TU Darmstadt, Darmstadt
The Superconducting Linear Accelerator S-DALINAC at the University of Darmstadt (Germany) is a recirculating Linac with two recirculations. Currently acceleration in the Linac section is done on crest of the accelerating field. The recirculation path is operated achromatic and isochronous. In this recirculation scheme the energy spread of the resulting beam in the ideal case is determined by the electron bunch length. Taking into account the stability of the RF system the energy spread increases drastically. In this work we will present a new non-isochronous recirculation scheme which helps canceling out these errors from the rf-control. This scheme uses longitudinal dispersion in the recirculation pathes and an acceleration off-crest with a certain phase with respect to the maximum. We will present beam dynamic calculations which show the usability of this system even in a Linac with only two recirculations and first experimental results
CERN, Geneva
CIEMAT, Madrid
IFIC, Valencia
UPC, Barcelona
EPSC, CASTELLDEFELS
The CLIC Test Facility (CTF3) at CERN was constructed by the CTF3 collaboration to study the feasibility of the concepts for a compact linear collider. The test beam line (TBL) recently added to the CTF3 machine was designed to study the CLIC decelerator beam dynamics and 12 GHz power production. The beam line consists of a F0D0 lattice with high precision BPM's and quadrupoles on movers for precise beam alignment. A total of 16 Power Extraction and Transfer Structures (PETS) will be installed in between the quadrupoles to extract 12 GHz power from the drive beam. The CTF3 drive beam with a bunch-train length of 140 ns, 12 GHz bunch repetition frequency and an average current over the train of up to 28 A will be used. Each PETS structure will produce 135 MW of 12 GHz power at nominal current. The beam will have lost more than 50 % of its initial energy of 150 MeV at the end of the beam line and will contain particles with energies between 67 MeV and 150 MeV. The beam line is completely installed and the PETS structures will be successively added until summer 2011. The paper will describe the first results obtained during commissioning of the beam line and the first PETS prototype.
CERN, Geneva
The CLIC (Compact LInear Collider) design is based on two-beam acceleration concept developed at CERN, where the RF power is generated by a high current electron-beam (Drive Beam) running parallel to the Main Beam. The Drive Beam is decelerated in special power extraction structures (PETS) and the generated RF power is transferred via waveguides to the accelerating structures (AS). The accelerating gradient must be very high (100 MV/m) to reach the high energy for the electron-positron collisions. To facilitate the matching of the beams, components are assembled in 2-m long modules, of few different types. In some of them the AS are replaced by quadrupoles used for the beam focusing. Their alignment and positioning is made by using the signals from the beam-position monitors (BPM). Special modules are needed in damping region or to carry out dedicated instrumentation and vacuum equipment. The module design and integration has to cope with challenging requirements from the different technical systems. This paper reports the status of the engineering design and reports on the main technical issues.
GSI, Darmstadt
ITEP, Moscow
IAP, Frankfurt am Main
To provide for the high beam currents as required of the FAIR project, the GSI Unilac High Current Injector (HSI) must deliver 18 mA of U4+ ions at the end of the prestripper section. With the design existing up to 2008, the RFQ could not reach the necessary beam currents at the RFQ output, as simulations had shown. Furthermore, parts of the existing LEBT must be modified, and a new straight source branch must be added to provide for the full required beam current. As a first step of an HSI frontend upgrade, the RFQ has been modernized in summer 2009 with a completely new electrode design. Commissioning of the HSI has shown that the transmission of the RFQ increased significantly (from 55% to 85% in high current Uranium operation, 95% in medium current operation). As expected, further bottlenecks for the transmission of the complete HSI (matching LEBT-to-RFQ, matching to the Superlens) have been detected. An upgrade of LEBT magnets is foreseen for 2010, the additional linear source branch will follow.
GSI, Darmstadt
NSCL, East Lansing, Michigan
IAP, Frankfurt am Main
Heavy, highly-charged ions (HCI) with only one or few electrons are interesting systems for precision experiments as for instance tests of the theory of quantum electrodynamics (QED). To achieve high precision, kinetic energy and spatial position of the ions have to be well controlled. This is in contradiction to the production process that employs stripping of electrons at high energies by sending relativistic highly-charged ions with still many electrons through matter. In order to match the production at 400 MeV/u with the requirements of the experiments - stored and cooled HCI at low energy - the linear decelerator facility HITRAP has been built at the experimental storage ring (ESR) at GSI in Darmstadt. The ions are first decelerated in the ESR from 400 to 4 MeV/u, cooled and extracted. The ion beam phase spaces are then matched to an IH-structure, decelerated from 4 to 0.5 MeV/u before a 4-rod RFQ reduces the energy to 6 keV/u. Finally, the HCI are cooled in a Penning trap to 4 K. Extensive ion optical calculations were performed and in recent tests up to one million highly-charged ions have been decelerated from 400 MeV/u to 0.5 MeV/u.
HIP, University of Helsinki
CERN, Geneva
To fulfill the mechanical requirements set by the luminosity goals of the CLIC collider, currently under study, the 2-m two-beam modules, the shortest repetitive elements in the main linac, have to be controlled at micrometer level. At the same time these modules are exposed to variable high power dissipation while the accelerator is ramped up to nominal power as well as when the mode of CLIC operation is varied. This will result into inevitable temperature excursions driving mechanical distortions in and between different module components. A FEM model is essential to estimate and simulate the fundamental thermo-mechanical behavior of the CLIC two-beam module to facilitate its design and development. Firstly, the fundamental thermal environment is created for different RF components of the module. Secondly, the first thermal and structural contacts for adjacent components as well as idealized kinematic coupling for the main module components are introduced. Finally, the thermal and structural results for the studied module configuration are presented showing the fundamental thermo-mechanical effects of primary CLIC collider operation modes.
Kyoto ICR, Uji, Kyoto
KEK, Ibaraki
A permanent magnet quadrupole lens with continuously adjustable strength originally designed by Gluckstern was fabricated for a final focus. It consists of five PMQ discs that rotate on their axis, where odd and even numbered discs rotate oppositely but with the same absolute angle. By setting their lengths appropriately, the coupling between x and y components can be minimized. In order to reduce multipole components higher than quadrupole, we adjust positions of magnet wedge pairs. At the same time we improve differences between the magnetic center and the mechanical center of the PMQ discs by measuring harmonics of fields in magnets. In order to carry out the beam test, a high precision movable table for the lens system is also fabricated. This table can evacuate the lens system from the beam line completely without vacuum breaking, which should ease the evaluation of the system at decreased strength region.
IHEP Beijing, Beijing
Work on the Chinese Spallation Neutron Source (CSNS) has been progressing well, including successful prototyping of some of the key components of the facility. The source incorporates an H- linac, with an output energy upgradable from 81 to 250 MeV. The status of the project will be described.
BNL, Upton, Long Island, New York
RLNR, Tokyo
It is commonly preferred to have a short distance between an RFQ and a consequent DTL, however many devices has to be accommodated within a limited space. Our new medium energy beam transport line for proton beam is categorized as one of the severest cases. High field gradient quadrupoles (65 Tm) and newly designed steering magnets (6.5 mm in length) were fabricated considering the cross-talk effects. Also a new half wave length 200 MHz buncher is being studied. In the conference, the electro-magnetic field designs and the measured result will be discussed.
CERN, Geneva
CEA, Gif-sur-Yvette
The construction of Linac4, the new 160 MeV CERN H- injector, has started with the goal of improving the LHC injection chain from 2015 with a new higher energy linac. The low energy front end of Linac4 is based on a 352 MHz, 3-m long Radiofrequency Quadrupole (RFQ) accelerator. The RFQ accelerates the 70 mA, 45 keV H- beam from the RF source to the energy of 3 MeV. The fabrication of the RFQ has started at CERN in 2009 and is presently in progress, aiming at the completion of the full structure by early 2011. The RFQ consists of three modules, one meter each; the fabrication alternates machining phases and stress relief cycles, for copper stabilization. Two brazing steps are required: one to assemble the four parts composing a module and a second one to install the stainless steel flanges. In order to monitor that the tight mechanical and alignment budget is not exceeded, metrology measurements at the CERN workshop and RF bead-pull measurements are performed during the fabrication process. In this paper we report results obtained during the machining and the assembly of the first two modules of the Linac4 RFQ and data produced by RF measurements performed during their fabrication.
ORNL, Oak Ridge, Tennessee
University of Tennessee, Knoxville, Tennessee
In radio frequency quadrupole (RFQ) structures, the fundamental quadrupole mode is used for focusing and acceleration of ion particles. The fields are maintained to have negligible interference with other unwanted modes of the structure using mode suppressors of different types especially in vane type RFQs that require dipole mode separation. The field distribution on the beam axis is usually measured and referenced using multiple loop-type magnetic probe antennas on the wall along the structure. Since the structures are equipped with many slug tuners on the outer wall for correction of fields, the tuner-probe interference can be a concern. In order to investigate the mode separation properties of the commonly used mode suppressors and the accuracies in field distribution with respect to localized perturbation due to the tuners, a systematic 3D simulation was carried out using a full-scale model of the SNS RFQ.
LBNL, Berkeley, California
Project X is a proposed multi-MW proton facility at Fermi National Accelerator Laboratory. It is the key element for future accelerator complex development intended to support world-leading High Energy Physics (HEP) programs. The Project X front-end would consist of H- ion source(s), a low-energy beam transport (LEBT), radio-frequency quadrupole (RFQ) accelerator(s), and a medium-energy beam transport (MEBT). To support current and future HEP experiments at Fermilab, a CW RFQ is required. One of the chosen RFQ designs has a resonant frequency at 325 MHz. The RFQ provides bunching of the 10 mA H- beam with acceleration up to 2.5 MeV and wall power losses of less than 250 kW. LBNL is currently developing the early designs for various components in the Project X front-end. The RFQ design concept and the preliminary RF and thermal analyses are presented here.
KAERI, Daejon
A Radio Frequency Quadrupole (RFQ) has being desinged for the post-acceleration of radio isotope beams from a radio isotope beam production system such as an isotpe separation on line (ISOL) or an in-flight separation. For simple and efficient beam acceleration, a chrage breeding system such as an electron cyclotron resonance ion source (ECRIS) or electron beam ion source (EBIS) The RFQ will operate at a resonant frequency of 70MHz at cw mode, and accelerate the beams to 300keV/nucleon. In the conference we will present the design of the RFQ.
INFN/LNL, Legnaro (PD)
The TRASCO RFQ will accelerate the 40 mA cw proton beam from the ion source to the energy of 5 MeV, for the production of intense neutron fluxes for interdisciplinary applications. The RFQ is composed of six modules of 1.2 m each, assembled by means of ultra high vacuum flanges. The structure is made of OFE copper and is fully brazed. RFQ modules were manufactured in CINEL Scientific Instruments S.r.l. while chemical treatments and brazing were done at CERN. This paper covers the brazing results of the last four modules and low power tests performed for preparation to the high power test of the first electromagnetic segment.
IHEP Beijing, Beijing
The CSNS is a spallation neutron research facility being built at Dongguan in Guangdong Province [1]. The 324MHz Alvarez-type Drift Tube Linac (DTL) will be used to accelerate the H- ion beam from 3 to 80.0 MeV with peak current 15mA. The R&D of a prototype structure at the low energy section of DTL is taking place at IHEP. The first unit tank 2.8m in length for the energy range from 3 to 8.88 MeV and 28 drift tubes containing electromagnetic quadrupoles are developed. This paper introduces the R&D status of the tank and 28 drift tubes. The measurement results of the focusing quadrupoles are also presented.
IHEP Beijing, Beijing
In the 324MHz CSNS Drift Tube Linac, the electromagnetic quadrupoles will be used for transverse focusing. The R&D of the quadrupole for the lower energy section of the DTL is a critical issue because the size of the drift tube at this section is so small that it is not possible to apply the conventional techniques for the fabrication. Then the electromagnetic quadrupoles containing the SAKAE coil and a drift tube prototype containing an EMQ have been developed. In this paper, the details of the design, the fabrication process, and the measurement results for the quadrupole magnet are presented.
IHEP Beijing, Beijing
In the China Spallation Neutron Source project [1], the 324HMz Alvarez-type DTL will be used to accelerate the H- ion beam from 3 to 80.0MeV. The DTL linac has been designed as four tanks and the electromagnetic quadrupoles will be used for the transverse focusing inside the drift tubes. The geometries of the DTL cells were optimized by using SUPERFISH and the beam dynamics simulation was performed with PARMILA code. In this paper both the physical design and the engineering designs are presented.
IMP, Lanzhou
The separated function DTL in SSC(Separated Sector Cyclotron)-linac is being designed. According to the design requirements, 238U34+ ions are accelerated from 0.143MeV/u to 0.976MeV/u throught the DTL. The method coupling DAKOTA(Design Analysis Kit for Optimization and Terascale Application) and beam simulation code BEAMPATH is used to analyze tolerance of the structure. The tolerance of beam parameters to various type of random errors and misalignment are studied with Monte Carlo simulation,so as to de ne the engineering tolerance and alignment. In this paper, the beam dynamics simulation and the tolerance analysis of the SSC-linac are presented.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
Transverse emittance growth was observed in J-PARC Drift Tube Linac (DTL). In order to suppress the growth, we searched for optimum parameters at MEBT1, by measuring transverse emittance using four wire scanner monitors at the exit of DTL. At 15 mA peak beam current in Dec 2009, horizontal and vertical rms emittance was reduced by 12 % and 10 %, respectively, by setting the amplitudes of the first and second bunchers to 120 % and 90 % with respect to the designed settings. The resulting normalized horizontal and vertical emittance was 0.230 and 0.205 pi mm mrad. At 20 mA in Jan 2010, horizontal and vertical rms emittance was reduced by 17 % and 10 %, respectively, by setting the amplitudes of the first and second bunchers to 110 % and 80 % with respect to the designed settings. The resulting normalized horizontal and vertical emittance was 0.273 and 0.253 pi mm mrad. At 15 mA, we further reduced the horizontal and vertical emittance to 0.171 and 0.200 pi mm mrad by increasing the eighth quadruple magnet field at MEBT1 by 20 % to the designed value. The measured transverse emittance dependence on buncher electric field and quadruple magnetic field will be compared with simulation.
ORNL, Oak Ridge, Tennessee
We present practical aspects of measuring beam profiles and applications using the profile data. Standard applications include (RMS) beam size calculation, Courant-Snyder parameter calculation, and beam matching. Each application becomes increasingly model dependant relying upon results of the preceding application. Because of the cascade of interdependence, of obvious concern is measurement error which propagates throughout the calculations. Also important is the accuracy of the beam model used to make calculations from measurement results; doubly so for matching where the model both estimates Courant-Snyder parameters and predicts new magnet strengths. Not as obvious are complications introduced by the long pulse nature of the SNS linac. Currently, we can sample the beam only through a 50 microsecond window along a macro pulse lasting up to 1 millisecond. Consequently the measurements available are not necessarily representative of the whole beam. Presented are quantitative results on measurement error, model accuracy, and sampling location, how these quantities vary along the linac, and the ramifications on matching techniques.
DESY Zeuthen, Zeuthen
INRNE, Sofia
The Photo-Injector Test Facility at DESY in Zeuthen, PITZ, is dedicated to development of high brightness electron sources for linac-based FELs like FLASH and the European XFEL. A key parameter to judge on the beam quality for an FEL is the transverse phase space distribution, wherefrom the PITZ beamline is equipped with three Emittance Measurement Systems as the only dedicated to that apparatus. In 2010 the diagnostics has been upgraded with a module for tomographic reconstruction comprising three FODO cells, each surrounded by two observation screens. The anticipated advantages of tomographic measurements are improved resolution for low charge beams and ability to evaluate both transverse planes simultaneously. Major operational challenges are the low beam energies the module will be used with - 15 - 30 MeV, strong space charge effects for high bunch charges and, consequently, difficulties to match the beam into the optics of the lattice. This contribution presents studies on the performance of the module for different initial conditions as bunch charge and temporal laser pulse shape. Influence of residual noise on the quality of the reconstructed phase space is discussed.
ORNL, Oak Ridge, Tennessee
This talk will give an overview of future demands of fast choppers with fast rise/fall time to reduce the beam extinction ratio further.
CERN, Geneva
ESS, Lund
Linac4 will be the new linear accelerator of the CERN accelerator chain delivering H- ions at 160 MeV from 2016. The increased injection energy compared to the 50 MeV of its predecessor Linac2, combined with a H- charge-exchange injection, will pave the way to reach ultimate goals for the LHC luminosity. Extensive commissioning for Linac4 is planned for the coming years. For this purpose, the beam will be studied after the exit of Linac4 in a straight line ending at the Linac4 dump, equipped with various beam instruments. An almost 180 m long transfer line will guide the beam to the charge exchange injection point at the entry of the Proton Synchrotron Booster. About 50 m upstream of this point, two measurement lines will be upgraded to perform transverse emittance measurements as well as energy and energy spread measurements of the Linac4 beam. A detailed description of the beam measurement principles and setups at these three Linac4 diagnostics lines related to distinct Linac4 commissioning phases will be given.
LLNL, Livermore, California
Compact dielectric wall (DWA) accelerator technology is being developed at the Lawrence Livermore National Laboratory [1]. The DWA accelerator's beam tube is a stack of high gradient insulators, consisting of alternating layers of insulators and conductors. Characteristically, insulators' surface breakdown thresholds go up as the applied voltages' pulse width goes down. To attain the highest accelerating gradient in the DWA accelerator, the accelerating voltage pulses should have the shortest possible duration. This can be done by appropriately timing the switches in the transmission lines, which feed the continuous HGI tube. The accelerating voltage pulses arrive at the accelerator axis along the beam tube at different times so as to appear to the charged particle bunch as a traveling accelerating voltage wave. We have studied the beam transport in a baseline DWA configuration by performing PIC simulations using the 3-D, EM PIC code, LSP [2]. Sensitivity of the output beam parameters to the switch timing will be presented. In addition to the baseline configuration, various alternative focusing schemes will be discussed.
[1] G. J. Caporaso, Y-J Chen and S. E. Sampayan, "The Dielectric Wall Accelerator", Rev. of Accel. Sci. and Tech., vol. 2, p. 253 (2009).
[2] Alliant Techsystems Inc., http://www.lspsuite.com/.
Fermilab, Batavia
Northern Illinois University, DeKalb, Illinois
Next generation accelerators, such as high-energy physics colliders and light sources, will be interested in phase space manipulations techniques within two degrees of freedom for enhanced performance. At the Fermilab A0 Photoinjector, a proof-of-principle experiment to demonstrate the exchange of the transverse and longitudinal emittances is ongoing. The emittance exchange beamline consists of a 3.9 GHz normal conducting deflecting mode cavity inserted between two doglegs. Electron bunches of varying charge levels from 250 pC to 1 nC and energy of 14.3 MeV are consistently sent through the exchange beamline. In this paper we will present our latest results on the effects of charge on the emittance exchange process.