Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Elektronen-Speicherring BESSY II, Berlin
The Helmholtz Zentrum Berlin (HZB) is proposing to build an Energy Recovery Linac Prototype, called BERLinPro, at its site in Berlin Adlershof. A gun test stand for a superconducting RF gun is already under construction at HoBiCaT. In this paper we concentrate on the recirculator part of the ERL and discuss the ERL requirements to the magnet optics. The current design of the magnet lattice will be described and main parameters and simulation results introduced. Since BERLinPro aims to demonstrate high current operation at short pulses according optics aspects will be also discussed. The focus here will be on longitudinal phase space manipulations and lattice layout options, suppressing the BBU instability and increasing its threshold currents.
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Elektronen-Speicherring BESSY II, Berlin
The Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB) proposes to construct an ERL test facility. To provide different operational modes for different scientific applications is one of the advantages of these new, linac-driven radiation sources. In contrast to the linear machine layouts of FELs, new challenges arise from incorporating the linac into a circular machine. One of them is the so called merger, a magnetic chicane that threads the low energy, low emittance, but high current bunch from the gun into the recirculator. The preservation of the ambitious gun parameters, the optimal collimation of dark current and flexibility to suit all user demands are the dominant design goals. Different design criteria and possible layouts are discussed and a preliminary merger design is proposed.
ISSP/SRL, Chiba
KEK, Ibaraki
AIST, Tsukuba
We are developing an Yb fiber laser system that drives an ERL photocathode gun. An Yb fiber laser is expected to have both high stability and high output power required for the drive laser of an ERL photocathode gun. First we started to develop an Yb fiber laser oscillator with a high repetition rate up to 1.3 GHz that is the RF frequency of a superconducting accelerating cavity and then a 30W preamplifier using an Yb doped photonic crystal fiber. We report our recent progress in this development.
ISSP/SRL, Chiba
JAEA/ERL, Ibaraki
KEK, Ibaraki
In ERLs, superconducting cavities accelerate low-emittance beams with high-gradient standing-wave RF fields. If alignment error of the cavities is considerable, they can harmfully affect the beam trajectory and quality because the cavities have strong transverse focusing. Achieving high alignment accuracy of the cavities is difficult compared with the other ERL elements such as magnets because the cavities are contained in cryomodules. Therefore we studied effects of the alignment error of main superconducting cavities with analytical approaches and simulations, using a one-loop model of the compact ERL as an example. In this paper, we present the effects of alignment error of main superconducting cavities on ERLs and their correction.
ISSP/SRL, Chiba
JAEA/ERL, Ibaraki
KEK, Ibaraki
In ERL-based light sources, higher accuracy is expected to be required for RF control and timing, because the ERL beam has much shorter bunch length (less than 100 fs at minimum) compared with that of the existing SR sources. We studied effects of RF amplitude and phase variation of main superconducting cavities and effects of timing jitter of beam injection from an injector, using a simulation code 'elegant'. In this paper, we present the simulation results and discuss tolerances for the RF amplitude and phase and the injection timing.
ISSP/SRL, Chiba
KEK, Ibaraki
Orbit correction in an ERL is more complicated than those of an ordinary linac and a transport line, because the ERL beam passes a straight section containing main superconducting cavities at least two times with different energies. A corrector in this section gives a different kick angle to the beam in a different turn. Therefore a sophisticated orbit correction method is required for ERLs and ERL-based light sources. The eigenvector method with constraints (EVC)* can perform global orbit correction under constraint conditions and has been proposed and used for uniting global and exact local orbit corrections mainly in storage-ring based SR sources**. We applied this EVC method to orbit correction in an ERL. In this paper, we present how to use the EVC method for an ERL and simulation results of orbit correction for the compact ERL.
* N. Nakamura et al., Nucl. Instr. Meth. A 556 (2006) 421-432.
** K. Harada et al., Nucl. Instr. Meth. A 604 (2009) 481-488.
HU/AdSM, Higashi-Hiroshima
We report that a lifetime of GaAs photocathode activated the surface to negative electron affinity (NEA) at various temperatures. An electron source with the NEA-GaAs photocathode is an important device for high-average-current electron accelerators, such as a next-generation light source based on an energy recovery linac, in which a high power laser is illuminated to the photocathode for generation of the electron beam of 100mA. For example, the laser power of 15W should be needed for the quantum efficiency of 1% and the wavelength of 800nm. Consequently the high power laser causes to rise the GaAs temperature. The degradation of photo emission from the cathode is enhanced by a thermal desorption of Cs due to the temperature rise, even if the beam is not extracted. We have measured the cathode lifetime at various temperatures between room temperature and 100 C.
HU/AdSM, Higashi-Hiroshima
JAEA/ERL, Ibaraki
KEK, Ibaraki
A NEA-GaAs photocathode is an important component for the next generation light source based on the ERL. Although the NEA-GaAs cathode has high quantum efficiency, deterioration of the NEA surface becomes serious with a high current operation. Therefore improvement of a vacuum in the cathode chamber is essential to get a long lifetime of the NEA-GaAs cathode. We are developing a photocathode test bench consisting of titanium (TP340) chamber, whose outgas rate is 1/1000 smaller than one of a SUS chamber, a cryo-pump (4000l/s) and a NEG pump (1900l/s). We report mainly the vacuum performance of the system.
JASRI/SPring-8, Hyogo-ken
Multiturn circulation of a beam from an energy recovery linac (ERL) in a light source with bunch-by-bunch switching devices with RF cavities can reduce the output current of the ERL by a factor of the number of turns of the circulation, keeping the average current of the light source*. This scheme eases the requirement of an electron gun and an ERL, and lead to the possibility of cost-effective multi-pass ERL scheme. In previous work*, the scheme to increase the number of circulation with a ring shaped beam transport was proposed. In this work we propose a scheme without ring-shaped transport and it can be applied to various shapes of ERLs and light sources. As an example, we show a nine-turn circulation light source with the combination of newly proposed three-turn circulation system. The detail of the system, the brightness including the growth of emittance and energy spread by radiation excitation, and the effect of round-to-flat beam conversion which is a possible method for the reduction of the growth of the horizontal emittance are discussed.
* T. Nakamura, Phys. Rev. ST Accel. Beams 11, 032803 (2008).
KEK, Ibaraki
Kyungpook National University, Daegu
KNU, Deagu
Start-to-end (S2E) simulation from electron gun to beam dump is required to estimate light source performance and beam loss, which are essential parts in synchrotron light source based on Energy Recovery Linacs (ERL). Since the beam energy is widely varied from eV to GeV order in the ERL, the S2E simulation have to include many effects, e.g., space charge (SC) effect, coherent synchrotron radiation (CSR), cathode model, wake function, ions and beam break up. In order to carry out the S2E simulation, the preparation of it using General Particle Tracer (GPT), which is a particle tracking code including SC routine, has been started for compact ERL (cERL) beamline. The cERL is a test accelerator to establish accelerator technologies for GeV-class synchrotron light source based on ERL, and consists of an injector with photo cathode DC gun, a merger section, SRF cavities for acceleration and energy recovery, return loops, and a beam dump. In this presentation, the result of the S2E simulation from gun to the middle of return loop with SC and CSR effects, and the results of bench marking for each part in cERL, e.g. injector, merger, SRF cavities and return loop section, are shown.
KEK, Ibaraki
Hiroshima University, Graduate School of Science, Higashi-Hiroshima
Tohoku University, School of Scinece, Sendai
Compact ERL (cERL) is a test accelerator to establish accelerator technologies for GeV-class synchrotron light source based on ERL (Energy Recovery Linac), and will be constructed in KEK. It consists of an injector with photo cathode 500 kV DC gun, a merger section, super conducting RF cavities for acceleration and energy recovery, return loops, and a beam dump. To operate and test the photo cathode gun before installing it in the cERL injector, Gun Test Facility is constructing in KEK, AR south experimental hall. The Gun Test Facility has two photo cathode guns, 200 kV gun developed by Nagoya University and new 500 kV gun which is being developed, laser system to be emitted electrons from photo cathode surface, beam transport lines, and a beam diagnostics system. The diagnostics system consists of a double slit emittance measurement system, beam position monitors, transverse profile monitors, and a deflecting cavity to measure the bunch length and the longitudinal profile. In this presentation, the progress in the construction of the Gun Test Facility and the beam dynamics simulation will be presented.
KEK, Ibaraki
UVSOR, Okazaki
JAEA/ERL, Ibaraki
JASRI/SPring-8, Hyogo-ken
HU/AdSM, Higashi-Hiroshima
ISSP/SRL, Chiba
Yamaguchi University, Ube-Shi
Nagoya University, Nagoya
Hiroshima University, Graduate School of Science, Higashi-Hiroshima
Tohoku University, School of Scinece, Sendai
AIST, Tsukuba
Future synchrotron light source using a 5-GeV-class energy recovery linac (ERL) is under proposal by our Japanese collaboration team, and we are conducting active R&D efforts for that. We are developing super-brilliant DC photocathode guns, two types of cryomodules for both injector and main superconducting linacs, 1.3 GHz high CW-power rf sources, and other important components. We are also constructing a compact ERL for demonstrating the recirculation of low-emittance, high-current beams using those key components. We present our recent progress in this project.
JAEA/ERL, Ibaraki
KEK, Ibaraki
HU/AdSM, Higashi-Hiroshima
Nagoya University, Nagoya
A 500-kV, 10-mA photocathode DC gun has been designed and is now under fabrication by the collaboration efforts of JAEA, KEK, Hiroshima Univ. and Nagoya Univ. The Cockcroft-Walton generator and the ceramic insulator are installed upright in the SF6 tank. We have adopted a multiple-stacked cylindrical ceramic insulator, because this type of ceramic insulator has shown good stability and robustness at the 200-kV Nagoya polarized gun and the 250-kV JAEA FEL gun. The vacuum chamber, the guard-rings and the support-rod electrode are made of titanium alloy with very low out-gassing and robustness to high voltage performances. The Cockcroft-Walton generator, the ceramic insulator, the vacuum chamber and the guard-rings have been assembled and a high-voltage test has been successfully done with up to 550kV. The high-voltage test and up-to-date status of the gun development will be presented in detail.
JAEA/ERL, Ibaraki
KEK, Ibaraki
ISSP/SRL, Chiba
HOM absorbers are one of the key components to determine the ERL cavity performance to reduce the HOM problem for the high current operation. When a beam line HOM damper is installed inside the cryomodule, the HOM absorber is cooled down to liquid nitrogen temperature. The RF absorber used for the HOM absorber is required to have good frequency and temperature properties at low temperature. The RF absorber was selected by permittivity and permeability measurement of some ferrites and ceramics from room temperature to 40 K. The HOM absorber is designed by optimizing the parameters such as length, thickness and position with microwave simulation codes. The HOM absorber test model was designed and fabricated to test the RF, mechanical, cooling and temperature properties.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
STFC/DL, Daresbury, Warrington, Cheshire
ISP, Novosibirsk
ALICE is an Energy Recovery Linac built at STFC Daresbury Laboratory to investigate the process of energy recovery. The project is an accelerator research facility intended to develop the technology and expertise required to build a New Light Source (NLS) in the UK based on a suite of Free-Electron Lasers. Currently the ALICE gun accommodates only a single photocathode at any one time, and the system must be vented to atmospheric pressure for photocathode replacement. To meet the stringent vacuum demands for good photocathode lifetime, the system then requires baking for up to three weeks. A new load-lock cathode preparation system has been designed as an upgrade to the ALICE gun. The load-lock can accommodate up to six photocathodes, and permits rapid transfer of photocathodes between the load-lock activation chamber and the gun, thus maintaining the vacuum. The photocathode preparation facility was successfully commissioned in spring 2009, and has since permitted a quantum yield of 15% to be achieved at a wavelength of 635 nm. Presently, a new gun vessel and photocathode transport system is under manufacture, with a view to this being fully-installed on ALICE in Spring 2012.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
The University of Liverpool, Liverpool
STFC/DL, Daresbury, Warrington, Cheshire
JLAB, Newport News, Virginia
STFC/DL/SRD, Daresbury, Warrington, Cheshire
Progress made in ALICE (Accelerators and Lasers In Combined Experiments) commissioning and a summary of the latest experimental results are presented in this paper. After an extensive work on beam loading effects in SC RF linac (booster) and linac cavities conditioning, ALICE can now operate in full energy recovery mode at the bunch charge of 40pC, the beam energy of 30MeV and train lengths of up to 100us. This improved operation of the machine resulted in generation of coherently enhanced broadband THz radiation with the energy of several tens of uJ per pulse and in successful demonstration of the Compton Backscattering x-ray source experiment. The next steps in the ALICE scientific programme are commissioning of the IR FEL and start of the research on the first non-scaling FFAG accelerator EMMA. Results from both projects will be also reported.
CLASSE, Ithaca, New York
Coherent Synchrotron Radiation (CSR) can be a detrimental effect on particle bunches with high charge and short bunch lengths. CSR can contribute to an increase in emittance and energy spread, and can limit the process of bunch compression. It is especially important in Energy Recovery Linacs (ERLs), because any relative energy spread induced at high energy is magnified after deceleration, and any energy lost by the particles is energy that cannot be recovered. Here we present CSR simulation results using the particle tracking code BMAD for the main operation modes in the proposed Cornell ERL, including an additional bunch compression mode. These simulations consider the effect of CSR shielding, as well as CSR propagation between bends.
CLASSE, Ithaca, New York
The current status of the lattice and layout for the proposed Cornell Energy Recovery Linac lightsource is presented. This design is centered about a new hard X-ray user facility to be located on Cornell's campus, and is adapted to the local topography in order to incorporate the existing CESR tunnel and Wilson Laboratory. Nonlinear charged-particle optics for this new machine have been designed and analyzed. The lattice is populated with various components for the appropriate accelerator physics requirements for orbit, bunch length, and emittance growth control, including a vacuum system compatible with rest-gas-scattering limits, a collimation system for halo from effects like Touschek scattering, and correction coils and BPMs for sub-micron beam stabilization. We also show calculations for an additional bunch compression mode, which compresses 19~pC bunches at a 1.3~GHz repetition rate to 25~fs.
BINP SB RAS, Novosibirsk
NSU, Novosibirsk
The Novosibirsk ERL has rather complicated magnetic system. One orbit (11-MeV) for terahertz FEL lies in the vertical plane. Other four orbits lie in the horizontal plane. The beam is directed to these orbits by switching on of two round magnets. In this case electrons pass through RF cavities four times, obtaining 40-MeV. At the 4th orbit the beam is used in FEL, and then is decelerated four times. At the 2nd orbit (20 MeV) we have a bypass with another FEL. When bypass magnets are switched on, the beam passes through this FEL. The length of bypass is chosen to provide the delay necessary to realize deceleration at the3rd pass through accelerating cavities. In 2008 two of four horizontal orbits were assembled and commissioned. The electron beam was accelerated twice and then decelerated down to low injection energy. First multi-orbit ERL operation was demonstrated successfully. In 2009 the first lasing at the second FEL, installed on the bypass of the second track, was achieved. The wavelength tunability range is 40 - 80 micron. Energy recovery of a high energy spread used electron beam was optimized. Third and fourth orbit assembly is in progress.
