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| MOP002 | Efficient Long-Pulse, Fully Loaded CTF3 Linac Operation | linac, beam-loading, acceleration, klystron | 31 | ||
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An efficient RF to beam energy transfer in the accelerating structures of the drive beam is on of the key points of the Compact Linear Collider (CLIC) RF power source. For this, the structures are fully beam-loaded, i.e. the accelerating gradient is nearly zero at the downstream end of each structure. In this way, about 96% of the RF energy can be transferred to the beam. To demonstrate this mode of operation, 1500 ns long beam pulses are accelerated in six fully loaded structures in the CLIC Test Facility (CTF3) Linac. In the paper we present the results of experimental studies on this mode of operation, compare them with theoretical predictions and discuss its potential use in CLIC.
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| MOP012 | Upgrade Status and Commissioning of BEPCII Linac | linac, positron, klystron, electron | 55 | ||
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BEPCII- an upgrade project of the BEPC is a factory type of e+e- collider. It requires its injector linac to have a higher beam energy (1.89 GeV) for on-energy injection and a higher beam current (40 mA e+ beam) for a higher injection rate (≥50 mA/min.). In five months from May 1st of 2005, we’ve installed and upgraded major parts of the machine, and then it ran for busy BSRF operation. We took a limited time to commission the machine and got a preliminary but satisfied result, the positron beam at the linac end was about 60mA. Now the linac is running smoothly, almost all design goals were reached. In this paper, we’ll present the upgrades for better beam quality, such as phasing system, beam feedback system, and report the present status of the BEPCII linac.
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| MOP013 | Low-Intensity, Pulsed-Beam Generation System Using the OPU Linac | electron, radiation, 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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| MOP015 | Linac Design for the FERMI Project | linac, controls, laser, electron | 61 | ||
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FERMI is a fourth generation light source under construction at Sincrotrone Trieste. This is based upon the conversion of the existing injector linac to a 1.2 GeV machine suitable to drive a seeded FEL. The linac will require significant improvements and the addition of several new accelerating modules. Important parameters are pulse to pulse energy stability and the jitter of the e-bunch time of arrival. This paper will cover the baseline design of the machine, as well as experimental results and the proposed technical solutions for the more critical sub-systems.
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| MOP020 | Status of the PITZ Facility Upgrade | cathode, emittance, diagnostics, booster | 76 | ||
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The upgrade of the Photo Injector Test Facility at DESY in Zeuthen towards the PITZ2 stage is continuously ongoing. In Spring 2006, an intermediate stage was taken into operation (PITZ1.6), including a new gun cavity that has been tuned and conditioned. Currently, three new emittance measurement systems are being installed along the beamline. After their commissioning, studies of the emittance conservation principle will be possible when using the available booster cavity. In the paper, the results of the RF commissioning of the new gun and the first beam measurements using recently installed diagnostics devices will be presented. The ongoing developments of further new diagnostics components will be discussed as well.
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| MOP021 | Recent Operation of the ORELA Electron LINAC at ORNL for Neutron Cross-Section Research | electron, klystron, vacuum, target | 79 | ||
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The ORNL electron LINAC, ORELA, began operation in 1969 and has been instrumental in providing improved neutron cross section data for many isotopes over the 0.002-60 MeV energy range. The ORELA utilizes a 4-30 ns <1000 Hz pulsed gridded electron gun, a 4 section RF Linac, and a water-cooled and moderated tantalum target to generate short neutron pulses. The short pulse lengths and long flight path provide high neutron energy resolution. Beam energy can range up to 180 MeV and a neutron production rate of up to 1014 n/sec can be generated with 50 kW of beam power. Recent operation is a 8 ns, 525 Hz pulse and a target power of 5-10 kW. RF power for the accelerator sections are provided by four 24 MW 1300 MHz klystrons. Recent activities have included improvements to the accelerator vacuum, klystrons, interlocks and other upgrades. The current ORELA program is focused on cross-section measurements for the Nuclear Criticality Safety Program and for nuclear astrophysics. Detection and data analysis capabilities have been developed for making highly accurate measurements of neutron capture, neutron total, (n,alpha), and (n,fission) cross sections simultaneously on different beam lines.
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| MOP022 | Simulation and Design of a Small LIA Stand | electron, linac, induction, simulation | 82 | ||
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A small LIA experiment stand is designed and manufactured at Accelerator Lab, Tsinghua University. It consists of a thermal cathode DC gun, two induction acceleration cells, pulse power supply system, beam transportation and diagnostics. The electron gun can produce an electron beam of 80 ns, 1.2A and 80keV. Two induction cells accelerate beam energy up to 240keV. The time interval of each two pulses is 300 ns, and the beam pulse flat-top is 80ns. Simulations of the beam transportation by PARMELA code and the optimized results of the beam line will be presented in this paper.
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| MOP024 | Electromagnetic Green's-Function-Based Simulations of Photocathode Sources | simulation, space-charge, cathode, electromagnetic-fields | 88 | ||
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We show the results of beam simulations for photocathode sources using a newly developed Green's function based code called IRPSS (Indiana Rf Photocathode Source Simulator). In general, a fully electromagnetic treatment of space-charge fields within simulations of photocathode sources is typically difficult since the beam is most often tightly bunched. The problem is further complicated by the inclusion of nearby conducting structures, i.e. cathode and cavity walls, from which the fields are reflected. The entire problem can be solved self-consistently using an electromagnetic Green's function method. Since Green's functions are generated by a Delta function source while simultaneously satisfying the boundary conditions of the system, they are an effective tool when solving for fields within photocathode source simulations. Using IRPSS we show the results of multiparticle simulations for a variety of photocathode source experiments.
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| MOP034 | Status of FS-FIR Project of the PAL | radiation, electron, 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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| TU1002 | Technologies Toward a 100-kW Free-Electron Laser | wiggler, electron, extraction, emittance | 205 | ||
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The challenges of a high-average-power (100 kW and above) FEL are not insurmountable. Some of these challenges however require technological solutions beyond the incremental improvements of existing mature technologies. Efforts are underway to develop novel technologies that could lead to a new level of FEL performance, e.g. 100-kW average power. These technologies include a high-average-current RF photo-injectors, spoke resonator RF cavities with energy recovery, high-gain amplifiers driven by high-brightness electron beams, beam-breakup instability suppression, and new concepts of tapered wiggler designs, e.g. stair-step taper, for efficient energy extraction. In this talk, these technologies, potential benefits and issues will be discussed.
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| TU3002 | Industrial Aspects of Linac Components | linac, radio-frequency, vacuum, electron | 237 | ||
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The industrial aspects of producing linac components from the particle sources, the accelerator structures, the magnet systems and RF systems will be discussed. The various aspects of working with national labs and universities will be covered. Such issues as to what type of Contract Form should be used; Organizational Conflict of Interest and Intellectual Property will be covered as well as how best to work with the labs and universities on SBIRs, CRADAs and Work for Others contract. Specific examples will be addressed including the unique issues for the ILC.
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| TUP001 | Linac Automated Beam Phase Control System | linac, controls, klystron, feedback | 241 | ||
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Adjustment of the rf phase in a linear accelerator is crucial for maintaining optimal performance. If phasing is incorrect, the beam will in general have an energy error and increased energy spread. While an energy error can be readily detected and corrected using position readings from beam position monitors at dispersion locations, this is not helpful for correcting energy spread in a system with many possible phase errors. Uncorrected energy spread results in poor capture efficiency in downstream accelerators, such as the Advanced Photon Source (APS’s) Particle Accumulator Ring (PAR) or Booster synchrotron. To address this issue, APS has implemented beam-to-rf phase detectors in the linac, along with software for automatic correction of phase errors. We discuss the design, implementation, and performance of these detectors and how they improved APS top-up operations. * Work supported by U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38.
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| TUP008 | The Low Emittance Photoinjector in Tsinghua University | emittance, cathode, laser, electron | 259 | ||
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A photocathode rf gun system is under developing in Tsinghua University for Thomson scattering. The microwave properties and the high power processing of this rf gun were finished. The UV laser system can provide a 266nm laser pulse with 1~10ps and 200μJ photo energy per pulse. The beam experiments are under way. This paper gives a general description of this photocathode rf gun and its preparation.
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| TUP018 | Low-Intensity Electron Beam Monitoring and Beam Applications at OPU Linac | electron, linac, monitoring, radiation | 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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| TUP026 | Status of the XFEL Testcavity Program | vacuum, electron, superconducting-RF, superconductivity | 302 | ||
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In preparation of the European XFEL-project a testcavity program of about 25 1.3GHz niobium single-cell cavities was launched at DESY beginning of 2005 in parallel to the accelerator nine-cell structure activities. After successful start-up of the DESY in-house fabrication main topics of the program are the optimisation of cavity electron beam welding preparation, the performance of large grain niobium and the qualification of further niobium vendors for cavity production. So far reproducibly all cavities (TESLA cell shape) exceed gradients of 30 MV/m at high Q-values. An electropolished mono-cell fabricated of large grain material reached 41 MV/m at Qo = 1.4·1010. The present status and results of the program are presented.
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| TUP038 | Status of the Sparc Photoinjector | laser, emittance, electron, cathode | 333 | ||
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The SPARC Project is starting the commissioning of its photo-injector. RF gun, RF sources, RF network and control, power supplies, emittance meter, beam diagnostics and control to measure the RF gun beam have been installed. The photocathode drive laser has been characterized in terms of pulse shape and quality. We will report also about first tests made on RF gun and on the emittance meter device. Additional R&D on X-band and S-band structures for velocity bunching are in progress, as well as studies on new photocathode materials . We will also discuss studies on solenoid field defects, beam based alignments and exotic electron bunch production via blow-out of short laser pulses.
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| TUP040 | Progress on a Cryogenically Cooled RF Gun Polarized Electron Source | cathode, vacuum, electron, ion | 339 | ||
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RF guns have proven useful in multiple accelerator applications. An RF gun capable of producing polarized electrons is an attractive electron source for the ILC or an electron-ion collider. Producing such a gun has proven elusive. The NEA GaAs photocathode needed for polarized electron production is damaged by the vacuum environment in an RF gun. Electron and ion backbombardment can also damage the cathode. These problems must be mitigated before producing an RF gun polarized electron source. In this paper we report continuing efforts to improve the vacuum environment in a normal conducting RF gun by cooling it with liquid Nitrogen after a high temperature vacuum bakeout. We also report on a design of a cathode preparation chamber to produce bulk GaAs photocathodes for testing in such a gun. Future directions are also discussed.
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| TUP044 | Shunt Impedance Measurement of the APS BBC Gun | impedance, cathode, electron, photon | 346 | ||
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The Advanced Photon Source (APS) ballistic bunch compression (BBC) injector is presently in use as a beam source for a number of experiments, including THz generation, beam position monitor testing for the Linac Coherent Light Source (LCLS), novel cathode testing, and radiation therapy source development. The APS BBC gun uses three independently powered and phased rf cavities, one cathode cell and two full cells, to provide beam energies from 2 – 10 MeV with variable energy spread, energy chirp, and, to an extent, bunch duration. The shunt impedance of an rf accelerator determines how effectively the accelerator can convert supplied rf power to accelerating gradient. The calculation of the shunt impedance can be complicated if the beam energy changes substantially during its transit through a cavity, such as in a cathode cell. We present the results of direct measurements of the shunt impedance of the APS BBC gun on an individual cavity basis, including the cathode cell, as well as report on achieved gradients. We also present a comparison of the measured shunt impedance with theoretical values calculated from the rf models of the cavities.
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| TUP045 | Photothermal Cathode Measurements at the Advanced Photon Source | cathode, laser, klystron, electron | 349 | ||
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The Advanced Photon Source (APS) ballistic bunch compression (BBC) injector presently uses an M-type thermionic dispenser cathode as a photocathode. This “photothermal” cathode offers substantial advantages over conventional metal photocathodes, including easy replacement and easy cleaning via the cathode’s built-in heater. We present the results of quantum efficiency measurements as a function of cathode heater power, laser pulse energy, and applied rf field strength.
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| TUP049 | Metal-Based Photocathodes For High-Brightness RF Photoinjectors | laser, cathode, vacuum, target | 358 | ||
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Advanced high brightness RF gun injectors require photocathodes with fast response, high quantum efficiency and good surface uniformity. Metal films deposited by various techniques on the gun back wall could satisfy these requirements. Two new deposition techniques have been recently proposed, i.e. pulsed laser ablation and vacuum arc. Several samples of various materials have been deposited by the two techniques: The emission performance and morphological changes induced on the cathode surface by laser beam are compared and discussed.
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| TUP055 | A Plasma Gun Driver for the SNS Ion Source | plasma, ion, ion-source, SNS | 370 | ||
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The ion source developed for the Spallation Neutron Source (SNS) is an RF-driven, multi-cusp source designed to produce ~ 40 mA of H- with a normalized rms emittance of less than 0.2 π mm mrad. To date, the source has been successfully utilized in the commissioning of the SNS accelerator producing 10–40 mA of H- with duty-factors of ~0.1%. Recently, we found the H- yield from the source could be increased dramatically with the introduction of streaming plasma particles injected into the primary RF plasma from a hemispherical glow discharge chamber located in the rear of the source. In some cases, a 50% increase in the H- beam current was observed. The system also eliminated the need for other plasma ignition systems like a secondary low-power RF generator. This report details the design of the plasma gun as well as the parametric dependence of H- current on source operating conditions. Comparisons are made with and without the gun energized. Finally, an off-line test stand was employed to characterize the plasma current emitted directly from the gun as well as perform lifetime characterization.
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SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U. S. Department of Energy. |
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| TUP056 | The Development of a High-Power, H- Ion Source for the SNS-Based on an External Antenna | plasma, SNS, ion, ion-source | 373 | ||
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The ion source developed for the Spallation Neutron Source* (SNS) is a radio frequency, multi-cusp H- source, which utilizes an internal antenna immersed within the source plasma. To date, the source has been utilized successfully in commissioning of the SNS accelerator delivering 10 - 40 mA with duty-factors of ~0.1% for periods of several weeks. Ultimately, the SNS facility will require beam currents of ~60 mA at 6% duty-factor. Tests have shown that the internal antenna is susceptible to failure at this duty-factor. Currently, two ion sources are being developed which feature ceramic plasma chambers surrounded by an external antenna. The first is a low-power, test version which employs a high-inductance external antenna and produces considerably higher H- beam currents than the original SNS source when both are operated without Cs. The second is a high-power version which features a Faraday shield with an integrated magnetic confinement structure and is designed to operate at full duty factor. The performance of this source should also greatly exceed that of the present SNS source. Details of the design and the measured performance of each source are discussed.
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| TUP057 | A Compact, Normal-conducting, Polarized Electron, L-band PWT Photoinjector for the ILC | emittance, electron, cathode, vacuum | 376 | ||
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The International Linear Collider (ILC) needs a polarized electron beam with a low transverse emittance. High spin-polarization (>85%) is attainable with a GaAs photocathode illuminated by a circularly polarized laser. Low emittance is achievable with an rf photoinjector. DULY Research has been developing an rf photoinjector called the Plane Wave Transformer (PWT) which may be suitable as a polarized electron source for the ILC. A 1+2(1/2) cell, L-band PWT photoinjector with a coaxial rf coupler is proposed for testing the survivability of GaAs cathode. It is planned to produce a high-aspect-ratio beam using a round-to-flat-beam transformation. In addition to its large vacuum conductance, the modified PWT has a perforated stainless steel sieve as a cavity wall, making it easy to pump the structure to better than 10-11 Torr at the photocathode. An L-band PWT gun can achieve a low emittance (0.45 mm-mrad for a 0.8nC round beam) with a low operating peak field (<25MV/m). A low peak field is beneficial for the survivability of the GaAs photocathode because electron backstreaming is greatly mitigated.
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| TUP058 | The RF Design of a HOM Polarized RF Gun for the ILC | cathode, emittance, electron, vacuum | 379 | ||
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The ILC requires a polarized electron beam. While a highly polarized beam can be produced by a GaAs-type cathode in a DC gun of the type currently in use at SLAC, JLAB and elsewhere, the ILC injector system can be simplified and made more efficient if a GaAs-type cathode can be combined with a low emittance RF gun. Since this type of cathode is known to be extremely sensitive to contamination including back bombardment by ions, any successful polarized RF gun must have a significantly improved operating vacuum compared to existing RF guns. We present a new RF design for an L-Band NC RF gun for the ILC polarized electron source. This design incorporates a higher order mode (HOM) structure, whose chief virtue in this application is an improved conductance for vacuum pumping on the cathode. Both 2-D and 3-D models have been used to optimize the RF parameters with two principal goals: first to minimize the required RF power; second to reduce the peak surface field relative to the field at the cathode in order to suppress field emitted electron bombardment. The beam properties have been simulated initially using PARMELA. Vacuum and cooling considerations for this design are discussed.
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| TUP062 | Experimental Optimization of TTF2 RF Photoinjector for Emittance Damping | emittance, booster, laser, damping | 391 | ||
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To get lasing and saturation at FEL facilities, we should generate high quality electron beams with a low emittance, a high peak current, and a low energy spread. Generally, the RF photoinjector is a key component to generate such a high quality beams. During DESY TESLA Test Facility (TTF) phase 2 commissioning, we optimized our L-band RF photoinjector and bunch compressor by comparing measurement results and simulation ones. In this paper, we describe our optimization experiences to get about 1.1 mm.mrad transverse normalized emittance for 1.0 nC single bunch charge and 4.4 ps RMS bunch length from TTF phase 2 RF photoinjector.
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| TUP063 | Commissioning of a New S-Band RF Gun for the Mark III FEL Facility at Duke University | cathode, linac, electron, emittance | 394 | ||
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At the Free Electron Laser (FEL) Laboratory of Duke University, there is an S-band linac based Mark III FEL facility which can supply coherent FEL photon in the infrared wavelength range. To supply high quality electron beams and to have excellent pulse structure, we installed one S-band RF gun with the LaB6 cathode for the Mark III FEL facility in 2005. Its longest macropulse length is about 6 us, and maximum repetition rates of macropulse and micropulse are 15 Hz and 2856 MHz, respectively. Therefore our new RF GUN can generate maximum 17142 bunches within a bunch train and maximum 257130 bunches within one second. In this paper, we describe recent commissioning experiences of our newly installed S-band RF GUN for the Mark III FEL facility.
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| TUP065 | Longitudinal Beam Dynamic Simulation of S-DALINAC Polarized Injector | electron, simulation, emittance, polarization | 400 | ||
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In future, a polarized gun will extend the experiment possibilities of the superconducting recirculating linear electron accelerator S-DALINAC. Therefore a new injector has to be designed where a new 100 keV polarized source SPIN will be added to the present unpolarized thermionic source. A polarization degree of 80%, a mean current of 60 uA and a 3 GHz cw structure are required. All features of the new source will be tested and measured at an offset beam line. The longitudinal beam dynamics of the injector are studied. The electron bunch length behind the gun is about 50 ps. The electrons has to be bunched to 5 ps for capturing the electrons to the main linac. Therefore a chopper/prebuncher system based on the devices used at MAMI is designed. The system consists of a harmonic chopper cavity, a slit, a first and a second harmonic prebuncher. The recent simulation results will be presented here.
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| TH3001 | Photoinjectors R&D for Future Light Sources and Linear Colliders | electron, emittance, cathode, laser | 549 | ||
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Linac-driven light sources and linear proposed colliders require high brightness electron beams. In addition to the small emittances and high peak currents, linear colliders also require spin-polarization and possibly the generation of asymmetric beam in the two transverse degree-of-freedom. Other applications (e.g. high power free-electron lasers) call for high duty cycle and/or angular-momentum-dominated electron beams (electron cooling). We review on-going R&D programs aiming at the production of electron beams satisfying these various requirements. We especially discuss R&D on photoemission electron sources (especially based on radio-frequency gun) along with the possible use of emittance manipulation techniques.
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| THP033 | Pulsed RF Heating Particularities in Normal-Conducting L-band Cavities | booster, cathode, linac, positron | 646 | ||
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For present projects, such as X-FEL and ILC, the SC technology is chosen for the main linacs. However, in some special parts, NC cavities are applied, operating with high electric and magnetic fields. RF gun cavities with an electric field up to 60 MV/m at the photo cathode are now under development. Capture cavities in the ILC positron source should operate with an accelerating gradient of up to 15 MV/m, practically the same value (14 MV/m), as for the CDS booster cavity in the Photo Injector Test Facility at DESY in Zeuthen (PITZ). High field strength leads to high specific RF heat loading. In combination with long RF pulses (~ 1ms) it results in substantial surface temperature rise, small cavity shape deformations and measurable frequency shifts. In this report we discuss both particularities and some general regularities related to long pulse operation of L-band cavities. Results of 3D numerical simulations for cavity surface temperature, displacements distributions and corresponding frequency shifts for different cavities are presented and compared with existing experimental data. The presented results will give the input for cavities optimization and sub-systems improvements.
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| THP043 | The RF System of the Sparc Photo-Injector @ LNF | klystron, linac, vacuum, controls | 676 | ||
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The S-band linear accelerator SPARC is in advanced phase of installation and test at the INFN Frascati Laboratories. The purpose of the machine is to produce low emittance, high peak current electron beams to drive a SASE-FEL experiment. The SPARC RF system consists of an RF gun followed by 3 S-band room-temperature accelerating structures, supplied by 2 pulsed high power klystrons. The use of waveguide power attenuators and phase-shifters is foreseen to adjust independently the accelerating structures field amplitude and phase; this will be helpful for tuning the linac working point in the initial machine set-up. This paper reviews the experience in installation, RF conditioning, and commissioning of the normal conducting linac accelerating structures and RF subsystems.
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| THP065 | High-Gradient Generation in Dielectric-Loaded Wakefield Structures | electron, simulation, laser, klystron | 731 | ||
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Dielectric loaded wakefield structures have potential to be used as high gradient accelerator components. Using the high current drive beam at the Argonne Wakefield Accelerator Facility, we employed cylindrical dielectric loaded wakefield structures to generate accelerating fields of up to 43 MV/m at 14 GHz. Short electron bunches (13 ps FWHM) of up to 86 nC are used to drive these fields, either as single bunches or as bunch trains. One of these structures consists of a 23 mm long cylindrical ceramic tube (cordierite) with a dielectric constant of 4.76, and inner diameter of 10 mm, inserted into a cylindrical copper waveguide. This standing-wave structure has a field probe near the outer edge of the dielectric to sample the RF fields generated by the electron bunches. The signal is sent to a mixer circuit, where the 14 GHz signal is down converted to 5 GHz and then sent to an oscilloscope. A similar structure, with smaller inner diameter and an operating frequency of 9 GHz, is ready for initial tests. Its accelerating fields will be twice as high as the fields in the 14 GHz structure, for the same bunch charge.
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| THP083 | Generation of Ellipsoidal Beam Through 3-D Pulse Shaping of a Photoinjector Drive Laser | laser, simulation, emittance, electron | 776 | ||
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Due to the linear space-charge force, an ellipsoidal beam is expected to have much smaller emittance in comparison with beams of other geometries, which is critical for many accelerator applications. Up to now, no practical way of generating such beams is available. In this paper we present a few schemes for 3-D laser pulse shaping that can be used to generate ellipsoidal laser pulses that in turn can be applied for generating ellipsoidal electron bunches from a photoinjector. Our simulations show that 3D laser pulse shaping can be realized through laser phase tailoring in combination with properly designed refractive and diffractive optics. Performance of an electron beam generated from such shaped laser pulses is compared with that of the ideal flat-topped and Gaussian electron bunches by numerical simulation, showing improvement in both beam dynamics and performance.
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| THP097 | FPGA BASED DIGITAL RF CONTROL FOR FLASH | controls, klystron, feedback, cathode | 809 | ||
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Most parts of the LLRF control system used in FLASH are based on the DSP processors. Actual computation power of the system is close to the limit, the algorithm is performed in a time longer than 1μs. The only way to extend the system with new features was to add more DSP processors. This solution requires integration of new DSP board into existing system. It may cause some additional problems and delays in the machine operations. During past years very fast progress on the FPGA market was observed. Nowadays FPGA chips have reached the computation power that can be compared with DSP processors. These chips offer variety of the embedded solutions such as PowerPC, Microblaze, Nios which can be easily used in addition to fast, parallel signal processing. Moreover large number of user pins makes it possible to integrate all the elements necessary for the control into one PCB board. Therefore, for the evaluation purposes, some parts of the system were replaced by FPGA based boards. This article summarizes the FPGA boards that are currently in use and describes algorithms executed by these boards.
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