SLAC, Menlo Park, California
Submitted for the Sector 0-20 Core Team. The SLAC 3km linear electron accelerator has been cut at the two-thirds point to provide beams to two independent programs. The last third provides the electron beam for the Linac Coherent Light Source (LCLS), leaving the first two-thirds available for FACET, the proposed new experimental facility for accelerator science and test beams. In this paper, we describe this separation and several projects to prepare the linac for the FACET experimental program.
KEK, Ibaraki
The KEKB-factory will be upgraded for 40 times higher lumnosity (SuperKEKB). The injector linac is required to increase the beam intensities (e-:1nC -> 5nC, e-:1nC -> 4nC) and reduce the emittances (e-:300 -> 20 um, e+: 2100 -> 10 um ) for the SuperKEKB. A photo-cathode RF gun will be introduced to generate the high-intensity and low-emittance electron beams. A positron damping ring will be constructed to reduce the emittance. A new matching device (a flux concentrator or a superconducing magnet) and an L-band capture section will be introduced to increase the positron intensity. Beam line layout down to the damping ring will be rearranged to have sufficient beam acceptance considering the positron emitttance. This paper describes details of the upgrade scheme of the injector linac.
LASTI, Hyogo
Sub-THz coherent synchrotron radiation (CSR) from the SPing-8 linac beam was observed after the injection into the NewSUBARU storage ring. The beam from the linac has much sorter bunch length than the stationary stored bunch in the ring. It had been reported that the injected linac beam emits CSR at just after the injection until it diluted to a longer bunch by its energy spread. However we observed CSR at after more revolutions. At some tens of microseconds after the injection we observed CSR produced by a fine time structure in a bunch. At after more revolutions, a half of the synchrotron oscillation period (0.1 ms), CSR was back because the bunch length became shorter again. At this timing we also expect CSR emitted from a structure produced by longitudinal and transverse coupling, which should depend on the chromaticity. We report results of CSR observation through these periods.
Diamond, Oxfordshire
The Diamond Light Source injection system consists of a 100MeV linac and a 3GeV full-energy booster. The injector is used to fill the storage ring from empty and to provide beam for a 10 minute top-up cycle. The high power RF for the linac is generated by two S‑band klystrons, the first powering a buncher and accelerating structure, and the second feeding a second accelerating structure. With the klystrons feeding the two accelerating structures independently, a failure in the klystron or modulator feeding the lower energy structure and bunchers renders the linac, and hence the injection system as a whole, inoperable. In order to address this problem, the RF feed to the linac has been reconfigured to enable either klystron to power the first structure and bunchers; this has involved a rebuild of the waveguide network in the linac vault to include two four-way S-band switches, and the development of a lower energy operating mode for the linac, booster and linac-to-booster transfer line. Details are presented in this paper of the installation and test of the switching network, and the first results are reported of the new operating mode.
CERN, Geneva
Compensating transient beam loading to maintain a 0.01% relative beam energy spread is a key issue for the CLIC two-beam acceleration technique. The combination of short pulses, narrow bandwidth rf components and the limited number of rf pulse shaping 'knobs' given by the drive beam generation scheme makes meeting this specification challenging. A dedicated model, which takes into account all stages of drive beam generation, including the delay loop and combiner rings, the single-bunch response of the power generation structure (PETS), the RF waveguide network transfer function and dispersive properties of the accelerating structure has been developed. The drive beam phase switching delays, resulting rf pulse shape, loaded and unloaded voltages and finally the energy spread are presented.
POSTECH, Pohang, Kyungbuk
KAPRA, Cheorwon
NFRI, Daejon
PAL, Pohang, Kyungbuk
An intense L-band electron linac is now being commissioned at ACEP (Advanced Center for Electron-beam Processing in Cheorwon, Korea) for irradiation applications. It is capable of producing 10-MeV electron beams with the 30-kW average beam power. The constant-impedance accelerating structure is operated under fully-beam-loaded condition with the RF power of peak 25 MW and the beam current of 1.45 A. The total attenuation coefficient of the structure is 0.17 and the RF filling time is 0.9 μs along the 2.3-m accelerating structure. To suppress the energy spread due to the transient beam loading effect, we consider three methods: modulating the beam current amplitude, modulating the RF amplitude, and adjusting the beam injection time. In this paper, we calculate the transient beam energy numerically for the above cases. We also propose the actual compensation method.
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.
ELSA, Bonn
DESY, Hamburg
In order to enhance the operating capabilities of the Bonn University Accelerator Facility ELSA, a new injector is currently under commissioning. Its purpose is to allow a single pulse mode as well as to increase the current of the unpolarized beam provided to the external hadron physics experiments. The injector will produce an up to 2 μs long pulse of 500 mA beam current or a single electron bunch with 2 A pulse current. Design and optimization of the injector were performed with Egun, PARMELA and numerical simulations based on the paraxial equation. A 1.5 ns long pulse is produced by a thermionic electron gun with 90 kV anode-cathode voltage, then compressed and pre-accelerated by a 500 MHz RF cavity and a four-cell travelling wave buncher. After acceleration of the electrons up to 25 MeV in the main linac the natural broadening of the energy distribution in the particle ensemble due to the acceleration process will be reduced by an energy compression system. Studies have been conducted concerning the adaptation of the optical elements in the transfer beamline to the booster synchrotron with respect to the new requirements of the injection into the synchrotron and its acceptance.
JAEA/LINAC, Ibaraki-ken
The J-PARC (Japan Proton Accelerator Research Complex) accelerator comprises the 400-MeV injector linac (at present 181 MeV), the 3-GeV Rapid-Cycling Synchrotron (RCS) and the 50-GeV Main Ring (MR). The 3-MeV RFQ, the 50-MeV DTL and the 181-MeV Separated-type DTL have been operated in the linac for experimental users. The 400-MeV energy upgrade of the linac started from March 2009. The ACS (Annular Coupled Structure) cavities, the RF sources, the beam monitors and the utilities are in production. Although some components are prepared in the annual summer shutdown separately, the all cavities will be installed and commissioned for 6 months from July 2012. In this paper, we present the current status and the preliminary results of the energy upgrade.
BNL, Upton, Long Island, New York
Kyushu University, Hakozaki
IAP, Frankfurt am Main
Department of Energy Sciences, Tokyo Institute of Technology, Yokohama
The EBIS based preinjector for the RHIC is now being commissioned. During the step-wise commissioning of the preinjector from January 2009 to June 2010, the RFQ was commissioned first using Test EBIS in January 2009 and then moved to its final location and commissioned again with RHIC EBIS in March 2010. The RFQ accelerates ions from 17 keV/u to 300 keV/u and operates at 100.625 MHz. The RFQ is followed by a short (81 cm) Medium Energy Beam Transport (MEBT), which consists of four quadrupoles and one buncher cavity. Temporary diagnostics for this commissioning included an emittance probe, TOF system, fast Faraday cup, and beam current measurement units. This contribution will report results of RFQ and MEBT commissioning with helium and gold beams.
IMP, Lanzhou
IAP, Frankfurt am Main
BNL, Upton, Long Island, New York
A compact RFQ for carbon ion beam from a Laser-ion souce is being tested in IMP, Lanzhou. It is the first example of LINAC structures for IMP. Testing schemes and first results are presented.
IMP, Lanzhou
IAP, Frankfurt am Main
BNL, Upton, Long Island, New York
A RFQ has been designed and built for research of direct plasma injection scheme (DPIS), which can provide high current and highly charged beams. Because of the strong space charge forces of beam from laser ion source, the beam dynamics design of the RFQ was carried out with a new code LINACSrfq which can treat space charge effectively due to equipartitioning design strategy. Another feature of the RFQ is its high energy gain in two-meter long which will be described in detail. Construction of the RFQ cavity and the 100MHz/250kW amplifier has been completed and ready for test. A laser ion source is being tested. The assembling of the whole system including the ion source, the RFQ, the beam analyzing and diagnostic system is being done. Preliminary test results will be presented.
KEK, Ibaraki
The KEK injector linac sequentially provides beams to four storage rings: a KEKB low-energy ring (LER) (3.5 GeV/positron), a KEKB high-energy ring (HER) (8 GeV/electron), a Photon Factory ring (PF ring; 2.5 GeV/electron), and an Advanced Ring for Pulse X-rays (PF-AR; 3 GeV/electron). So far, beam injection to the PF ring and PF-AR had been carried out twice a day, whereas the KEKB rings had been operated in the continuous injection mode (CIM) for keeping stored currents almost constant. The KEK linac upgrade project has started since 2004 so that the PF top-up and KEKB CIM can be operated at the same time. The goal is to inject the beams of different energy into the three independent rings in every 20 ms, where the common DC magnet settings are utilized for beams having different energy and charge, whereas different optimized rf phases are applied to each beam acceleration by using a fast low-level rf control up to 50 Hz. With this noble operation scheme, a simultaneous top-up operation for different three rings was achieved for the first time over the world, and has been stably in operation since last April. We report the operation scheme and status in detail.
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.
Fermilab, Batavia
Muons, Inc, Batavia
Magnetrons are the lowest cost microwave source in dollars/kW, and they have the highest efficiency (typically greater than 85%). However, the frequency stability and phase stability of magnetrons are not adequate when used as power sources for accelerators. Novel variable frequency cavity techniques have been developed to phase and frequency lock the magnetrons, allowing their use for either individual cavities, or cavity strings. Ferrite or YIG (Yttrium Iron Garnet) materials are placed in the regions of high magnetic field of radial-vaned, π−mode structures of a selected ordinary magnetron. A variable external magnetic field that is orthogonal to the magnetic RF field of the magnetron surrounds the magnetron to vary the permeability of the ferrite or YIG material. Measurements of a prototype magnetron will be described.
Siemens AG, Healthcare Technology and Concepts, Erlangen
An RF accelerator driver concept is introduced, which integrates a distributed solid-state RF power source with the RF resonator. The resulting structure plays a double role as RF combiner and particle accelerating structure [1]. The key enabling technologies are Silicon Carbide RF transistors and a power combiner concept which includes insulating parallel cavities to ensure consistent RF current injection. An experimental direct drive lamda/4 cavity with a power rating of 500kW at 150MHz has been constructed. The Direct Drive RF power source consists of 64 RF modules constructed from Silicon Carbide vJFETs, radial power combiner and isolation cavity. The initial results from the integration of the direct drive RF source are presented. These results demonstrate experimentally for the first time the validity of the direct drive concept and the key characteristics of such a drive.
[1] O. Heid, T Hughes. "Compact Solid State Direct Drive RF LINAC" presented at IPAC 2010, Kyoto, Japan.
KEK, Ibaraki
A new laser-based alignment system is under development in order to precisely align accelerator components along an ideal straight line at the KEKB injector linac. The new alignment system is strongly required in order to stably accelerate high-brightness electron and positron beams with high bunch charges and also to keep the beam stability with higher quality towards the next generation of B-factories. The new laser-based alignment system consists of the LD mounted on auto stage, vacuum duct, photo diode (PD) and PD detector. To eliminate the laser beam size dependent response of PD, the collimated laser beam propagation along the linac (around 500-m-long) is strongly required. In this paper, we will report the design of collimated laser beam optics for the KEKB injector linac alignment system in detail.
KEK/JAEA, Ibaraki-Ken
KEK, Ibaraki
On the beam line after linac in high power proton accelerators, like J-PARC, debuncher system plays an important role for beam injection to the succeeding ring. The debuncher system usually gives two functions, namely, to correct the center energy jitter and to minimize momentum spread and adjust beam energy at the injection. To mitigate the nonlinear effects of RF field, a debuncher system with two debuncher cavities was designed for the 181-MeV operation of J-PARC linac. In this design, the first debuncher is expected to deal with center energy jitter. Then, the second debuncher is utilized to control the injection momentum spread according to the requirements from the ring. Although the debuncher system was originally designed to minimize the momentum spread, beam-commissioning results show a different requirement for the injection momentum spread to minimize the beam loss in the ring. Based on the original design and the experimental findings with 181-MeV operation, we have designed a debuncher system for the energy upgrade of J-PARC linac to 400 MeV. In this paper, the beam dynamics design of the new debuncher system is presented together with some particle simulation results.
KU Leuven, Kortrijk
Tomsk Polytechnic University, Nuclear Physics Institute, Tomsk
Large synchrotron radiation facilities have become one of the most powerful instruments for research today. All over the world new facilities are being constructed or designed. The biggest disadvantage of a large synchrotron facility is that the scientific experiments, which are often very sensitive and complex, have to be performed in a dedicated place, sometimes far away from the researcher's home laboratory. Promising compact synchrotron radiation sources, that fit in a typical research lab, have been proposed recently. In this paper results are presented of an initial study of a single body magnet, low electron energy storage ring, performed with the Finite Element (FE) and Finite Difference Time-Domain (FDTD) modeling possibilities in the CST Studio Suite 2010 software package. Insights were obtained for the most crucial components: the magnet yoke, the internal RF cavity and the resonance injection component. Finally, the model of the storage ring was verified using the particle tracker solver which tracks the injected electrons along the ring.