Kyoto ICR, Uji, Kyoto
KEK, Ibaraki
Funding: Work partially supported by the Ministry of Education, Science, Sports and Culture, Grant-in-Aid for Scientific Research (A), 18204023(2006)
Although the base line technology of the Final Focus Doublet for ILC is superconducting magnet, which is supposed to be conventional, the slender structure may be suffered from its vibration. The permanent magnets, however, do not have any vibration source in it at the steady state. The five-ring-singlet configuration, proposed by R. L. Gluckstern adds 100% strength adjustability to permanent magnet quadrupole (PMQ) lens. A prototype of this lens is fabricated and under evaluation. It was originally designed for ILC that also has the extra hole for the outgoing beam. In order to realize the beam test at ATF2, the inner bore is enlarged from D20mm to D50mm to clear the background photons from Shintake-Monitor. The magnet is described.
CERN, Geneva
Pre-cycles for setting up the main magnets of the Large Hadron Collider are necessary for ensuring field reproducibility and low field-decay rates at injection. In this paper we propose standard pre-cycles for the main magnets of the LHC. We study the influence of the pre-cycle parameters on the field decay at injection by two different models. One already proven model is semi-empirical based on magnetic measurements of the magnets. The other is a new network based model of a Rutherford cable which directly calculates the current redistribution and associated magnetization change in the cable strands. The pre-cycle to be used may depend on the history of the machine or may have to be changed because of unforeseen phenomena in the machine. The choice of a new pre-cycle on the basis of magnetic measurements alone is a lengthy process. We confirm the usefulness of the network based model as a tool for selecting new pre-cycles, including decay-blocking degaussing pre-cycles, and compare with magnetic measurements.
LBNL, Berkeley, California
ICST, Harbin
UMiss, University, Mississippi
Funding: This work is supported by funds under the “985-2” plan of HIT. This work is also supported by the Office of Science, US-DOE under DOE contract DE-AC02-05CH11231 and by NSF through NSF-MRI-0722656.
The superconducting coupling solenoid for MuCOOL and MICE will have an inside radius of 750 mm, and a coil length of 285 mm. The MuCOOL coupling coil is identical to the MICE coupling coils. The MICE coupling magnet will have a self inductance of 592 H. When operated at it maximum design current of 210 A (the highest momentum operation of MICE), the magnet stored energy will be about 13 MJ. These magnets will be kept cold using a pair of pulse tube cryocoolers that deliver 1.5 W at 4.2 K and 55 W at 60 K. This report describes the progress on the MuCOOL and MICE coupling magnet design and engineering. The progress on the construction of the first coupling coil will also be presented.
ORNL, Oak Ridge, Tennessee
LANL, Los Alamos, New Mexico
Funding: Research sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory (ORNL), managed by UT-Battelle, LLC for the U. S. Department of Energy
Plasmas produced by helicon wave excitation typically develop higher densities, particularly near the radial plasma core, at lower operating pressures and RF powers than plasmas produced using traditional inductive RF coupling methods. Approximately two years ago we received funding to develop an H- ion source based on helicon wave coupling. Our approach was to combine an existing high-density, hydrogen helicon plasma generator developed at ORNL for the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) project with the SNS external antenna H- source. To date we have achieved plasma densities >1013 e/cm3 inside the ion source using <10kW of RF power and <5 SCCM of H2 gas flow. This report discusses the first cesiated H- beam current extraction measurements from the source.
J-PARC, KEK & JAEA, Ibaraki-ken
For operation of the JPARC Main Ring, low loss of the high-intensity bunches during the injection and acceleration processes is crucial to avoid radiation damage of the machine. This requires identification and correction the most dangerous resonances, which should be done in combination with the collective effects, in particular, the low energy space charge effects. In frame of this talk we review the status of the Main Ring commissioning process and compare it with the simulation results for the low intensity beam. For the future operation of the Main Ring with the moderate beam power we review the status of the simulation work and discuss the budget of the beam losses.
Fermilab, Batavia
Rutgers University, The State University of New Jersey, Piscataway, New Jersey
Funding: This manuscript has been authored by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The promise of next-generation light sources depends on the availability of ultra-low emittance electron sources. One method of producing low transverse emittance beams is to generate a low longitudinal emittance beam and exchange it with a large transverse emittance. Experiments are underway at Fermilab's A0 Photoinjector and ANL's Argonne Wakefield Accelerator using the exchange scheme of Kim and Sessler. Experiments as the A0 photoinjector exchange a large longitudinal emittance with a small trasverse emittance. AWA expects to exchange a large transvserse emittance with a small logitudinal emittance. In this paper we discuss recent results at A0 and AWA and future plans for these experiments.
UMAN, Manchester
Here we present initial results on an alternate design for CLIC main accelerating linacs which is moderately damped and detuned structure. In order to suppress the wake-fields, we detune the lowest dipole modes as they have significant impact on the beam emittance compared to the other multipoles. In order to mitigate the reappearance of the wake-field of a detuned accelerator structure, we provide moderate damping by coupling cells to manifolds which run parallel to each accelerator structure. The manifolds are designed such that they are non-propagating at the acceleration mode frequency. The cell parameters are optimised by considering the r.f. breakdown, pulse surface heating and beam dynamics constraints.
Euclid TechLabs, LLC, Solon, Ohio
KEK, Ibaraki
Ceramics Ltd., St. Petersburg
Fermilab, Batavia
Funding: This work was supported by the US Department of Energy
Euclid TechLabs LLC is developing BST based ferroelectric elements designed to be used as the basis for new advanced accelerator components operating in the 1.3 GHz frequency range and intended for Project X and ILC applications. These new ferroelectric elements are designed for the fast active tuner for SC cavities that can operate in air at low biasing DC fields in the range of 15 kV/cm. 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. The overall goal of the program was to design an L-band externally-controlled fast ferroelectric tuner for controlling the coupling of superconducting RF cavities for the future linear colliders. The tuner prototype has been built; a time response of <30 ns, or 1 deg. in 0.5 ns has been reached. . The following problems are addressed: (i) lowering the losses in the ferroelectric material; (ii) improving the technique of the ferroelectric element metallization and brazing; and (iii) improvement breakdown threshold at high voltage bias.
Far-Tech, Inc., San Diego, California
We describe a novel acceleration structure for acceleration of electron and ion beams where the cell-to-cell coupling is provided by slot resonances in the wall of adjacent accelerator cells. As with the side-coupled linac, the concept allows for the operation of a standing-wave structure in a phase and amplitude stabilized pi/2 mode. We explore the applications of such a structure to electron and ion accelerators.
Fermilab, Batavia
Muons, Inc, Batavia
CERN, Geneva
Funding: supported in part by USDOE STTR Grant DE-FG02-08ER86350
The great advantage of the helical ionization cooling channel (HCC) is its compact structure that enables the fast cooling of muon beam 6-dimensional phase space. This compact aspect requires a high average RF gradient, with few places that do not have cavities. Also, the muon beam is diffuse and requires an RF system with large transverse and longitudinal acceptance. A traveling wave system can address these requirements. First, the number of RF power coupling ports can be significantly reduced compared with our previous pillbox concept. Secondly, by adding a nose on the cell iris, the presence of thin metal foils traversed by the muons can possibly be avoided. We show simulations of the cooling performance of a traveling wave RF system in a HCC, including cavity geometries with inter-cell RF power couplers needed for power propagation.
HUST, Wuhan
Funding: Nation Nature Science Foundation of China,10435030
At Huazhong University of Science and Technology (HUST), the design study of a 10 MeV compact cyclotron CYCHU-10 for the application of Positron Emission Tomography (PET) has been developed since 2007. This paper describes the recent status of RF cavities including numerical calculation results of basic parameters, the capacitive trimmer to overcome frequency shift when in operation and the construction and cold test of the 1:1 scale prototype. The inductive coupling loop design and matching simulation with the RF power generator are also presented
BNL, Upton, Long Island, New York
Omega-P, Inc., New Haven, Connecticut
Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
A novel tuner has been developed by the Omega-P company to achieve fast control of the accelerator RF cavity frequency. The tuner is based on the ferroelectric property which has a variable dielectric constant as function of applied voltage. Tests using a Brookhaven National Laboratory (BNL) 1.3 GHz RF cavity have been carried out for a proof-of-principle experiment of the ferroelectric tuner. Two different methods were used to determine the frequency change achieved with the ferroelectric tuner. The first method is based on a S11 measurement at the tuner port to find the reactive impedance change when the voltage is applied. The reactive impedance change then is used to estimate the cavity frequency shift. The second method is a direct S21 measurement of the frequency shift in the cavity with the tuner connected. The estimated frequency change from the reactive impedance measurement due to 5 kV is in the range between 3.2 kHz and 14 kHz, while 9 kHz is the result from the direct measurement. The two methods are in reasonable agreement. The detail description of the experiment and the analysis will be discussed in the paper.
CLASSE, Ithaca, New York
Funding: Work supported by NSF Grant PHY 0131508
This paper reports results of cold measurements characterizing the electro-mechanical properties of the Cornell ERL injector cryomodule, which houses five superconducting niobium elliptical 2-cell cavities developed for a high-current (100 mA) low-emittance electron beam. Each cavity is equipped with a blade tuner. The Cornell ERL blade tuner is a modified version of the INFN-Milano design, and incorporates 4 piezoelectric actuators and accelerometers enabling concurrent slow/fast cw RF frequency control and mechanical vibration measurements. Cavity microphonics and fast tuner electro-mechanical transfer functions for all of the cavities have been measured and show the feasibility of stable feedback control at microphonic noise frequencies below ~100 Hz.
DESY, Hamburg
JLAB, Newport News, Virginia
A coaxial coupling device located in the beam pipe of the TESLA type superconducting cavities provides for better propagation of Higher Order Modes (HOMs) and their strong damping in appropriate HOM couplers. Additionally, it also provides efficient coupling for fundamental mode RF power into the superconducting cavity. The whole coupling device can be designed as a detachable system. If appropriately dimensioned, the magnetic field can be minimized to a negligible level at the flange position. This scheme, presented previously*, provides for several advantages: strong HOM damping, flangeable solution, exchangeability of the HOM damping device on a cavity, less complexity of the superconducting cavity, possible cost advantages. This contribution will describe the results of the first cryogenic test.
*J. Sekutowicz et al., Proceedings LINAC08, Victoria, Canada, 2008.
Fermilab, Batavia
Euclid TechLabs, LLC, Solon, Ohio
KEK, Ibaraki
The accelerating gradient required for the ILC project exceeds 30 MeV/m. With current technology the maximum acceleration gradient in SC structures is determined mainly by the value of the surface RF magnetic field. In order to increase the gradient, the RF magnetic field is distributed homogeneously over the cavity surface (low-loss structure), and coupling to the beam is improved by introducing aperture "noses" (re-entrant structure). These features allow gradients in excess of 50 MeV/m to be obtained for a singe-cell cavity. Further improvement of the coupling to the beam may be achieved by using a TW SC structure with small phase advance per cell. We have demonstrated that an additional gradient increase by up to 46% may be possible if a pi/2 TW SC structure is employed. However, a TW SC structure requires a SC feedback waveguide to return the few GW of circulating RF power from the structure output back to the structure input. Advantages and limitations of different techniques of exciting the traveling wave in this structure are considered, including an analysis of mechanical tolerances. We also report on investigations of transient processes in the SC TW structure.
Fermilab, Batavia
Omega-P, Inc., New Haven, Connecticut
Yale University, Physics Department, New Haven, CT
Funding: Sponsored in part by US Department of Energy, Office of High Energy Physics.
A preliminary design is presented for a two-cavity 7th harmonic multiplier, intended as a high-power RF source for use in experiments aimed at developing high-gradient structures for a future collider. The harmonic multiplier is to produce power in K-band using as an RF driver an XK-5 S-band klystron (2.856 GHz). The device is to be built with a TE111 rotating mode input cavity and interchangeable output cavities, a principal example of which is a TE711 mode cavity running at 19.992 GHz. Design of the harmonic multiplier is described that uses a 250 kV, 20 A injected laminar electron beam. With 10 MW of S-band drive power, 4.7 MW of 20-GHz output power is predicted. Details are described of the gun beam optics, beam dynamics in the RF system, and of the magnetic circuit. The theory of an azimuthally distributed coupler for the output cavity is presented, as well as the conceptual design of the entire RF circuit.
HRC, Santa Clara, California
Funding: Work performed under the auspices of the U.S. Department of Energy SBIR Grant No. DE-FG02-08ER85197.
The salient features and design parameters of a dual resonant ring system configured for evaluating the high gradient performance of 11.424 GHz TW linear accelerator structures are presented; and the inherent rapid protection mechanism that automatically limits energy deposition during breakdown of the structure, and minimizes RF source reflections, is discussed. The diagnostic characteristics of the RF bridge load monitors and their unique capability of detecting the power imbalance caused by a feedback loop phase change of less than 2 parts in 10000, representing a 2 to 3 degree phase change of the linac structure, is described. The transient and steady-state power apportionment within the ring system is analyzed; and, in considering initial high power tests using an 18-cavity CLIC/KEK/SLAC structure, the results indicate that the demonstration of an unloaded average accelerating gradient of 108 MV/m will require a source power of 26 MW.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
EMMA is a prototype non-scaling FFAG that requires a demanding RF system. Production for the final RF system is due for completion in Spring 09 and testing of the combined hardware has taken place. This paper describes the high power verification tests of the IOT transmitter, waveguide distribution, RF cavity and LLRF control system.
BESSY GmbH, Berlin
PTB, Berlin
Funding: Work funded by Physikalisch-Technische Bundesanstalt
The Metrology Light Source (MLS) [1] is in user operation since 2008 at operating energies ranging from 105 MeV up to 630 MeV and with multi bunch currents up to 200 mA. At the injection energy of 105 MeV as soon as the beam current exceeds a few mA, the beam is strongly blown up in all three spatial dimensions and strong oscillations at very different spectral frequencies can be observed. These effects are caused by the interaction of beam charge with ions present and their strength and characteristic time scales depend on several machine parameters. As ion effects can strongly deteriorate the performance of the MLS, we report on first investigations.
LBNL, Berkeley, California
BNL, Upton, Long Island, New York
Funding: Supported by DOE BES contract DE-AC03-76SF00098.
Several years ago experiments at the APS demonstrated the possibility of creating crabbed beam through vertically kicking the beam and letting it oscillate for a half of a synchrotron period. Such a crabbed beam would allow the possibility of creating a few ps xrays. At the ALS we have repeated these experiments. In this paper we will present the results obtained and compare them to theoretical predictions.
LSU/CAMD, Baton Rouge, Louisiana
To control the emittance coupling in the CAMD Light Source, new power supplies have been constructed which adjust the currents in the individual coils of the normal lattice sextupoles, thereby creating skew quadrupole fields. The new power supplies add or subtract current through the pre-energized coils. Performance contributing factors include a summing network with a temperature coefficient less than 1ppm/°C, a water cooled resistive shunt, and linear optical signal isolation. High density & modularity control boards and water cooled power cards are mounted as pull-out units in a 19” rack. Active limiters and fault indicators can provide reliability and portability to higher power designs. The use of these skew quadrupoles in controlling and minimizing the emittance coupling is presented.
UTNL, Ibaraki
The University of Tokyo, Nuclear Professional School, Ibaraki-ken
A, Kawasaki, Kanagawa
AET Japan, Inc., Kawasaki-City
We are developing X-ray nondestructive testing (NDT) system using with portable X-band linac. This system uses 9.4 GHz X-band linac and 250 kW magnetron. Our system energy is 950 keV for Japanese regulation. Therefore we can use it on-site using local radiation protection. We measured electron beam and X-ray. We have started X-ray imaging test. We will use this system for condition based maintenance of pump-impeller at nuclear plants. The linac based X-ray source can generate pulsed X-ray. Therefore we can get still images without stopping rotation when x-ray repetition rate synchronizes impeller's rotaion rate. We are successfull in proof of principle using a simple fan and a synchronized circuit. We prepare real-time imaging for conventional pump. In this paper, we will explain the detail of this system and expermental results.
HUST, Wuhan
Funding: Nation Nature Science Foundation of China,10435030
The design study of Cyclotron CYCHU 10MeV has been developed at Huazhong University of Science and Technology (HUST). Because of the low center frequency (100MHz) of it’s RF system, we should choose suitable directional couplers for the RF system which is supposed to be high-directivity and tight-structure. This paper analyses and synthesizes kinds of directional couplers, espacially microstrip structure, for it’s tinier volume at the low center frequency compared with stripline and branch structures. The achievement of the high-directivity with microstrip configuration is carried out by the distributed capacitor to decrease the even and odd mode phase difference. Capacitive compensation is performed by the interdigital capacitors. The proposed structure is easy to fabricate and incorporate another microwave device due to planner microstrip.
INFN-Napoli, Napoli
UCR, Riverside, California
Funding: World Wide Collaboration of a large fraction of the international agencies.
Muon ionization cooling provides the only practical solution to prepare high brilliance beams necessary for a neutrino factory or muon colliders. The muon ionization cooling experiment (MICE) is under development at the Rutherford Appleton Laboratory (UK). It comprises a dedicated beam line to generate a range of input emittance and momentum, with time-of-flight and Cherenkov detectors to ensure a pure muon beam. A first measurement of emittance is performed in the upstream magnetic spectrometer with a scintillating fiber tracker. A cooling cell will then follow, alternating energy loss in liquid hydrogen and RF acceleration. A second spectrometer identical to the first one and a particle identification system provide a measurement of the outgoing emittance. By April 2009 it is expected that the beam and first set of detectors will have been commissioned, and a first measurement of input beam emittance may be reported. Along with the plan of measurements of emittance and cooling that will follow in the second half of 2009 and in 2010.
STFC/RAL/ISIS, Chilton, Didcot, Oxon
Funding: Supported by STFC/RAL/ASTeC and by EC Research Infrastructure Activity (FP6) "Structuring the European Research Area" programme (CARE, contract number RII3-CT-2003-506395).
A description is given of the development of a slow-wave chopper structure for the 3.0 MeV, 60 mA, H‾ MEBT on the RAL Front-End Test Stand (FETS). Two candidate structures, the so called RAL ‘Helical’ and ‘Planar’ designs have been previously identified, and are being developed to the prototype stage. Three test assemblies have been designed by modelling their high frequency electromagnetic properties in the time domain, using a commercial 3D code, and their subsequent manufacture, using standard NC machining practice, has helped to validate the selection of machine-able ceramics and copper alloys. In addition, an electro-polishing technique has been developed that enables the ‘fine tuning’ of strip-line characteristic impedance, and edge radius. Measurements of the transmission line properties of the ‘Helical’ and ‘Planar’ test assemblies are presented.
TUB, Beijing
Funding: This work is supported by National Natural Science Foundation of China(Project 10735050) and National Basic Research Program of China (973 Program)(Grant No. 2007CB815102).
The X-band photocathode RF gun can be utilized to generate electron beams with ultra-low emittance. In this paper, we present the design of a coaxial coupler for the X-band RF gun to avoid the emittance growth caused by field asymmetries. A detailed 3D simulation of the coupler is performed. The microwave circuit analysis is accomplished, and the relationship between the coupling factor and the coaxial coupler size is obtained. This paper likewise presents the beam dynamics parameters of the X-band RF gun with a coaxial coupler.
CAEP/IFP, Mainyang, Sichuan
Funding: Hongtao Li is with the Institute of Fluid Physics, China Academy of Engineering Physics (CAEP), Mianyang City, Sichuan, China. (Fax:86-816-2282695; e-mail: lht680526@ 21cn.com).
In order to study the physics of fast Z-pinches and research the key issues of pulse power technology, a 10MA/6MV z-pinch primary test stand (PTS) composed of 24 modules will be built in IFP. The prototype module adopted capacitive storage scheme is composed of the 6MV/300kJ Marx-generator (MG), intermediate storage capacitor (IC), laser-triggered switch (LTS), pulse forming line (PFL), water self-breakdown switch (WS), and tri-plate pulse transmission line (PTL). The measured output current of the prototype is approximate 520kA, and output voltage is approximate 2.1MV. The unique multi-stage LTS based on uniform field distribution design and multi-pin unsymmetrical WS make the prototype modules have low systemic delay jitter which is necessary for synchronization of multi-module facility. 1-δ jitter of delay of the system is less than 4ns.
CERN, Geneva
Fast kicker magnets are used to inject beam into and eject beam out of the CERN SPS accelerator ring. These kickers are generally ferrite loaded transmission line type magnets with a rectangular shaped aperture through which the beam passes. Unless special precautions are taken the impedance of the ferrite yoke can provoke significant beam induced heating, even above the Curie temperature of ferrite. In addition the impedance can contribute to beam instabilities. In this paper different variants of the coaxial wire method, both for measuring longitudinal and transverse impedance, are briefly discussed in a tutorial manner and do's and don'ts are shown on practical examples. In addition we present the results of several impedance measurements for SPS kickers using the wire method and compare those results with theoretical models.
SLAC, Menlo Park, California
ORNL, Oak Ridge, Tennessee
Funding: Work supported by the Department of Energy under contract No. DE-AC02-76SF00515.
SLAC National Accelerator Laboratory is developing a next generation H-bridge switch plate*, a critical component of the SNS High Voltage Converter Modulators**. As part of that effort, a new IGBT gate driver has been developed. The drivers are an integral part of the switch plate, which are essential to ensuring fault-tolerant, high-performance operation of the modulator. The redesigned drivers improve upon the existing gate drives in several ways. The new gate driver has improved fault detection and suppression capabilities; suppression of shoot-through and over-voltage conditions, monitoring of excess di/dt and Vce,sat, and redundant power isolation are some of the added features. Also, triggering insertion delay is reduced by a factor of four compared to the existing driver. This presentation details the design and performance of the new IGBT gate driver. A detailed schematic and description of the construction are included. Operation of the fast over-current detection circuits, active IGBT over-voltage protection circuit, shoot-through prevention and control power isolation breakdown detection circuit are discussed.
*W. A. Reass, et al., “Design, Status, and First Operations of the Spallation Neutron Source Polyphase Â…”, PAC, 2003
**M.A. Kemp, et al., “Next Generation IGBT Switch Plate Â…,” LINAC, 2008.
NSRRC, Hsinchu
The correction power supplies are working in the storage ring of NSRRC. They are required to output high quality and high performance current that is long-term stability and output current ripple are required to be under 100ppm. The storage ring consists of more than one hundred units of independence power supplies working together when beam current in 1.5GeV status. The power supplies also are all working under current mode. We just build a new conduction EMI (Electromagnetic Interference) and EMC (Electromagnetic Compatibility) measurement laboratory to measure and test the switching power supplies. That is AC to DC voltage bus source to supply for the switching correction power supply. Using the LISN to obtain conduction noise, it is high frequency voltage noise generated by the switching mode of power supply conduction noise. The current signal pass AC source impendence stabilize network LISN and spectrum analyzer will obtain the conduction noise. We can use a noise separator to separate common EMI noise and difference-mode EMI noise for EMI filtering design. The measurement result will be illustrated in the paper.
Rome University La Sapienza, Roma
RadiaBeam, Marina del Rey
UCLA, Los Angeles, California
INFN/LNF, Frascati (Roma)
We present here the design, including RF modelling, cooling, and thermal stress and frequency detuning, of an S-band RF gun capable of running near 500 Hz, for application to FEL and inverse Compton scattering sources. The RF design philosophy incorporates many elements in common with the LCLS gun, but the approach to managing cooling and mechanical stress diverges significantly. We examine the new proprietary approach of RadiaBeam Technologies for fabricating copper structures with intricate internal cooling geometries. We find that this approach may enable very high repetition rate, well in excess of the nominal project this design is directed for, the SPARX FEL.
*C.Limborg et al.,“RF Design of the LCLS Gun”,LCLS Technical Note LCLS-TN-05-3
**P. Frigola et al.,“A Novel Fabrication Technique for the Production of RF Photoinjectors”,published in EPAC08.
ORNL, Oak Ridge, Tennessee
University of Tennessee, Knoxville, Tennessee
MIT Lincoln Laboratory, Boston MA
Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725.
Investigations of the rf properties of certain twisted waveguide structures show that they support favorable accelerating fields. This makes them potential candidates for accelerating cavities. Using the particle tracking code, ORBIT, We examine the beam - rf interaction in the twisted cavity structures to understand their beam transport and acceleration properties. The results will show the distinctive properties of these new structures for particle transport and acceleration, which have not been previously analyzed.
IHEP Beijing, Beijing
PKU/IHIP, Beijing
CIAE, Beijing
A high-duty factor proton RFQ accelerator has been constructed at IHEP, Beijing for the basic study of Accelerator Driven Subcritical System. The ADS basic study is supported by a national program for nuclear waste transmutation which is regarded essential for the rapid development of nuclear power plants in China. In the initial commissioning of the 3.5MeV RFQ with an ECR ion source showed a nice performance with a transmission rate about 93% with an output beam of 46mA. The 352MHz RFQ is design for CW operation with the RF power source from LEP-II of CERN. This paper presents the beam commissioning and recent progress in high-duty factor operation from 7% to 15%.
Fermilab, Batavia
LBNL, Berkeley, California
The production of an Electron Cloud poses stability issues for future high intensity running of the Fermilab Main Injector. Recent experiements have shown the presense of the electron cloud can be detected by the phase shift of a TE wave propagated along the beampipe. This technique has been employed to provide very sensitive measurements of the electron cloud development in the Fermilab Main Injector.
LBNL, Berkeley, California
JLAB, Newport News, Virginia
UMiss, University, Mississippi
The international muon ionization cooling experiment (MICE) requires low frequency and normal conducting RF cavities to compensate for muon beams’ longitudinal energy lost in the MICE cooling channel. Eight 201-MHz normal conducting RF cavities with conventional beam irises terminate by large and thin beryllium windows are needed. The cavity design is based on a successful prototype cavity for the US MUCOOL program. The MICE RF cavity will be operated at 8-MV/m in a few Tesla magnetic fields with 1-ms pulse length and 1-Hz repetition rate. The cavity design, fabrication, post process plans and as well as integration to the MICE cooling channel will be discussed and presented in details.
SLAC, Menlo Park, California
Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515.
We present a concept for powering the main linacs of the International Linear Collider (ILC) by delivering high power RF from the surface via overmoded, low-loss waveguides at widely spaced intervals. The baseline design employs a two-tunnel layout, with klystrons and modulators evenly distributed along a service tunnel running parallel to the accelerator tunnel. This new idea eliminates the need for the service tunnel. It also brings most of the warm heat load to the surface, dramatically reducing the tunnel water cooling and HVAC requirements. In the envisioned configuration, groups of 70 klystrons and modulators are clustered in surface buildings every 2.4 km. Their outputs are combined into two half-meter diameter circular TE01 mode evacuated waveguides. These are directed via special bends through a deep shaft and along the tunnel, one upstream and one downstream. Each feeds approximately 1.2 km of linac with power tapped off in 10 MW portions at 38 m intervals. The power is extracted through a novel coaxial tapoff (CATO), after which the local distribution is as it would be from a klystron. This tapoff design is also employed in reverse for the initial combining.
ELETTRA, Basovizza
Funding: The work was supported in part by the Italian Ministry of University and Research under grant FIRB-RBAP045JF2 or grant FIRB-RBAP06AWK3 or grants FIRB-RBAP045JF2 and FIRB-RBAP06AWK3
The FERMI@ELETTRA project will use the existing ELETTRA linac. The linac includes seven accelerating sections, each section is a backward traveling (BTW) structure comprised of 162 nose re-entrant cavities coupled magnetically. Furthermore, there are specialized input and output cavities specifically designed to match the structure to the RF source and load. These BTW accelerating structures work on the 3pi/4 mode which was chosen to optimize the structure efficiency and to achieve a simple RF tuning setup. These accelerating sections are powered by a TH2132A 45 MW klystron providing a 4.5 microsecond rf pulse and are coupled to a Thomson CIDR. In this paper the 3pi/4 backward BTW structures are investigated and the results of the electromagnetic simulations are presented.
IAP/RAS, Nizhny Novgorod
Yale University, Physics Department, New Haven, CT
Yale University, Beam Physics Laboratory, New Haven, Connecticut
Funding: Research sponsored by US Department of Energy, Office of High Energy Physics
Experimental investigations of an active Ka-band microwave pulse compressor are presented. The compressor is based on a running wave three mirror quasi-optical resonator utilizing a diffraction grating whose channels embody plasma discharge tubes as the active switch. The principle of compression is based on quickly changing the output coupling coefficient (Q-switching) by initiating plasma discharges in the grating channels. Excitation of the resonator was achieved with a few 100 kW of 34.29 GHz microwaves in 700 nS pulses from the magnicon in the Yae Ka-band Test Facility. A power gain of at least 7:1 in the compressed pulse with a duration of 10-15 nS was achieved.
INFN/LASA, Segrate (MI)
DESY, Hamburg
Three superconducting 3.9 GHz cavity prototypes have been fabricated for the XFEL linac injector, with minor modifications to the rf structures built by FNAL for the FLASH linac. This paper describes the production and preparation experience, the initial measurements, the plans for the XFEL series production and the cryogenic test infrastructure under preparation at INFN Milano.
BNL, Upton, Long Island, New York
Niowave, Inc., Lansing, Michigan
MHI, Kobe
NSLS-II is a new ultra-bright 3GeV 3rd generation synchrotron radiation light source. The performance goals require operation with a beam current of 500mA and a bunch current of at least 0.5mA. Ion clearing gaps are required to suppress ion effects on the beam. The natural bunch length of 3mm is planned to be lengthened by means of a third harmonic cavity in order increase the Touschek limited lifetime. After an extensive investigation of different cavity geometries a passive, superconducting 2-cell cavity has been selected for prototyping. The cavity is HOM damped with ferrite absorbers on the beam-pipes. The 2-cell cavity simplifies the tuner design as compared to two independent cells. Tradeoffs between the damping of the higher order modes, thermal isolation associated with the large beam tubes and overall cavity length are described. A copper prototype has been constructed and measurements of fundamental and higher order modes will be compared to calculated values.
PKU/IHIP, Beijing
Funding: Supported by National Basic Research Program(No. 2002CB713600) and NSFC(No. 10775010).
The 3.5-cell cavity for the PKU DCSC photoinjector requires the main coupler and the pickup be on the same side of the cavity, which will cause crosstalk between them. At room temperature, serious distortion of the RF response is caused. This paper applies a clear understanding of the RF signal; numerical and experimental study shows that the crosstalk will be negligible in superconducting (SC) status. Furthermore, a method to calculater resonant frequency and loaded quality factor from the crosstalk signal is provided
SLAC, Menlo Park, California
Funding: This work was supported by DOE Contract No. DE-AC02-76SF00515 and used resources of NERSC supported by DOE Contract No. DE-AC02-05CH11231, and of NCCS supported by DOE Contract No. DE-AC05-00OR22725.
In this paper, we present a 800MHz crab cavity conceptual design for LHC upgrade, including the cell shape optimization, and LOM, SOM, HOM and input coupler design. The compact coax-to-coax coupler scheme is proposed to couple to the LOM and SOM modes which can provide strong coupling to the LOM and SOM modes. HOM coupler design uses a two-stub antenna with a notch filter to couple to the HOM modes in the horizontal plane and reject the operating mode at 800MHz. All the damping results for the LOM/SOM/HOM modes satisfy their damping requirements. The multipacting in cell and couplers is simulated as well. And the issue of the cross-coupling between the input coupler and LOM/SOM couplers due to cavity asymmetry is addressed. The power coming out of the LOM/SOM/HOM couplers are estimated. All the simulations are carried out using SLAC developed parallel EM simulation codes Omega3P, S3P and Track3P.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
Cockcroft Institute, Lancaster University, Lancaster
The ILC crab cavities require very tight phase control in order to operate within the ILC parameters. In order to verify that the phase control system met the design tolerances, two single-cell niobium 3.9GHz superconducting dipole-mode cavities were tested in a liquid helium cryostat. The preparation of the cavities, design of the testing apparatus and performance of the phase control system are described in this paper.
BARC, Trombay, Mumbai
Indian Institute of Technology Bombay, Mumbai
CERN, Geneva
An RF system model has been created for the CERN Linac2 Tanks. RF systems in this linac have both single and double feed architectures. The main elements of these systems are: RF power amplifier, main resonator, feed-line and the amplitude and phase feedback loops. The model of the composite system is derived by suitably concatenating the models of these individual sub-systems. For computational efficiency the modeling has been carried out in the base band. The signals are expressed in in-phase - quadrature domain, where the response of the resonator is expressed using two linear differential equations, making it valid for large signal conditions. MATLAB/SIMULINK has been used for creating the model. The model has been found useful in predicting the system behaviour, especially during the transients. In the paper we present the details of the model, highlighting the methodology, which could be easily extended to multiple feed RF systems.
UPC, Barcelona
CELLS-ALBA Synchrotron, Cerdanyola del Vallès
The conventional electrical model analogy of a RF cavity is a shunt RLC circuit supplied by two current sources representing the RF amplifier and the beam. In the literature, the impedance of the cavity is often calculated in the Fourier domain. This type of cavity modelling has two drawbacks: First, it assumes a perfect matching between the cavity and the amplifier therefore it neglects the reflected voltage. And, second, it does not provide any information about the cavity transient response, for example at startup or upon beam arrival, while this information can be very important for the design of the regulation loops. In this work we will remove these drawbacks by calculating the cavity impedance in Laplace domain taking the reflected voltage into account. We will then modify our model so that it also includes the influence of the beam on the cavity. For transient RF simulations, though, a typical problem is the long simulation time due to the relatively slow transient response compared to the RF period. To overcome this problem, finally, we will use a mathematical method to map the cavity frequency response from RF to baseband to reduce the simulation time significantly.
SLAC, Menlo Park, California
Funding: Work supported by the DOE under contract DE-AC02-76SF00515.
The Multi-TeV colliders should have the capability to accelerate low emittance beam with high rf efficiency, X-band normal conducting high gradient accelerating structure is one of the promising candidate. However, the long range transverse wake field which can cause beam emittance dilution is one of the critical issues. We examined effectiveness of dipole mode damping in three kinds of X-band, π-mode standing wave structures at 11.424GHz with no detuning considered. They represent three damping schemes: damping with cylindrical iris slot, damping with choke cavity and damping with waveguide coupler. We try to reduce external Q factor below 20 in the first two dipole bands, which usually have very high (RT/Q)T. The effect of damping on the acceleration mode is also discussed.
PSI, Villigen
MAX-lab, Lund
Utilizing a large number of non-dispersive (24) and dispersive (6) skew quadrupoles the betatron coupling and the vertical spurious dispersion can be simultaneously reduced to extremely small values. As a result the achieved vertical emittance begins to approach its ultimate limit, set by the fundamental quantum nature of synchrotron radiation, which in the SLS case is ~0.55 pm.rad. At the same time emittance measurements based on the fitting of a diffraction limited vertical photon beam from a dipole have been pushed to the limit in order to verify this ultra-low vertical emittance.
KIT, Karlsruhe
FZK, Karlsruhe
IMFD, Freiberg
The next step towards introducing superconductive undulators as the new generation of insertion devices is to understand the impact of dynamic effects in the superconducting coils on the accelerator beam. These effects are seen as a temporal drift of the beam orbit, originating from transients of the magnetic field. The first systematic time resolved measurements of such drifts have been performed ANKA. Orbit displacement during several different ramping cycles, for different ramp rates and relaxation times, has been investigated. This contribution summarises the results of the measurements. The persistent current effects in the superconducting wires, as well as eddy currents in the yoke are discussed as possible sources for the transients.
BNL, Upton, Long Island, New York
The reduction of beta* beyond the 1m design value at RHIC has been consistently achieved over the last 6 years of RHIC operations, resulting in an increase of luminosity for different running modes and species. During the recent 2007-08 deuteron-gold run the reduction to 0.70 from the design 1 m achieved a 30% increase in delivered luminosity. The key ingredients in allowing the reduction have been the capability of efficiently developing ramps with tune and coupling feedback, orbit corrections on the ramp, and collimation at injection and on the ramp, to minimize beam losses in the final focus triplets, the main aperture limitation for the collision optics. We will describe the operational strategy used to reduce the b*, at first squeezing the beam at store, to test feasibility, followed by the operationally preferred option of squeezing the beam during acceleration, and the resulting luminosity increase obtained in the Cu-Cu run in 2005, Au-Au in 2007 and the deuteron-Au run in 2007-08. We will also include beta squeeze plans and results for the upcoming 2009 run with polarized protons at 250 GeV.
CERN, Geneva
BNL, Upton, Long Island, New York
Various LHC injection tests were performed in August and early September 2008 in preparation for the circulating beam operation. These tests provided the first opportunity to measure with beam the available mechanical aperture in two LHC sectors (2-3 and 7-8). The aperture was probed by exciting free oscillations and local orbit bumps of the injected beam trajectories. Intensities of a few 109 protons were used to remain safely below the quench limit of superconducting magnets in case of beam losses. In this paper the methods used to measure the mechanical aperture, the available on-line tools, and beam measurements for both sectors are presented. Detailed comparisons with the expected results from the as-built aperture models are also presented. It is shown that the measurements results are in good agreement with the LHC design aperture.
CERN, Geneva
BNL, Upton, Long Island, New York
KEK, Ibaraki
In 2008 beam successfully circulated in the LHC. Thanks to an excellent functioning of the BPM system and the related software, injection oscillations were recorded for the first 90 turns at all BPMs. The analysis of these data gives the unique opportunity of evaluating the periodic optics and inferring possible error sources.
KEK, Ibaraki
Crab cavities were installed at KEKB at the beginning of 2007. The beam operation with the crab cavities is in progress. In this paper, machine performance with crab crossing is described focusing on a specific luminosity and a beam lifetime issue related to the dynamic beam-beam effects.
UMAN, Manchester
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
The Accelerator Test Facility (ATF2) at KEK aims to experimentally verify the local chromaticity correction scheme to achieve a vertical beam size of 37nm. The facility is a scaled down version of the final focus design proposed for the future linear colliders. In order to achieve this goal, high precision tuning methods are being developed. One of the methods proposed for ATF2 is a novel method known as the ‘rotation matrix’ method. Details of the development and testing of this method, including orthogonality optimisation and simulation methods, are presented.
Fermilab, Batavia
Muons, Inc, Batavia
Northern Illinois University, DeKalb, Illinois
Funding: Supported in part by USDOE STTR Grant DE-FG02-06ER86282 and by FRA under DOE Contract DE-AC02-07CH11359
MANX is a six-dimensional muon ionization cooling demonstration experiment based on the concept of a helical cooling channel in which a beam of muons loses energy in a continuous helium or hydrogen absorber while passing through a special superconducting magnet called a helical solenoid. The goals of the experiment include tests of the theory of the helical cooling channel and the helical solenoid implementation of it, verification of the simulation programs, and a demonstration of effective six-dimensional cooling of a muon beam. We report the status of the experiment and in particular, the proposal to have MANX follow MICE at the Rutherford-Appleton Laboratory (RAL) as an extension of the MICE experimental program. We describe the economies of such an approach which allow the MICE beam line and much of the MICE apparatus and expertise to be reused.
CLASSE, Ithaca, New York
Funding: Support provided by the US National Science Foundation and the US Department of Energy.
The Cornell Electron Storage Ring has been reconfigured as a test accelerator (CesrTA) for low emittance damping ring R&D for the International Linear Collider (ILC). We are developing low emittance tuning techniques with a goal of 1) achieving a vertical emittance approaching that of the ILC damping rings and 2) Gaining an understanding of the effectiveness of those techniques. We will use gain mapping to characterize beam position monitor (BPM) electrode gains, orbit response analysis to determine BPM button misalignments, betatron phase and coupling measurements to characterize optical errors, and orbit and dispersion measurements to locate sources of vertical dispersion. We are investigating a nondestructive dispersion measurement that depends on exciting a synchrotron oscillation and monitoring the phase and amplitude at each BPM. We have developed the analysis tools necessary to correct magnet and alignment errors. An x-ray beam size monitor is being deployed that will allow us to monitor vertical emittance in real time, allowing for empirical tuning of beam size. We will describe the measurement and correction techniques and show data demonstrating their efficacy.
Euclid TechLabs, LLC, Solon, Ohio
ANL, Argonne
KEK, Ibaraki
Funding: DoE SBIR 2008 Phase II, DE-FG02-07ER84821
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. Using a 20nC bunch train (bunch length of 1.5 mm) at the Argonne Wakefield Accelerator (AWA) facility, we expect to obtain a steady 26GHz output power of 148 MW. The extractor has been fabricated and bench tested along with a 26GHz Power detector. The first high power beam experiments should be performed prior to the Conference. Detailed results will be reported.
IAP/RAS, Nizhny Novgorod
A new two-beam accelerating structure based on periodic chain of rectangular shape multi-mode cavities was suggested recently*. The structure is aimed to increase threshold breakdown surface field and thus to provide a high gradient. This threshold increase is to be brought about by designing cavities of the structure to operate simultaneously in several harmonically-related TMn,n,0 modes, thereby reducing the effective exposure time of the cavity surface to the peak fields. The more number of the operating modes is the more reduction of the exposure time. Unfortunately, a big amount of modes leads to limitation for cavity length and practical limitation of filling factor. In order to avoid this, it is suggested to operate with several TMn,n,l modes with non-zero longitudinal indices. These modes are able to provide the long interaction of a moving bunch with RF fields along the cavity. Such regime requires for the longitudinal index l to be strictly proportional the mode frequency. A cylindrical shape cavity design is also considered.
*S.V. Kuzikov, S.Yu. Kazakov, M.E. Plotkin, J.L. Hirshfield, High-Gradient Multi-Mode Two-Beam Accelerating Structure, Proc. of EPAC’08 Conf., Genoa, June 23-27, 2008, WEPP133.
LBNL, Berkeley, California
Funding: US Department of Energy
Staging Laser Plasma Accelerators (LPA), which is necessary in order to substantially increase the electron beam energy, requires incoupling additional laser beams into accelerating stages. To preserve high accelerating gradient of LPA, it is imperative to minimize the distance that is needed for laser incoupling. Using a conventional mirror with PW-class lasers will require the incoupling distance to be as long as tens of meters due to limitations imposed by laser induced damage of the optic. In this presentation we will describe a new approach for the laser incoupling that is based on planar water jet plasma mirror. The plasma mirror can operate as close as few cm to the focus of the laser thus minimizing the coupling distance. Using a water jet instead of a solid target avoids mechanical scanning of the target surface as well as contamination of the vacuum by laser breakdown debris. Experimental results showing performance of the water jet plasma mirror will be presented and progress in staging experiments will be discussed
MIT/PSFC, Cambridge, Massachusetts
The University of Texas at Austin, Austin, Texas
Funding: US Department of Energy, Office of High Energy Physics
Negative refraction metamaterials (NR MTL) have been developed at microwave, THz, and optical frequencies. At present, microwave MTL's are studied for applications such as microwave filters and patch antennas. Accelerator-relevant applications, such as measuring electron bunch length using its inverse Cherenkov radiation in a NR MTL, have also been proposed. Here we propose a MTL based linear accelerator structure. The MTL is built as an array of complimentary split-ring resonators cut in two metallic plates. The accelerating electron bunch traverses between the plates. The operating mode's properties and standard accelerator parameters (R/Q, accelerating gradient, etc.) of the proposed structure will be reported.
USTC/NSRL, Hefei, Anhui
Funding: the National Nature Science Foundation of China, Grant No. 10375060, 10375061 and 10675116
One of the major concerns in the development of hybrid dielectric-iris-loaded structure is the performance of the used dielectric. The previous dielectric is machinable but the loss tangent is slightly high. So we adopt the new dielectric (Mg-Ca-Ti-O) with loss tangent of about 2·10-4. Because of its high hardness and brittleness, the machining technology and methods are attempted. In this paper, we present a new design of the structure. The model cavities and the coupler for this structure with the new dielectric are investigated experimentally. The experiment results are accorded with the simulated results. In the end, the amplitude and phase shift of the electric field and R/Q of this structure at the operation frequency are even got by a bead-pull experiment.
USTC, Hefei, Anhui
USTC/NSRL, Hefei, Anhui
Funding: National Nature Science Foundation of China, Grant No. 10675116 and 10375060
We present the new experimental results for an X-band (11.42GHz) metallic PBG accelerating cavity. A coupler of a single cavity was fabricated and cold tested. An X-band traveling-wave PBG accelerator was designed based on CST MWS transient analysis. The X-band PBG accelerator is now under construction, future work will focus on the structure to be cold tested and tuned.
CERN, Geneva
The usual approach for the resistive pipe wall assumes the beam moves with the speed of light. For many low energy rings, such as the Proton Synchrotron Booster (PBS), possible performance limitations may arise from non relativistic resistive wall wake fields. In this regime not only the head of the bunch can interact with the tail but also the vice versa holds. In this paper we analyze numerical results showing the resistive wake field calculated from non relativistic impedance models. In addition we analyze the well known two particles model assuming that even the trailing particle can affect the leading one. We observe significant changes in the stability domain.
GSI, Darmstadt
IHEP Beijing, Beijing
In the conventional design of rf linacs, the space-charges are not in three-dimension thermal equilibrium. The space-charge couples the longitudinal and transverse will cause equipartitioning process which causes the emittance growth and the halo formation. In the design of the Chinese Spallation Neutron Source (CSNS) linac], three cases are investigated using the Hofmann stability charts to analysis and optimize the layout. In this paper, we present the equipartitioning beam study of the CSNS Alvarez DTL linac.
KEK, Ibaraki
Crossing different types of resonances is unavoidable for the high beam power operation of the JPARC Main Ring. The ‘lattice’ resonances are cause by the realistic machine imperfection including the field and alignment errors. In addition the ‘space charge’ resonances will lead to the emittance growth. The mechanism of the emittance dilution for the realistic machine imperfection in combination with the space charge effects should be studied in the self-consistent manner. In frame of this report we analyze different coherent modes of the space charge dominated beam at the injection energy for the JPARC Main Ring for some basic operation scenario of the machine. This analysis allows to identify the most dangerous resonances and to understand the effect of the emittance dilution remaining after the resonance correction. The study has been performed by using the PTC{}ORBIT code.
Kyoto ICR, Uji, Kyoto
MPI-K, Heidelberg
Kyoto IAE, Kyoto
HU/AdSM, Higashi-Hiroshima
AEC, Chiba
NIRS, Chiba-shi
JINR, Dubna, Moscow Region
Funding: This work is supported by Advanced Accelerator Development Project of MEXT and the Global COE program "The Next Generation of Physics, Spun from Universality and Emergence".
Transverse laser cooling experiments of 24Mg+ beam have been carried out at S-LSR, which is a small ion storage and cooler ring. According to a simulation, it is expected that under such a condition as the difference of synchrotron and betatron tunes is near integer, synchro-betatron coupling occurs and transverse laser cooling will be achieved*. In order to confirm this situation, the horizontal beam size and momentum spread are measured optically with CCD camera and PAT (post acceleration tube), respectively**,***. CCD camera observes fluorescence from the beam at the laser cooling section. Typical measured horizontal beam size is 0.5mm (1 σ). In some condition, an increase of fluorescence strength is observed, which indicates the beam concentration to the center, where the beam and the laser can interact. PAT is utilized for measurement of a longitudinal beam velocity profile. By application of electric potential to the PAT, the beam velocity is slightly modified. Since only particles which have velocities in a certain region can interact with the laser, the time variation of the florescence during voltage sweep represents the longitudinal velocity profile of the beam.
*H. Okamoto, Phys. Rev. E 50, 4982 (1994)
**B. Wanner et al., Phys. Rev. A 58, 2242 (1998)
***T. Ishikawa, Master's thesis, Kyoto University (2008)
BNL, Upton, Long Island, New York
Three-dimensional electromagnetic simulations have suggested a variety of measures to mitigate the problem of button BPM trapped mode heating. A test fixture, using a combination of commercial-off-the-shelf and custom machined components, was assembled to validate the simulations. We present details of the fixture design, measurement results, and a comparison of the results with the simulations.
BNL, Upton, Long Island, New York
Funding: This work was supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Continuing interest in computing the coupling impedance of cylindrical multi-layer beam tubes led to several recent publications. A novel matrix method is here presented in which radial wave propagation is treated in analogy to longitudinal transmission lines. Starting from the Maxwell equations the solutions for monopole and dipole electromagnetic fields are in each layer described respectively by a 2×2 and 4×4 matrix. Assuming isotropic material properties within one layer, the radially transverse field components at the inner boundary of a layer are uniquely determined by matrix transfer of the field components at its outer boundary. By imposing power flow constraints on the matrix, field matching between layers is enforced and replaced by matrix multiplication. The wall impedance is found as eigen solution to the scalar Helmholtz equation with the additional boundary condition that the longitudinal magnetic field vanishes at the inner beam tube wall. The matrix method is demonstrated via the example of the longitudinal impedance of a multi-layer HOM absorber, involving a ceramic tube with metal coating and an external ferrite layer.
TEMF, TU Darmstadt, Darmstadt
GSI, Darmstadt
Funding: This work is supported by the GSI.
Beam coupling impedances have been identified as an appropriate quantity to describe collective instabilities caused through beam-induced fields in heavy ion synchrotron accelerators such as the SIS-18 at the planned SIS-100 at the GSI facility. The impedance contributions caused by the multiple types of beamline components need to be determined to serve as input condition for later stability studies. This paper will present an approach exploiting the abilities of commercial FDTD wake codes such as CST PARTICLE STUDIO® for a benchmark problem with cylindrical geometry. Since exact analytical formulae are available, the obtained numerical results will be compared. Special attention is paid towards the representation of the particle beam as the source of the EM fields and conductive losses.
The Andrzej Soltan Institute for Nuclear Studies, Centre Swierk, Swierk/Otwock
Funding: Institute for Nuclear Studies, Swierk, Poland
The five parameter method of tuning of biperiodic π/2 linear accelerating structure is presented. The method consists in analytical calculation of the five parameters determining the dispersion relation of such structure: two eigen frequencies fa and fc of accelerating and coupling cavities, the first coupling coefficient kac and two second coupling coefficients kaa and kcc, using five measured dispersion frequencies. Usually the process of tuning is based on sets of 3 cavities however, to include directly also the second coupling coeffients kaa and kcc, one should consider sets composed of five cells. For each such set, using the dispersion relation, a set of five equations for five unknowns is solved by successive elimination of unknowns by expressing them in terms of Fa = fa/f π/2. For Fa one obtains biquadratic equation. Coefficients of this equation are expressed as functions of measured quantities: dispersion phases and frequencies. Knowing Fa all other parameters are easily calculated and the Stop Band SB = fa – fc . In this way, on each step of building up the structure one can control precision of measurements and the Stop Band.
Far-Tech, Inc., San Diego, California
The emittance exchange experiment planned at the Argonne Wakefiel Accelerator facility will rely on a set of cavity-based beam diagnostics in order to map the transport matrix through the beamline. These will include cavity BPM and time-of-flight diagnostics, as well as quadrupole cavity x-y coupling diagnostics. The measurement system will be designed to fit within compact space requirements, while also maintaining a sufficient clear aperture and sensitivity. The RF design of the system, as well as RF cold-test data for the BPM cavities, is presented.
Kyungpook National University, Daegu
Royal Holloway, University of London, Surrey
KEK, Ibaraki
PAL, Pohang, Kyungbuk
UCL, London
SLAC, Menlo Park, California
Fermilab, Batavia
CHEP, Daegu
University of Cambridge, Cambridge
The ATF2 international collaboration is intending to demonstrate nanometer beam sizes required for the future Linear Colliders. The position of the electron beam focused down at the end of the ATF2 extraction line to a size as small as 35 nm has to be measured with nanometer resolution. For that purpose a special Interaction Point(IP) beam position monitor (BPM) was designed. In this paper we report on the features of the BPM and electronics design providing the required resolution. We also consider the results obtained with BPM triplet which was installed in the ATF beamline and the first data from ATF2 commissioning runs.
LBNL, Berkeley, California
CLASSE, Ithaca, New York
Funding: Supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
We report on the optimization of TE Wave measurements at the Cesr-TA ring at Cornell University. The CESR storage ring is currently used as a testbed for technologies to be used in the damping rings of the International Linear Collider. The TE Wave measurement method utilizes capacitive buttons (BPMs) in the ring to excite and detect a propagating electromagnetic wave corresponding to the beampipe's fundamental TE mode. The presence of low-energy electrons along the wave path changes its propagation characteristics, which can be detected by analyzing the received signal. By choosing the machine fill pattern (gaps and bunch trains length) it is possible to modulate the density of the electron cloud and derive information on its rise and fall times by observing the detected signal spectrum. The possibility of circulating both electron and positron beams in the ring enabled us to separate the contribution of primary photoelectrons, which are independent on the circulating particle nature, from the transverse resonant mechanism, which can increase the primary electron density many times over and which only takes place with a circulating positron beam.
LBNL, Berkeley, California
Y.Y. Labs, Inc., Fremont, California
Funding: Work supported by the U.S. Department of Energy under Contract No.
By coupling the emitted synchrotron light into an optical fiber, it is possible to transmit the signal at substantial distances from the light port, without the need to use expensive beamlines. This would be especially beneficial in all those cases when the synchrotron is situated in areas not easily access because of their location, or due to high radiation levels. Furthermore, the fiber output can be easily switched, or even shared, between different diagnostic instruments. We present the latest results on the coupling and dispersion measurements performed at the Advanced Light Source in Berkeley.
IN2P3-LAPP, Annecy-le-Vieux
ICEPP, Tokyo
KEK, Ibaraki
University of Tokyo, Tokyo
Funding: Work supported by the Agence Nationale de la Recherche of the French Ministry of Research (Programme Blanc, Project ATF2-IN2P3-KEK, contract ANR-06-BLAN-0027).
Future linear collider projects like ILC and CLIC will have beam sizes of a few nm. Vibration sources like ground motion can hamper the beam collisions. Relative jitter tolerance between the final focus magnets and the Interaction point (IP) is a fraction of the beam size. The ATF2 project proposes a test facility with a projected beam of 37nm. To measure the beam size with only 2% of error, vertical relative jitter tolerance (above 0.1Hz) between the final doublet magnets (FD) and the IP (with a Shintake beam Size Monitor: BSM) is of the order of 7nm while ground motion is of about 150nm. Thanks to determined adequate instrumentations, investigations were done to design supports for FD. Since ground motion measurements showed that this one is coherent up to 4m, more than the distance between FD and BSM, we chose a stiff support for FD fixed to the ground on its entire surface. Thus, FD and BSM should move in a coherent way. Vibration measurements show that relative motion between FD and BSM is only of 4.8nm and that flowing water in FD does not add any significant jitter. The FD support has been consequently validated on site at ATF2 to be within the vibration specifications.
JAI, Oxford
OXFORDphysics, Oxford, Oxon
Funding: Work supported by the STFC LC-ABD collaboration and the Commission of the European Communities under the 6th Framework Programme Structuring the European Research Area, contract RIDS-011899
We present the latest results on the development of a high power fibre laser system for the laser-wire project on ILC-like laser based beam diagnostics. The laser consists of a crystal oscillator at ~ 1um that can be synchronised to an external frequency reference followed by chirped pulse amplification in ytterbium doped double clad fibre. This system produces 1uJ pulses in an adjustable burst envelope at a chosen frequency. These pulses are further amplified in a large mode area rod type photonic crystal fibre, allowing amplification to high pulses energies whilst maintaining a single spatial mode. The fibre is pumped in pulsed mode by a specially commissioned 400W diode laser fixed at the absorption peak of ytterbium at 976nm, independent of pumping regime. Pumping in a pulsed mode allows the high energies required for laser-wire at MHz repetition rates to be created without the need for active cooling of the laser. The light is frequency doubled to ~500nm to achieve higher laser-wire resolution.
ASCo, Clayton, Victoria
Emittance coupling in the Australian Synchrotron storage ring is currently controlled using a total of 28 skew quadrupoles. The LOCO method was used to calculate the skew quadrupole settings, using measured vertical dispersion and transverse coupling. This information is used to create a calibrated model of the machine, which is then used to calculate the required skew quadrupole settings needed to minimise coupling. This method has thus far achieved encouraging results for achieving ultra low (<2pm) vertical emittance. In this study we seek to explore the validity of the LOCO model based on empirical measurements and possible improvements of this method.
IHEP Beijing, Beijing
JAI, Egham, Surrey
KEK, Ibaraki
ICEPP, Tokyo
SLAC, Menlo Park, California
University of Tokyo, Tokyo
Funding: NSFC 10525525 and 10775154. CNRS-IN2P3 and ANR.
The ATF2 project is the final focus system prototype for ILC and CLIC linear collider projects, with a purpose to reach a 37nm vertical beam size at the interaction point. We report on techniques developed based on simulation studies to adjust the horizontal and vertical beam waists independently in the presence of errors, at two different IP locations where the beam size can be measured with different accuracies. During initial commissioning, we will start with larger than nominal β-functions at the IP, to reduce the effects from higher-order optical aberrations and thereby simplify the optical corrections needed. The first measurements in such intermediate β-configurations are reported.
CLASSE, Ithaca, New York
This paper describes the results of measurements compared with the analysis of errors for a method of determining accelerator Twiss and coupling parameters from the singular value decomposition of beam position monitor data, taken on a turn-by-turn basis for a storage ring in fully coupled transverse beam coordinates. Using the transversely coupled-coordinate formalism described by Billing et al*, the measurement technique expands on the work of Wang et al**, which describes the SVD of the same data under the assumptions of no transverse coupling of the beam parameters. This particular method of data analysis requires a set of BPM measurements, taken when the beam is resonantly excited in each of its two dipole, betatron normal-modes of oscillation
*M. Billing, et al, to be published in Phys. Rev. S T – Accel Beams
**C. Wang, et al, Phys. Rev. S T – Accel Beams 6, 104001 (2003)
CERN, Geneva
Fermilab, Batavia
Funding: Work partly supported by Fermilab, operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy
Through May to September 2008, further beam commissioning of the SPS to LHC transfer lines was performed. For the first time, optics and dispersion measurements were also taken in the last part of the lines, and into the LHC. Extensive trajectory and optics studies were conducted, in parallel with hardware checks. In particular dispersion measurements and their comparison with the beam line model were analysed in detail and led to propose the addition of a “dispersion-free” steering algorithm in the existing trajectory correction program.
IUCF, Bloomington, Indiana
ORNL, Oak Ridge, Tennessee
Funding: Division of Materials Science, U.S. Department of Energy, under contract number DE-AC05-96OR22464 with UT-Battelle Corporation for Oak Ridge National Laboratory
In order to achieve a more robust and optimal performance, the difference between the real machine and its underlying model should be understood and eliminated. Discrepancies between the measuremed and predicted linear optics suggest possible errors of the focusing magnets and diagnostic devices. To find and correct those errors, a widely used method, orbit response matrix (ORM)* approach is applied to the SNS storage ring, which successfully brings the tune deviation from 3% to 0.1%, improves horizontal beta beating from 15% to 3%, and perfectly flattens the orbit. In this article, we discussed the progress and possible future improvements with the SNS ring optics correction.
*J. Safranek, "Experimental determination of storage ring optics using closed orbit response measurements", Nucl. Inst. and Meth. A388, (1997), pg. 27
INFN/LNF, Frascati (Roma)
University of Pisa and INFN, Pisa
SLAC, Menlo Park, California
The novel crab waist collision scheme under test at the DAΦNE Frascati phi-factory finds its natural application to the SuperB project, the asymmetric e+e- flavour factory at very high luminosity with low beam currents and reduced background possibly located at Tor Vergata University. The SuperB accelerator design requires a careful choice of beam parameters to reach a good trade-off between different effects. We present here simulation results for the Touschek backgrounds and lifetime obtained for the latest machine design. Distributions of the Touschek particle losses at the at the interaction region have been tracked into the detectors for further investigations. A set of collimators is foreseen to stop Touschek particles. Their position along the rings has also been studied, together with their shape optimization.
KEK, Ibaraki
The value calculated by using general-purpose computer code SAD for the accelerator is sometimes different from actual measurements. This is because many kinds of factor cause error, like machine error, so we can’t include such error exactly in SAD. Therefore, on the contrary, we consider the model which includes error by using measurement data and derive Hamiltonian from it.
Northern Illinois University, DeKalb, Illinois
ANL, Argonne
Funding: M.R. and P.P. was supported by the US DOE under Contracts No. DE-FG02-08ER41532 with NIU. W.G. and J.P are supported by the U.S. DOE under Contract No. DE-AC02-06CH11357 with ANL.
Transverse to longitudinal phase space manipulation hold great promises, e.g., as a potential technique for repartitioning the emittances of a beam. A proof-of-principle experiment to demonstrate the exchange of a low longitudinal emittance with a larger transverse emittance is in preparation at the Argonne Wakefield Accelerator using a 15 MeV electron beam. In this paper we explore the limiting effects of this phase space manipulation method associated to high order optics and collective effects. A realistic start-to-end simulation of the planned proof-of-principle experiment including jitter studies is also presented.
PPPL, Princeton, New Jersey
Funding: Supported by the U.S. Department of Energy.
Courant-Snyder (CS) theory is generalized to the case of coupled transverse dynamics with two degree of freedom. The generalized theory has the same structure as the original CS theory for one degree of freedom. The four basic components of the original CS theory, i.e., the envelope equation, phase advance, transfer matrix, and the CS invariant, all have their counterparts, with remarkably similar formal expressions, in the generalized theory presented here. The unique feature of the generalized CS theory is the non-commutative nature of the theory. In the generalized theory, the envelope function is generalized into an envelope matrix, and the envelope equation becomes a matrix envelope equation with matrix operations that are not commutative. The generalized theory gives a new parameterization of the 4D symplectic transfer matrix that has the same structure as the parameterization of the 2D symplectic transfer matrix in the original CS theory.
SOLEIL, Gif-sur-Yvette
SOLEIL, the French 2.75 GeV third generation synchrotron light source, was commissioned 3 years ago. Thanks to beam-based measurements, the theoretical model of the storage ring lattice model has been improved. First, the quadrupole lengths in the hard edge model were finely tuned to get good agreement with the experimental measurements of betatron tunes for different optics. Second, the non-linear model was modified to better fit with beam-based on-momentum frequency map measurements. A thick sextupole model has been introduced in addition to the non-linear effect of the fringe field in quadrupoles. Simulated and measured tune shifts with transverse amplitudes are then compared. Finally a coupled machine model has been built thanks to crosstalk closed orbit acquisitions. A comparison with another model which is based on turn by turn beam position monitor data is presented. As a validation check, the coupling effect of the 10 m long HU640 undulator is evaluated through these coupled models.
RCNS, Sendai
KEK, Ibaraki
Tohoku University, School of Scinece, Sendai
We have designed a beam orbit tilt monitor for stabilizing a beam orbit in ATF2. Once we can measure a beam orbit tilt angle with high precision at one point, we can relate this data with the beam position profile at the focal point. This monitor is composed of a single rectangular cavity and waveguides to extract the signal. This monitor can measure the beam orbit tilt with a single cavity. We extract the signal of one basic resonance mode from the cavity. This electric field mode is perpendicular to the nominal beam axis, and is excited by beam tilt. The magnitude of extracted signal gives us the beam tilt data. According to our simulation, the expected sensitivity is about 30 nrad.
UCL, London
Royal Holloway, University of London, Surrey
Cavity beam position monitors (CBPM) made a significant progress in the last 10 years with an entire nano-beamline relying on them being currently commissioned at ATF2 (KEK). The major improvement was the introduction of the mode selective coupling allowing for efficient rejection of unwanted monopole modes. We propose another step towards creating a simple and cost effective CBPM - a cavity using just one coupler (instead of 2 or even 4) to couple out both polarisations of the dipole mode. The x and y signals are then split in the mixing stage of the electronics, so that only one expensive high-frequency electronics front-end is used for both x and y. A very good separation of the x and y signals can be achieved with a reasonable performance mixer assembly. In this paper we present the concept and provide some simulation results proving this processing scheme.
UCL, London
Royal Holloway, University of London, Surrey
Kyungpook National University, Daegu
KEK, Ibaraki
SLAC, Menlo Park, California
Fermilab, Batavia
University of Cambridge, Cambridge
The ATF2 international collaboration is intending to demonstrate nanometre beam sizes required for the future Linear Colliders. An essential part of the beam diagnostics needed to achieve this goal is the high resolution cavity beam position monitors (BPMs). In this paper we report on the S-band system installed in the final focus region of the new ATF2 extraction beamline. It only includes 4 BPMs, but they are mounted on the most critical final focus magnets squeezing the beam down to 35 nm. We discuss both the design and the first operational experience with the system.
SLAC, Menlo Park, California
KEK, Ibaraki
Life Imaging Technology, Palo Alto, California
Funding: Work sponsored by U.S. Department of Energy Contract DE-AC03-76SF00515 and Office of Basic Energy Sciences, Division of Chemical Sciences.
A two-slit interferometer has been installed in the SPEAR3 diagnostic beam line to measure vertical beam size at a dipole source point. The diagnostic beam line accepts unfocused, visible light in a 3.5 x 6.0 mrad aperture so that at the slit location 17 m from the source, the vertical extent of the beam is 100mm. For typical source sizes of sigy~15 um (0.1% emittance coupling) a slit separation of 80 mm produces fringe visibility of order V=0.5. Hence a significant plot of fringe visibility vs. slit separation can be generated to infer source size via Fourier transformation. In this paper we report on the interferometer construction, beam size measurement and potential deficiencies of the system, and compare with theoretical results.
SLAC, Menlo Park, California
ORNL, Oak Ridge, Tennessee
Funding: work supported by the Department of Energy under contract number DE-AC03-76SF00515 and DE-AC05
Fields induced by a beam and penetrated outside the beam pipe can be used for a beam diagnostic. Wires placed in longitudinal slots in the outside wall of the beam pipe can work as a beam pickup. This has a very small beam-coupling impedance and avoids complications of having a feed-through. The signal can be reasonably high at low frequencies. We calculate the beam-coupling impedance due to a long longitudinal slot in the resistive wall and the signal induced in a wire placed in such a slot and shielded by a thin screen from the beam. We present a field waveform at the outer side of a beam pipe, obtained as a result of calculations and measurements. Such kind of diagnostic can be used in storage rings, synchrotron light sources, and free electron lasers, like LINAC coherent light source.
JLAB, Newport News, Virginia
Receivers designed for diagnostic applications range from those having moderate sensitivity to those possessing large dynamic range. Digital receivers have a dynamic range which are a function of the number of bits represented by the ADC and subsequent processing. If some of this range is sacrificed for extreme sensitivity, noise power can then be used to perform two-point load calibrations. Since load temperatures can be precisely determined, the receiver can be quickly and accurately characterized; minute changes in system gain can then be detected, and systematic errors corrected. In addition, using receiver pairs in a balanced approach to measuring X+, X-, Y+, Y-, eliminates systematic offset errors from non-identical system gains, and changes in system performance. This paper describes and demonstrates a balanced BPM-style diagnostic receiver, employing Dicke-switching to establish and maintain real-time system calibration. Benefits of such a receiver include wide bandwidth, solid absolute accuracy, improved position accuracy, and phase-sensitive measurements. System description, static and dynamic modeling, and measurement data are presented.
USTC/NSRL, Hefei, Anhui
Funding: National “985 Project” （173123200402002); National Natural Science Foundation(10875117)
A new high brightness injector is planned to be installed at HLS, NSRL. It is based on a new photocathode RF electron gun. To steer the beam along the optimal trajectory, higher precision controlling of beam position is required. The positional resolution of the BPM system designed for the new RF gun should be higher than 10 μm. A new cavity BPM design is then given instead of old stripline one because of its higher positional resolution. In a normal symmetrical pill-box BPM design, machining tolerance will result in x-y coupling, which will cause cross-talk problem. A novel design is then presented here. To solve the problem before, a position cavity which has a racetrack cross section is used instead of a pill-box one. The ideal resolution of this design could be less than 3 nm.
KEK, Ibaraki
The University of Liverpool, Liverpool
SLAC, Menlo Park, California
One of the goals of the Accelerator Test Facility (ATF) at KEK is to demonstrate ultra-low vertical emittance for linear colliders. Highly precise correction of the vertical dispersion and betatron coupling will be needed to achieve the target of 2 pm (which will be required for ILC). Optics correction and tuning must be supported by an accurate model, which can be developed from a variety of beam measurements, including orbit response to dipole kicks, beta functions at the quadrupoles, etc. Here, we report experimental data and the status of the model and low-emittance tuning.
LAL, Orsay
KEK, Ibaraki
SLAC, Menlo Park, California
Funding: CNRS-IN2P3, ANR
The purpose of ATF2 is to deliver a beam with stable very small spotsizes as required for future linear colliders such as ILC or CLIC. To achieve that, precise controls of aberrations such as dispersion and coupling are necessary. Initially, coupling correction upstream of the final focus line of the ATF2 will be performed with only two skew quadrupoles (SQ) in the extraction line (EXT). We thus first examine the feasability of coupling correction in the EXT with those two SQ, considering several possible coupling error sources. The correction is first based on an algorithm of minimisation of vertical emittance with successive skew scans, implemented in the Flight Simulator code*. We will then investigate new methods to measure and extract the first order four coupling parameters of the beam matrix in order to perform a more direct and accurate coupling correction.
*G. White et al., "A flight simulator for ATF2…", TUPP016 EPAC08
LANL, Los Alamos, New Mexico
IUCF, Bloomington, Indiana
Funding: US DOE #DE-AC52-06NA25396
Orbit response matrix techniques have been used in numerous electron storage rings to elucidate various optical properties of the machines. Such measurements in a long-pulse accumulator ring have unique complications. We present here the techniques and results of such a measurement at the Los Alamos Proton Storage Ring*. We also show the deficiencies in previous models of the ring and a comparison of the beta-functions as fit by the orbit response method to direct measurements by quadrupole magnet variations.
*LA-UR- 08-07694
SLAC, Menlo Park, California
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
KEK, Ibaraki
LAL, Orsay
UMAN, Manchester
CERN, Geneva
Funding: Work supported in part by Department of Energy Contract DE-AC02-76SF00515
Using a new extraction line currently being commissioned, the ATF2 experiment plans to test a novel compact final focus optics design using a local chromaticity correction scheme, such as could be used in future linear colliders*. Using a 1.3 GeV beam of ~30nm normalised vertical emittance extracted from the ATF damping ring, the primary goal is to achieve a vertical IP waist of 35nm. We discuss our planned strategy, implementation details and early experimental results for tuning the ATF2 beam to meet the primary goal. These optics require uniquely tight tolerances on some magnet strengths and positions, we discuss efforts to re-match the optics to meet these requirements using high-precision measurements of key magnet elements. We simulated in detail the tuning procedure using several algorithms and different code implementations for comparison from initial orbit establishment to final IP spot-size tuning. Through a Monte Carlo study of 100's of simulation seeds we find we can achieve a spot-size within 10% of the design optics value in at least 90% of cases. We also ran a simulation to study the long-term performance with the use of beam-based feedbacks.
*"ATF2 Proposal", ATF2 Collaboration (Boris Ivanovich Grishanov et al.)., KEK-REPORT-2005-2, Aug 23, 2005.
The University of Liverpool, Liverpool
Cockcroft Institute, Warrington, Cheshire
The specified vertical emittance for the ILC damping rings is 2 pm. A major objective for the Accelerator Test Facility (ATF) at KEK is to demonstrate reliable operation in this low emittance regime. LOCO is a tool for identifying optics errors in storage rings, based on fitting a lattice model to the measured closed orbit response matrix. This technique can be used to determine corrections to minimise vertical dispersion and betatron coupling, and hence reduce the vertical emittance. So far, efforts to apply LOCO to the ATF to achieve 2 pm vertical emittance have met with limited success. This paper presents the results of simulations aiming to identify possible limitations in the technique. We consider the effects of varying parameters controlling the fit of the lattice model to the measured data, and investigate possible degeneracies (e.g. between skew quadrupole strengths and tilts of the corrector magnets) that may limit the quality of the correction achievable using this technique.
IF-UFRGS, Porto Alegre
The question is whether an anisotropic system of collisionless particles coupled by long-range space-charge forces will equipartition and, if so, how. Results show that collective effects tend to cause an initial beam with strongly nonuniform density to relax, rapidly, to a state that is equlibrium-like. In order to understand the initial dynamical behavior of an anisotropic beams, in particular, to study possible mechanisms of equipartition connected with phase space we have to know how we can compute the variables (volume, area of surface, and area projected) that characterize the anisotropic beam in phase space. The purpose of this paper is to propose one definiton of the anisotropic equipartition. In the state of anisotropic equipartition, the temperature is stationary, the entropy grows in the cascade form, there is a coupling of transversal emittance, the beam develops an elliptical shape with a increase in its size along one direction and there is halo formation along one direction preferential.
ANL, Argonne
Euclid TechLabs, LLC, Solon, Ohio
Technion, Haifa
Funding: DOE
Particle Acceleration by Stimulated Emission of Radiation (PASER) is method of particle acceleration in which a beam gains energy from an active medium through stimulated emission. To obtain the required sitmulated emission for the PASER effect the particle beam intensity is modulated at the frequency corresponding to the energy difference between the levels in which population inversion is achieved in the active medium. We propose to use solid-state active medium based on the Zeeman effect (triplet systems) for the PASER. Modulation of the beam at the frequency of the transition to obtain stimulated emission can be produced by means of a deflecting cavity. A transverse "beamlet" pattern will be produced on the AWA photocathode gun by using a laser mask. The transverse beam distribution will be transformed into a longitudinal beam modulation as the beam passes through the deflecting cavity. In this paper we report on the development of active media and the first RF bench test.
ANL, Argonne
Illinois Institute of Technology, Chicago, Illinois
Euclid TechLabs, LLC, Solon, Ohio
We report on the design of a dual-frequency higher-order-mode dielectric-loaded power extraction set. This power extraction set consists of a dual-frequency dielectric-loaded decelerating structure (decelerator) and two changeable output couplers. In the decelerator, the TM02 mode synchronizes with an ultra-relativistic electron beam at 20.8GHz, and the TM03 mode synchronizes with the beam at 35.1GHz. These frequencies are both harmonics of 1.3GHz, the operating frequency of the electron gun and linac at the Argonne Wakefield Accelerator. The power generated in the unwanted TM01 mode is effectively suppressed for bunch train operation with a novel mode suppression technique. To extract power from the decelerator to standard rectangular waveguides, a TM02-TE10 output coupler was designed with S21 = -0.26dB at 20.8GHz, and a TM03-TE10 output coupler with S21 = -0.66dB at 35.1GHz. 90.4MW and 8.68MW rf power are expected to be extracted from a drive beam with charge of 50nC per bunch, at 20.8GHz and 35.1GHz respectively.
LBNL, Berkeley, California
Funding: This work supported by DARPA and US DoE Office of High Energy Physics under contract DE-AC02-05CH11231.
Ultrashort terahertz pulses with energies in the μJ range can be generated with laser wakefield accelerators (LWFA), which produce ultrashort electron bunches with energies up to 1 GeV* and energy spreads of a few-percent. At the plasma-vacuum interface these ultrashort bunches emit coherent transition radiation (CTR) in a wide bandwidth (~ 1 - 10 THz) yielding terahertz pulses of high intensity**,***. In addition to providing a non-invasive bunch-length diagnostic**** and thus feedback for the LWFA, these high peak power THz pulses are suitable for high field (MV/cm) pump-probe experiments. Maximizing the radiated energy was done by controlling the THz mode quality and by optimizing both the energy and the charge of the electron bunches via pre-pulse control on the driver beam. Here we present the study of three different techniques for pre-pulse control and we demonstrate the production of μJ-class THz pulses using energy-based and single-shot electro-optic measurements.
*W.P. Leemans et al., Nature Physics 2, 696 (2006)
**W.P. Leemans et al., PRL 91, 074802 (2003)
***C.B. Schroeder et al., PRE 69, 016501 (2004)
**** J. van Tilborg et al., PRL 96, 014801 (2006)
PBPL, Los Angeles
UCLA, Los Angeles, California
Manhattanville College, Purchase, NY
The millimeter-scaleμAccelerator Platform (MAP)–essentially a “particle accelerator on a chip”–will ultimately allow for revolutionary medical and industrial applications due to its manageable size and reproducibility. The MAP consists of an electron source and an all-dielectric, laser powered, particle accelerator. The dielectric structure has two slab-symmetric reflecting mirrors with a vacuum gap between them. A periodic coupling mechanism allows laser power to enter transversely through one mirror. This mechanism is analogous to the slots of an optical diffraction grating, with coupling period and vacuum gap equal to the wavelength of the laser (800nm in this study). Work to date has included designing, fabricating and testing a prototype relativistic structure using a patterned gold layer. To go further, we have studied the fabrication techniques and electromagnetic designs of an all-dielectric (non-metallic) structure. Fabrication of the final structure is modeled after Vertical-Cavity Surface-Emitting Lasers (VCSEL) and Distributed Bragg Reflector (DBR) techniques. Preliminary numerical studies of the sub-relativistic structure are also presented.
RadiaBeam, Marina del Rey
UCLA, Los Angeles, California
Manhattanville College, Purchase, NY
Funding: This project is supported by DOE SBIR Grant DE-FG02-08ER85038.
Laser-powered dielectric accelerating structures, which have attracted attention in recent years, trade fabrication challenges and extremely small beam apertures for the promise of high gradients and new bunch formats. The slab-symmetric, periodically-coupledμAccelerator Platform (MAP) is one such dielectric accelerator, and has been under development through a RadiaBeam-UCLA collaboration for several years. Intended applications of the structure include the production of radiation for medical treatments, imaging, and industrial uses. Prototype MAP structures are now being fabricated, and a program has been undertaken to test this device using externally injected electron beams. Plans are underway to install structures in the E163 facility at SLAC. In this paper we describe the testing methods, diagnostics and expectations. Progress and results to date are also presented.
SOLEIL, Gif-sur-Yvette
Diamond, Oxfordshire
Good understanding of instabilities is of great importance in light source rings that provide high current beams. The inherently large machine impedance, which often evolves with continuous changes of insertion devices, enhances collective effects that need to be well controlled to assure the machine performance. The problem is usually not straightforward, as one must quantify short and long range wakes that excite single and multi bunch instabilities, the coupling between instabilities and different planes, as well as Landau effects in arbitrary filling modes. The paper presents the study made on DIAMOND and SOLEIL using the multiparticle tracking codes sbtrack and mbtrack. While sbtrack performs a 6-dimensional single bunch tracking, mbtrack does its direct extension to multibunches. The most recent code development includes a MATLAB version and a high precision Fourier analysis of collective modes. The study emphasises the use of realistic impedance models, either empirically or numerically constructed, and aims to elucidate the relative importance of different physical effects by closely comparing with experimental observations.
EPFL, Lausanne
CERN, Geneva
A detailed knowledge of the beam coupling impedance of the CERN synchrotrons is required in order to identify the impact on instability thresholds of potential changes of beam parameters, as well as additions, removal or modifications of hardware. To this end, an update of the impedance database was performed, so that impedance results from theoretical calculations using new multilayer models, impedance results from electromagnetic field simulations and impedance results from bench measurements can be compiled. In particular, the impedance database is now set to separately produce the dipolar and quadrupolar transverse impedance and wakes that the HEADTAIL simulation code needs to accurately simulate the effect of the impedance on the beam dynamics.
EPFL, Lausanne
INFN/LNF, Frascati (Roma)
CERN, Geneva
BNL, Upton, Long Island, New York
UMAN, Manchester
A detailed knowledge of the beam coupling impedance of the CERN Super Proton Synchrotron (SPS) is required in order to operate this machine with a higher intensity for the foreseen Large Hadron Collider (LHC) luminosity upgrade. A large number of Beam Position Monitors (BPM) is currently installed in the SPS, and this is why their contribution to the SPS impedance has to be assessed. This paper focuses on electromagnetic simulations and bench measurements of the longitudinal and transverse impedance generated by the horizontal and vertical BPMs installed in the SPS machine.
CERN, Geneva
Wendel GmbH, Dillenburg
During the 2007 run with the nominal LHC proton beam, electron cloud has been clearly identified and characterized in the PS using a dedicated setup with shielded button-type pickups. Efficient electron cloud suppression could be achieved with a stainless steel stripline-type electrode biased to negative and positive voltages up to ± 1 kV. For the 2008 run, a second setup was installed in straight section 84 of the PS where the stainless steel was replaced by a stripline composed of an enamel insulator with a resistive coating. In contrast to ordinary stripline electrodes this setup presents a very low beam coupling impedance and could thus be envisaged for long sections of high-intensity machines. Here, we present first comparative measurements with this new type of enamel clearing electrode using the nominal LHC beam with 72 bunches and 25 ns bunch spacing.
Fermilab, Batavia
Funding: work supported by the US Department of Energy
Stability issues of the mu2e proton beam are discussed. These include space-charge distortion of bunch shape, microwave instabilities, head-tail instabilities, as well as electron cloud effects.
Illinois Institute of Technology, Chicago, Illinois
IIT, Chicago, Illinois
Fermilab, Batavia
Funding: This work supported by NSF grant No. 0237162, and DOE SCIentific Discovery through Advanced Computing: Accelerator science and simulation DE-PS02-07ER07-09
The FNAL Booster is a combined-function proton synchrotron with a bunch intensity of ~6·1010 protons; significantly greater than expected in the original design. The injection energy is 400 MeV (gamma factor 1.4), low enough for space charge forces to play a role in beam dynamics. The magnets are used directly as vacuum tanks, so the laminated pole surfaces contribute significantly to impedance. A study of the transverse coupling dependence on beam intensity is presented here. Experimental results are being analyzed using Synergia, a high-fidelity, parallel, fully 3D modeling code that includes both space charge and impedance dynamics. Previously, Synergia has always shown good agreement with experimental data. Our initial studies show that the direct space charge contribution to beam dynamics is too small to account for the increase in the coupling seen experimentally, corroborating analytic results. Parametric studies of the impedance needed to match the measured coupling are being done. Agreement between simulation and experiment should provide an independent measure of the Booster impedance, which has been analytically modeled and calculated elsewhere.
PPPL, Princeton, New Jersey
Funding: Research supported by the U.S. Department of Energy.
The Paul Trap Simulator Experiment (PTSX) is a compact laboratory Paul trap that simulates a long, thin charged-particle bunch coasting through a kilometers-long magnetic alternating-gradient (AG) transport system by putting the physicist in the frame-of-reference of the beam. Results are presented from experiments in which the axial distribution function is modified by lowering the axial confinement barrier to allow particles in the tail of the axial distribution function to escape. Measurements of the axial energy distribution and the transverse density profile are taken to determine the effects of the modified distribution function on the charge bunch. It is observed that the reduced axial-trapping potential leads to an increase of the transverse effective temperature.
SLAC, Menlo Park, California
Funding: Work supported by the DOE under contract DE-AC02-76SF00515.
Facilities for Accelerator Science and Experimental Test Beams (FACET) is a proposed facility at SLAC that would use the initial two-thirds of the linac to transport e+ and e- beams to an experimental region. A principal use of this facility is to identify the optimum method for accelerating positrons in a beam driven plasma wakefield accelerator. To study this, a positron bunch, followed ½ an rf cycle later by an electron bunch, will be accelerated to an asymmetric chicane designed to move the positrons behind the electrons, and then on to the plasma wakefield test stand. A major focus of study was the coupling of jitter of the positron bunch to the electron bunch via linac wakes. Lucretia is a Matlab toolbox for the simulation of electron beam transport systems, capable of multi-bunch tracking and wakefield calculations. With the exception of the lack of support for tracking of electrons and positrons within a single bunch train, it was well suited to the jitter coupling studies. This paper describes the jitter studies, including modifications made to Lucretia to correctly simulate tracking of mixed-species bunch trains through a lattice of magnetic elements and em wakes.
SLAC, Menlo Park, California
A proposed high-brightness synchrotron light source (PEP-X) is under design at SLAC. The 4.5-GeV PEP-X storage ring has four theoretical minimum emittance (TME) cells to achieve the very low emittance and two double-bend achromat (DBA) cells to provide spaces for IDs. Damping wigglers will be installed in zero-dispersion straights to reduce the emittance below 0.1nm. In this paper, we present a preliminary estimation of the threshold of the transverse mode coupling instability(TMCI). Three approaches have been used in the estimation and they agree well with each other.
BNL, Upton, Long Island, New York
Funding: Work performed under auspices of the U.S. Department of Energy under Contract No. DE-AC02-98CH10886 with Brookhaven Science Associates, LLC.
The role of relational database (RDB) technology plays in accelelerator control and operation continues to grow in such areas as electronic log books, machine parameter definitions, and facility infrastructure management. RDBs are increasingly relied upon to provide the official 'master' copy of these data. The services provided by the RDB have traditionally not been 'mission critical'. The availability of modern RDB management systems is now equivalent to that of standard computer file-systems, and thus RDBs can be relied on to supply (pseudo-)realtime response to operator and machine physicist requests. This paper describes recent developments in the IRMIS RDB (1) project. Generic lattice support has been added, serving as the driver for model-based machine control. Abstract physics name service, with introspection has been added. Specific emphasis has been placed both on providing fast response time to accelerator operators and modeling code requests, as well as high (24/7) availability of the RDB service.
CERN, Geneva
The PIMS will accelerate an H- beam from 100 MeV to 160 MeV, the output energy of Linac4. The cell length is constant within each of the 12 seven-cell cavities, but increases from cavity to cavity according to the increasing beam velocity. Its mechanical design is derived from the five-cell normal conducting LEP cavities, which were in operation at CERN for approximately 15 years. Even though the shunt impedance is around 10% lower than for a Side-Coupled Linac (SCL) operating at 704 MHz, the PIMS has the advantage of using the same RF frequency (352 MHz) as all the other accelerating structures in Linac4, thus simplifying and standardising the linac RF system. Furthermore, the simplified mechanical construction of the PIMS, which uses only 84 cells instead of over 400 for the SCL, also reduces construction costs and tuning effort. In this paper we present the electromagnetic design of the PIMS, including the arguments for the choice of a 5% cell-to-cell coupling factor, the shape of the coupling cells, the dimensioning of the wave-guide ports, and the expected field errors during operation.
CERN, Geneva
A one meter long hot prototype of the LINAC4 DTL, built in a collaboration with INFN Legnaro, was delivered to CERN in 2008. It was then copper plated at CERN is and is presently prepared for high-power testing at the CERN test stand in SM18. In this paper we present 2D/3D simulations and the first RF low-power measurements to verify the electromagnetic properties of the cavity and to tune it before the high-power RF tests. In particular, the influence of the post couplers was studied in order to guarantee stabilization of the accelerating field during operation. We present an equivalent circuit model of the DTL, together with a comparison of 3D simulations and measurement results for the hot model.
IAP, Frankfurt am Main
GSI, Darmstadt
For the research program with cooled antiprotons at FAIR a dedicated 70MeV, 70mA proton injector is needed. The main acceleration of this room temperature injector will be provided by six coupled CH-cavities operated at 325MHz. Each cavity will be powered by a 3 MW klystron (6 in total). For the second acceleration unit from 11.7 to 24.3 MeV measurements on a 1:2 scaled model are performed. This tank is now ready for construction and will be used for RF power tests at GSI. The RF power test installations are underway. This paper presents the CH-DTL design and especially the status of the first power cavity.
IAP, Frankfurt am Main
The superconducting CH-cavity is the first multi-cell drift tube cavity for the low and medium energy range of proton and ion linacs. A 19 cell, beta=0.1 cavity has been developed and tested successfully with gradients of up to 7 MV/m. A piezo based fast tuner system has been developped. First horizontal tests of the cavity in a cryo-module with tuner are presented. Additionally, the construction of a new superconducting 325 MHz 7-gap CH-cavity has started. This cavity has an optimized geometry with respect to tuning possibilities, high power RF coupling and minimized end cell lengths. After low power tests it is planned to test this cavity with a 11.4 MeV/u beam delivered by the Unilac at GSI.
INFN- Sez. di Padova, Padova
INFN/LNL, Legnaro (PD)
Consorzio RFX, Associazione Euratom-ENEA sulla Fusione, Padova
The IFMIF-EVEDA RFQ is a 9.8 m long cavity, whose working frequency is equal to 175 MHz. In the base line design the accelerator tank is composed of 9 modules flanged together and a pattern of lateral CF100 flanges allows to host the dummy tuners and the couplers, and a pattern of CF 150 flanges the apertures for vacuum pumping manifolds as well. The construction procedure of each module foresees the horizontal brazing of four half –module length electrodes and then the vertical brazing of two brazed assembly. The progresses in the design and engineering phase, as well the description of all the fabrication phases are reported.
KAERI, Daejon
Funding: This work is supported by MEST of the Korean Government
A 100 MeV DTL as a main accelerating section of the PEFP proton linac is under development. The PEFP proton linac consists of a 50 keV proton injector based on a duoplasmatron ion source, 3 MeV four-vane RFQ, 20 MeV DTL and 100 MeV DTL. The 100 MeV DTL is composed of 7 tanks and each tank is an assembly of 3 sections. The tank is made of seamless carbon steel and inside surface is electroplated with copper. Each drift tube contains an electroquadrupole magnet which is made of hollow conductor and iron yoke with epoxy molding. Following the fabrication of tanks and drift tubes, a precise alignment of drift tubes and field flatness tuning procedure are performed. Currently four DTL tanks out of seven are completed and the rest are under fabrication. The status of development and test results of the fabricated parts are reported in this paper.
TUB, Beijing
Funding: Work supported by National Science Foundation of China (No. 10775079)
On the basis of an X-band 2MeV on-axis standing wave electron linear accelerator, a compact 4MeV/2.5MeV X-band accelerator is being developed at Tsinghua University for non-destructive testing. The single tube can deliver two kinds of x-rays, with dose rate of >100cGy/min@m at 4MeV or >50cGy/min@m at 2.5MeV. To suppress the nearby modes, the coupler is set in the middle of the long coupled cavity chain. The coupled circuit model is applied to analyze the RF characteristic and the dynamic is investigated by CAV code. The prototype has being machined and tuned at our laboratory.
jfhua@mail.tsinghua.edu.cn
ENEA C.R. Frascati, Frascati (Roma)
SPARKLE S.r.l., Casarano (Lecce)
SPARKLE company is setting up in the south of Italy (Casarano) a new cyclotron facility based on a 18 MeV, 150 uA IBA Cyclone 18/9. The aim is to create a multidisciplinary research site for the medical applications of accelerators. The main activity will be the production of standard and new radionuclides, by internal targets and one external beam line. Another opposite beam line has been reserved for low current proton irradiations for radiotherapy studies, and a linac booster between 18 and 24 MeV was designed and built to this end. The beam line, which focuses and matches the beam to the linac, includes a chopping system to synchronize the beam to the pulsed linac and to collect 99% of the beam not synchronous to the linac. The linac uses a 3 GHz SCDTL structure powered by a magnetron modulator system. In the paper we report an overview of the beam line, component design, and tests.