Uppsala University, Uppsala
At CERN the feasibility of CLIC (Compact LInear Collider) a multi-TeV electron-positron collider is being studied. In this scheme the RF power to accelerate the main beam is produced by a high current drive beam. To demonstrate this scheme a test facility (CLIC Test Facility 3, CTF3) has been constructed at CERN. Recently, the complex to generate the drive beam has been successfully commissioned producing a beam with a current around 30A. This beam is now being used to test the power production. The results of the test facility provide vital input for the CLIC conceptual design report to be finished by the end of 2010. This talk describes CTF3 activities and their importance for CLIC; it comments on design readiness for CLIC after a successful CTF3 demonstration.
KURRI, Osaka
Electron beam can be accelerated in two accelerator tubes up to 46 MeV at KURRI-LINAC. The development of irradiation field is planned to provide lower energy electron beam. For this purpose we had regulated several parameters, which results showed that low energy electron beam was obtained by acceleration in only the first accelerator tube, without the second one, which was filled with microwave from klystron operated at reduced voltage. Moreover, the timing between electron emission and microwave introduction into the first accelerator tube was varied to increase the electron energy loss in the second one, thereby reducing high-energy component of the beam. In this study we obtain lower energy electron beam by the following regulations: 1) the increase of the emission current from the electron gun relative to energy filled into the first accelerator tube results in the decrease of acceleration energy for each electron and 2) the total control of the timing and the buncher phase of microwave and the width of electron pulse eliminates a part of electron expected to be high-energy component. The regulations described above yield the low-energy electron beam with peak of 5.2 MeV.
NSCL, East Lansing, Michigan
FRIB, East Lansing, Michigan
The Facility for Rare Isotope Beams (FRIB) will accelerate stable beams of heavy ions to > 200 MeV/u with beam powers of up to 400 kW onto an in-flight fragmentation target to produce rare isotopes. The accelerator system will include a room-temperature front end, a double-folded superconducting driver linac, and a beam delivery system. The front end will include superconducting ECR ion sources, a beam bunching system and a radio frequency quadrupole. The driver linac will include three acceleration segments using superconducting quarter-wave and half-wave cavities with frequencies of 80.5 and 322 MHz, and two 180 degree folding systems to minimize the cost of conventional construction. Charge-stripping and multi-charge-state beam acceleration will be used for the heavier ions to increase acceleration efficiency. The beam delivery system will transport accelerated stable beams to the in-flight fragmentation target. End-to-end beam simulations with errors have been performed to evaluate the performance of the driver linac. We will discuss recent progress in the accelerator design and the beam dynamics studies for the baseline accelerator system.
INFN/LNL, Legnaro (PD)
CIAE, Beijing
The low-beta section of the ALPI linac at Laboratori Nazionali di Legnaro is being upgraded in order to double its energy gain from about 10 MV to 20 MV. This upgrade, performed with a rather limited investment in the background of the standard accelerator activities, is based on the replacement of some rf system components and minor modifications to the cryostats. The cavities, working at 80 MHz, require a 3 dB rf bandwidth of 15 Hz (obtained by means of strong overcoupling) to be locked in the presence of the large Helium pressure fluctuations of ALPI. Their average gradient, although exceeding 6 MV/m at the nominal 7 W power, is presently kept around 3 MV/m during operation, limited by the maximum available rf power in the linac. The ongoing upgrade requires the modification of all low-beta cryomodules to allow new, liquid Nitrogen cooled rf couplers and new, 1 kW amplifiers. A fully equipped prototype cryostat with four, beta=0.047 QWRs has been constructed and tested on line, and operated at 6 MV/m reaching or exceeding all the design goals. The test results will be reported and discussed and the project status will be presented.
ANL, Argonne
Tech-X, Boulder, Colorado
We are developing a model of arcing to explain breakdown phenomena in high-gradient rf systems used for particle accelerators. This model assumes that arcs develop as a result of mechanical failure of the surface due to electric tensile stress, ionization of fragments by field emission, and the development of a small, dense plasma that interacts with the surface primarily through self sputtering and terminates as a unipolar arc capable of producing field emitters with high enhancement factors. We are modeling these mechanisms using Molecular Dynamics (mechanical failure, Coulomb explosions, self sputtering), Particle-In-Cell (PIC) codes (plasma evolution), mesoscale surface thermodynamics (surface evolution), and finite element electrostatic modeling (field enhancements). We believe this model may be more widely applicable and we are trying to constrain the physical mechanisms using data from tokamak edge plasmas.
SLAC, Menlo Park, California
Typical surface damage in travelling wave accelerator structures occurs on the high field region of the iris. As the damage accumulates the coupling between cavities is affected resulting in changes in the phase shift between cells. This issue can be reduced by use of SW cells that are fed in parallel. RF breakdown is contained to the cell where it originates and the available electromagnetic energy for a given gradient is minimized by the parallel feed. Several schemes[1] have been proposed for parallel fed SW structures. Some of the proposed designs fed several cells from each arm, which reduces the advantage of localizing a RF breakdown to an individual cavity. In addition they use a standing wave in the feed arms which allows coupling between cells. We are proposing a somewhat more complex approach using a directional coupler on each cell and serpentine waveguide connection between couplers. This design approach isolates the cells and gives an individual rf feed to each cell resulting in the maximum increase in the operational robustness of the accelerator structure.
1. O. N. Brezhnev, P. V. Logatchev, V. M. Pavlov, O. V. Pirogov, S. V. Shiyankov,' Parallel-Coupled Accelerating Structures', Proceedings of LINAC 2002, Gyeongju, Korea, pg 215-217
ANL, Argonne
Euclid TechLabs, LLC, Solon, Ohio
New technology needs to be developed for future compact linear colliders. The AWA Facility is dedicated to the study of advanced accelerator concepts towards this goal. The facility uses high charge short electron bunches to drive wakefields in dielectric loaded structures as well as in metallic structures (iris loaded, photonic band gap, etc). Accelerating gradients as high as 100 MV/m have been reached in dielectric loaded structures, and RF pulses of up to 44 MW have been generated at 7.8 GHz. In order to reach higher accelerating gradients, and also be able to generate higher RF power levels, several facility upgrades are underway: a new RF gun with a higher QE photocathode; a witness beam to probe the wakefields; additional klystrons and linac structures to bring the beam energy up to 75 MeV. The drive beam will consist of bunch trains of up to 32 bunches of 60 nC, corresponding to a beam power of 6 GW. The goal of future experiments is to reach accelerating gradients of several hundred MV/m and to extract RF pulses with GW power level. A key advantage of wakefield acceleration in structures is the ability to act on electrons and positrons in basically identical fashion.
Naples University Federico II and INFN, Napoli
NRT, Aprilia
INFN/LNS, Catania
Universita' degli Studi di Milano & INFN, Segrate
INFN/LASA, Segrate (MI)
ADAM, Geneva
INFN-Napoli, Napoli
Bari University, Science Faculty, Bari
INFN-Bari, Bari
ACLIP is a 3 GHz proton SCL linac designed as a booster for a 30 MeV commercial cyclotron. The whole accelerator is a 5 module structure coupled together. The final energy is 62 MeV well suitable for the therapy of ocular tumors. In order to treat deep-seated tumors the energy can be raised up to 230 MeV by adding a second linac. The possibility of using magnetrons, as the source of RF power, to reduce the overall cost of the machine, and the tile design (covered by a patent), named Back-to-Back Accelerating Cavity (BBAC), to efficiently accelerate protons starting from a low energy are two of the more relevant features of this project. The first module (from 30 to 35 MeV) has been full power RF tested in December 2008, showing that the design accelerating field could be easily reached. Then this module, along with all elements of the RF power setup, has been transferred to INFN-LNS in Catania at the end of April 2010 to carry out beam acceleration tests using a 30 MeV proton beam from the Superconducting Cyclotron. In this paper we will review the main features of the linac and discuss the results of the acceleration measurements carried out on this prototype.
ANL, Argonne
An integral part of the ongoing ATLAS efficiency and intensity upgrade is an RFQ to replace the first section of the existing injector. The proposed RFQ is 3.8 m long made of 106 cells with 30 keV/u input energy and 260 keV/u output energy. The RFQ was designed using the DesRFQ code which produces a file consisting of the length, modulation and the 8 coefficients of the 8-term potential for every cell. To independently check the design we created full 3D models of the RFQ including cell modulation in both Micro-Wave Studio (MWS) and Electro-Magnetic Studio (EMS). The MWS model was used to verify the phasing and energy gain along the RFQ using particle tracking and the EMS model was used to extract the electric field cell by cell assuming the electrostatic approximation. A very good agreement was obtained between the full 3D model and the 8-term potential description in TRACK. In addition to the standard sinusoidal vane profile we studied the option of converting the cells with maximum modulation (~ 40 cells) into trapezoidal cells. The output energy was increased from 260 keV/u to ~ 300 keV/u with minimal change to beam dynamics. This option is the final RFQ design.
JAEA/LINAC, Ibaraki-ken
KEK, Ibaraki
The operation of the DTL and the Separated type DTL (SDTL) of the J-PARC started in November 2006. The DTL and SDTL are currently running stable and accelerating the beam. For stable operation of the DTL/SDTL, We have done maintenance of the equipments, like an RF coupler, and improved the troubles. In this paper, we will present the operation experiences of the DTL and the SDTL.
LANL, Los Alamos, New Mexico
Muon accelerators are studied for future neutrino factory and muon colliders (NF/MC). On the other hand, a compact muon accelerator can be applicable to muon radiography which is a promising probe to investigate large objects. We worked on simulation studies on a compact muon linear accelerator. The designed linac has a large energy and a phase acceptance to capture lower energy pion/muon (10 - 100 MeV) than the NF/MC scenario and accelerates them to 200 MeV without any beam cooling. Our current design adopts 805 MHz zero-mode normal-conducting cavities with 35 MV/m peak field*. The superconducting solenoids are used to provide 5-T focusing field on the normal conducting cavities. We developed a Monte Carlo simulations code to optimize linac parameters. Muon energy loss and scattering effects at the aperture windows are included, too. The simulation showed that about 10 % of the pion/muon injected into the linac can be accelerated to 200 MeV. Further acceleration can be done with superconducting linac.
* S. Kurennoy et al., IPAC 2010.
MHI, Kobe
C-band RF pulse compressor is a device that generates high peak RF-power by saving, and compressing the RF-power output from the klystron. XFEL project is scheduled to be installed 64 pulse compressor units, 2009 of December we have completed the fabrication and RF measurement of all units. A high-power examination was conducted in the test stand at RIKEN. The RF output of the pulse compressor is 260 MW in peak value, and the acceleration gradient of the accelerating structure is achieved to be 40 MV/m.It reports on the mass production passage of these 64 C-Band RF pulse compressors and on the installation result of injector section.
Fermilab, Batavia
Front end of a CW linac of the Project X contains a H- source, an RFQ, a medium energy transport line with the beam chopper, and a SC low-beta linac that accelerates H- from 2.5 MeV to 160 MeV. SC Single ' spoke Resonators (SSR) will be used in the linac, because Fermilab already successfully developed and tested a SSR for beta 0.21. Two manufactured cavities achieve 2-3 times more than design accelerating gradients. One of these cavities completely dressed, e.g. welded to helium vessel with integrated slow and fast tuners, and tested in CW and pulse regimes. Successful tests of beta=0.21 SSR give us a confidence to use this type of cavity for low beta (0.117) and for high- beta (0.4) as well. Both types of these cavities are under development. In present report the basic constrains, parameters, electromagnetic and mechanical design for all the three SSR cavities, and first test results of beta=0.21 SSR are presented.
Fermilab, Batavia
Capture Cavity II is the first operational component at the SRF Beam Test Facility now under construction at Fermilab. This 9-cell 1.3 GHz cavity, previously operated in another venue on the Fermilab site, was transported to this facility in early 2009. We will summarize its transport and operation in its new (permanent) home compared to previous performance and also present results of studies, particularly Low Level RF, microphonics/vibration, and Lorentz force de-tuning compensation that have been recently carried out with it.
UBC & TRIUMF, Vancouver, British Columbia
TRIUMF, Vancouver
The ISAC-II superconducting linac consists of forty quarter wave bulk niobium cavities. There are eight and twelve 106MHz cavities at beta=5.7% and 7.1% respectively and twenty cavities at 141MHz at beta=11%. The first twenty have been operating since 2006 (Phase I) and the remainder have been installed for first commissioning in April 2010 (Phase II). Cavity performance statistics of the 2006 cavities have been accumulated to look for signs of systematic degradation in performance. These will be presented. In addition single cavity test results and in situ characterization tests of the first operation of the Phase II cavities will be presented.
Fermilab, Batavia
Over the last decade there has been significant progress in developing the concepts and technologies needed to produce, capture and accelerate O(1021) muons/year. This development prepares the way for a new type of neutrino source (Neutrino Factory) and a new type of very high energy lepton-antilepton collider (Muon Collider). A review is given of the motivation, design and R&D for Neutrino Factories and Muon Colliders.