GANIL, Caen
The Eurisol heavy ion post-accelerator and the Spiral2 deuton/ion MEBT should transport a continuous wave (cw) beam from respectively a 88.05 MHz RFQ (β respectively 0.036 and 0.04) to a drift-tube linac. A high frequency chopper is being studied to select only 1 bunch over N, 10 < N < 10000 as asked by the physicists. It requires pulses higher than 3 kV, rising in less than 7 ns at a repetition rate up to 8.8 MHz. These figures are at the border of what can be provided by the travelling wave fast choppers and the capacitive-type chopping technologies. We have reviewed the current fast and slow chopping structures and their associated pulse generator. Some preliminary RF simulations to adapt the present chopping devices to our requirements are presented. The main limitations of these technologies when applied to isolate bunches in ion cw accelerators are also shown. Our first studies and results to solve the arising problems are discussed.
FZJ, Julich
The Relativistic Heavy Ion Collider (RHIC) is designed to provide luminosity over a wide range of beam energies and species, including heavy ions, polarized protons, and asymmetric beam collisions. In the first seven years of operation there has been a rapid increase in the achieved peak and average luminosity, substantially exceeding design values. Work is presently underway to achieve the Enhanced Design parameters in about 2008. Planned major upgrades include the Electron Beam Ion Source (EBIS), the RHIC-II electron cooling upgrade, and construction of an electron-ion collider (eRHIC). We review the expected RHIC upgrade performance. Electron cooling and its impact on the luminosity at various collision energies both for heavy ions and protons are discussed in detail.
GSI, Darmstadt
ORNL, Oak Ridge, Tennessee
The GSI UNILAC, a heavy ion linac originally dedicated for low current beam operation, together with the synchrotron SIS 18 will serve as an high current injector for FAIR (International Facility for Antiproton and Ion Research). The UNILAC post stripper accelerator consists of five Alvarez tanks with a final energy of 11.4 MeV/u. In order to meet the requirements of FAIR (15emA 238U28+, transverse normalised emittances of 0.8mm mrad and 2.5mm mrad) an UNILAC upgrade program is foreseen to increase the primary beam intensity as well as the beam brilliance. A detailed understanding of the beam dynamics during acceleration and transport of space charge dominated beams is necessary. For this purpose the study of the beam brilliance dependency on the phase advances in the Alvarez DTL is suited. Machine investigations were performed with various beam diagnostics devices established in the UNILAC. Measurements done in 2006 using an high intensity heavy ion beam coincide with the beam dynamics work package of the European JRA "High Intensity Pulsed Proton Injector" (HIPPI). Results of these measurements are presented as well as corresponding beam dynamics simulations.
BNL, Upton, Long Island, New York
IAP, Frankfurt am Main
ANL, Argonne, Illinois
Northern Illinois University, DeKalb, Illinois
A multi-charge-state injector for high-intensity heavy-ion LINAC is being developed at ANL. The injector consists of an all-permanent magnet ECR ion source, a 100 kV platform and a Low Energy Beam Transport (LEBT). The latter comprises two 60-degree bending magnets, electrostatic triplets and beam diagnostics stations. The first results of beam measurements in the LEBT will be presented.
ANL, Argonne, Illinois
The Office of Science of the Department of Energy is currently considering options for an advanced radioactive beam facility in the U. S. The U. S. facility will complement capabilities both existing and planned elsewhere. As envisioned at ANL, the facility, called the Advanced Exotic Beam Laboratory (AEBL), would consist of a heavy-ion driver linac, a post-accelerator and experimental areas. The proposed design of the AEBL driver linac is a cw, fully superconducting, 833 MV linac capable of accelerating uranium ions up to 200 MeV/u and protons to 580 MeV with 400 kW beam power. An extensive research and development effort has resolved many technical issues related to the construction of the driver linac and other systems required for AEBL. This paper presents the status of planning, some options for such a facility, as well as, progress in related R&D.
LLNL, Livermore, California
LBNL, Berkeley, California
TU Darmstadt, Darmstadt
ITEP, Moscow
GSI, Darmstadt
IPCP, Chernogolovka, Moscow region
NSCL, East Lansing, Michigan
The Spallation Neutron Source (Oak Ridge), the proposed 8 GeV Proton Driver (Fermilab), and the proposed Rare Isotope Accelerator use multicell elliptical SRF cavities to provide much of the accelerating voltage. This makes the elliptical cavity segment the most expensive part of the linac. A new type of accelerating structure called a half-reentrant elliptical cavity can potentially improve upon existing elliptical designs by reducing the cryogenic load by as much as 30% for the same accelerating voltage. Alternatively, with the same peak surface magnetic field as traditional elliptical cavities, it is anticipated that half-reentrant designs could operate at up to 25% higher accelerating gradient. With a half-reentrant shape, liquids can drain easily during chemical etching and high pressure rinsing, which allows standard multicell processing techniques to be used. A half-reentrant cavity for β = v/c = 1, suitable for the proposed ILC, has been designed and fabricated, with RF tests in progress*. In this paper, we present electromagnetic designs for three half-reentrant cell shapes suitable for an ion or proton linac (β = 0.47, 0.61 and 0.81, f = 805 or 1300 MHz).
* M. Meidlinger et al., in Proc. XXIII Int. Linac Conf., Knoxville, TN, Aug 2006
SAIC, Alamo, California
LLNL, Livermore, California
LBNL, Berkeley, California
The Pulse-Line Ion Accelerator* (PLIA) is a helical distributed transmission line. A rising pulse applied to the upstream end appears as a moving spatial voltage ramp, on which an ion pulse can be accelerated. This is a promising approach to acceleration and longitudinal compression of an ion beam at high line charge density. In most of the studies carried out to date, using both a simple code for longitudinal beam dynamics and the Warp PIC code, a circuit model for the wave behavior was employed; in Warp, the helix I and V are source terms in elliptic equations for E and B. However, it appears possible to obtain improved fidelity using a "sheath helix" model in the quasi-static limit. Here we describe an algorithmic approach that may be used to effect such a solution.
*R. J. Briggs, PRST-AB 9, 060401 (2006).
CEA, Gif-sur-Yvette
IPN, Orsay
GANIL, Caen
LPSC, Grenoble
Nikken Sekkei Civil Ltd, Tokyo
Northern Illinois University, DeKalb, Illinois
ANL, Argonne, Illinois
An Exotic Beam Facility is one of the highest priority projects in the DOE 20-year plan and a major strategic initiative for Argonne. The main components of the facility are a high-power multi-beam superconducting heavy-ion accelerator, a production complex, and finally a high-efficiency post-accelerator. This talk revolves around new approaches to heavy-ion beam dynamics for the central part, the Fragment Separators. To this end, it will summmarize the theories developed, software written, and simulations done that lead to better understanding of basic beam dynamics, more insight towards the best design choices, and optimization of the system?s parameters, including the integrated beam optics-nuclear physics approach.
ANL, Argonne, Illinois
LANL, Los Alamos, New Mexico
TechSource, Santa Fe, New Mexico
NSCL, East Lansing, Michigan
LBNL, Berkeley, California
RIAPMTQ/IMPACT is a pair of linked beam-dynamics simulation codes that have been developed for end-to-end computer simulations of multiple-charge state heavy-ion linacs for future exotic-beam facilities. The simulations can extend from the low-energy beam transport after the ECR source to the end of the linac. The work has been performed by a collaboration including LANL, LBNL, ANL, MSU, and TechSource. The code RIAPMTQ simulates the linac front end including the LEBT, RFQ, and MEBT, and the code IMPACT simulates the main superconducting linac. The codes have been benchmarked for rms beam properties against previously existing codes at ANL and MSU. The codes allow high-statistics runs on parallel supercomputing platforms, such as NERSC at LBNL, as well as runs on desktop PC computers for low-statistics design work. We will show results from 10-million-particle simulations of RIA designs by ANL and MSU, carried out at the NERSC facility. These simulation codes will allow evaluations of candidate designs with respect to beam-dynamics performance including beam losses.
CERN, Geneva
The tight mechanical aperture for the LHC imposes severe constraints on both the beta and dispersion beating. Robust techniques to compensate these errors are critical for operation of high intensity beams in the LHC. We present simulations using realistic errors from magnet measurements and alignment tolerances in the presence of BPM noise. Correction reveals that the use of BPM calibration and model independent observables are key ingredients to accomplish optics correction. Experiments at RHIC to verify the algorithms for optics correction are also presented.
Tech-X, Boulder, Colorado
BNL, Upton, Long Island, New York
JINR, Dubna, Moscow Region
The traditional electron cooling system used in low-energy coolers employs an electron beam immersed in a longitudinal magnetic field. In the first relativistic cooler, which was recently commissioned at Fermilab, the friction force is dominated by the non-magnetized collisions between electrons and antiprotons. The design of the higher-energy cooler for Relativistic Heavy Ion Collider (RHIC) recently adopted a non-magnetized approach which requires a low temperature electron beam. However, to avoid significant loss of heavy ions due to recombination with electrons in the cooling section, the temperature of the electron beam should be very high. These two contradictory requirements are satisfied in the design of the RHIC cooler with the help of the undulator fields. The model of the friction force in the presence of an undulator field was benchmarked vs direct numerical simulations with an excellent agreement. Simulations of ion beam dynamics in the presence of such a cooler and helical undulator is discussed in detail, including recombination suppression and resulting luminosities.
BNL, Upton, Long Island, New York
An Electron Beam Ion Source (EBIS), capable of producing high charge states and high beam currents of any heavy ion species in short pulses, is ideally suited for injection into a synchrotron. An EBIS-based, high current, heavy ion preinjector is now being built at Brookhaven to provide increased capabilities for the Relativistic Heavy Ion Collider (RHIC), and the NASA Space Radiation Laboratory (NSRL). Benefits of the new preinjector include the ability to produce ions of any species, fast switching between species to serve the simultaneous needs of multiple programs, and lower operating and maintenance costs. A state-of-the-art EBIS, operating with an electron beam current of up to 10 A, and producing multi-milliamperes of high charge state heavy ions, has been developed at Brookhaven, and has been operating very successfully on a test bench for several years. The present performance of this high-current EBIS will be presented, along with details of the design of the scaled-up EBIS for RHIC, and the status of its construction. Other aspects of the project, including design and construction of the heavy ion RFQ, Linac, and matching beamlines, will also be mentioned.
PPPL, Princeton, New Jersey
A numerical scheme for the electromagnetic particle simulation of high-intensity charged-particle beams has been developed which is a modification of the Darwin model. The Darwin model neglects the transverse induction current in Ampere?s law and therefore eliminates fast electromagnetic (light) waves from the simulations. The model has been incorporated into the nonlinear delta-f Beam Equilibrium Stability and Transport(BEST) code. As a benchmark, we have applied the model to simulate the transverse electromagnetic Weibel-type instability in a single-species charged-particle beam with large temperature anisotropy. Results are compared with previous theoretical and numerical studies using the eighenmode code bEASt. The nonlinear stage of the Weibel instability is also studied using BEST code, and the mechanism for nonlinear saturation is identified.