CERN, Geneva
The Compact Linear Collider (CLIC) is studied by a growing international collaboration. Main feasibility issues should be demonstrated until 2010 with the CLIC Test Facility (CTF3) constructed at CERN. The CLIC design parameters have recently been changed significantly. The rf frequency has been reduced from 30 GHz to 12 GHz and the loaded accelerating gradient from 150 MV/m to 100 MV/m. The consequences and logic of these changes will be reviewed and coherent parameter sets for a 3 TeV and a 500 GeV machine will be presented. The status and perspectives of the CLIC feasibility study will be presented with a special emphasis on experimental results obtained with CTF3 towards drive beam generation as well as progress on the high gradient accelerating structure development. The frequency change allows using high power X band test facilities at SLAC and KEK for accelerating structure testing at 11.4 GHz. The design gradient of 100 MV/m has been achieved in a recent test at SLAC with a very low breakdown-rate.
CLS, Saskatoon, Saskatchewan
Funding: CLS supports the upgrade of the 250 MeV linac.
The Canadian Light Source (CLS) 250 MeV linac, originally constructed in the 1960's, serves as the injector for the 2.9 GeV synchrotron radiation facility[1] located on the University of Saskatchewan campus. The linac has operated reasonably well for routine operation of the light source. However, the long-term goal of operating the CLS storage ring in top-up mode will place increased demands on the linac for stability and availability that cannot be met with the existing system. Consequently, an upgrade is planned over the next two years to get higher beam stability, reliability and reproducibility. In this paper, the existing linac system will be described and the planned upgrade will be reported.
TRIUMF, Vancouver
Victoria University, Victoria, B.C.
TRIUMF, in collaboration with university partners, proposes to construct a megawatt-class electron linear accelerator (e-linac) as a driver for U(γ,f) of actinide targets for nuclear astrophysics studies, and 9Be(γ,p)8Li for beta-NMR materials science. The e-linac is part of a broader proposal for an expansion of the TRIUMF rare isotope beams capability through a new facility to be named ARIEL. The e-linac design and prospects for funding are elaborated.
CEA, Bruyeres-le-Chatel
The design of a 15 MeV, 2 kA peak current, electron accelerator for the DEINOS project is presented. It is dedicated to a new radiographic facility. The accelerator design is based on a dc photo-injector and a rf superconducting linac. Up to twenty electron micro-pulses, 100 ps time duration and 200 nC bench charge are emitted at 352 MHz repetition rate from a CS2Te photocathode and accelerated to 2.5 MeV in the dc diode before injection into a superconducting linac. A general description of the main accelerator components and the beam dynamics simulations are presented.
CEA, Gif-sur-Yvette
CERN, Geneva
LAL, Orsay
The CLIC project based on the innovative Two Beams Acceleration concept is currently under study at CTF3 where the acceleration of a probe beam will be demonstrated. This paper will describe in details the status of the probe beam linac called CALIFES. This linac (170 MeV, 1 A) is developed by CEA Saclay, LAL Orsay and CERN. It will be installed in the new experimental area of CTF3 to deliver short bunches (1.8 ps) with a charge of 0.6 nC to the CLIC 12 GHz accelerating structures. The linac consists in an rf gun triggered by a laser beam, three LIL sections for bunching and acceleration, a beam diagnostic system and a single klystron with a pulse compression cavity and a dedicated rf network. We report new results of beam dynamic simulation considering the new CLIC parameters. We will give an estimation of the energy and phase deviation over the bunch train (140 ns long) by transient calculation of beam loading. Details about the fabrication of the rf gun, the cavity BPM, the HV modulator and the power phase shifter will be described. New results from laser system studies are discussed. The construction of CALIFES and the start of commissioning will be also reported.
ELSA, Bonn
DESY, Hamburg
Since 1966 a Varian factored injector is in use at the accelerator complex of the University of Bonn serving several experiments to investigate the subnuclear structure of matter. This injector will have to be replaced for several reasons. The new injector will operate in a single bunch mode of 2 A beam current and is currently under construction. Also a 2 μs long pulse mode of 500 mA beam current will be available for ordinary accelerator operation for hadron physics experiments. Produced by a pulsed thermionic 90 kV gun, compression of the pulses is achieved by a 500 MHz prebuncher as well as one β-matching travelling wave buncher running at the linac frequency of 3 GHz. The injector has been designed and optimised using the software package EGUN and numerical simulations based on the paraxial differential equations. The single bunch mode will allow to investigate single bunch instabilities within the Helmholtz alliance "Physics at the Terascale".
TU Darmstadt, Darmstadt
Funding: Work supported by the DFG through SFB 634
After 15 years operating the S-DALINAC the design quality factor for the superconducting cavities has still not been reached. Currently, the cavities are heat treated at 850 C in an UHV furnace installed in Darmstadt three years ago. We will report about the furnace, the heat treatment procedure and the results of subsequent surface resistance measurements. Prior to the heat treatment the field flatness of some of the 20 cell elliptical cavities has been measured, leading to unexpected operational findings to be reported: operating and frequency-tuning the cavity for several years led to heavy distortions of the field flatness. This might be an indication that the frequency tuning of the cavity done by compressing the cavity longitudinally, does not act uniformly on each cell even though the cavity is only supported at the end cells. The paper will close with a status report on machine operation and modifications undertaken during the last two years.
TU Darmstadt, Darmstadt
TEMF, TU Darmstadt, Darmstadt
IKP, Mainz
ANL, Argonne
Funding: Work supported by the DFG through SFB 634
At the superconducting Darmstadt linear accelerator S-DALINAC currently two upgrades of the injector are underway: The current upgrade for the injector mainly involves the superconducting rf part. In order to increase the maximum current from 60 uA to 150 or 250 uA the power coupler design had to be modified, resulting in major changes in the whole cryo-module. Second, an additional polarized electron source (SPIN) has been set-up at an offline test area. There, the polarized electrons are produced by photoemission at a strained GaAs cathode on a 100 kV platform. The test beam line includes a Wien filter for spin manipulation, a Mott polarimeter for polarization measurement and additional diagnostic elements. We will give an overview over the project, report on the status and present first measurement results including the proof of polarisation.
DESY, Hamburg
The Linac II at DESY consists of a 6A/150kV DC electron gun, a 400 MeV primary electron linac, a 800 MW positron converter, and a 450 MeV secondary electron/positron linac. The Particle Intensity Accumulator (PIA) is also considered part of the injector complex accumulating and damping the 50 Hz beam pulses from the linac and transferring them with a rate of 6.25 Hz or 3.125 Hz into the Synchrotron DESY II. The typical positrons rates are 6·1010/s. DESY II and Linac II will serve as injectors for the two synchrotron light facilities PETRA III and DORIS. Since PETRA III will operate in top-up mode, Linac availability of 98-99% are required. DORIS requires positrons for operation. Therefore during top-up mode positrons are required for both rings. In order to maintain its reliability over the operation time of the new facility PETRA III, the major components of the linac were renovated. Some components were redesigned taking into account experience from 30 years of operation.
KEK, Ibaraki
GUAS/AS, Ibaraki
MELCO SC, Tsukuba
IHEP Beijing, Beijing
The 8 GeV Linac at KEK provides electrons and positrons to Photon Factory (PF) and B-Factory (KEKB). Simultaneous top-up injections have been considered for both PF and KEKB rings in order to improve the injection efficiency and the stability. Fast beam-switching mechanisms are being implemented, upgrading the timing and control systems. While the present system provides precise timing signals for 150 devices, many of the signals will be dynamically switched using an event system. A new scheme has been developed and tested to enable double-fold synchronization between rf signals. Fast controls of low-level rf, beam instrumentation, a kicker, a gun, and beam operation parameters will also be upgraded.
KEK, Ibaraki
KEKB injector linac supplies electron and positron beams to the KEKB storage rings and the synchrotron radiation facility rings (PF, AR) as well. Injection modes to these four destinations are switched by inserting and extracting positron generation target, changing magnet parameters and acceleration rf phases. To enable pulse-by-pulse switching in three out of the four modes, a pulse bend and pulse steerings are introduced. For DC quads and DC steerings, compatible beam-optical settings for beams of different beam-energy profiles are introduced. We have been performing beam studies to establish the pulse-by-pulse mode switching for daily beam operation. This paper describes a scheme for the mode switching and reports on an achievement of the beam studies.
KEK, Ibaraki
The KEKB linac continuously injects 8 GeV electron and 3.5 GeV positron beams into the KEKB rings: HER(high energy ring) and LER(low energy ring). The energy spread of the 8-GeV electron beam, which is accelerated to an 1.7 GeV 180-degree arc section and reaccelerated after this arc to a final energy of 8 GeV, is optimized by adjusting rf acceleration phases so as to assure efficient injections. When rf phases are slightly changed or drifted for some reasons, the beam not only shows larger energy spreads but also indicates two clusters on a beam profile monitor located at large energy dispersions. In this connection, a longitudinal beam profile was measured after the arc section with a streak-camera system utilizing an OTR(Optical Transition Radiation) bunch monitor. The observed bunch shape clearly shows a two-microbunch structure, suggesting that it could be generated in the arc section. Various experimental data as well as some CSR-related speculations are presented.
KEK, Ibaraki
KEK injector linac provides an injection beam for four storage rings, KEKB high energy electron ring(HER), low energy positron ring(LER), PF-AR electron ring, and PF electron ring. The injection beams for these rings have different energies and intensities. Recently, a requirement of simultaneous injection among these rings arises to make a top-up injection possible. Magnetic fields of DC magnets to confine the beam to the accelerating structures can not be changed between pulse to pulse, although the beam energy can be controlled by fast rf phase shifters of klystrons. This implies that a common magnetic field of the bending magnets and the quadrupole magnets should be utilized to deliver beams having different characteristics. Therefore, we have designed multi-energy optics for the KEKB-HER electron ring(8 GeV, 1 nC/pulse), the PF electron ring(2.5 GeV, 0.1 nC/pulse), and the KEKB-LER positron ring(3.5 GeV, 0.4 nC/pulse). We present a performance of the multi-energy injector linac.
KEK, Ibaraki
The KEK electron/ positron linac is a 600 m long linear accelerator with the maximum energy 8 GeV electron and 3.5 GeV positron, and it is used as an injector for 4-rings (KEKB e-/ e+, PF, PF-AR). To increase the operation efficiency, we have an injector upgrade plan for a simultaneous injection operation. In this paper, we will present the operation scheme and the progress of upgrade project.
IHEP Beijing, Beijing
After the major upgrade in 2005, the BEPC injector linac has been commissioning and working smoothly for more than two years. A 2.1 GeV, 66 mA positron beam at the linac end has been obtained, and the highest injection rate into the ring of 80 mA/min. at 50 pps is reached, much higher than the design goal of 50 mA/min. The machine is working stable, the mal function was about 2% in the past two years, including the system test and the commissioning.
CERN, Geneva
An automatic beam steering application for CTF 3 is being designed in order to automatize operation of the machine, as well as providing a test-bed for advanced steering algorithms for CLIC. Beam-based correction including dispersion free steering have been investigated. An approach based on a PLACET on-line model has been tested. This paper gives an overview of the current status and the achieved results of the CTF3 automatic steering.
CERN, Geneva
The CERN CLIC test facility (CTF3) aims at assessing the feasibility of the future multi-TeV Compact Linear Collider (CLIC). The CTF3 Tail Clipper Collimator (TCC) will serve to adjust the bunch train length of the beam extracted from the combiner ring, in combination with a fast kicker magnet. In addition, the TCC will operate, when required, as an internal beam dump. The challenge of the TCC design is to meet the requirements of both collimator and dump operational modes for a low energy e- beam (100-300 MeV) of 35 A peak intensity. The TCC collimator will be installed at the end of 2008 in the TL2 transfer line of CTF3. This paper describes the final design of the TCC and the main issues related to its integration in the line.
NSC/KIPT, Kharkov
Funding: The present work is supported by the STCU project #P233
The accelerator driven subcritical assembly facility is under development in the National Science Center Kharkov Institute of Physics and Technology. The important component of the facility is an electron linac with energy of particles of 100-200 MeV and average beam current of 1 mA. In this paper we focus on the S-band electron linac design. The accelerator scheme includes the injector based on evanescence waves, rf chopper, five accelerating structures and energy compression system. The results of calculation of accelerating structure performances and linac systems are considered in the paper
NSC/KIPT, Kharkov
The results of beam dynamic simulation in an S-band injector that can be used for creation of the powerful electron linac are presented in the report. The injector consists of a diode electron gun with beam current of up to 2 A at energy of electrons of 25 keV, the klystron type prebuncher and the three cavity buncher. In the buncher, due to the special choice of eigen frequencies of resonators, maximal amplitude of the field on the axis of resonators exponentially increase from the first (downstream of the beam) resonator to the last resonator. It allows effective bunching the intensive electron beam and accelerating it to relativistic velocities. For providing of low transversal beam emittance the injector is placed in the external magnetic field. The injector provides more than 1 A of beam current at particle energies of about 1 MeV. Attention is paid to research of transients and stability of injector work.
SAIC, Los Alamos, New Mexico
LANL, Los Alamos, New Mexico
LLNL, Livermore, California
NSTec, Los Alamos, New Mexico
Voss Scientific, Albuquerque, New Mexico
The DARHT-II accelerator produced a 2 kA, 17 MeV beam over a 1600 ns flattop. After exiting the accelerator, the long pulse is sliced into four short pulses by a kicker and quadrupole septum and then transported and focused on a target for conversion to bremsstrahlung for radiography. We describe the initial commissioning tests of the kicker, septum, transport, and multi-pulse converter target. The results of beam measurements made during the commissioning of the accelerator downstream transport are described. Beam optics simulations of the commissioning results are described.
SLAC, Menlo Park, California
Funding: US DOE
This paper reports the design and test results on novel topology, high-efficiency, and low operating temperature, 1,320-watt power modules for high availability power supplies. The modules permit parallel operation for N+1 redundancy with hot swap capability. An embedded DSP provides intelligent start-up and shutdown, output regulation, general control and fault detection. PWM modules in the DSP drive the FET switches at 20 to 100 kHz. The DSP also ensures current sharing between modules, synchronized switching, and soft start up for hot swapping. The module voltage and current have dedicated ADCs (>200 kS/sec) to provide pulse-by-pulse output control. A Dual CAN bus interface provides for low cost redundant control paths. Over-rated module components provide high reliability and high efficiency at full load. Low on-resistance FETs replace conventional diodes in the buck regulator. Saturable inductors limit the FET reverse diode current during switching. The modules operate in a two-quadrant mode, allowing bipolar output from complimentary module groups. Controllable, low resistance FETs at the input and output provide fault isolation and allow module hot swapping.
LBNL, Berkeley, California
Funding: This work was supported by the Office of Science, U.S. Department of Energy under DOE contract number DE-AC03-76SF00098.
In this paper, we will report on a billion macroparticle simulation of beam transport in a free electron laser (FEL) linac for future light source applications. The simulation includes a self-consistent calculation of 3D space-charge effects, short-range geometry wakefields, longitudinal coherent synchrotron radiation (CSR) wakefields, and detailed modeling of rf acceleration and focusing. We will discuss the needs and the challenges for such large-scale simulation. Application to the study of microbunching instability in the FEL linac will also be presented.