaction region gives rise to a novel dispersion curve yielding a unique wave-particle interaction. We demonstrate that this novel wave-particle interaction gives rise energy exchange from wave to beam over an extended interaction regime. We also discuss the benefits and issues that arise from having a metamaterial in a high vacuum high power environment with a specific focus on the issue of loss in metamaterial structures.
UCLA, Los Angeles
PBPL, Los Angeles
Manhattanville College, Purchase, New York
Pyroelectric crystals, which produce large surface electric fields during heating and cooling, have been proposed as a mechanism for constructing a stand-alone electron beam source. We report on experimental tests of this concept, using a variety of field emission tips combined with a pyroelectric crystal to produce a low-energy electron beam during thermal cycling. The mechanism is suitable for generating very small electron bunches, with energies up to tens of kilovolts, for use in microaccelerator structures.
UCLA, Los Angeles
PBPL, Los Angeles
Manhattanville College, Purchase, New York
This paper extends the physics of the Micro-Accelerator Platform (MAP), which is in development as an optical structure for laser acceleration of relativistic electrons. The MAP is a resonant, optical-scale, slab-symmetric device that is fabricated from dielectric materials using layer-deposition techniques. For stand-alone applications, low-energy electrons (beta ~ 0.3) must be synchronously accelerated to relativistic speeds for injection into the MAP. Even lower energies are desired for other particle species (e.g. protons or muons). In this paper, we present design and simulation studies on a tapered geometry and associated coupling scheme that can produce synchronous acceleration at beta < 1 within a MAP-like structure.
LETI, Saint-Petersburg
Euclid TechLabs, LLC, Solon, Ohio
The analysis of Vavilov-Cherenkov radiation generated by wide high current relativistic electronic bunch in a rectangular waveguide with multilayered dielectric filling is carried out. One ceramic layer of the structure possesses ferroelectric properties, which allow the waveguide frequency spectrum to be controlled by varying the permittivity of this ferroelectric layer by external electric field. On the basis of decomposition on orthogonal eigenmodes of a rectangular multilayered waveguide analytical expressions are received and numerical modeling of wakefield electromagnetic fields and the radial forces deflecting the bunch is spent.
NSC/KIPT, Kharkov
IERT, Kharkov
To excite intensive accelerating fields a multi-zone dielectric structures can be used*. As have shown already carried out researches, at their excitation by relativistic charged particle bunches the maximal amplitude of an accelerating field significantly depends on group velocity of energized waves. Till now these effects in wakefield multi-zone dielectric accelerators in details are not investigated. In addition the large charge of drive bunches requires the obligatory account of its space charge on bunch dynamics. To account the specified effects we built the nonlinear self-consistent theory of wake field excitation in the multilayered dielectric resonators. Expressions for excited fields, functionally depending on position of bunch particles in the resonator are found analytically. Excited fields are presented in the form of superposition solenoidal (LSE and LSM types) and potential fields. The nonlinear theory built in a general view is valid for any number of dielectric layers. Use of the constructed theory for the account of nonlinear and groups velocity effects is demonstrated on an example of 5-zone dielectric resonator with parameters close to experiment**.
* C. Wang et.al. In Proc. PAC 2005. IEEE, 2005, p. 1333.
** G.V.Sotnikov et.al. AIP Conf. proc. V.1086, p.415.
MIT/PSFC, Cambridge, Massachusetts
Photonic bandgap (PBG) structures show promising results for use in future collider applications. Both acceleration and wakefield damping have been demonstrated experimentally. The breakdown performance of a single cell PBG structure was tested at X-band at SLAC and found to have significant contributions from magnetic field effects. A new structure has been designed at 17.1 GHz to be tested at MIT to investigate the scaling of these and other breakdown effects with frequency. The 17.1 GHz structure will also use the open nature of the PBG lattice to greatly improve the breakdown diagnostics. Finally, a novel PBG structure has been designed for testing at SLAC using elliptical inner rods. This design significantly reduces the pulsed heating in the structure and should therefore improve the breakdown performance.
Euclid TechLabs, LLC, Solon, Ohio
ANL, Argonne
High frequency, high power rf sources are needed for many applications in particle accelerators, communications, radar, etc. We have developed a 26GHz high power rf source based on the extraction of wakefields from a relativistic electron beam. The extractor is designed to couple out rf power generated from a high charge electron bunch train traversing a dielectric loaded waveguide. The first high beam experiment has been performed at Argonne Wakefield Accelerator facility. The experimental results successfully demonstrate the 15ns 26GHz rf pulse generated from the wakefield extractor with a bunch train of 16 bunches. Meanwhile, ~ 30MW short rf pulse has been achieved with a bunch train of 4 bunches. Beam Breakup has prevented charge transport through the power extractor beyond 10nC. We are doing simulations and developing methods to alleviate the BBU effect.
CERN, Geneva
The PS2 lattice, based on Negative Momentum Compaction (NMC) arc cells is being optimized in order to accommodate a new all-doublet long-straight section (LSS) design. Apart from smoothing the optics and enabling different tuning solutions for H- injection, the optimization focuses on increasing the available magnet-to-magnet drift space and reducing the quadrupole types and strengths. The variation of lattice parameters for a wide range of working points is presented.
SOLEIL, Gif-sur-Yvette
SOLEIL, the French 2.75 GeV high brilliance third generation synchrotron light source is delivering photons to 20 beam lines and is presently equipped with 17 insertion devices. Significant reduction of injection efficiency and beam lifetime are observed when using some undulator configurations in daily operation. Measurements on electron beam, such as beam lifetime versus RF voltage, have shown that the energy acceptance is strongly reduced by the combined non linear effects of the four U20 in-vacuum undulators and the HU640 10m long undulator used in linear vertical polarization mode. This paper will present the on and off momentum frequency map measurements that have been performed in order to investigate such effects. The reduction of the on momentum dynamic aperture in the presence of the U20 undulators is confirmed. The off momentum frequency map measurements confirm that the energy acceptance of the bare machine is very large as predicted by tracking calculations, and clearly exhibit the strong energy acceptance reduction due to undulators.
PAL, Pohang, Kyungbuk
A superconducting RF cavity is used in the storage ring of the Pohang Light Source (PLS) upgrade project (PLS-II) at Pohang Accelerator Laboratory (PAL) for increasing the electron beam current and energy from 2.5GeV/200mA to 3.0GeV/400mA. In order to meet the requirement of lower beam emittance and higher photon energies, as well as more straight sections for insertion devices, the vacuum chambers in the storage ring need to be reconstructed. To control the spurious harmonic resonances' effect to beam position monitors (BPMs) in the PLS and PLS-II storage ring vacuum chamber, the TE mode distribution in vacuum chambers has been analyzed by both numerical simulation and experiment. Based on this analysis, the proper method to control the strength of TE mode at the position of BPMs is suggested.
Diamond, Oxfordshire
JAI, Oxford
Diamond operates with 10 in-vacuum insertion devices at 5 mm gap, two Apple-II, two superconducting and two normal conducting wigglers. We report here the correction of the linear optics of wigglers and measurements of nonlinear effects such as dynamic aperture and frequency maps and their impacts on injection efficiency, lifetime and loss distribution in operation of the storage ring.