DESY, Hamburg
The three stage bunch compression system proposed for the European XFEL will be able to achieve overall compression of about 100. This would lead to the reduction of the bunch length up to 2.5 10-5 m for the designed bunch charge of 1nC. It is anticipated that the final compression would be limited here mainly by rf tolerances (jitter) which are determined by technical specifications of the manufacturer. For a large variety of experiments it could be however desirable to go to shorter bunches even on cost of less radiation power. A good possibility to achieve this might be to operate the injector at lower than 1nC bunch charge. In this paper the possibility of the operation of the injector with low charge bunches was investigated. On this issue simulations with ASTRA code have been done in order to find suitable working points for the low charge regimes and to figure out the dependence of the bunch parameters on the initial bunch charge at the cathode. The results of these simulations for the injectors at FLASH and XFEL as well as the discussion about possible problems are presented.
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
Fermilab, Batavia
Royal Holloway, University of London, Surrey
The low emittance transport had been identified as one of the feasibility issues for CLIC. We discuss beam dynamics challenges occurring in the beam lines of the RTML connecting the damping rings and the main linac. And we outline how these motivate design choices for the general RTML layout as well as its integration into the overall CLIC layout. Constraints originating from longitudinal dynamics and stabilization requirements of beam energy and phase at the main linac entrance are emphasized.
ANL, Argonne
A new cryomodule is being designed for the ongoing ATLAS efficiency and intensity upgrade. The cryomodule consists of 7 Quarter-Wave Resonators (QWR) with β-G=0.075 and 4 SC solenoids to replace the existing split-ring cavities. To reduce the resonator frequency jitter due to micro-phonics we choose a frequency of 72.75 MHz instead of 60.625 MHz. At 72.75 MHz, the cavity is shorter by about 20 cm. The choice of the design β was optimized based on the beam dynamics and the actual performance of ATLAS cavities. To reach a record high accelerating voltage of 2.5 MV per cavity or higher, the EM design was carefully optimized. The main goal of the optimization was to minimize the peak magnetic and electric fields while still keeping good values for the stored energy, the shunt impedance (R/Q) and the geometric factor (Rs/Q). The cavity height was also another important parameter. The optimization has lead to a final shape which is cylindrical in the bottom and conic on the top keeping a high real-estate gradient. The optimization also included the internal drift tube face angle required for beam steering correction.
RAS/INR, Moscow
DESY Zeuthen, Zeuthen
DESY, Hamburg
HZB, Berlin
The DESY PITZ booster cavity, based on the Cut Disk Structure (CDS), is completed in construction. The L-band normal conducting cavity is intended to operate with accelerating rate up to 12.5 MV/m and RF pulse length up to 800 mks to increase the electron bunch energy in the PITZ facility at 20 MeV. The cavity was vacuum conditioned to reduce the out-gassing rate for operation in the facility with photo cathodes. The cavity is mounted in the PITZ tunnel and RF conditioning is started. The results of RF tuning before and after cavity brazing, together with first results of conditioning, are presented.
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.
Fermilab, Batavia
We have been collecting data on the conditioning of the high-gradient accelerating cavities in the Fermilab 400 MeV H-Minus Linac for over 16 years [1]. This linac was upgraded in 1989 from a 201 MHz Alverez structure to include 805 MHz side-coupled cavities. Automated measurements of the sparking rate have been recorded since 1994 and are reported here. The sparking rate has declined since the beginning, but there are indications that this rate may have leveled off now. The X-rays emitted by the cavities are continuing to decrease.
[1] Kroc, et al., Proceedings of LINAC96, pp 338-340
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.
BNL, Upton, Long Island, New York
IAP, Frankfurt am Main
Kyushu University, Hakozaki
The EBIS based preinjector for RHIC is now being commissioned. The Linac was delivered in April 2010 and commissioning started in May, 2010. It accelerates ions from 0.3 MeV/u to 2 MeV/u with 27 accelerating gaps, one internal quadrupole triplet, and operates at 100.625 MHz. The Linac is followed by a beam transport line to Booster which includes seven quadrupoles, two bunchers, and an achromatic bend system with resolution of 500 at 2 MeV/u to select the required charge state. Diagnostics include a pepperpot emittance probe, phase probes , fast Faraday cup, adjustable slits, three sets of multiwire profile monitors, three current transformers, two Faraday cups, and two beam stops. This contribution will report results of linac tuning and cold measurements, and commissioning of the Linac and high energy transport line with helium and gold beams.
DESY Zeuthen, Zeuthen
YerPhI, Yerevan
NSC/KIPT, Kharkov
Recent successes in existing linac based FEL facilities operation and improvements in future FEL designs became possible due to detailed research in high-brightness electron beam production. The Photo Injector Test facility in Zeuthen (PITZ) is the DESY center for electron source characterization and optimization. New slice emittance diagnostics was recently commissioned at PITZ. In the measurement approach a bunch is accelerated off-crest in the accelerating cavity downstream the gun, a part of the bunch is selected after a dipole with a slit perpendicular to the dispersive direction, and the transverse emittance of the bunch part is measured using a quadrupole or a slit scan. Test measurement results are presented for 1 nC charge, flat-top and Gaussian longitudinal laser shapes.
HZB, Berlin
A review of the SRF and cryomodule R&D for various ERL projects around the world. Many challenging R&D problems will be addressed such as high average current SRF injectors and CW high gradient SRF modules.
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.
BNL, Upton, Long Island, New York
Kyushu University, Hakozaki
IAP, Frankfurt am Main
This talk will present commissioning of a new heavy ion pre-injector at Brookhaven National Laboratory. This preinjector uses an Electron Beam Ion Source (EBIS), and an RFQ and IH Linac, both operating at 100.625 MHz, to produce 2 MeV/u ions of any species for use, after further acceleration, at the Relativistic Heavy Ion Collider, and the NASA Space Radiation Laboratory. Among the increased capabilities provided by this preinjector are the ability to produce ions of any species, and the ability to switch between multiple species in 1 second, to simultaneously meet the needs of both physics programs.
