| Paper | Title | Other Keywords | Page | ||
|---|---|---|---|---|---|
| MO3001 | Intense Heavy-Ion Beam Production with ECR Sources | plasma, ion, ion-source, coupling | 18 | ||
|
An average increase of about one order of magnitude per decade in the performance of ECR ion sources was obtained up to now since the time of pioneering experiment of R. Geller at CEA Grenoble and this trend is not deemed to get the saturation at least in the next decade, according to the increased availability of powerful magnets and microwave generators. Electron density above 1013 cm-3 can be obtained by 28 GHz microwave heating, but only an adequate plasma trap may allow to exploit that plasma for heavy elements ionization. A study about the optimization of the magnetic field and of the other different parameters affecting the ECRIS plasma is presented, with a special emphasis on the coupling of microwaves to plasma. Long-term perspectives are presented finally, with an analysis of the possibilities opened by higher frequency generators, as 60 GHz gyro-TWTs, with the use of moderate confinement trap, by combining the large plasma density with larger escape rates in order to get larger ion beam currents.
|
|
|
||
| MOP005 | Beam Dynamics for Intense L-band Electron Linac | linac, bunching, simulation, focusing | 37 | ||
|
We are now developing an intense L-band electron linac with a traveling-wave accelerating structure for irradiation applications. It is capable to produce 10 MeV electron beams of 30 kW by a pulsed klystron of 25 MW with a 60 kW average power. Bunching and accelerating cavities operated with 2π/3 mode at 1.3 GHz are designed by the SUPERFISH code. Focusing solenoids are designed by the POISSON code. Using electromagnetic field configurations obtained by these codes, a simulational study on the beam dynamics is conducted by the PARMELA code. As results, the beam envelope supports a transmission efficiency over 91% with the E-gun current of 1.6 A.
|
|
|
||
| MOP006 | A Bunch Compressor for the CLIC Main Beam | emittance, radiation, synchrotron, synchrotron-radiation | 40 | ||
|
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.
|
|
|
||
| MOP007 | Turn Around Loop and Chicane for Bunch Compression and Path Length Tuning in the CLIC Drive Beam | emittance, kicker, simulation, dipole | 43 | ||
|
The phase feedback of the CLIC drive beam consists of phase and energy measurement stations in front of the turn around loops and chicanes for bunch compression and path length correction behind the loops. The chicanes are foreseen to compress the bunches from 4 mm to 0.4 mm and should allow a path length tuning of at least 0.1 mm. Suitable layouts for the turn around loops and the chicanes and results of beam dynamics simulations including incoherent and coherent synchrotron radiation are presented.
|
|
|
||
| MOP008 | Design and Performance of Optics for Multi-Energy Injector Linac | injection, optics, linac, quadrupole | 46 | ||
|
Injector linac provides injection beams for four storage rings, KEKB high energy electron ring (HER), KEKB low energy positron ring (LER), PF-AR electron ring, and PF electron ring. The injection beams for these rings have different energies and intensities. Recently, a requirement of simultaneous injection among these rings arises to make a top-up injection possible. Magnetic fields of DC magnets to confine the beam to the accelerating structures can not be changed between pulse to pulse, although the beam energy can be controlled by fast rf phase shifters of klystrons. This implies that common magnetic fields of bending magnets and quadrupole magnets should be utilized to deliver beams having different characteristics. Therefore, we have designed multi-energy optics for KEKB high energy electron ring (8 GeV, 1 nC/pulse) and PF electron ring (2.5 GeV, 0.1 nC/pulse) and present a performance of the multi-energy injector linac.
|
|
|
||
| MOP009 | Dragon-I Linear Induction Accelerator | induction, emittance, cathode, linac | 49 | ||
|
The best quality induction linac in the world, named Dragon-I, has been built at Institute of Fluid Physics, China Academy of Engineering Physics. It can produce 2.5~3kA high current electron beam with energy of 20MeV and pulse width of 70ns. The spot size of about 1mm diameter has been achieved with beam current greater than 2.5kA. The design of Dragon-I facility is introduced briefly. The commissioning and results of Dragon-I are presented in the paper including the most recent time resolved measurements of beam parameters.
|
|
|
||
| MOP010 | Massively Parallel Wake Field Computations in Long Accelerator Structures | simulation, vacuum, shielding, diagnostics | 52 | ||
|
The X-FEL project and the ILC require a high quality beam with ultra short bunches. The knowledge of the short-range wakefields in the TESLA cavities and the collimators is needed to predict the beam quality in terms of the single bunch energy spread and emittance. Especially for the high energy collimators these calculations are limited by numerical dispersion. Earlier we presented wake field calculations for short bunches in long structures for rotationally symmetric components with the code ECHO. Now we present first results from our new wake field code in fully 3D. To calculate the effect of the longitudinal and transverse wakefields we have used the time domain numerical approach. For sufficient resolution of the geometric boundaries and the short bunches (down to the nm-range), huge computational resources are needed. Thus in 3D massive parallelisation of the code is necessary. In addition we used the technique of a moving grid, which gives access also to very long structures, i.e. a complete module of eight TESLA cells or a high energy collimator.
|
|
|
||
| MOP012 | Upgrade Status and Commissioning of BEPCII Linac | linac, positron, gun, klystron | 55 | ||
|
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.
|
|
|
||
| MOP013 | Low-Intensity, Pulsed-Beam Generation System Using the OPU Linac | gun, radiation, linac, cathode | 58 | ||
|
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.
|
|
|
||
| MOP015 | Linac Design for the FERMI Project | linac, controls, laser, gun | 61 | ||
|
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.
|
|
|
||
| MOP016 | SRF Linac Solutions for 4GLS at Daresbury | linac, damping, acceleration, superconducting-RF | 64 | ||
|
The proposed 4th Generation Light Source (4GLS) facility, anticipated to be located at Daresbury Laboratory in the UK, will extensively utilise Superconducting RF (SRF) Linacs for each stage of its multi-beam acceleration. IR, XUV and VUV FEL devices, and particularly the ability to combine these sources for users, provide a unique capability for this Energy Recovery Linac (ERL) based accelerator. The CW mode of operation for the SRF Linacs necessitates that adequate provision is made for delivering the required RF power and also damping of the beam induced HOMs to manageable levels. This paper outlines the RF requirements and proposed solutions for each of the 4GLS Linacs.
|
|
|
||
| MOP019 | Methods to Reduce the Electron Beam Energy Spread at the S-DALINAC | linac, recirculation, controls, feedback | 73 | ||
|
The S-DALINAC is a recirculating superconducting electron linac operating at 3 GHz. The accelerator delivers a cw beam with energies up to 130 MeV to serve electron scattering experiments where highest momentum resolutions, typ. below 1·10-4 are required. Current activities aim to reduce the energy spread of the accelerator by two methods: Long term drifts, mainly a result of temperature drifts, will be corrected by a feedback system which measures the energy variation of the extracted beam continuously using rf-monitors. By means of time-of-flight analysis in a modified beamline a correction signal can be generated as a feedback for the rf control of the accelerating cavities. This system was set-up recently and first results will be reported. Furthermore, the influence of short term fluctuations, e.g. triggered by micro-phonics, on the electron energy can significantly be reduced utilizing the inherent stability of a microtron, if the synchronous phase and longitudinal dispersion are chosen properly. The concept, particle simulations and the experimental verification will be shown as well as necessary modifications to the recirculation scheme to use it in an all-day operation.
|
|
|
||
| MOP021 | Recent Operation of the ORELA Electron LINAC at ORNL for Neutron Cross-Section Research | gun, klystron, vacuum, target | 79 | ||
|
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.
|
|
|
||
| MOP022 | Simulation and Design of a Small LIA Stand | linac, induction, simulation, gun | 82 | ||
|
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.
|
|
|
||
| MOP026 | Positron Source from X-rays Emitted by Plasma Betatron Motion | positron, plasma, photon, ion | 94 | ||
|
A new method for generating positrons has been proposed that uses betatron X-rays emitted by an electron beam in a high-K plasma wiggler. The plasma wiggler is an ion column produced by the head of the beam when the peak beam density exceeds the plasma density. The radial electric field of the beam blows out the plasma electrons transversely, creating an ion column. The focusing electric field of the ion column causes the beam electrons to execute betatron oscillations about the ion column axis. At the proper plasma density, this leads to synchrotron radiation in the 1-50 MeV range. These photons strike a thin (.5Xo), high-Z target and create electron-positron pairs. A computational model was written and matched with experimental results taken at the Stanford Linear Accelerator Center. This model was then used to design a more efficient positron source, giving positron yields of 0.44 positrons/electron, a number that is close to the target goal of 1-2 positrons/electron for future positron sources.
|
|
|
||
| MOP029 | Laser Beat-Wave Microbunching of Relativistic Electron Beam in the THz Range | laser, undulator, plasma, radiation | 100 | ||
|
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.
|
|
|
||
| MOP034 | Status of FS-FIR Project of the PAL | radiation, gun, linac, undulator | 112 | ||
|
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.
|
|
|
||
| MOP036 | Status of the PAL-XFEL Project | laser, undulator, linac, radiation | 118 | ||
|
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.
|
|
|
||
| MOP037 | Applications of Time-of-Flight Measurements at FLASH | linac, vacuum, laser, undulator | 121 | ||
|
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.
|
|
|
||
| MOP067 | Higher Order Mode Wakefield Simulations and Beam Dynamics Simulations in the ILC Main Linacs | emittance, linac, simulation, superconductivity | 199 | ||
|
The progress of approximately 3000 electron (and positron) bunches down the main linacs of the ILC (International Linear Collider) can readily give rise to dipole modes which distrupt the progress of the beam. We investigate the transverse modes which are excited and monitor the resulting emittance dilution which occurs down the linac. At present there are two design configurations for the ILC: the BCD (Baseline Configuration Design) and the ACD (Alternate Configuration Design). We investigate the wake fields and beam dynamics for both configurations. In particular, the influence of trapped modes on the emittance of the beam is studied.
|
|
|
||
| TU1002 | Technologies Toward a 100-kW Free-Electron Laser | wiggler, gun, extraction, emittance | 205 | ||
|
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.
|
|
|
||
| TU1003 | Modern Electron Induction Linacs | target, induction, cathode, linac | 208 | ||
|
Several high power induction linacs are in existence and a couple are being built around the world. Typically, they are capable of delivering about 100 micro-coulombs of e-beam to the target in a single burst and are built for radiographic application. DARHT 2nd Axis induction linac under construction at Los Alamos National Laboratory is the first of its kind, designed to deliver multiple e-beam pulses to the target. This incorporates the latest advances in the induction linac technology. An overview of the existing as well as the DARHT induction linac will be presented in this paper.
|
|
|
||
| TU1004 | Development of High-Current, High-Duty-Factor H- Injectors | emittance, SNS, ion, plasma | 213 | ||
|
SNS, FNAL, and CERN have projects that require the production of H- beams with increased intensity and increased duty factors. The most demanding requirements are set by SNS, which plans to upgrade its power to 3 MW. This power level requires a LINAC peak current of 59 mA, which results from an RFQ input current between 67 and 95mA when injecting with rms-emittances between 0.20 and 0.35 Pi-mm-mrad, respectively. Predicted downstream losses exclude the use of higher emittance beams. Ion source lifetime and reliability requirements are also stringent to meet the 99.5% availability goal for the injector of a user facility with 95% availability. LEBT options are currently being studied to optimally match the ion source output into the RFQ with a minimal distortion of the beam emittance. Several ion source and LEBT options under consideration will be discussed.
|
|
|
||
| TU3002 | Industrial Aspects of Linac Components | linac, gun, radio-frequency, vacuum | 237 | ||
|
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.
|
|
|
||
| TUP004 | Intense L-Band Electron Linac for Industrial Applications | coupling, linac, impedance, klystron | 250 | ||
|
An intense L-band travelling-wave electron linac is under development for irradiation applications. It is capable of producing 10 MeV electron beams of 30 kW average beam power. The operating energy is limited to prevent neutron production. On the other hand, the current is limited by the beam loading effect in the given structure. The accelerating structure operated with 2π/3 mode is constant-impedance and disk-loaded waveguides. We determined the optimum operating parameters by adjusting the duty factor, which is again governed by the available high-power pulsed klystron. The SUPERFISH code was used to design the bunching and accelerating cavities. The PARMELA code gives the result of beam dynamics. We present design details of the intense travelling-wave linac powered by a 1.3 GHz, 25 MW pulsed klystron with a duty factor of 0.21%. We also present cold test results for the prototype cavities.
|
|
|
||
| TUP007 | Low-Energy Linacs and Their Applications in Tsinghua University | linac, klystron, positron, scattering | 256 | ||
|
During these years, several kinds of low energy linacs were developed for cargo inspection, non-destructive-test and irradiation in Tsinghua University cooperated with NUCTECH company. The newly finished interlaced pulse dual energy 9/6MeV linac for material distinguishing cargo inspection and several others will be described here. The beam dynamics simulation and the experiment results together with some applications of these linacs will be given in this paper.
|
|
|
||
| TUP008 | The Low Emittance Photoinjector in Tsinghua University | emittance, cathode, gun, laser | 259 | ||
|
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.
|
|
|
||
| TUP013 | Using Higher Order Modes in Superconducting Accelerating Cavities for Beam Monitoring | monitoring, controls, dipole, single-bunch | 271 | ||
|
Dipole modes have been shown to be successful diagnostics for the beam position in superconducting accelerating cavities at the VUV Free Electron Laser (FEL) facility at DESY. By help of downmixing electronics the signals from the two higher order mode couplers mounted on each cavity are monitored. Due to the non-symmetric placement of the couplers and the overlapping of the two polarizations of the modes, the calibration is somewhat more complicated than in standard position monitors. A method based on the model independent analysis has been developed. The calibration measurements made at the VUV FEL will be presented.
|
|
|
||
| TUP014 | Electron Signal Detection for the Beam-Finder Wire of the Linac Coherent Light Source Undulator | undulator, scattering, simulation, photon | 274 | ||
|
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.
|
|
|
||
| TUP015 | Linac Coherent Light Source (LCLS) Bunch-Length Monitor Using Coherent Radiation | radiation, synchrotron, synchrotron-radiation, storage-ring | 277 | ||
|
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.
|
|
|
||
| TUP017 | A Damper System for the Electron Cooling Beam in the Recycler | damping, antiproton, feedback, controls | 283 | ||
|
The antiproton stacking rate in the Fermilab Recycler has been dramatically improved with the commissioning of the Electron Cooling system last year. Various disturbance sources such as mechanical vibrations in the Pelletron , power line fluctuations and coupling from beam ramps in the nearby Main Injector have added noise components in the electron beam position in the 0.5 to 200 Hz range. An AC coupled damping feedback loop with corrector coils for horizontal and vertical position correction at two upstream points from the BPMs was added to the existing BPM system . The system provides 10 – 20 dB damping in the frequency range above without interfering with other DC beam positioning control loops.
|
|
|
||
| TUP018 | Low-Intensity Electron Beam Monitoring and Beam Applications at OPU Linac | linac, monitoring, radiation, gun | 286 | ||
|
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.
|
|
|
||
| TUP020 | The J-PARC L3BT Monitor System for RCS Injection | injection, linac, beam-losses, pick-up | 290 | ||
|
The J-PARC linac-3GeV rapid cycling synchrotron (RCS) beam transport line (L3BT) monitor system will be used to tune the intensity of 5mA-50mA linac beam. The monitor system is composed of BPMs and multi wire profile scanners (MWPS) in L3BT line and RCS injection area. A non-destructive beam momentum spread monitor using a 4-stripline pickups is also developed in order to measure and control the momentum spread of linac beams. The spatial resolution of less than 0.3mm and momentum spread of less than 0.1% is required for RCS injection to avoid uncontrolled beam losses. In this paper, beam position monitor, profile monitor and momentum spread measurement for J-PARC linac is described. Preliminary results of beam size and m value measurement with quadrupole mode of the signal of 4-stripline BPMs in the KEK MEBT1 are also discussed.
|
|
|
||
| TUP021 | Wire Profile Monitors in J-PARC Linac | linac, proton, simulation, rfq | 293 | ||
|
We plan to install wire scanners for J-PARC linac in order to measure beam profile and emittance. They have been designed to capture electrons in H-, 7um-diameter carbon wires are used in 3MeV point and 30um-diameter tungsten wires are used for 50-181MeV point. We plan to set 36 wire scanners in linac and beam dumps. In this paper, we report the result of beam test with 3MeV beam at KEK and the calculation about signal and wire temperature.
|
|
|
||
| TUP025 | Optimization of Surface Treatment of High-Gradient Single-Cell Superconducting Cavities at KEK | superconductivity, vacuum, pick-up, cryogenics | 299 | ||
|
We have continued the study of a series of single cell superconducting cavities at KEK. These tests are aimed at establishing a prescription for a surface treatment that would reliably allow cavities to reach gradients in excess of 45 MV/m in vertical tests. The cavity profiles were all of the KEK Low Loss design, and were fabricated from deep drawn Niobium half shells using electron beam welding. The cavity initial surface preparation followed an established KEK procedure of centrifugal barrel polishing, high temperature annealing, light chemical polishing, electropolishing. and final a high pressure water rinse. Early results from this series test demonstrated that reaching gradients as high as 50 MV/m is feasible. However, the initial yield was of order 50%. In this paper we will discuss our studies of further improvement of the surface treatment aimed at increasing the yield.
|
|
|
||
| TUP026 | Status of the XFEL Testcavity Program | vacuum, gun, superconducting-RF, superconductivity | 302 | ||
|
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.
|
|
|
||
| TUP035 | Investigation of Hot Spots as a Function of Material Removal in a Large-grain Niobium Cavity | vacuum, pick-up | 324 | ||
|
The performance of a single-cell cavity made of RRR > 200 large-grain niobium has been investigated as a function of material removal by buffered chemical polishing (BCP). Temperature maps of the cavity surface at 1.7 and 2 K were taken for each step of chemical etching and revealed several “hot-spots”, which contribute to the degradation of the cavity quality factor as a function of the radio-frequency (RF) surface field. It was found that number of “hot-spots” decreased for larger material removal. Interestingly, the losses of the “hot-spots” at different locations evolved differently for successive material removal. The cavity achieved peak surface magnetic fields of about of 130 mT and was limited mostly by thermal quench. By measuring the temperature dependence of the surface resistance at low field between 4.2 K and 1.7 K, the variation of material parameters such as the ratio between the energy gap and the critical temperature, the residual resistance and the mean free path as a function of material removal could also be investigated. This contribution shows the results of the RF tests along with the temperature maps and the analysis of the losses caused by the “hot-spots”.
|
|
|
||
| TUP038 | Status of the Sparc Photoinjector | laser, emittance, gun, cathode | 333 | ||
|
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.
|
|
|
||
| TUP040 | Progress on a Cryogenically Cooled RF Gun Polarized Electron Source | gun, cathode, vacuum, ion | 339 | ||
|
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.
|
|
|
||
| TUP044 | Shunt Impedance Measurement of the APS BBC Gun | impedance, cathode, gun, photon | 346 | ||
|
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.
|
|
|
||
| TUP045 | Photothermal Cathode Measurements at the Advanced Photon Source | cathode, laser, gun, klystron | 349 | ||
|
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.
|
|
|
||
| TUP057 | A Compact, Normal-conducting, Polarized Electron, L-band PWT Photoinjector for the ILC | emittance, cathode, vacuum, gun | 376 | ||
|
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.
|
|
|
||
| TUP058 | The RF Design of a HOM Polarized RF Gun for the ILC | gun, cathode, emittance, vacuum | 379 | ||
|
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.
|
|
|
||
| TUP059 | Photoinjector Production of a Flat Beam with Transverse Emittance Ratio of 100 | emittance, quadrupole, simulation, laser | 382 | ||
|
The generation of a flat electron beam directly from a photoinjector is an attractive alternative to the electron damping ring as envisioned for linear colliders. It also has potential applications to light sources such as the generation of ultrashort x-ray pulses or Smith-Purcell free electron lasers. In this paper, we report on the experimental generation of a flat beam with a measured transverse emittance ratio of 100±20 for a bunch charge of ≅0.5~nC*. The experimental data, obtained at the Fermilab/NICADD Photoinjector Laboratory, are compared with numerical simulations and the expected scaling laws. Possible improvement of the experiment along with application for such a flat beams are discussed
|
* P. Piot, Y.-E. Sun and K.-J. Kim, Phys. Rev. ST Accel. Beams 9, 031001 (2006) |
|
||
| TUP060 | Status of the EBIS Project at Brookhaven | ion, rfq, linac, injection | 385 | ||
|
The EBIS Project at Brookhaven National Laboratory will replace the Tandem Van de Graaff accelerators with an Electron Beam Ion Source, an RFQ, and short linac, as the heavy ion preinjector for RHIC. This project, jointly funded by DOE and NASA, will provide a modern preinjector which will have increased flexibility in providing beams to the various programs running simultaneously, will be capable of providing beams not presently available for RHIC and the NASA Space Radiation Laboratory, and will be simpler and less costly to operate. Presently in the first year of the four-year project, the detailed design is nearly complete, and some major procurements have been placed. The overall status of the project will be presented, as well as some unique features in the design, and results from the R&D using the prototype EBIS.
|
|
|
||
| TUP061 | The HERA RF-Driven Multicusp H- Ion Source | plasma, vacuum, coupling, SNS | 388 | ||
|
The HERA RF-Volume Source is the only source that delivered routinely a H- current of 40 mA without Cs. This current has been improved to 60 mA. For HERA a pulse length of less than 200 μsec is necessary. It was possible to demonstrate a pulse length of 3 msec with the HERA source at DESY in a cooperation with SNS, FNAL and CERN. RF H- sources are now in permanent use for accelerators like HERA or SNS. The reliability of these sources becomes very important. Special techniques for a reliable external RF coupling to the plasma, ignition, filter field, collar transition for extraction and electron dumping have been developed at DESY. The physics of the extraction plasma region was the subject of very detailed investigations with special sets of collars, cones and Langmuir probes.
|
|
|
||
| TUP063 | Commissioning of a New S-Band RF Gun for the Mark III FEL Facility at Duke University | gun, cathode, linac, emittance | 394 | ||
|
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.
|
|
|
||
| TUP065 | Longitudinal Beam Dynamic Simulation of S-DALINAC Polarized Injector | gun, simulation, emittance, polarization | 400 | ||
|
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.
|
|
|
||
| TUP092 | Emittance Exchange at FNPL | emittance, coupling, klystron, pick-up | 478 | ||
|
An experiment to attempt the exchange of the transverse emittance with the longitudinal emittance of the Fermilab/NICADD PhotoInjector electron beam is being developed. The emittance exchange occurs by placing a TM110 mode RF cavity in the maximum dispersive region of a magnetic chicane. Properly employed, the cavity's longitudinal shearing Electric field zeros the momentum spread at the cost of generating a non-zero betatron oscillation amplitude. We report on the beam line modeling, beam line design, the RF cavity design, present status as well as the future program.
|
|
|
||
| WE1002 | The 4GLS at Daresbury | linac, radiation, simulation, undulator | 481 | ||
|
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.
|
|
|
||
| WE1003 | The TTF/VUV-FEL (FLASH) as the Prototype for the European XFEL Project | linac, laser, free-electron-laser, radiation | 486 | ||
|
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.
|
|
|
||
| WE2005 | HOM Damping and Power Extraction from Superconducting Cavities | damping, linac, coupling, impedance | 506 | ||
|
Damping of Higher Order Modes plays an important role in achieving and preserving low emittance and low energy modulation of beams in accelerators based on the superconducting technology. In the overview, various damping schemes and damping devices and their advantages and disadvantages will be discussed.
|
|
|
||
| TH1001 | The Linac Coherent Light Source (LCLS) Accelerator | linac, feedback, undulator, diagnostics | 511 | ||
|
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.
|
|
|
||
| TH2002 | Timing and Synchronization in Large-Scale Linear Accelerators | laser, diagnostics, radiation, linac | 536 | ||
|
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.
|
Interim Report of the Scientific and Technical Issues (XFEL-STI) Working Group ona European XFEL facility in Hamburg, January 11, 2005. |
|
||
| TH2004 | Nuclear Photo-Science and Applications with Thomson-Radiated Extreme X-Ray (T-REX) Sources | laser, scattering, photon, brightness | 546 | ||
|
The Thomson scattering of picosecond and femtosecond duration laser pulses off of low emittance electron beams is an effective method of producing mono-chromatic, MeV-range gamma-rays with unprecedented peak brightness. With peak brightness at 1 MeV > 15 orders of magnitude beyond 3rd generation synchrotrons, these sources open the possibility for a host of new nuclear applications based on photons. In this presentation an overview of the requisite photo-gun, short pulse laser and linear accelerator technologies required for production of high brightness gamma-rays will be presented. Potential applications of these unique sources of radiation will be discussed with particular emphasis given to the excitation and use of nuclear resonance fluorescence (NRF) for isotope detection and imaging of special nuclear materials of importance to homeland security.
|
|
|
||
| TH3001 | Photoinjectors R&D for Future Light Sources and Linear Colliders | gun, emittance, cathode, laser | 549 | ||
|
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.
|
|
|
||
| TH3002 | Normal-Conducting Energy Recuperator | emittance, linac, free-electron-laser, optics | 554 | ||
|
Energy recovery linacs (ERLs) for different applications were discussed intensively at last decade. The normal conducting RF ERLs offer the possibility to provide high average currents at relatively low beam energies and long electron bunches. The comparison of normal conducting and superconducting RF is described briefly. To illustrate some interesting features of normal conducting ERLs some details of design, operational experience and prospects of the Novosibirsk FEL ERL are presented.
|
|
|
||
| THP003 | Integrated Optical Timing and RF Reference Distribution System for Large-Scale Linear Accelerators | laser, feedback, linac, controls | 565 | ||
|
Highly-stable timing and RF reference distribution systems are required to meet the tight specifications in large scale accelerators for next generation light sources. In this paper, we present an approach based on the distribution of an optical pulse train from a mode-locked laser via timing stabilized fiber links. The timing information is contained in the precise repetition rate of the optical pulse train (~50 MHz), so RF can be extracted at end stations with a stability on the order of 10 fs. Less timing critical signals such as ADC clocks and trigger signals can be transmitted through the same stabilized fiber using a modulated cw laser operating at a different wavelength with sub-ps stability. As multiple wavelengths can propagate without interference through the fiber, it is also possible to integrate data communication in such a fiber system. This paper will review the timing system requirements and present a conceptual layout of an optical timing and reference frequency distribution system based on work done at MIT and DESY for the XFEL.
|
|
|
||
| THP011 | High Gradient Operation with the CEBAF Upgrade RF Control System | controls, resonance, feedback, linac | 589 | ||
|
The CEBAF Accelerator at Jefferson Lab is presently a 6 GeV five pass electron accelerator consisting of two superconducting linacs joined by independent magnetic transport arcs. It is planned to increase the energy to 12 GeV with the addition of 10 new high gradient cryomodules (17+ MV/m). The higher gradients pose significant challenges beyond what the present analog low level RF (LLRF) control systems can handle reliably; therefore, a new LLRF control system is needed. A prototype system has been developed incorporating a large FPGA and using digital down and up conversion to minimize the need for analog components. The new system is more flexible and less susceptible to drifts and component nonlinearities. Because resonance control is critical to reach high gradients quickly, the new cryomodules will include a piezoelectric tuner for each cavity, and the LLRF controls must incorporate both feedback and feed-forward methods to achieve optimal resonance control performance. This paper discusses development of the new RF system, system performance for phase and amplitude stability and resonance control under Lorentz detuning measured during recent tests on a prototype cryomodule.
|
|
|
||
| THP021 | Study of Vacuum Insulator Flashover for Pulse Lengths of Multi-Microseconds | plasma, cathode, vacuum, diagnostics | 610 | ||
|
We have studied the flashover of vacuum insulators for applications where high voltage conditioning of the insulator and electrodes is not practical and for pulse lengths on the order of several microseconds. The study was centered about experiments performed with a 100-kV, 10-μs pulsed power system and supported by a combination of theoretical and computational modeling. The base line geometry for the experiments was a cylindrically symmetric, +45° insulator between flat electrodes. In the experiments, flashovers or breakdowns were localized by operating at field stresses slightly below the level needed for explosive emissions with the base line geometry. The electrodes and/or insulator were then seeded with an emission source, e.g. a tuff of velvet, or a known mechanical defect. Our study differs from most vacuum insulator studies in that our emphasis was on flashovers originating at the anode triple junction as well as bulk breakdowns within the insulator. Various standard techniques were employed to suppress cathode-originating flashovers/breakdowns. We present the results of our experiments and discuss the capabilities of modeling insulator flashover.
|
|
|
||
| THP035 | Design on Accelerating Tube of High-Power Electron Linac for Irradiation Processing | linac, beam-losses, bunching, simulation | 652 | ||
|
There is an unstable phenomenon for high-power electron linacs for irradiation processing. The main source of the instability of this type of linac comes from the thermal effect of the accelerator tube under an intense heat load. If a lot of injected electrons are lost in the tube, they can cause an intense and uneven heat load on the tube that may deform the cavities of the accelerator tube and deviate the correct acceleration phase relationship. In this paper, a constant gradient accelerating structure is chosen to accelerate the electron beam, and the designed phase velocity is gradually increased along the tube. By adjusting the size of the accelerating cavities and the phase velocity function, a high capture-efficiency is reached. After a series of simulations studies, we obtained a 90% capture-efficiency, which minimizes the probability of the unstable phenomenon in the high power electron linac.
|
|
|
||
| THP053 | Simulations and Optimizations of a New Power Coupler for 3.9-GHz Superconducting Cavities at Fermilab | simulation, coupling, impedance, cryogenics | 701 | ||
|
3.9 GHz third harmonic superconducting cavities have been used to increase the peak bunch current and to compensate for non-linear distortions in the longitudinal phase space due to sinusoidal 1.3 GHz accelerating cavity voltage. The power coupler is one of the important and complicated components of the third harmonic system for the TTF3 project. From electromagnetic, multipacting, and thermal simulations of the power coupler, optimized designs have been achieved, enabling one to minimize or eliminate potential problems in advance. This paper presents our recent work on simulation and optimization of the power coupler.
|
|
|
||
| THP065 | High-Gradient Generation in Dielectric-Loaded Wakefield Structures | simulation, laser, gun, klystron | 731 | ||
|
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.
|
|
|
||
| THP077 | A High-Gradient Test of a 30-GHz Copper Accelerating Structure | linac, pick-up, vacuum, acceleration | 761 | ||
|
The CLIC study is investigating a number of different materials at different frequencies in order to find ways to increase achievable accelerating gradient and to understand what are the important parameters for high-gradient operation. So far a series of rf tests have been made with a set of identical-geometry 30 GHz and X-band structures in copper, tungsten and molybdenum. A new test of a 30 GHz copper accelerating structure has been completed in CTF3 with pulse lengths up to 100 ns. The new results are presented and compared to the previous structures to determine dependencies of quantities such accelerating gradient, material, frequency, pulse length, power flow, conditioning rate, breakdown rate and surface damage.
|
|
|
||
| THP081 | Study on Fault Scenarios of Coaxial Type HOM Couplers in SRF Cavities | SNS, coupling, radiation, vacuum | 770 | ||
|
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.
|
|
|
||
| THP082 | Industrialization of TESLA-Type SRF Technology at ACCEL | vacuum, cryogenics, controls, monitoring | 773 | ||
|
In the last 15 years the worldwide TESLA collaboration under the leadership of DESY performed successful developements of SRF technology for possible use in a future international linear collider (ILC). Today this technology is also the baseline for other demanding projects like the European X-FEL at DESY site, 4GLS at Daresbury, BESSY FEL, Cornell-ERL, FEL at Peking University and others. Through all these years ACCEL has followed and supported this tremendous developement by producing and processing SRF cavities, couplers and complete accelerator modules. The current ability and future prospects of ACCEL for manufacturing and processing such key components as well as turnkey SRF modules with guaranteed performance for such projects are described.
|
|
|
||
| THP083 | Generation of Ellipsoidal Beam Through 3-D Pulse Shaping of a Photoinjector Drive Laser | laser, simulation, emittance, gun | 776 | ||
|
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.
|
|
|
||
| THP091 | Experimental Study of Positron Production from Monocrystalline Targets at the KEKB Injector Linac | target, positron, radiation, linac | 797 | ||
|
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.
|
*Email address: tsuyoshi.suwada@kek.jp |
|
||
| THP092 | Control System for a Limitation of an Integrated Amount of Beam Charges Delivered from the KEKB Injector Linac | injection, controls, linac, positron | 800 | ||
|
A new control system is under construction for radiation safety at the KEKB injector linac. The control system restricts the integrated amount of the beam charges delivered from an electron gun in order to keep the radiation safety with high reliability in a daily operation of the linac. The old control system of the radiation safety has been working based on a software control implemented on a UNIX-based workstation. However, this control system is not possible to be implemented for the long-term linac operation with high reliability. The new control system comprises a charge-integration-type analog circuit mounted along with a CPU chip and a data acquisition system based on programmable logic controllers. The fast analog circuit can detect the beam-charge signals delivered from a wall-current monitor, and control the beam-abort trigger pulses pulse-by-pulse. The new hardware-based control system may stabilize the radiation safety control for the long-term linac operation. In this report the design of the new control system is described along with preliminary test results.
|
|
|
||
| THP094 | GeV Laser Wakefield Acceleration and Injection Control at LOASIS | laser, plasma, simulation, injection | 806 | ||
|
Experiments at the LOASIS laboratory of LBNL have demonstrated production of GeV electron beams with low energy spread and divergence from laser wakefield acceleration. The pondermotive force of a 40 TW laser pulse guided by a 3 cm capillary discharge plasma density channel drove an intense plasma wave (wakefield), producing acceleration gradients on the order of 50 GV/m. Electrons were trapped from the background plasma and accelerated. Beam energy was increased from 100 to 1000 MeV*, compared to earlier experiments**, by using a longer guiding channel at low density, demonstrating the anticipated scaling to higher beam energies. Particle simulations are used to understand the trapping and acceleration mechanisms. Other experiments and simulations are also underway to control injection of particles into the wake, and hence improve beam quality and stability further. Recent experimental and simulation results from channel guided laser acceleration, and initial injection results, will be presented.
|
*W. P. Leemans et al, submitted. |
|
||
| FR1002 | SPring-8 Compact SASE Source | emittance, undulator, cathode, radiation | 813 | ||
|
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.
|
SCSS-Web Site: www-xfel.spring8.or.jp. |
|