| Paper | Title | Other Keywords | Page | ||
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| MOPA002 | Performance Limitations in High-Energy Ion Colliders | ion, luminosity, electron, injection | 122 | ||
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Funding: Work supported by U.S. DOE under contract No DE-AC02-98CH10886. |
High-energy ion colliders (hadron colliders operating with species other than protons) are premier research tools for nuclear physics. The collision energy and high luminosity are important design and operations considerations. However, the experiments also expect flexibility with frequent changes in the collision energy, lattice configuration, and ion species, including asymmetric collisions. For the creation, acceleration, and storage of bright intense ion beams, attention must be paid to space charge, charge exchange, and intra-beam scattering effects. The latter leads to luminosity lifetimes of only a few hours for heavy ions. Ultimately cooling at full energy is needed to overcome this effect. Currently, the Relativistic Heavy Ion Collider at BNL is the only operating high-energy ion collider. The Large Hadron Collider, under construction at CERN, will also run with heavy ions. |
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| MPPE060 | Quadrupole Beam-Based Alignment at RHIC | quadrupole, injection, alignment, optics | 3493 | ||
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Funding: Work performed under the auspices of the U.S. Department of Energy |
Successful implementation of a beam-based alignment algorithm, tailored to different types of quadrupoles at RHIC, provides significant benefits to machine operations for heavy ions and polarized protons. This algorithm is used to calibrate BPM centers relative to interaction region (IR) quadrupoles to maximize aperture. It is also used to determine the optimal orbit through transition jump quadrupoles to minimize orbit changes during the transition jump for heavy ion acceleration. This paper provides background discussion and results from first application during the RHIC 2005 run. |
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| MPPT068 | A Compact High Gradient Pulsed Magnetic Quadrupole | quadrupole, multipole, ion, induction | 3771 | ||
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Funding: This work was supported by the Director, Office of Science, Office of Fusion Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098. |
A design for a high gradient, low inductance pulsed quadrupole magnet is presented. The magnet is a circular current dominated design with a circular iron return yoke. Features include a five turn eddy current compensated solid conductor coil design which theoretically eliminates the first four higher order multipole field components, a single layer "non-spiral bedstead" coil design which both minimizes utilization of radial space and maximizes utilization of axial space, and allows incorporation of steering and correction coils within existing radial space. The coils are wound and stretched straight in a special winder, then bent in simple fixtures to form the upturned ends, simplifying fabrication and assembly. |
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| MPPT069 | A Pulsed Solenoid for Intense Ion Beam Transport | ion, quadrupole, beam-transport, acceleration | 3798 | ||
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Funding: This work was supported by the Director, Office of Science, Office of Fusion Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098. |
A design for a pulsed solenoid magnet is presented. Some simple design formulas are given that are useful for initial design scoping. Design features to simplify fabrication and improve reliability are presented. Fabrication, assembly, and test results are presented. |
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| TOAC003 | Stochastic Cooling for Bunched Beams | ion, synchrotron, kicker, pick-up | 310 | ||
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Funding: Work performed under the auspices of the U.S. DOE. |
A longitudinal stochastic cooling system for RHIC is under construction and partial commissioning is planned for the upcoming run. The state of the system and future plans are discussed. |
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| TPAP053 | IR Optics Measurement with Linear Coupling's Action-Angle Parameterization | coupling, optics, dipole, background | 3218 | ||
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Funding: Work supported by U.S. DOE under contract No. DE-AC02-98CH10886. |
The interaction region (IP) optics are measured with the two DX/BPMs close to the IPs at the Relativistic Heavy Ion Collider (RHIC). The beta functions at IP are measured with the two eigenmodes' phase advances between the two BPMs. And the beta waists are also determined through the beta functions at the two BPMs. The coupling parameters at the IPs are also given through the linear coupling's action-angle parameterization. All the experimental data are taken during the driving oscillations with the AC dipole. The methods to do these measurements are discussed. And the measurement results during the beta* squeezings are also presented. |
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| TPAP054 | Helium Flow Induced Orbit Jitter at RHIC | monitoring, injection, quadrupole, emittance | 3262 | ||
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Funding: Work performed under the auspices of the US Department of Energy. |
Horizontal beam orbit jitter at frequencies around 10 Hz has been observed at RHIC for several years. The distinct frequencies of this jitter have been found at superconducting low-beta qudrupole triplets around the ring, where they coincide with mechanical modes of the cold masses. Recently, we have identified liquid helium flow as the driving force of these oscillations. |
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| TPAT036 | Ferroelectric Plasma Source for Heavy Ion Beam Charge Neutralization | plasma, ion, electron, focusing | 2452 | ||
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Funding: Research supported by the U.S. Department of Energy. |
Plasmas are employed as a medium for charge neutralizing heavy ion beams to allow them to focus to a small spot size. Calculations suggest that plasma at a density of 1-100 times the ion beam density and at a length ~ 0.1-1 m would be suitable. To produce 1 meter plasma, large-volume plasma sources based upon ferroelectric ceramics are being considered. These sources have the advantage of being able to increase the length of the plasma and operate at low neutral pressures. The source will utilize the ferroelectric ceramic BaTiO3 to form metal plasma. The drift tube inner surface of the Neutralized Drift Compression Experiment (NDCX) will be covered with ceramic. High voltage (~ 1-5 kV) is applied between the drift tube and the front surface of the ceramic by placing a wire grid on the front surface. A prototype ferroelectric source 20 cm long produced plasma densities ~ 5x1011 cm-3. The source was integrated into the experiment and successfully charge neutralized the K ion beam. Presently, the 1 meter source is being fabricated. It will be characterized and integrated into NDCX for charge neutralization experiments. Experimental results will be presented. |
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| TPAT040 | Actual Stationary State for Plasma Lens | plasma, electron, ion, acceleration | 2619 | ||
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The electrostatic plasma lens (PL) provides an attractive and unique tool for manipulating high-current heavy ion beams. The fundamental concept of the PL is based on the use of magnetically insulated electrons and equipotentialization of magnetic field lines. Rigorous application of PL is, however, limited. The reason is the estimation behaviour of electrons for complicated magnetic fields runs into severe difficults.We show that there are specific conditions that admit steady-state of a longitudinal motion, and consider a question of it stability. These results are needed to develop an optimized PL with minimal spherical aberation, in party by optimization of the magnetic field conficuration in the low-magnetic-field range.
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| TPAT069 | Numerical Studies of Electromagnetic Instabilities in Intense Charged Particle Beams with Large Energy Anisotropy | plasma, focusing, simulation, vacuum | 3780 | ||
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Funding: Research supported by the U.S. Department of Energy. |
In intense charged particle beams with large energy anisotropy, free energy is available to drive transverse electromagnetic Weibel-type instabilities. Such slow-wave transverse electromagnetic instabilities can be described by the so-called Darwin model, which neglects the fast-wave portion of the displacement current. The Weibel instability may also lead to an increase in the longitudinal velocity spread, which would make the focusing of the beam difficult and impose a limit on the minimum spot size achievable in heavy ion fusion experiments. This paper reports the results of recent numerical studies of the Weibel instability using the Beam Eigenmode And Spectra (bEASt) code for space-charge-dominated, low-emittance beams with large tune depression. To study the nonlinear stage of the instability, the Darwin model is being developed and incorporated into the Beam Equilibrium Stability and Transport(BEST) code. |
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| TOPC002 | Residual-Gas-Ionization Beam Profile Monitors in RHIC | emittance, electron, coupling, background | 230 | ||
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Funding: Work performed under Contract #DE-AC02-98CH10886 under the auspices of the U.S. Department of Energy. |
Four ionization profile monitors (IPMs) are in RHIC to measure vertical and horizontal beam profiles in the two rings. These work by measuring the distribution of electrons produced by beam ionization of residual gas. During the last two years both the collection accuracy and signal/noise ratio have been improved. An electron source is mounted across the beam pipe from the collector to monitor microchannel plate (MCP) aging and the signal electrons are gated to reduce MCP aging and to allow charge replenishment between single-turn measurements. Software changes permit simultaneous measurements of any number of individual bunches in the ring. This has been used to measure emittance growth rates on six bunches of varying intensities in a single store. Also the software supports FFT analysis of turn-by-turn profiles of a single bunch at injection to detect dipole and quadrupole oscillations. |
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| TPPE011 | A Compact High-Brightness Heavy-Ion Injector | emittance, ion, plasma, extraction | 1263 | ||
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Funding: This work has been performed under the auspices of the U.S. DOE by UC-LBNL under contract DE-AC03-76SF00098 and by UC-LLNL under contract W-7405-ENG-48, for the Heavy Ion Fusion Virtual National Laboratory. |
To provide compact high-brightness heavy-ion beams for Heavy Ion Fusion (HIF) accelerators, we have been experimenting with merging multi-beamlets in an injector which uses an RF plasma source. In an 80-kV 20-microsecond experiment, the RF plasma source has produced up to 5 mA of Ar+ in a single beamlet. An extraction current density of 100 mA/cm2 was achieved, and the thermal temperature of the ions was below 1 eV. More than 90% of the ions were in the Ar+ state, and the energy spread from charge exchange was found to be small. We have tested at full voltage gradient the first 4 gaps of a 61-beamlet injector design. Einzel lens were used to focus the beamlets while reducing the beamlet to beamlet space charge interaction. We will report on a converging 119 multi-beamlet source. Although the source has the same optics as a full 1.6 MV injector system, the test will be carried out at 400 kV due to the test stand HV limit. We will measure the beam’s emittance after the beamlets are merged and have been transported through an electrostatic quadrupole. Our goal is to confirm the emittance growth and to demonstrate the technical feasibility of building a driver-scale HIF injector. |
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| TPPT061 | Prototyping of a 352 MHz, beta=0.17 Superconducting Coaxial Half Wave Resonator | linac, proton, ion, vacuum | 3547 | ||
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We have designed a 352 MHz superconducting coaxial half wave resonator with beta=0.17. The cavity has a mechanical design similar to the LNL beta=0.31 one developed in 2004. It is very compact (232 mm real-estate length) and it is equipped with a side tuner not exposed to liquid helium, to make it insensitive to pressure fluctuations. Operation is foreseen at 4.2 K. The beta=0.17 cavity fills the gap from 5 to ~25 MeV between the LNL proton RFQ, under construction, and and the existing beta=0.31 half wave resonator. This allows a 5¸100 MeV proton linac working at 352 MHz with 2 types of coaxial HWR cavities with large velocity acceptance, thus able to accelerate also other ion species (e.g. deuterons). A similar scheme was previously proposed for Spoke resonators; the aim of the HWR choice is compactness and cost reduction. The beta=0.17 cavity is presently under construction in the SPES R&D program at LNL; first test results are expected by the end of 2005.
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| TOPD003 | Cooler Storage Ring at China Institute of Modern Physics | ion, dipole, injection, lattice | 271 | ||
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CSR, a new ion cooler-storage-ring project in China IMP, is a double ring system, and consists of a main ring (CSRm) and an experimental ring (CSRe). The two existing cyclotrons SFC (K=69) and SSC (K=450) of the Heavy Ion Research Facility in Lanzhou (HIRFL) will be used as its injector system. The heavy ion beams with the energy range of 7–30 MeV/nucleus from the HIRFL will be accumulated, cooled and accelerated to the higher energy range of 100–500 MeV/ nucleus in CSRm, and then extracted fast to produce radioactive ion beams or highly charged heavy ions. Those secondary beams will be accepted and stored or decelerated by CSRe for many internal-target experiments or high precision spectroscopy with beam cooling. On the other hand, the beams with the energy range of 100–1000MeV/ nucleus will also be extracted from CSRm by using slow extraction or fast extraction for many external-target experiments. CSR project was started in the end of 1999 and will be finished in 2006. In this paper the outline and the activities of the project will be described.
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| WPAE031 | Mechanical Design of a Heavy Ion Beam Dump for the RIA Fragmentation Line | radiation, ion, dipole, vacuum | 2185 | ||
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The RIA fragmentation line requires a beam stop for the primary beam downstream of the first dipole magnet. The beam may consist of U, Ca, Sn, Kr, or O ions. with a variety of power densities. The configuration with highest power density is for the U beam, with a spot size of 3 cm x 3 cm and a total power of up to 300 kW. The mechanical design of the dump that meets these criteria consists of a 50 cm diameter aluminum wheel with water coolant channels. A hollow drive shaft supplies the coolant water and connects the wheel to an electrical motor located in an air space in the floor above the dump. The beam strikes the wheel along the outer perimeter and passes through a thin window of aluminum where 10% of its power is absorbed and the remainder of the beam is absorbed in flowing water behind the window. Rotation of the wheel at 400 RPM results in maximum aluminum temperatures below 100 C and acceptably low thermal stresses of 5 ksi. Rotating the wheel also results in low radiation damage levels by spreading the damage out over the whole perimeter of the wheel. For some of the other beams, a stationary dump consisting of a thin aluminum window with water acting as a coolant and absorber appears to be feasible.
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| WPAE053 | Neutronics Assessments for a RIA Fragmentation Line Beam Dump Concept | multipole, radiation, proton, ion | 3227 | ||
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Funding: Work performed under the auspices of the U.S. Department of Energy by University of California Lawrence Livermore National Laboratory under Contract W-7405-Eng-48. |
Heavy ion and radiation transport calculations are in progress for conceptual beam dump designs for the fragmentation line of the proposed Rare Isotope Accelerator (RIA). Using the computer code PHITS, a preliminary design of a motor-driven rotating wheel beam dump and adjacent downstream multipole has been modeled. Selected results of these calculations are given, including neutron and proton flux in the wheel, absorbed dose and displacements per atom in the hub materials, and heating from prompt radiation and from decay heat in the multipole. |
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| WPAE054 | Irradiation Effects on RIA Fragmentation Cu Beam Dump | ion, radiation, target, simulation | 3265 | ||
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Funding: U.S. Department of Energy by University of California Lawrence Livermore National Laboratory under Contract W-7405-Eng-48. |
Within the scope of conceptual R&D activities in support of the Rare-Isotope Accelerator (RIA) facility, high priority is given to the development of high-power fragmentation beam dumps. A pre-study was made of a static water-cooled Cu beam dump that can meet requirements for a 400 MeV/u uranium beam. The issue of beam sputtering was addressed and found to be not a significant issue. Preliminary radiation transport simulations show significant damage (dpa) in the vicinity of the Bragg peak of uranium ions. Experimental data show that defects in Cu following neutron or high-energy particle irradiation tend to saturate at doses between 1 and 5 dpa, and this saturation in defect density also results in saturation of mechanical property degradation. However, effects of swift heavy ion irradiation and the production of gaseous and solid transmutant elements still need to be addressed. Initial calculations indicate that He concentrations on the order of 100 appm are produced in the beam dump after several weeks of continuous operation and He embrittlement should be a concern. Recommendations are made for further investigation of Cu irradiation effects RIA-relevant conditions. |
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| WPAT082 | An Improved Pneumatic Frequency Control for Superconducting Cavities | vacuum, feedback, pick-up, ion | 4090 | ||
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Funding: U.S. Department of Energy. |
The ATLAS (Argonne Tandem Linear Accelerator System) superconducting cavities use a pneumatic system to maintain the cavity eigenfrequency at the master oscillator frequency. The present pneumatic slow tuner control has a limitation in the tuning slew rates. In some cases, the frequency slew rate is as low as 30 Hz/sec. The total tuning range for ATLAS cavities varies from 60 KHz to as high as 450 KHz depending on the cavity type. With the present system, if a cavity is at the extreme end of its tuning range, it may take an unacceptable length of time to reach the master oscillator frequency. We have designed a new slow tuner control system that increases the frequency slew rates by at least a factor of ten to a factor of three hundred in the more extreme cases. This improved system is directly applicable for use on the RIA (Rare Isotope Accelerator) cavities. This paper discusses the design of the system and the results of a prototype test. |
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| RPAT022 | Optical Faraday Cup for Heavy Ion Beams | ion, diagnostics, target, radiation | 1805 | ||
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Funding: Work performed under the auspices of the U.S. Department of Energy by the university of California, Lawrence Berkeley National Laboratory under Contract No. DE-AC03-76F00098. |
We have been using alumina scintillators for imaging beams in heavy-ion beam fusion experiments in 2 to 4 transverse dimensions.* The scintillator has limitations on lifetime, linearity, and time response. As a possible replacement for the scintillator, we are studying the technique of imaging the beam on a gas cloud. A gas cloud for imaging the beam may be created on a solid hole plate placed in the path of the beam, or by a localized gas puff. It is possible to image the beam using certain fast-quenching optical spectral lines that closely follow beam current density and are independent of gas density. We describe this technique and show experimental data using a nitrogen line at 394.1 nm. This approach has promise to be a new fast beam current diagnostic on a nanosecond time scale. *FM Bieniosek, L Prost, W Ghiorso, Beam imaging diagnostics for heavy ion beam fusion experiments, Paper WPPB050, PAC 2003. |
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| RPAT027 | Tomographic Measurement of Longitudinal Emittance Growth Due to Stripping Foils | emittance, ion, booster, electron | 2000 | ||
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Funding: Work performed under the auspices of the US Department of Energy. |
During beam acceleration at the Brookhaven accelerator complex, heavy ions are stripped off their electrons in several steps. Depending on the properties of the stripping foils, this process results in an increased energy spread and therefore longitudinal emittance growth. A tomographic phase space reconstruction technique has been applied to quantify the associated emittance growth for different stripping foil materials. |
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| ROAB003 | Highly Compressed Ion Beams for High Energy Density Science | ion, target, plasma, acceleration | 339 | ||
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Funding: Work performed under auspices of USDOE by U. of CA LLNL & LBNL, PPPL, and SNL, under Contract Nos. W-7405-Eng-48, DE-AC03-76SF00098, DE-AC02-76CH03073, and DE-AC04-94AL85000, and by MRC and SAIC. |
The Heavy Ion Fusion Virtual National Laboratory (HIF-VNL) is developing the intense ion beams needed to drive matter to the High Energy Density (HED) regimes required for Inertial Fusion Energy (IFE) and other applications. An interim goal is a facility for Warm Dense Matter (WDM) studies, wherein a target is heated volumetrically without being shocked, so that well-defined states of matter at 1 to 10 eV are generated within a diagnosable region. In the approach we are pursuing, low to medium mass ions with energies just above the Bragg peak are directed onto thin target "foils," which may in fact be foams or "steel wool" with mean densities 1% to 100% of solid. This approach complements that being pursued at GSI, wherein high-energy ion beams deposit a small fraction of their energy in a cylindrical target. We present the requirements for warm dense matter experiments, and describe suitable accelerator concepts, including novel broadband traveling wave pulse-line, drift-tube linac, RF, and single-gap approaches. We show how neutralized drift compression and final focus optics tolerant of large velocity spread can generate the necessarily compact focal spots in space and time. |
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| ROPB006 | Filling in the Roadmap for Self-Consistent Electron Cloud and Gas Modeling | electron, ion, simulation, quadrupole | 525 | ||
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Funding: This work was performed under the auspices of the U.S. Department of Energy by University of California, LLNL and LBNL under contracts W-7405-Eng-48, and DE-AC03-76F00098. |
Electron clouds and gas pressure rise limit the performance of many major accelerators. A multi-laboratory effort to understand the underlying physics via the combined application of experiment,* theory, and simulation is underway. We present here the status of the simulation capability development, based on a merge of the three-dimensional parallel Particle-In-Cell accelerator code WARP and the electron cloud code POSINST, with additional functionalities.** The development of the new capability follows a "roadmap" describing the different functional modules, and their inter-relationships, that are ultimately needed to reach self-consistency. Newly developed functionalities include a novel particle mover bridging the time scales between electrons and ions motion.*** Samples of applications of the new capability to the modeling of intense charge dominated beams**** and LHC beams***** will be shown as available. *A.W. Molvik, these proceedings. **J.-L. Vay, Proc. "ECLOUD04," Napa (California), 2004. ***R.H. Cohen, these proceedings. ****P.A. Seidl, these proceedings. *****M.A. Furman, these proceedings. |
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| RPPE034 | Measurements of the Energy Deposition Profile for 238U Ions with Energy 500 and 950 MEV/U in Stainless Steel and Copper Targets | ion, target, energy-calibration, vacuum | 2318 | ||
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Funding: Supported by the grant of the GSI-INTAS #03-54-3588. |
Sub-millimeter wall thickness is foreseen for the vacuum tubes in the magnets of the superconducting dipoles of the SIS100 and SIS300 of the FAIR Project. The Bragg peak of the energy deposition by the U ions in these walls may lie dangerously close to the superconducting cables. Thus the precise knowledge of the dE/dx profile is essential for estimating the heat load by the lost ions in the vicinity of the superconducting wires. Here we present the results of the measurement of the U ion beam energy deposition profile in Cu and stainless steel targets and compare the measured data with the Monte-Carlo simulation using the SHIELD code. |
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| ROPC003 | RIKEN RI Beam Factory Project | ion, cyclotron, extraction, acceleration | 320 | ||
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The world-top-class radioactive-isotope-beam (RIB) facility, which is called ?RI beam factory (RIBF)?, is under construction at RIKEN. This facility is based on the so-called ?in-flight RI beam separation? scheme. Late in 2006, a new high-power heavy-ion accelerator system consisting of a cascade of three ring cyclotrons with K=570 MeV (fixed frequency, fRC), 980 MeV (Intermediate stage, IRC) and 2500 MeV (superconducting, SRC), respectively, will be commissioned. This new accelerator system will boost energies of the output beams from the existing K540-MeV ring cyclotron up to 440 MeV/nucleon for light ions and 350 MeV/nucleon for very heavy ions. These energetic heavy-ion beams are converted into intense RI beams via the projectile fragmentation or in-flight fission of uranium ions by the superconducting isotope separator, BigRIPS, under construction. The combination of the SRC and BigRIPS will expand our nuclear world into presently unreachable region. Major experimental installations are under priority discussion as the second phase program. Construction of the second phase is expected to start in 2006.
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| FPAE004 | Optical Matching of Slowly Extracted Beam with Transport System at HIMAC | simulation, extraction, emittance, optics | 910 | ||
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The optical matching between the ring and the transport line plays important role in order to control the beam size and profile after the transport. At HIMAC, thus, we have studied the optical matching of the slowly extracted beam. As a result, it was verified that the beam size of the slowly extracted beam were controlled owing to the optical matching. It was also found that small deviation of quadrupole strength in the ring brings orbit distortion at the transport system.
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| FPAE027 | Status of the ISAC-II Accelerator at TRIUMF | linac, acceleration, vacuum, ion | 2003 | ||
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A heavy ion superconducting linac is being installed at TRIUMF to increase the final energy of radioactive beams at ISAC. A first stage of 20MV consisting of five medium beta cryomodules each with four quarter wave bulk niobium cavities and a superconducting solenoid is being installed with initial beam commissioning scheduled for Dec. 2005. The initial cryomodule has met cryogenic and rf performance specifications. In addition we have demonstrated acceleration of alpha particles in an off-line test. A 500W refrigerator system has been installed and commissioned in Jan. 2005 with cold distribution due for commissioning in Sept. 2005. A transfer beamline from the ISAC accelerator and beam transport to a first experimental station are being installed. The status of the project will be presented.
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| FPAE068 | Charge Strippers in the RIKEN RI-Beam Factory | ion, cyclotron, injection, factory | 3751 | ||
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In the RIKEN RI-Beam Factory, ions from hydrogen to uranium are planned to be accelerated by four cyclotrons and linacs using four stripper sections. The charge stripping schemes for typical ions and the selection of the charge strippers are described. The results of the measurements on charge state fractions are presented.
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| FPAP016 | Initial Self-Consistent 3-D Electron-Cloud Simulations of LHC Beam with the Code WARP+POSINST | electron, simulation, ion, proton | 1479 | ||
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Funding: This work was performed under the auspices of the U.S. Department of Energy by University of California, LLNL and LBNL under contracts W-7405-Eng-48, and DE-AC03-76F00098. |
We present initial results from the self-consistent beam-cloud dynamics simulations of a sample LHC beam, using a newly developed set of modeling capability based on a merger of the three-dimensional parallel Particle-In-Cell accelerator code WARP and the electron cloud code POSINST.*,** Although the storage ring model we use as a test bed to contain the beam is much simpler and shorter than the LHC, its lattice elements are realistically modeled, as is the beam and the electron cloud dynamics. The simulated mechanisms for generation and absorption of the electrons at the walls are based on previously validated models available in POSINST.*** *J.-L. Vay, these proceedings. **J.-L. Vay, Proc. "ECLOUD04," Napa (California), 2004. ***M.T.F. Pivi and M.A. Furman, Phys. Rev. STAB, PRSTAB/v6/i3/e034201. |
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| FPAP021 | A Cross-Platform Numerical Model of Ion-Wall Collisions | ion, simulation, electron, vacuum | 1707 | ||
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Ion collisions with beam-pipe walls is a significant source of secondary electron clouds and desorbed neutral gasses in particle accelerators. Ions may reflect from beam-pipe walls and undergo further collisions downstream. These effects can cause beam degradation and are expected to be problematic in the design of heavy ion accelerators. The well-known SRIM code provides physically-based monte carlo simulations of ion-wall collisions. However, it is difficult to interface SRIM with high-performance simulation codes. We present details on the development of a package of Python modules which integrate the simulation of ion-wall interactions at grazing incidences with the high-performance particle-in-cell and electron cloud codes WARP and POSINST. This software package, called GriPY, calculates reflected angles and energies of ions which strike beam-pipe walls at grazing incidences, based upon interpolation of monte carlo statistics generated by benchmark simulations run in SRIM for a variety of relevant incident angles and energies. We present here solutions for 1.8 MeV K+ ions and 1 Gev protons incident on stainless steel.
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| FPAP026 | Multispecies Weibel Instability for Intense Ion Beam Propagation Through Background Plasma | plasma, ion, background, electron | 1952 | ||
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Funding: Research supported by the U.S. Department of Energy. |
In application of heavy ion beams to high energy density physics and fusion, background plasma is utilized to neutralize the beam space charge during drift compression and/or final focus of the ion beam. It is important to minimize the deleterious effects of collective instabilities on beam quality associated with beam-plasma interactions. Plasma electrons tend to neutralize both the space charge and current of the beam ions. It is shown that the presence of the return current greatly modifies the electromagnetic Weibel instability (also called the filamentation instability), i.e., the growth rate of the filamentation instability greatly increases if the background ions are much lighter than the beam ions and the plasma density is comparable to the ion beam density. This may preclude using underdense plasma of light gases in heavy ion beam applications. It is also shown that the return current may be subject to the fast electrostatic two-stream instability. |
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| FPAP027 | Hybrid Quantum Mechanical–Quasi-Classical Model for Evaluating Ionization and Stripping Cross Sections in Atom-Ion Collisions | ion, target, electron, plasma | 1988 | ||
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Funding: Research supported by the U.S. Department of Energy. |
Ion-atom ionization cross sections are needed in many applications employing the propagation of fast ions through matter. When experimental data or full-scale theoretical calculations are non-existent, approximate methods must be used. The most robust and easy-to-use approximations include the Born approximation of quantum mechanics and the quasi-classical approach utilizing classical mechanics together with the Bohr-Sommerfeld quantization rule.* The simplest method to extend the validity of both approaches is to combine them, i.e., use the two different approaches but only for the regions of impact parameters in which they are valid, and sum the results to obtain the total cross section. We have recently investigated theoretically and experimentally the stripping of more than 18 different pairs of projectile and target atoms in the range of 3-38 MeV/amu to study the range of validity of various approximations. The results of the modified approach agree better with the experimental data than either the Born approximation or the quasi-classical approach, applied separately. *I. D. Kaganovich et al., "Formulary and scaling cross sections for ion-atom impact ionization," http://arxiv.org/abs/physics/0407140. |
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| FPAP033 | Beam Energy Scaling of Ion-Induced Electron Yield from K+ Ions Impact on Stainless Steel Surfaces | electron, ion, target, diagnostics | 2287 | ||
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Funding: This work was performed under the auspices of the U.S. Department of Energy by University of California, LLNL under contract No. W-7405-Eng-48, and by LBNL under Contract DE-AC03-76F00098. |
The cost of accelerators for heavy-ion inertial fusion energy (HIF) can be reduced by using the smallest possible clearance between the beam and the wall from the beamline. This increases beam loss to the walls, generating ion-induced electrons that could be trapped by beam space charge potential into an "electron cloud," which can cause degradation or loss of the ion beam. In order to understand the physical mechanism of production of ion-induced electrons we have measured impact of K+ ions with energies up to 400 KeV on stainless steel surfaces near grazing incidence, using the ion source test stand (STS-500) at LLNL. The electron yield will be discussed and compared with experimental measurements from 1 MeV K+ ions in the High-Current Experiment at LBNL.* *A.W. Molvik et al., PRST-AB 7, 093202 (2004). |
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| FPAT020 | A Fast Chopper for Intensity Adjustment of Heavy-Ion Beams | impedance, linac, ion, vacuum | 1692 | ||
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Funding: CRDF Grant. |
There are several heavy-ion linac projects being developed worldwide. For example, the Rare Isotope Accelerator Facility [J.A. Nolen, Nucl. Phys. A. 734 (2004) 661] currently being designed in the U.S. will use both heavy-ion and light ion beams to produce radionuclides via the fragmentation and spallation reactions, respectively. With simultaneous beam delivery to more than one target independent adjustment of relative beam intensities is essential. A fast traveling wave chopper can be used to modulate cw beam intensity at low energy ~200 keV/u. Such a device should have high frequency characteristics at high power level. By increasing the wave impedance of the traveling wave structure up to 200 Ohm one can reduce power requirements to the fast voltage pulser. Several design options of the high-impedance structure are discussed. |
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| FPAT028 | Extraction Compression and Acceleration of High Line Charge Density Ion Beams | ion, acceleration, space-charge, simulation | 2032 | ||
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Funding: This work was supported by the Director, Office of Science, Office of Fusion Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098. |
HEDP applications require high line charge density ion beams. An efficient method to obtain this type of beams is to extract a long pulse, high current beam from a gun at high energy, and let the beam pass through a decelerating field to compress it. The low energy beam bunch is loaded into a solenoid and matched to a Brillouin flow. The Brillouin equilibrium is independent of the energy if the relationship between the beam size (a), solenoid magnetic field strength (B) and line charge density is such that (Ba)2 is proportional to the line charge density. Thus it is possible to accelerate a matched beam at constant line charge density. An experiment, NDCX-1c is being designed to test the feasibility of this type of injectors, where we will extract a 1 microsecond, 100 mA, potassium beam at 160 keV, decelerate it to 55 keV (density ~0.2 microC/m), and load it into a 2.5 T solenoid where it will be accelerated to 100–150 keV (head to tail) at constant line charge density. The head-to-tail velocity tilt can be used to increase bunch compression and to control longitudinal beam expansion. We will present the physics design and numerical simulations of the proposed experiment |
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| FOAD004 | Laser Cooling of Relativistic Heavy Ion Beams | ion, laser, synchrotron, electron | 401 | ||
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Funding: Partially funded by the german BMBF (06ML183). |
We report on the first laser cooling of a bunched beam of multiply charged C3+ ions performed at the ESR (GSI) at a beam energy of E=1.47GeV. Moderate bunching provided a force counteracting the decelerating laser force of one counterpropagating UV laser beam. This versatile type of laser cooling lead to longitudinally space-charge dominated beams with an unprecedented relative momentum spread of 10-7. Concerning the beam energy and charge state of the ion, the experiment depicts an important intermediate step from the established field of laser cooling of ion beams at low energies toward the laser cooling scheme proposed for relativistic beams of highly charged heavy ions at the future GSI facility FAIR. |
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