BNL, Upton, Long Island, New York
Operational experience on crossing RHIC transition as well as observed beam dynamics effects are described. The techniques to provide the successful transition crossing without beam losses and deterioration of the beam quality in both transverse and longitudinal plane are reviewed. Presently the ion beam intensity is limited by the transverse instability happenning at the transition region. It was observed that the threshold of the instability was significantly affected by the presence of the electron cloud. The results of recent studies of the intensity limiting instability are presented.
IUCF, Bloomington, Indiana
ORNL, Oak Ridge, Tennessee
SLAC, Menlo Park, California
Recently, discrepancies between model-based and observed linear optics, such as the tune and the closed orbit, have been observed in the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory. Accurate accelerator modeling is very important for machine control during the ongoing power ramp up. The Orbit Response Matrix (ORM) method is applied here to find and correct errors in the linear optics of the SNS ring. With the closed orbit data (4472 data points), we are able to calibrate the strength of the steering magnets, the BPM gain factors, and 6 quadrupole power supplies. Current results and remaining challenges will be presented and discussed.
LANL, Los Alamos, New Mexico
TechSource, Santa Fe, New Mexico
Recent beam studies have focused on understanding the main sources and locations of electron clouds (EC) which drive the observed e-p instability at the PSR. New results using a recently developed electron diagnostic will be reported which demonstrate the important role of EC activity in quadrupole magnets, including definitive evidence that ~80% or more of the drift space EC signal is “seeded” by electrons ejected by ExB drifts from adjacent quadrupole magnets*. Other observations include distinctive brown colored tracking in various dipole and quadrupole vacuum chambers, which we hypothesize is caused by energetic electrons striking the wall during beam-induced multipacting. The tracking observations point to a simple and useful signature for regions of EC activity. Modeling of EC observations using a modified version of the POSINST** code shows general agreement on many features of the observations, given the large uncertainties in the distribution of seed electrons from beam loss which is a key input into the simulations. Progress will be reported on resolving the features not in agreement.
* R. Macek et al, PRSTAB, 11, 010101 (2008).
** M. T. F. Pivi and M. A. Furman, PRSTAB, 6, 034201 (2003).
UMD, College Park, Maryland
Space charge can significantly affect the resonant properties of rings. The University of Maryland Electron Ring is a scaled experiment in which we have circulated beams with unprecedented intensities. Here we discuss the resonance analysis performed using the electrostatic particle-in-cell code WARP, to understand the effect of space charge on the ring resonances. Beams with varying degrees of space charge in both the emittance- and space-charge-dominated regimes are attempted. The operating point is scanned to map the tune diagram under various lattice and injection errors. The results of the simulation study are compared to experimental measurements.
GSI, Darmstadt
ORNL, Oak Ridge, Tennessee
CEA, Gif-sur-Yvette
Systematic measurements on transverse rms-emittance growth along the Alvarez DTL of the GSI UNILAC were performed. A high intensity argon beam was used to measure rms-growth for different transverse phase advances along the DTL. The transverse tune depression varied from 21% to 43%. For benchmarking of the experimental results four different beam dynamics codes were used: DYNAMION, PARMILA, PARTRAN, and LORASR. This paper is on the results of the experiments, the reconstruction of the initial conditions for the simulations, and on the agreement between simulations and experiments. Additionally, successful suppression of rms-growth by systematic matching is reported.
CERN, Geneva
CEA, Gif-sur-Yvette
Linac4 is a normal conducting H- linac to be built at CERN as a new injector to the PS Booster and later on as a front end of a possible MultiMegaWatt Linac Facility. The layout consists of a H- RF source, a magnetic LEBT, a RFQ (accelerating the beam from 45 keV to 3 MeV), a chopper line, a conventional Drift Tube Linac (from 3 MeV to 50 MeV), a Coupled Cavity Drift Tube Linac (from 50 MeV to 100 MeV) and a pi-mode structure (PIMS, from 100 to 160 MeV), all operating at a frequency of 352 MHz. End-to-end beam dynamics simulations have been carried out to optimise the design and performance of the accelerator. An extensive statistical campaign of transverse error studies was then launched for accessing the required alignment tolerances and steering correction system.
CERN, Geneva
UPC, Barcelona
A 50 GeV proton synchrotron machine to replace the current PS (PS2) is foreseen in the framework of the LHC complex upgrade. For high intensity beams, losses constitute a great concern in terms of hands-on maintenance and radioactivation. To minimize the uncontrolled losses all around the ring a collimation system is required. Lattice design and collimation studies are carried out in parallel in order to optimize the cleaning efficiency. To this end the robustness of the system is tested for different lattice configurations against orbit errors and optics distortions.
KEK, Ibaraki
Beam commissioning of J-PARC Main Ring (MR) has been started in May, 2008. The 3-GeV beams extracted from the rapid cycling synchrotron (RCS) are injected into the MR and captured by rf, and then extracted to a 3-GeV beam dump. In this paper, we present results of the first-stage commissioning run from May to June 2008. After five months shutdown for installation of fast extraction and slow extraction devices, the second-stage commissioning run will be started in December 2008.
GSI, Darmstadt
The double synchrotron complex SIS100 and SIS300 is the central part of the FAIR project. SIS100 is a fast ramped superconducting synchrotron optimized for high intensity, low-charge state heavy ion operation. However, similar to the existing heavy ion synchrotron SIS18, SIS100 will also be used to accelerate all other ion species down to protons, In order to enable such a flexible operation and to avoid transition energy crossing, a triplet structure with three independent power circuits has been chosen. For the low charge state operation, a new lattice design concept has been applied which provides an optimized separation of ionized beam particles. Low charge state operation is enabled by means of the cryopumping of the actively cooled, thin wall vacuum chambers. The stability of the residual gas pressure is an essential precondition for this operation. The project status and the status of the major device developments will be presented.
KAERI, Daejon
The main purposes of the proton engineering frontier project (PEFP) are developing 100-MeV proton linac and supplying 20-MeV and 100-MeV proton beams to user group. The 20-MeV part of the linac with 24% beam duty has been successfully installed and tested at the KAERI site. Now we are supplying 20-MeV proton beams to users in a restricted beam condition. The fabrication of the remaining part of the DTL with the beam duty of 8% is in progress. The PEFP user facility includes 5 beam lines for 20-MeV and 100-MeV beams, respectively. Form the user surveys the purposes and beam specs are determined for the beam lines. The characteristics of the PEFP beam supplying systems are using the AC magnets to periodically distribute proton beams into several beam lines. At the same time, PEFP concentrates on developing the potential user group of the high intensity proton beams. Several beam utilization programs are under way for this purpose. The civil construction is scheduled to start at the end of this year. The present status and progress of the project are summarized in detail.