CERN, Geneva
Linac4 is a 160 MeV, 40 mA H- linear accelerator which will be the source of particles for all CERN proton accelerators from 2013. Its construction has started in 2008, as part of a program for the progressive replacement or upgrade of the LHC injectors during the next decade. Linac4 will initially inject into the PS Booster and at a later stage into a 4 GeV Superconducting Proton Linac (SPL), which could ultimately be upgraded to high duty cycle operation. For this reason accelerating structures, rf hardware and shielding of Linac4 are dimensioned for higher duty from the initial phase. Linac4 is normal-conducting, 80 m long and consists of an rf volume ion source, an RFQ, a beam chopping section and a cascade of three different types of 352 MHz accelerating structures. Its main design requirements are high reliability, high beam brightness and low beam loss. The accelerator will be housed in an underground tunnel on the CERN site, which can eventually be extended to the SPL, with equipment installed in a surface building above. The main parameters, the status of the main components, the planning, the project organisation and the civil engineering infrastructure are presented.
Fermilab, Batavia
TRIUMF, Vancouver
Muons, Inc, Batavia
JLAB, Newport News, Virginia
Modern technology allows us to consider operating an 8 GeV Linac in a cw mode to accelerate a high-current H- beam. By using appropriate accumulation rings, the linac could provide simultaneous beams for direct neutrino production, neutrino factories, fixed target experiments, and muon colliders. Several other unique accelerator applications could also be served and improved by the same continuous beam, including studies of energy production and nuclear waste reduction by transmutation, rare muon decay searches, and muon catalyzed fusion. The trade-offs between cw operation compared to pulsed operation that are considered include the maximum rf gradient and corresponding linac length or energy, the rf frequency, rf peak power and coupler requirements, and refrigeration. Methods for accumulating the beam from a cw linac to serve the special needs of the potential future Fermilab programs mentioned above are considered. In this paper we also examine the use of a cyclotron as a source of high current beams to reduce the cost and complexity of the linac front end.
BNL, Upton, Long Island, New York
Kyushu University, Department of Applied Quantum Physics and Nuclear Engineering, Fukuoka
Direct plasma injection scheme has been developed recently for producing and accelerating intense pulsed heavy ion beams with high charge states. This new method uses a combination of a laser ion source and an RFQ linear accelerator and its repetition rate is determined by the laser system. Fixed field alternating gradient (FFAG) accelerator is being focused as a high repetition synchrotron. An integration of these new techniques enables one to produce a large beam power with heavy ion beams. At Ito campus of Kyushu University, a proton FFAG is being installed. We propose to construct a new injector linac for the FFAG. The planned operating parameters are 100 Hz repetition rate, 20 mA of fully stripped carbon beam and 200 MHz operating frequency for the linac.
CEA, Gif-sur-Yvette
The purpose of the IFMIF-EVEDA (International Fusion Materials Irradiation Facility-Engineering Validation and Engineering Design Activities) demonstrator is to accelerate a 125 mA cw deuteron beam up to 9 MeV. Therefore, the project requires that the ion source and the low energy beam transport (LEBT) line deliver a 140 mA cw deuteron beam with an energy of 100 keV and an emittance of 0.25 π .mm.mrad (rms normalized) at the entrance of the RFQ. The deuteron beam is extracted from a 2.45 GHz ECR source based on the SILHI design*. A LEBT with a two solenoids focusing system is foreseen to transport and adapt the beam for the RFQ injection. In order to validate the LEBT design, intensive beam dynamics simulations have been carried out using a parallel implementation of a particle-in-cell 3D code which takes into account the space charge compensation of the beam induced by the ionisation of the residual gas. The simulations results (in particular from the emittance growth point of view) performed under several conditions of gas species or gas pressure in the beam line are presented.
*R. Gobin et al, Rev. Sci. Instrum. 79, 02B303 (2008).
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
KEK, Ibaraki
JAEA, Ibaraki-ken
KEK/JAEA, Ibaraki-Ken
In the design of the very high intensity proton beam of the J-PARC LINAC, precise control of transverse beam dynamics is extremely important for suppression of beam loss. We present results of transverse beam matching and orbit corrections. The linac has 7 matching sections, each of which consists of 4 quadrupole magnets and 4 wire scanners. At 5 matching sections, beam widths at wire scanners are designed to agree with each other. This condition is used in the newly developed algorithm of quadrupole field correction based on a transport model, XAL. Excellent matching performance has been achieved with mismatch factor less than 5% at beam current of 5 to 30 mA. Control of beam parameters from linac into RCS is important for RCS paint injection. Beam studies and comparison to a model have been performed with linac wire scanners combined with multi-wire proportional monitors in the injection line. Orbit corrections with dipole steering magnets based on XAL model have been performed. Orbit deviations were suppressed within 1 mm in horizontal and vertical directions in the whole linac. For these measurements, detailed comparisons to a multi-particle simulation will be shown.
NIIEFA, St. Petersburg
Saint-Petersburg State University, Saint-Petersburg
AN Krylov SRI, St. Petersburg
Funding: Rosatom corp.
We present results of calculations of the neutron generation processes in metal targets induced by protons with energies up to 1 GeV using GEANT4 framework. Results on the neutron yield in large targets and neutron generation as a function of target's dimensions are presented. Energy deposit in the target is also given. The obtained results are to be used for multiplying blanket ADS target design.
KEK/JAEA, Ibaraki-Ken
The J-PARC linac has been successfully commissioned up to its design energy and almost design peak intensity. The unique methods and hardware features adopted in the J-PARC linac, such as the Cs-free H- ion source, macro-pulse generation method, stable one-shot operation method, rf chopper system related with the J-PARC 30mA-RFQ (Radio Frequency Quadrupole linac) design and its operation parameter, one-turn injection method into the following J-PARC RCS (Rapid Cycling Synchrotron), transverse matching using TRACE3D PMQ (Permanent Magnet Quadrupole) elements approximating the fringe field effects of the electro-quadrupole magnets, 2 cavity behavior of SDTL (Separated Drift tube Linac) fed with one Klystron and so on, will be reported in this talk.
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.
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.
BESSY GmbH, Berlin
Funding: Work partially funded by the European Commission in the Sixth Framework Program, contract no. 011935 EUROFEL-DS5, BMBF and Land Berlin.
Most concepts for next generation light sources base on linear accelerators (linac) due to their excellent beam properties. In case of high electron energies and extreme average currents Energy Recovery Linacs (ERL) are mandatory. In this paper we investigate the rf field stability in a generic superconducting, cw operated ERL. By using rf control cavity simulations and longitudinal beam dynamics the influence of rf field stability on the energy recovery process is analyzed. Since the ERL aims for a small net beam loading cavities are operated at a high loaded quality factor. Therefore they are operated at a low bandwidth and are very susceptible to microphonics detuning. We considered the field stability under the influence of limited rf power, mechanical cavity detuning, varying beamloading, synchronization deviations and varying bunch parameters at injection into the linac. The resulting temporal and energy jitter at the linac end will be transformed in the return arc and leads to rf phase deviations on the return path. Implications of varying beam loading on the ERL performance are examined.
Diamond, Oxfordshire
Several modifications have been made to the 100 MeV Diamond Light Source pre-injector linac since initial commissioning in 2005 to improve beam stability and reliability and to increase the scope of operation of the system. Stability enhancements include tighter thermal control of low-level rf electronics, and a modified timing system for gun and linac operation. The linac has been optimised for multibunch filling of the storage ring and for single-bunch top-up operation with gun charge and timing determined by the state of the storage ring fill. Low-energy beam generation has been studied for fault-mode operation using one of the two rf stations, and a study of the options available for Diamond based on routine operation in this mode has been carried out. A summary of operational experience is presented, together with options for future development
NPS, Monterey, California
Niowave, Inc., Lansing, Michigan
MIT, Middleton, Massachusetts
Stanford University, Stanford, Califormia
Funding: This research is supported by the Office of Naval Research and the Joint Technology Office.
The Naval Postgraduate School (NPS) has begun the design and assembly of the NPS Free-Electron Laser (NPS-FEL). As part of this effort, the original dc gun-based injector system is being refurbished and upgraded. As described in the accompanying paper 'Status of the NPS-FEL' (these Proceedings), the overall NPS-FEL design parameters are for 40 MeV beam energy, 1 nC bunch charge, and 1 mA average beam current, in an energy-recovery linac configuration. As we move towards this configuration, the injector system will be incrementally upgraded to add photocathode capability, have a higher final beam energy, and improve the beam brightness, to meet the demands of the overall experimental program. This paper describes the current status of the injector system, the initial set of experiments planned, and the projected upgrade path.
BNL, Upton, Long Island, New York
The Source Development Laboratory (SDL) at the National Synchrotron Light Source (NSLS) is a laser linac facility dedicated for laser seeded FEL and beam physics R&D. The SDL consists of a RF synchronized Ti:sapphire laser, a BNL photocathode RF gun, a four-magnet chicane bunch compressor, and a 300 MeV linac. To further improve the performance of the laser seeded FEL at the NSLS SDL, we have carried out a systematic experimental characterization of the high-brightness electron beam generated by the photocathode RF gun. We will present the experimental studies of both transverse and longitudinal emittance of electron beam as a function of RF gun phase and solenoid magnet for electron beam charge ranging from 350 pC to 1 nC and their influences on FEL output.
JASRI/SPring-8, Hyogo-ken
At the SPring-8 1 GeV linac, a beam current or charge is measured by means of an integrator circuit. A signal from a current transformer is processed into an integrated voltage. The Fast Gated Integrator and Boxcar Averager Module (Stanford Research Systems) is presently used as the integrator. However we plan to expand a dynamic range and an integration time of the integrator. Because the noise level of the present integrator becomes too large for the expansion, we developed a low-noise and high-resolution integrator. Both the present and developed integrators have the same functions such as signal gating, accumulation of analog signal and sample hold. The principal noise of the integrator was found to be a switching noise of the gate switch. To reduce the switching noise a GaAs transfer switch SW-283-PIN (M/A-COM) was adopted as the gate switch. The experimental data of the developed integrator showed 1/10 of the noise level of the present integrator.
KEK, Ibaraki
A new beam-charge interlock system has been developed for radiation safety and machine protection at the KEKB injector linac. Although the previous software-based interlock system was working, it was replaced by the new hardware-based one. The new interlock system restricts the integrated amount of beam charges delivered to four different storage rings (KEKB e+, KEKB e-, PF, PF-AR) at six locations along the linac. When the integrated amount of beam charges exceeds a certain threshold level prescribed at each location, the beam-abort requests are directly sent through a twisted hardwire cable to the safety control system of the linac. The new interlock system boosted its reliability in comparison with the previous system. The full-scale operation of the new interlock system has been started since the end of March 2008. In this report we describe the operational performance of the new beam-charge interlock system.
ORNL, Oak Ridge, Tennessee
The latest operational experiences of the SNS 1 GeV superconducting H- linac will be presented as the beam power is increased and losses and beam halo become more important. The talk will include a comparison of the advantages and disadvantages of superconducting cavities. For example, issues arising from the use of different sets of SC cavities at different times will be described, along with the operational consequences on emittance and halo development.
SLAC, Menlo Park, California
Funding: Work supported by Department of Energy contract DE-AC03-76SF00515.
A 5-cell, normal-conducting, 1.3 GHz, standing-wave cavity was built as a prototype capture accelerator for the ILC positron source. Although the ILC uses predominately super-conducting cavities, the capture cavity location in both a high radiation environment and in a solenoidal magnetic field requires it to be normal conducting. With the ILC requirements of relatively long beam pulse on-time (1 msec at 5 Hz) and high gradient for efficient positron capture (15 MV/m), achieving adequate cavity cooling to prevent detuning was challenging. This paper presents the operational performance of this cavity including its breakdown characteristics as a function of gradient, pulse length and solenoidal magnetic field strength. In addition, these results are compared with those from other normal-conducting cavities at various frequencies