TU Darmstadt, Darmstadt, Germany
IAP, Frankfurt am Main, Germany
GSI, Darmstadt, Germany
HZDR, Dresden, Germany
HIJ, Jena, Germany
FZD, Dresden, Germany
IOQ, Jena, Germany
Institute for Plasma Research, Bhat, Gandhinagar, India
Pandit Deendayal Petroleum University, Gandhinagar, India
sbanerje@ipr.res.in
sudhir@ipr.res.in
Institute for Plasma Research
BNL, Upton, Long Island, New York, USA
IAP, Frankfurt am Main, Germany
The construction and initial commissioning phase of a new heavy ion preinjector was completed at Brookhaven in September, 2010, and the preinjector is now operational. This preinjector, using an EBIS source to produce high charge state heavy ions, provided helium and neon ion beams for use at the NASA Space Radiation Laboratory in the Fall of 2010, and gold and uranium beams are being commissioned during the 2011 run cycle for use in RHIC. The EBIS operates with an electron beam current of up to 10 A, to produce mA level currents in 10 to 40 μs beam pulses. The source is followed by an RFQ and IH linac to accelerate ions with q/m > 0.16 to an energy of 2 MeV/amu, for injection into the Booster synchrotron. The performance of the preinjector is presented, including initial operational experience for the NASA and RHIC programs.
BNL, Upton, Long Island, New York, USA
PKU/IHIP, Beijing, People's Republic of China
Stony Brook University, Stony Brook, USA
The future electron-ion collider eRHIC requires a high average current (~50 mA), short bunch (~3 mm), low emittance (~20 μm) polarized electron source. The maximum average current of a polarized electron source so far is more than 1 mA, but much less than 50 mA, from a GaAs:Cs cathode [1]. One possible approach to overcome the average current limit and to achieve the required 50 mA beam for eRHIC, is to combine beamlets from multiple cathodes to one beam. In this paper, we present the feasibility studies of this technique.
BNL, Upton, Long Island, New York, USA
Kyushu University, Department of Applied Quantum Physics and Nuclear Engineering, Fukuoka, Japan
The Electron Beam Ion Source (EBIS) at Brookhaven National Laboratory is a new heavy ion-projector for RHIC and NASA Space Radiation Laboratory. Laser Ion Source (LIS) with solenoid can supply many kinds of ion from solid targets and is suitable for long pulse length with low current as ion provider for RHIC-EBIS. In order to understand a plasma behavior for fringe field of solenoid, we measure current, pulse width and total ion charges by a new ion probe. The experimental result indicates that the solenoid confines the laser ablation plasma transversely.
BNL, Upton, Long Island, New York, USA
After reconfiguration of the low energy (35 keV) and the medium energy (750 keV) transport lines in 2009-10, the Brookhaven linac is now delivering the highest intensity beam since it was built in 1970 (~120 μA average current of H− to the Brookhaven Linac Isotope Producer). It is also now delivering lower emittance polarized H− ion beam for the polarized program at RHIC. To increase the intensity further, we are replacing the buncher in the 750 keV line with one with higher Q value, to allow operation at higher power. Also, to improve polarization, we are replacing the magnetic solenoid before the RFQ in the 35 keV line by a solenoid-einzel lens combination. The paper will report on the results of these changes.
LBNL, Berkeley, California, USA
The NDCX-II accelerator has been designed for target heating experiments in the warm dense matter regime. It will use a large diameter (≈ 10.9 cm) Li+ doped alumino-silicate source with a pulse duration of 0.5 μs, and beam current of ≈ 93 mA. Characterization of a prototype lithium alumino-silicate sources is presented. Using 6.35 mm diameter prototype emitters (coated and sintered on a ≈ 75% porous tungsten substrate), at a temperature of ≈1275° C, a space-charge limited Li+ beam current density of ≈ 1 mA/cm2 was measured. At higher extraction voltage, the source is emission limited at around ≈ 1.5 mA/cm2, weakly dependent on the applied voltage. The lifetime of the ion source is ≈ 50 hours while pulsing the extraction voltage at 2 to 3 times per minute. Measurements under these conditions show that the lifetime of the ion source does not depend only on beam current extraction, and lithium loss may be dominated by neutral loss or by evaporation. The thickness of the coating does not affect the emission density. It is inferred that pulsed heating, synchronized with the beam pulse rate may increase the life time of a source.
LBNL, Berkeley, California, USA
A microwave ion source has been designed and constructed for use with a sealed-tube, high-yield neutron generator. When operated with a tritium-deuterium gas mixture the generator will be capable of producing 5 · 1011 n/s in non-proliferation applications. Microwave ion sources are well suited for such a device because they can produce high extracted beam currents with a high atomic fraction at low gas pressures of 0.2 − 0.3 Pa required for sealed tube operation. The magnetic field strength for achieving electron cyclotron resonance (ECR) condition, 87.5 mT at 2.45 GHz microwave frequency, was generated and shaped with permanent magnets surrounding the plasma chamber and a ferromagnetic plasma electrode. This approach resulted in a compact ion source that matches the neutron generator requirements. The needed proton-equivalent extracted beam current density of 40 mA/cm2 was obtained at moderate microwave power levels of ∼ 400W. Results on magnetic field design, pressure dependency and atomic fraction measured for different wall materials are presented.
Muons, Inc, Batavia, USA
ORNL, Oak Ridge, Tennessee, USA
In this project we are developing an RF H− surface plasma source (SPS) with saddle (SA) RF antenna which will provide better power efficiency for high pulsed and average current, higher brightness with longer lifetime and higher reliability. Several versions of new plasma generators with a small AlN test chamber and different antennasandmagneticfieldconfigurationsweretestedin the SNS ion source Test Stand. A prototype SA SPS was installed in the Test Stand with a larger, normal-sized SNS AlN chamber that achieved unanalyzed peak currents of up to 67 mA with an apparent efficiency of 1.6 mA/kW. Control experiments with H− beam produced by SNS SPS with internal and external antennas were conducted. A new version of the RF triggering plasma source (TPS) has been designed. A Saddle antenna SPS with water cooling is being fabricated for high duty factor testing.
ORNL RAD, Oak Ridge, Tennessee, USA
University of Tennessee, Knoxville, Tennessee, USA
ORNL, Oak Ridge, Tennessee, USA
The RF ion source at Spallation Neutron Source has been upgraded to meet higher beam power requirement. One important subsystem for efficient operation of the ion source is the 2MHz RF impedance matching network. The real part of the antenna impedance is very small and is affected by plasma density for 2MHz operating frequency. Previous impedance matching network for the antenna has limited tuning capability to cover this potential variation of the antenna impedance since it employed a single tuning element and an impedance transformer. A new matching network with two tunable capacitors has been built and tested. This network can allow precision matching and increase the tunable range without using a transformer. A 5-element broadband matching network also has been designed, built and tested. The 5-element network allows wide band matching up to 50 kHz bandwidth from the resonance center of 2 MHz. The design procedure, simulation and test results are presented.
ORNL, Oak Ridge, Tennessee, USA
ORNL RAD, Oak Ridge, Tennessee, USA
Running routinely with ~40-mA, 1-MW beams, the SNS linac is fed from the ion source with ~1ms long, ~50-mA H− beam pulses at 60 Hz. This requires the daily extraction of ~230 C of H− ions, which exceeds the routine daily production of other H− accelerator sources by almost an order of magnitude. The source service cycle has been extended from 2, to 3, to 4, and up to 5.6 weeks without age-related failures. The 7-9 kC of H− ions delivered in single service cycles exceed the service cycle yields of other accelerator sources. The paper discusses the findings as well as the issues and their mitigations, which enabled the simultaneous increase of the beam current, the duty factor, the availability, and the service cycle.
PPPL, Princeton, New Jersey, USA
BNL, Upton, Long Island, New York, USA
BINP SB RAS, Novosibirsk, Russia
Basic limitations on the high-intensity H− ion beam production were experimentally studied in charge-exchange collisions of the neutral atomic hydrogen beam in the Na- vapor jet ionizer cell. These studies are the part of the polarized source upgrade (to 10 mA peak current and 85% polarization) project for RHIC. In the source the atomic hydrogen beam of a 3-5 keV energy and total (equivalent) current up to 5 A is produced by neutralization of proton beam in pulsed hydrogen gas target. Formation of the proton beam (from the surface of the plasma emitter with a low transverse ion temperature ~0.2 eV) is produced by four-electrode spherical multi-aperture ion-optical system with geometrical focusing. The hydrogen atomic beam intensity up to 1.0 A /cm2 (equivalent) was obtained in the Na-jet ionizer aperture of a 2.0 cm diameter. At the first stage of the experiment H− beam with 36 mA current, 5 keV energy and ~1.0 cm-mrad normalized emittance was obtained using the flat grids and magnetic focusing. The experimental results of the high-intensity neutral hydrogen beam generation and studies of the charge-exchange polarization processes of this intense beam will be presented.
