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| MOAP01 | Approach to a very high intensity beam at J-PARC | linac, proton, hadron, rfq | 1 | ||
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| MOCP02 | High-power accelerators in China: status and outlook | linac, target, proton, dipole | 39 | ||
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High intensity accelerator research is a relatively new subject in China. Recent program includes the accelerator-driven sub-critical power generation and the Beijing Spallation Neutron Source (BSNS) project. The Beijing Spallation Neutron Source (BSNS) is a newly approved project based on a H- linear accelerator and a rapid cycling synchrotron. During the past year, several major revisions were made on the design including the type of the front end, the linac frequency, the transport layout, the ring lattice, and the type of ring components. Possible upgrade paths were also laid out: based on an extension of the warm linac, the ring injection energy and the beam current could be raised doubling the beam power on target to reach 200 kW; an extension with a superconducting RF linac of similar length could raise the beam power near 0.5 MW. Based on these considerations, research and development activities are started. In this paper, we discuss the rationale of design revisions and summarize the recent works.
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| MOCP03 | Status of the LHC | proton, luminosity, cryogenics, superconducting-magnet | 44 | ||
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For the LHC to provide particle physics with proton-proton collisions at a centre of mass energy of 14 TeV with a luminosity of 1034 cm-2s-1, the machine will operate with high-field dipole magnets using NbTi superconductors cooled to below the λ point of helium. The construction follows a decade of intensive R&D and technical validation of major collider sub-systems. Installation of the accelerator system is in full swing. Commissioning of the injector complex is well advanced, including beam transfer through one of the transfer lines from SPS to LHC. In the LHC machine, commissioning of the cryogenic system and powering system has started. The status of the LHC accelerator and a brief outlook to operation and its consequences for the machine protection systems will be given. The strategy for the machine protection and beam cleaning will have a major impact on commissioning and operation since each of the two LHC proton beam has a stored energy of about 360 MJ. A fraction of less than 10-3 of the full beam threatens to damage accelerator equipment in case of uncontrolled beam loss, and only 10-8 protons could already quench a magnet.
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| TUAX02 | Coherent Instabilities at the Fermilab Booster | impedance, vacuum, dipole, booster | 69 | ||
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Fermilab booster is a fast cycling synchrotron operating on 15 Hz. To exclude problem of eddy currents excited in the vacuum chamber by fast changing magnetic field Booster does not have a conventional vacuum chamber. Instead, the vacuum chamber is formed by poles of the laminated combined function magnets. The exposed magnet laminations result in large transverse and longitudinal impedances affecting both the transverse and longitudinal stability of the beam. Presently, the transverse instability is suppressed by large chromaticity negatively affecting the dynamic aperture and the beam lifetime. Earlier attempts to stabilize the instability by transverse feedback system were unsuccessful. Recently we performed experimental studies to find out the reason. We observed that at reduced chromaticity at injection the most unstable mode is the multibunch high order head-tail mode with growth time of about 12 turns. It develops at synchro-betatron tune with very small fractional part where the transverse impedance is at a maximum. Analytical calculations and numerical simulations verify the observations and allowed us to compute the value of transverse impedance. Another persistent probl
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Work supported by the Universities Research Assos., Inc., under contract DE-AC02-76CH03000 with the U. S. Dept. of Energy. |
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| TUAX05 | Studies of e-cloud build up for the FNAL main injector and for the LHC | electron, dipole, simulation, cryogenics | 102 | ||
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We present a summary of recent simulation studies of the electron-cloud (EC) build-up for the FNAL Main Injector and for the LHC. In the first case we pay particular attention to the dependence on bunch intensity (Nb) at injection energy, and we focus on the dipole magnets and field-free regions. The saturated value of the average EC density shows a clear threshold in Nb beyond which the beam will be approximately neutralized on average. For the case of the LHC we limit our discussion to arc dipoles at collision energy, and bunch spacings tb=25 ns or tb=75 ns. The main variables exercised in this study are Nb and the peak value of the secondary emission yield (dmax). For tb=25 ns we conclude that the EC power deposition is comfortably below the available cooling capacity of the cryogenic system if dmax is below ~1.2 at nominal Nb. For tb=75 ns, the EC power deposition is insignificant. As a byproduct of this exercise, we reach a detailed understanding of the significant role played by the backscattered secondary electrons.
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| TUAZ05 | Comparison of Graphite and Diamond Structured Carbon Stripper Foils under Operational Conditions at the Los Alamos PSR | proton, radiation, beam-losses, electron | 112 | ||
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In the Los Alamos Proton Storage Ring H–Ions merge with circulating protons in a bending magnet and are stripped of their two electrons in a carbon stripper foil. The circulating protons continue to interact with the foil. Despite efforts to minimize the number of these foil hits, like “painting” of the vertical phase space, they can not totally be eliminated. As a result foil heating and radiation damage limit the lifetime of these foils. In recent years LANL has collaborated with KEK to improve the graphite foils in use at PSR and these foils now last typically for two months. Recently an alternative in the form of diamond structured carbon foils has been proposed for use at SNS. Depending on the grain size these are referred to as microcrystalline or nanocrystalline foils. Both types have been tested in PSR, with quite different results. While the microcrystalline foil failed catastrophically before production beam currents were reached the nanocrystalline foil was successfully used in normal operation for several weeks. Advantages of the diamond foil concept as well as some noteworthy differences that we observed with respect to the LANL graphite foils will be discussed here.
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| TUAZ06 | Development of hybrid typoe carbon stripper foils with high durability against 1800K for RCS of J-PARC | linac, vacuum, laser, ion | 122 | ||
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We have successfully made long-lived and hybrid , thick, boron mixed carbon stripper foils for high energy and high intensity accelerators. The foils were made by the controlled DC arc-discharge method, and the thickness is wide range from 50 to 600 ug/cm2. The lifetime of the foils was tested with use of 3.2 MeV Ne+DC beams of 2.5 uA, in which a significant of energy was deposited in the foils and thus we could simulate the condition by high power accelerator. The lifetime in maximum was shown to be extremely long, 102 and 410 times longer those of diamond and commercially available best carbon foils, respectively.
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| TUBX05 | Cures for beam instabilities in the CERN SPS and their limitations | synchrotron, emittance, beam-loading, feedback | 153 | ||
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The LHC beam in the SPS is unstable with a threshold almost an order of magnitude below the nominal intensity. The cures used to stabilise this beam against coupled bunch instabilities apart from beam feedback, feed-forward and longitudinal damping, include a fourth harmonic RF system and controlled emittance blow-up. The limitations of the two last methods were studied experimentally and are analysed here from the point of view of beam quality requirements at extraction and future intensity increases up to ultimate value.
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| TUBZ01 | The Beam Diagnostics System for J-PARC Synchrotrons | proton, electron, beam-losses, pick-up | 128 | ||
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The beam diagnostics system for J-PARC synchrotrons (RCS and MR) will be presented. The design of the system will be described for high current machines. Some test results will be reported.
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| WEAX02 | Space charge simulation of J-PARC main ring | space-charge, resonance, sextupole, emittance | 177 | ||
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The space charge effect in combination with the intrinsic field nonlinearity like the sextupole nonlinearity, used for the chromaticity correction, could lead to significant particle losses in a high beam intensity proton machine. For J-PARC Main Ring (MR) the total particle losses at the ring’s collimator should be less than 1% from the expected maximum beam power of 45kW at the injection energy of 3GeV. To keep the particle losses during the injection process within the required limit it is necessary to optimize the beam parameters from the injector (J-PARC RCS), the collimator aperture of the beam-line from RCS to MR and the collimator aperture of MR. Influence of the structure and non-structure high-order resonances for different working points is discussed. The budget of the beam losses for different MR commissioning scenario is presented.
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| WEAX04 | High Intensity Cyclotron Simulations: Towards Quantitative Predictions | simulation, cyclotron, space-charge, proton | 202 | ||
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PSI operates the most powerful cyclotron worldwide to the benefit of a multi-user, cross-disciplinary research facility. The accelerator complex consists of a Cockcroft-Walton pre-injector, a 72-MeV separated sector injector cyclotron and a 590-MeV separated sector Ring Cyclotron. A beam current of 1.9 mA is routinely extracted from the Ring Cyclotron overall absolute losses are below 1·10-3. The facility has a considerable potential for further improvements, an ongoing upgrade project aims at a beam current of 3 mA. The purpose of our multi-scale three-dimensional parallel code and methods development is to make the step from qualitative to quantitative predictions. Their simulation requires the accurate three-dimensional modeling of large and complicated accelerator structures including space charge, beam lines, collimation, and in the future secondary effects. We will show methods, both numerically and computational, that we use presently and give an overview on future directions. Measurements from the cyclotrons and beamlines will be compared with simulations carried out in the frame of the high intensity upgrade program.
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| WEAX05 | Space-Charge Beam Physics Research at the University of Maryland Electron Ring (UMER)* | space-charge, quadrupole, dipole, lattice | 218 | ||
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The University of Maryland electron ring (UMER) is a low-energy, high current recirculator for beam physics research with relevance to any applications that rely on intense beams of high quality. We review the space-charge physics issues, experimental and computational investigations, which are currently being conducted at the UMER facility. The physics issues cover a broad range, but we focus on transverse beam dynamics: halo formation, strongly asymmetric beams, Montague resonances, equipartitioning, etc. Furthermore, we report on recent developments in experiments, simulations, and improved diagnostics for space-charge dominated beams.
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| WEAX06 | Measurements and Synergia simulations of emittance dilution at the Fermilab Booster. | simulation, resonance, space-charge, booster | 236 | ||
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We present a study of the beam evolution in the Fermilab Booster operating both under nominal conditions and in the vicinity of the sum resonance for different beam currents. We simultaneously recorded the horizontal and vertical beam profiles using the Ion Profile Monitor and beam current. Our analysis extracted 2-D emittances and beam shape information from the IPM data. We compare the results with Synergia simulations including 3-D space charge and higher-order optics to analyze and interpret the experimental results.
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| WEAY03 | Experimental studies of stability issues at HIMAC cooler | ion, electron, resonance, feedback | 197 | ||
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We have investigated coherent transverse instability when high-density circulating-ion beam was obtained with cool-stacking injection in the HIMAC synchrotron. By using a cooled beam and the Oxygen gas-sheet beam profile monitor, further, we have observed a particle trapping in resonance crossing. We will report these experimental studies at the HIMAC synchrotron.
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| WEAY05 | New experimental results on electron cooling at COSY-Juelich | electron, proton, ion, scattering | 223 | ||
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Recent electron cooling results of a proton beam at COSY – Juelich are summarized. The influence of residual gas ions trapped in the electron beam on the cooled beam stability as well as methods to suppress the instabilities are described. Results on the numerical simulation for the formation of a crystalline proton beam in COSY using the BETACOOL code and results of experimental investigations of the cooling process at extremely low proton beam intensity are reported. Future plans are briefly addressed.
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| WEAZ01 | Overview of beam loss mechanisms in injection and extraction | extraction, beam-losses, linac, emittance | 172 | ||
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| WEBX02 | Observation of Emittance Growth at the injection in the KEK PS Main Ring | emittance, proton, simulation, space-charge | 250 | ||
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We have been studying the emittance growth and beam loss mechanism during the injection period of the 12 GeV main ring of the KEK proton synchrotron to achieve higher intensity. The typical beam loss is about 30 % during the injection period of 500 milliseconds for the high intensity operation. Measurement of the transverse beam profiles using flying wires has revealed a characteristic temporal change of the beam profile within a few milliseconds after the injection. Horizontal emittance growth was observed when the horizontal tune was close to the integer. The effect was more enhanced for higher beam intensity and could not be explained with the injection mismatch. A resonance created by the space charge field was the cause of the emittance growth. A multiparticle tracking simulation program, ACCSIM, taking account of space charge effects has successfully reproduced the beam profiles.
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| WEBX06 | Analysis of emittance growth in the Fermilab Booster | emittance, quadrupole, space-charge, resonance | 271 | ||
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Multi-particle similations are performed to study emittance growth in the Fermilab Booster. Analysis shows that the sourcce of the vertical emittance growth comes mostly from random errors in skew quadrupoles as well as the transverse space-charge force. Random errors in the dipole fields and the Montague resonance do contribute but to a much lesser extent. The effect of random errors in the quadrupoles is small because the betatron envelope tunes are resonably far away from the half-integer stopband.
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| WEBZ02 | BEAM TRACKING FOR J-PARC 3 GEV RCS INJECTION | septum, electron, emittance, quadrupole | 253 | ||
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In the J-PARC 3 GeV RCS injection system, the orbit-bump magnets of large-bore are located close with each other, and the incoming beam passes through the non-linear field region of the ring quadrupole magnet. Beam behavior under these conditions is analysed by means of the Runge-Kutta method in the three dimensional magnetic field distribution. The charge exchange foil is inserted between the bump magnets. Orbit of the stripped electrons from the foil is also investigated.
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| THAW03 | RF Barrier Cavity Option for the SNS Ring Beam Power Upgrade | electron, space-charge, proton, target | 298 | ||
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RF barrier cavities present an attractive option for facilitating the path to higher beam intensity in the SNS power upgrade. Barrier cavities lead to flat longitudinal current densities, thus minimizing bunch factor effects. In addition to allowing more beam to be injected in this fashion, flat current profiles may lead to increased e-p instability thresholds due to reduced multipacting during the trailing stage of the bunch. Finally, it is possible to inject self-consistent beam distributions into barrier buckets, thus providing the additional advantages of uniform transverse beam density (good for meeting target constraints) and little or no halo (good for low losses). Simulations addressing all these issues will be presented and discussed.
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| THAW04 | Experimental Characterization of the “1st Pulse” e-p Instability at the LANL PSR | electron, accumulation, diagnostics, controls | 311 | ||
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A puzzling aspect of the e-p instability at PSR is the so called “1st Pulse” instability phenomenon. It shows up on the first beam pulse after a period (10 to 30 minutes or more) of beam off time. This pulse has a significantly lower threshold than subsequent beam pulses that follow with the standard time separation. While the standard PSR operation for Lujan Center operation is unaffected by this phenomenon, it does interfere with some high intensity, single pulse experiments using PSR beam. We will summarize the present experimental data characterizing this phenomenon as compared with the typical e-p instability observed at higher repetition rates at PSR and discuss some possible explanations.
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| THAY02 | Progress in slip stacking and barrier-RF | booster, target, antiproton, simulation | 293 | ||
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Slip stacking for pbar production has been operational since December 2004 and increased the beam intensity on pbar target more than 60%. We plan to use slip stacking for NuMI neutrino experiment for effectively increasing intensity to NuMI target by about a factor two in a 2.2 sec MI cycle. In parallel with slip stacking, we plan to study fast momentum stacking using barrier buckets. One barrier rf system has been installed and tested, and second system is being installed during the current shutdown.
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| THAZ02 | SNS Commissioning Strategies and Tuneup Algorithms | linac, target, controls, quadrupole | 283 | ||
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The Spallation Neutron Source (SNS) has been recently commissioned. The strategies for the initial beam commissioning of the superconducting linac (SCL) and storage ring will be discussed. The SCL commissioning had to accommodate an unanticipated wide range of cavity performance, compared to design expectations. Methods for setting cavity phases and determination of amplitudes will be discussed. The ring commissioning involved the usual establishment of a circulating beam, and then measurement and correction the tune and beta functions, all with a low intensity beam. Then the gradual increase of beam intensity and commissioning of RF and phase space painting were investigated. The methods to accomplish these tasks will be discussed. In general, the first order beam behavior is well understood. Key factors in the successful commissioning are: flexibility in accommodating beam conditions that are different from the design, good communication between the different groups, and attention to detail. Examples for these factors will be emphasized.
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| THAZ03 | Safe LHC Beam Commissioning | dumping, extraction, collimation, beam-losses | 306 | ||
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Due to the large amount of energy stored in magnets and beams, safe operation of the LHC is essential. The commissioning of the LHC machine protection system will be an integral part of the general LHC commissioning program. A brief overview of the LHC Machine Protection System will be given, identifying the main components: the Beam Interlock System, the Beam Dumping System, the Collimation System, the Beam Loss Monitoring system and the Quench Protection System. An outline is given of the commissioning strategy of these systems during the different commissioning phases of the LHC: without beam, injection and the different phases with stored beam depending on beam intensity and beam energy.
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| THAZ06 | Commissioning scenarios for the J-PARC accelerator complex | linac, extraction, closed-orbit, acceleration | 329 | ||
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The J-PARC accelerator complex consists of a 400-MeV linac, a 3.0-GeV rapid-cycling synchrotron (RCS), a 50-GeV main ring (MR) and associated beam transport lines to experimental facilities, which use the 3- and 50-GeV proton beams. It is now under construction in the Tokai campus of JAEA as a joint project between JAEA and KEK. The beam commissioning of each accelerator is scheduled to start for linac in December 2006, RCS in September 2007 and MR in May 2008. The commissioning strategy for the accelerator complex will be presented.
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| THBZ02 | Commissioning strategies for J-PARC linac and L3BT | linac, beam-transport, controls, quadrupole | 347 | ||
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We plan to start the beam commissioning of J-PARC linac with reduced energy of 181 MeV in the end of this year. Detailed commissioning strategies for the linac and the succeeding beam transport line, to which we refer as L3BT or Linac-to-3-GeV-synchrotron Beam Transport, will be presented in this talk. The emphasis will be put on the commissioning procedures for two debuncher cavities and a transverse collimator system located in L3BT, because they are key elements in determining the final beam quality at the injection point to the succeeding 3-GeV synchrotron. The unique design and features of the collimator system are also presented.
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| FRAP03 | Summary of Working Group C+G (Part I) | beam-losses, extraction, target, collimation | 365 | ||
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