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| MOP029 | Laser Beat-Wave Microbunching of Relativistic Electron Beam in the THz Range | electron, laser, plasma, radiation | 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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| MOP034 | Status of FS-FIR Project of the PAL | radiation, electron, gun, linac | 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, linac, radiation | 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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| MOP037 | Applications of Time-of-Flight Measurements at FLASH | electron, linac, vacuum, laser | 121 | ||
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As a prototype of the XFEL, VUV-FEL has been build and commissioned at DESY by an international collaboration. It is a linear electron accelerator with an undulator arrangement to produce laser pulses by the 'Self-Amplified Spontaneous Emission' (SASE) process. To generate the laser pulses, electron bunches are compressed in longitudinal direction to reach the necessary peak current of about 2.5 kA. To control the compression process a number of 'Phase Monitors' are installed at the accelerator. They measure the time of the bunch passages. Differences of the bunch passage times at different linac locations yield the 'Time-Of-Flight' (TOF) between these locations. The system is installed with regard to the planned installation of a further RF module operating at the third harmonic RF frequency. This 'third harmonic cavity' is required to optimize the longitudinal bunch charge distribution. Its effect is examined by the TOF measurements. The paper presents the Phase Monitor system to measure the TOF at VUV-FEL. The principle is shown, the determination of 'on-crest'-phases is demonstrated and first measurements of the momentum compaction coefficients, R56 and T566, are discussed.
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| TUP009 | First Operation of the FLASH Machine Protection System with Long Bunch Trains | beam-losses, linac, radiation, 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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| TUP014 | Electron Signal Detection for the Beam-Finder Wire of the Linac Coherent Light Source Undulator | electron, scattering, simulation, photon | 274 | ||
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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. The tight tolerances for positioning the electron beam close to the undulator axis calls for the introduction of Beam Finder Wire (BFW) device. A BFW device close to the upstream end of the undulator segment and a quadrupole close to the down stream end of the undulator segment will allow a beam-based undulator segment alignment. Based on the scattering of the electrons on the BFW, we can detect the electron signal in the main dump bends after the undulator to find the beam position. We propose to use a threshold Cherenkov counter for this purpose. According to the signal strength at such a Cherenkov counter, we then suggest choice of material and size for such a BFW device in the undulator.
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| TUP050 | Microwave Helical Undulator-Based Production of Polarized Photons and Positrons | positron, radiation, 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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| WE1002 | The 4GLS at Daresbury | linac, electron, radiation, simulation | 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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| TH1001 | The Linac Coherent Light Source (LCLS) Accelerator | electron, linac, feedback, diagnostics | 511 | ||
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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. Such an FEL requires a high energy, high brightness electron beam to drive the FEL instability to saturation. When fed by an RF-photocathode gun, and modified to include two bunch compressor chicanes, the SLAC linac will provide such a high quality beam at 14 GeV and 1-micron normalized emittance. In this talk, we report on recent linac studies, including beam stability and tolerances, longitudinal and transverse feedback systems, conventional and time-resolved diagnostics, and beam collimation systems. Construction and installation of the injector through first bunch compressor will be complete by November 2006, and electron commissioning is scheduled to begin in December of that year.
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| FR1002 | SPring-8 Compact SASE Source | emittance, electron, cathode, radiation | 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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