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| MOP001 | Pressurized Hydrogen-Filled Linacs for Muon Cooling | emittance, linac, collider, scattering | 28 | ||
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New techniques for muon ionization cooling require low-Z energy absorber, strong magnetic fields for focusing and emittance exchange, and high gradient RF cavities to replace the energy lost in the absorber. RF cavities pressurized with hydrogen gas are being developed to provide the most muon beam cooling possible in the short lifetime of the muon. We report the status of the cavity development, including the breakdown suppression due to the gas and new results showing that pressurized cavities show no degradation of performance in strong magnetic fields. We also comment on the development of the designs of the associated muon cooling linacs.
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| MOP006 | A Bunch Compressor for the CLIC Main Beam | emittance, electron, synchrotron, synchrotron-radiation | 40 | ||
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The second bunch compressor chicane in the main beam line of the multi TeV linear collider CLIC is foreseen to compress the electron bunches from 250 μm to 30 μm. It is specified that the emittance growth in this chicane, which is mainly due to incoherent and coherent synchrotron radiation, should not exceed 30 nm·rad in the horizontal plane and 1 nm·rad in the vertical plane. To achieve these values the chicane layout and the optics functions have been optimized and the influence of shielding due to the vacuum chamber including resistive wall wake fields has been studied. A chicane layout and the corresponding electron beam parameters are presented, which allow to preserve the emittance within the specifications.
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| MOP013 | Low-Intensity, Pulsed-Beam Generation System Using the OPU Linac | electron, gun, linac, cathode | 58 | ||
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An ultra low intensity pulsed electron beam generation system has been developed, which consists of an electron linear accelerator (linac), highly sensitive beam current monitors and beam profile monitors. The beam current has been attenuated to be about ten orders of magnitude weaker than the ordinary beam current by using several methods, e.g. the reduction of the cathode emission in an injector and the use of a narrow slit. The minimum beam charge so far obtained has been estimated to be about several attocoulomb in one beam macropulse. The beam from a linac is controllable, collimated and synchronized with the trigger signal of the linac. The features are much advantageous compared with those of β-rays from radioisotopes which have been used in low intensity beam irradiation experiments. The final goal of this work is to generate a single electron beam.
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| MOP029 | Laser Beat-Wave Microbunching of Relativistic Electron Beam in the THz Range | electron, laser, undulator, plasma | 100 | ||
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Laser-driven plasma accelerators have recently demonstrated a ~1GeV energy gain of self-trapped electrons in a several-centimeter-long plasma channel. Potential staging of such devices will require external injection of an electron beam prebunched on the scale of 1-10 THz into a plasma accelerating structure or plasma LINAC. Seeded FEL/IFEL techniques can be used for modulation of the electron beam longitudinally on the radiation wavelength. However a seed source in this spectral range is not available. At the UCLA Neptune Laboratory a Laser Beat-Wave (LBW) microbunching experiment has begun. Interaction of the electron beam and the LBW results in ponderomotive acceleration and energy modulation on the THz scale. This stage is followed by a ballistic drift of the electrons, where the gained energy modulation transfers to the beam current modulation. Then the beam is sent into a 33-cm long undulator, where a coherent start-up of THz radiation takes place providing efficient bunching of the whole beam. The performance of LBW bunching is simulated and analyzed using 3D FEL code for the parameters of an existing photoinjector and two-wavelength TW CO2 laser system.
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| MOP033 | The Operation Concept of SARAF | controls, cryogenics, instrumentation, target | 109 | ||
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The Soreq Applied Research Accelerator Facility (SARAF) is a 5 - 40 MeV, 0.04 -2 mA proton/deuteron RF superconducting linear accelerator, which is under construction at Soreq NRC and is planned to start generating a beam by the end of 2010. SARAF will be a multi-user facility, whose main activities will be neutron physics and applications, radio-pharmaceuticals development and production, and basic nuclear physics research. The operational concept of SARAF will be ‘one target at a time’ and during irradiation, appropriate shielding will enable preparation and maintenance at other stations. This paper presents the planned facility operation program, the planned operations group, the location and layout of the main control room and the architecture of the main control system, including its interfaces with safety and applications. Emphasis is given to the design considerations for each of the discussed subjects.
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| MOP034 | Status of FS-FIR Project of the PAL | electron, gun, linac, undulator | 112 | ||
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At the Pohang Accelerator Laboratory (PAL), a femto-second far infrared radiation (fs-FIR) facility is under construction. It is a THz radiation source using 60-MeV electron linac, which consists of an S-band photocathode RF-gun with 1.6 cell cavity, two S-band accelerating sturctures, two chicane bunch compressors, and a 1-m long planar undulator. We installed the gun and measured the characteristics. In this article, we will present the construction status of the fs-FIR facility as well as the simulation results and the measurement results of the electron gun.
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| MOP036 | Status of the PAL-XFEL Project | electron, laser, undulator, linac | 118 | ||
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PAL-XFEL, the new X-ray FEL machine that is going to be built at Pohang Accelerator Laboratory, is under intensive design study. The electron beam energy will be 3.7 ~ 4.0 GeV and the target wavelength will be 0.3 nm. The results as well as the strategy and the difficulties in the PAL-XFEL design are presented in this paper.
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| MOP068 | Beam-Loss Measurement and Simulation of Low-Energy SNS Linac | linac, SNS, simulation, beam-losses | 202 | ||
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We have installed a number of Neutron detectors from the MEBT to the end of CCL [186 MeV]. These detectors are made in collaboration with INR. In this paper we present our implementation and simulation of the losses by inserting Faraday Cups at different energies. We also calibrated neutron detectors and their high voltage dependence. The measured losses are simulated by 3-D transport codes during SCL commissioning. We also discuss future improvements such as interpreting the loss signal in terms of beam current lost in warm part of SNS linac with accurate longitudinal loss distribution as well as plan to automate voltage dependence of the neutron detectors. We compare two different sets of Beam Loss Monitors: Ionization Chambers (detecting X-ray and gamma radiation) and Photo-Multiplier Tubes with a neutron converter (detecting neutrons). We outline such combination is better way to deal with the beam losses than relying on detectors of one type.
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| TUP009 | First Operation of the FLASH Machine Protection System with Long Bunch Trains | undulator, beam-losses, linac, laser | 262 | ||
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The linac-based free electron laser facility FLASH at DESY Hamburg is designed to transport an electron beam with an average power of more than 50 kW. To avoid serious damage to accelerator components, a fast active machine protection system (MPS) stops the production of new bunches if hazardous machine conditions are detected. This paper gives an overview of the MPS topology and its subsystems. Furthermore, we present results from the commissioning of the fast beam interlock system that has for the first time allowed to operate the accelerator with macropulses of up to 600 bunches.
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| TUP015 | Linac Coherent Light Source (LCLS) Bunch-Length Monitor Using Coherent Radiation | electron, synchrotron, synchrotron-radiation, storage-ring | 277 | ||
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The Linac Coherent Light Source (LCLS) is a SASE x-ray Free-Electron Laser (FEL) based on the final kilometer of the Stanford Linear Accelerator. One of the most critical diagnostic devices is the bunch length monitor (BLM). We are planning to install BLM right after each compressor utilizing coherent radiation from the last bending magnet. We will calculate the signal strength, and simulate the signal propagation using well-accepted simulation tools in synchrotron radiation community in general, and THz radiation in particular. We will also discuss issues of optics layout, and detectors.
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| TUP018 | Low-Intensity Electron Beam Monitoring and Beam Applications at OPU Linac | electron, linac, monitoring, gun | 286 | ||
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Low intensity beams are generated with a 18 MeV S-band electron linac at Osaka Prefecture University (OPU). The minimum charge of electrons in a pulsed beam has been estimated to be about several attocoulomb. In order to measure the intensity and the profile of the beams with thermoluminescence dosimeters and two-dimensional radiation dosimeters, the characteristics of the dosimeters have been investigated by using the electron beams. For the charge of the beam above one picocoulomb, charge-sensitive type beam monitors have been used. The linear relation between the output signal of the dosimeter and the irradiation dose of the beam has been obtained. From the results it has been found that these dosimeters can be applied to monitoring the low intensity electron beam. The beam applications under preparation are presented.
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| TUP050 | Microwave Helical Undulator-Based Production of Polarized Photons and Positrons | undulator, positron, polarization, linear-collider | 361 | ||
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Linac-driven undulator technology and capabilities are considered for production of polarized positrons and polarized high-brightness X-rays. Challenging requirements for polarized positron production reveal a number of benefits of a microwave undulator compared with a conventional magnetic undulator: larger gap, simpler construction, shorter length, reduced requirements on tolerances and alignment. Two novel approaches are introduced for open and closed structures: cross-polarized excitation of a circular waveguide and a twisted structure. For the CLIC project the microwave undulator becomes an integral part of the TBA, and as it is naturally powered by the same decelerator. Other applications include emittance dampers, synchrotron radiation sources, and FELs. Additionally the twisted undulator provides unique opportunity for studies of circular dichroism and multi-photon anomalous diffraction (MAD) in protein crystallography.
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| TUP090 | Advances of NPK LUTS Contraband Detection System | rfq, proton, linac, acceleration | 472 | ||
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Principle and project of NPK LUTS contraband detection technological complex (CDTC) was presented by authors at EPAC 2002. This paper reviews researches connected with 433 MHz ion linacs creation for the last four years. Main part is description of designing and testing of RFQ and APF resonators. State of affairs of other CDTC system is described briefly.
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| WE1002 | The 4GLS at Daresbury | linac, electron, simulation, undulator | 481 | ||
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4GLS is a next generation proposal for an advanced light source to be built at Daresbury Laboratory. The facility will consist of three integrated accelerator systems: a 25-60 MeV linear accelerator driving an Infra-Red Free-Electron Laser (FEL) at 13 MHz; a 750-950 MeV branch driving a 10-100 eV XUV-FEL at 1 kHz; a 600 MeV energy recovery linac carrying 100 mA current driving a suite of spontaneous sources at 1.3 GHz or a VUV-FEL (up to 10 eV) at 4 MHz. The latter two accelerator systems share a common superconducting linac based on 1.3 GHz TESLA technology, which will simultaneously accelerate the two bunch types (1 nC and 77 pC) whilst decelerating the returning 77 pC bunches. This paper will outline the project and its key features, including the 35 MeV ERL Prototype accelerator presently being commissioned, and will discuss the accelerator physics and technology challenges to be explored in the present Design Study.
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| WE1003 | The TTF/VUV-FEL (FLASH) as the Prototype for the European XFEL Project | linac, laser, electron, free-electron-laser | 486 | ||
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The European X-ray Free-Electron Laser Facility (XFEL) is going to be built in an international collaboration at the Deutsches Elektronen-Synchrotron (DESY), Germany. The Technical Design Report was published recently. The official project start will be before end of this year. The new facility will offer photon beams at wavelengths as short as 1 Angstroem with highest peak brilliance being more than 100 million times higher than present day synchrotron radiation sources. The radiation has a high degree of transverse coherence and the pulse duration is reduced from ~100 picoseconds down to the ~10 femtosecond time domain. The overall layout of the XFEL will be described. This includes the envisaged operation parameters for the linear accelerator using superconducting TESLA technology. The complete design is based on the actually operated VUV Free-Electron Laser at DESY. Experience with the operation during first long user runs will be described in detail. Many of the different subsystems of the XFEL could be tested. Specially developed electron beam diagnostics was commissioned. A summary of the status of the XFEL preparation work will be given.
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| TH2002 | Timing and Synchronization in Large-Scale Linear Accelerators | laser, diagnostics, electron, linac | 536 | ||
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New coherent light sources are based on large scale linear accelerator; the adopted single pass acceleration scheme allows the preservation of bunch 6D phase space leading to ultra short (<100fsFWHM) and ultra bright (average Brilliance = 1024 (1) ph/sec/mm2/mrad2/0.1%bw) pulses of coherent radiation in the DUV-x-ray regions. Femto-second lasers are deeply integrated in the electron bunch and photon pulse generation, in diagnostic set-ups and in time resolved experiments: the timing may be as low as 10% of pulse duration. The requirements on the stability of RF acceleration call for distribution of ultra-stable and ultra-low phase noise reference signal for the Low Level RF feedback loops. A non reversible breakthrough into the adoption of optical and O/E techniques is on-going which is taking advantage on five order of magnitude reduction in the period of the carrier. Being the current limit represented by the carrier-envelope stabilization techniques, sub-fs jitters have been demonstrated in the laboratory; the preservation of laboratory levels of jitters and stability over the whole accelerator premises is the next step. On-going efforts and results let us be optimistic.
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Interim Report of the Scientific and Technical Issues (XFEL-STI) Working Group ona European XFEL facility in Hamburg, January 11, 2005. |
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| THP002 | Exception Detection and Handling for Digital RF Control Systems | controls, klystron, linac, feedback | 562 | ||
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Exception detection and handling routines will play an important role in future large scale accelerator to ensure high availability and beam stability in presence of interlock trips, varying operational parameters, and operation close to the performance limit. For superconducting linacs typical examples for exception situations include cavity quenches, coupler and klystron gun sparcs, operation close to klystron saturation, and errors in vector-sum calibration. The goal is to identify all possible exception situations which will lead to performance degradation or downtime, detect these situations and take appropriate actions as necessary.
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| THP016 | Active Compensation of Lorentz Force Detuning of a TTF 9-Cell Cavity in CRYHOLAB | simulation, klystron, controls, feedback | 598 | ||
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Linear colliders and free-electron lasers projects based on the superconducting RF technology require high gradient pulsed operation of superconducting elliptical multicells. The cavities are subject to Lorentz force detuning which reflects on an increased RF power consumption when trying to stabilize the accelerating field during the beam passage. This pulsed detuning can be mechanically compensated using a fast piezoelectric tuner. A new tuner with integrated piezoelectric actuators has been developed in the framework of CARE/SRF european program. The tuning system has been tested on a fully equipped 9-cell TTF cavity in the CRYHOLAB horizontal cryostat using the pulsed 1.3 GHz 1 MW RF source. In virtue of the high pulse to pulse repeatability of the detuning, the compensation of Lorentz detuning was achieved successfully using a simple feed forward scheme.
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| THP023 | Status of and Future Plan for the NSRL Microwave Power System | linac, klystron, power-supply, controls | 616 | ||
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In this paper, 20MW microwave power system for NSRL (National synchrotron radiation Laboratory) Linac is introduced. The power system includes five s-band 20MW klystrons and their modulators. In 2002, the klystron modulators and the control system were upgraded. Constant-current, switching power supplies were employed to replace the old conventional LC resonant charging facilities. The new system has run for four years and played an important role in the operation of the 200MeV LINAC. A new soft x-ray FEL project (HTF) is now proposed in NSRL, the energy of electron beam will be increase from 200MeV to 800MeV. Seven s-band 80 MW klystrons and modulators will be employed as the new microwave power sources. The low energy spread specification of the Linac sets a stringent requirement to the stability of the klystron modulators. The paper also presents the technical considerations and preliminary design of the new system
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| THP031 | Pulse Cables For XFEL Modulators | klystron, impedance, simulation, pulsed-power | 640 | ||
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For the XFEL, housed in a single tunnel, most of the modulators will be placed in a central modulator building outside of the tunnel. The pulse transformers and the klystrons will be positioned inside the tunnel near the superconducting linac. Therefore the energy has to be transported via pulse cables. These cables have lengths between 350m and 1.7 km. The power is up to 16.8 MW per pulse with a repetition rate of 10 Hz. In order to keep the rise time short and match the klystron impedance four 25Ohm cables will be put in parallel. A tri-axial design was chosen to prevent magnetic field outside of the cables in order not to disturb electronics or electron beam. A prototype of the cable was produced in industry and delivered to DESY. A set of four 1.5km long parallel cables is in test at present at one of the modulators of the TTF/VUV-FEL at DESY. The cable design criteria and test results are presented in this paper.
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| THP075 | RF Performance of a Superconducting S-Band Cavity Filled with Liquid Helium | vacuum, pick-up, superconductivity, controls | 755 | ||
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Copper RF cavities filled with hydrogen gas at high pressure have been studied recently by Muons, Inc. and IIT for simultaneous acceleration and ionisation cooling of a muon beam. A further step in this direction would be a superconducting RF cavity filled with liquid helium. One might imagine that this would make the cavity less vulnerable to thermal breakdown, field emission, and multipacting. A disadvantage is that magnetostatic focussing of the beam could not be done simultaneously. Preliminary RF testing has been done on a 2.45 GHz single-cell elliptical cavity filled with liquid helium. Low-field results indicate little or no increase in the power dissipation, consistent with predictions and measurements in the literature. The frequency shift with pressure for a cavity filled with saturated liquid is about 100 times greater than for a cavity under vacuum, consistent with published values of liquid helium permittivity as a function of temperature. Investigation of the high-field performance of a liquid-filled cavity is in progress.
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| THP076 | Prototyping of a Superconducting Elliptical Cavity for a Proton Linac | proton, linac, SNS, vacuum | 758 | ||
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A superconducting cavity has been designed for acceleration of particles travelling at 81% the speed of light (β = 0.81). Possible applications include the proposed Fermilab Proton Driver Linac. The cell shape is similar to the β = 0.81 cavity for the Spallation Neutron Source Linac, but the resonant frequency is 1.3 GHz rather than 805 MHz and the beam tube diameter matches that of the 1.3 GHz cavity for the TeSLA Test Facility. Six single-cell prototypes are being fabricated and tested. Three of these cavities are being formed from standard high purity fine grain niobium sheet. The rest are being fabricated from large grain niobium, following up on the work at Jefferson Lab to investigate the potential of large grain material for cost savings and/or improved RF performance. The fabrication of two 7-cell cavity prototypes (one fine grain, one large grain) is planned. A status report on this prototyping effort will be presented.
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| THP081 | Study on Fault Scenarios of Coaxial Type HOM Couplers in SRF Cavities | SNS, electron, coupling, vacuum | 770 | ||
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Coaxial type couplers are adopted in many superconducting radio-frequency (SRF) cavities to suppress higher order modes for beam dynamics and cryogenic loads issues. HERA (Hadron-Electron Ring Accelerator) and TTF (Tesla Test Facility) are equipped with this type coupler and showed successful performances. It is, however, under suspicion that a limitation or a fault could be initiated from this type of coupler at certain combinations between cavity operating conditions and engineering designs of the coupler. Some possible scenarios are summarized and also some observations in the SNS (Spallation Neutron Source) SRF cavities are also reported.
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| THP091 | Experimental Study of Positron Production from Monocrystalline Targets at the KEKB Injector Linac | target, positron, electron, linac | 797 | ||
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Intense positron sources are widely investigated for the next-generation of linear colliders and B-factories. A new method utilizing an axially-oriented crystal as a positron-production target is one of the bright schemes since it provides a powerful photon source through channeling and coherent bremsstrahlung processes when high-energy electrons penetrate the target. A series of positron-production experiments with tungsten crystal alone and diamond target combined with an amorphous tungsten plate have been carried out at the KEKB injector linac. The tungsten crystals with different thicknesses (2.2, 5.3, 8.9, 12.0 and 14.2 mm) and the diamonds with different thicknesses (4.57 and 7.25 mm) were tested on a goniometer by using 4 and 8-GeV electron beams, respectively. The positron-production yields were measured with a magnetic spectrometer at the positron momentum of 10 and 20 MeV/c. In this report the experimental results are summarized on the enhancements of the positron yield from these crystal targets compared to amorphous targets of the same thickness.
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*Email address: tsuyoshi.suwada@kek.jp |
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| FR1002 | SPring-8 Compact SASE Source | emittance, electron, undulator, cathode | 813 | ||
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The 8-GeV Japanese XFEL Project has been funded in 2006. Construction is scheduled 2006-2010, first beam in 2010. In order to develop technology required to XFEL, we have been carrying out R&D program at RIKEN since 2002, where thelow emittance thirmionic-gun and various key technologies were developed. To verify technologies, SCSS Prototype Accelerator has been constructed. The first lasing was obserbed in the prototype accelerator at June 20 at 60 nm.
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SCSS-Web Site: www-xfel.spring8.or.jp. |
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