Demonstration of an intense lithium beam for forward-directed pulsed neutron generation.

As an alternative to research nuclear reactors, a compact accelerator-driven neutron generator that uses a lithium beam driver could be a promising candidate since it produces almost no undesired radiation. However, providing an intense lithium-ion beam has been difficult, and it has been thought that the practical application of such a device would be impossible. The most critical problem of insufficient ion fluxes has been solved by applying a direct plasma injection scheme.

Plasma instability inside solenoid with laser ion source.

Using a solenoid with a laser ion source can suppress divergence of the expanding plasma; however, it has been found that the plasma becomes unstable in a certain magnetic field region. In the previous research, instability of the plasma after the solenoid was found. In this study, we investigated how the plasma instability changes inside the solenoid.

Feasibility study of a compact heavy ion source for investigation of laboratory magnetospheric plasma.

We are developing a laser ion source to provide a high brightness multi-charged heavy ion beam as a part of the heavy ion beam probe system, which will be used to diagnose plasma potential in the Ring Trap 1 device at the University of Tokyo. As a probe beam, Nb was selected, and a detailed laser irradiation condition was explored. It was found that the laser power density of 1.

Optimization of laser-target parameters for the production of stable lithium beam.

A laser ion source coupled with a radio frequency quadrupole linac accelerator is being proposed as a suitable system for the production of a low energy, high-current stable lithium beam. In order to maximize the lithium yield, plasmas generated by laser ablation of different materials based on lithium (Li, LiOH, and LiNbO) have been characterized by using a Faraday cup and an electrostatic ion analyzer in the time of flight configuration. A wide range of laser power density has been investigated (10-10 W/cm) using two Nd:YAG lasers operating at different wavelengths (1064 nm and 532 nm), pulse durations (6 ns and 17 ns), and maximum energies (1400 mJ and 210 mJ).

Design of target irradiation and diagnostic chamber to study ps-laser generated plasma as a source of singly charged ions for external injection into an electron beam ion source.

High repetition-rate (∼10 kHz) ps-lasers are becoming available on the market with reasonable cost and may offer several advantages compared to ns-lasers by generating nearly continuous beams of singly charged ions appropriate for the "slow" injection mode into the Electron Beam Ion Source (EBIS). To evaluate these advantages, we will perform studies of a ps-laser generated plasma using a laser with a pulse duration of 8 ps and energy up to 5 mJ per pulse. A vacuum chamber equipped with a 3D target positioner, a focusing lens, and a Faraday Cup has been designed and built for this study.

Low charge state lithium beam production from chemical compounds with laser ion source.

In recent years, the primary ion source for the Brookhaven National Laboratory has been the laser ion source, which provides many types of ions within a short switching time of several seconds. The task is difficult for other ion sources. In the previous work, we tested metallic lithium as a target material of the laser irradiation.

Laser power density dependence on charge state distribution of Ta ion laser plasma.

Laser power density per pulse, which is commonly expressed with the unit of "W/cm," is an important parameter to characterize ablation plasma. To match a design charge state of heavy ion beam induced by a laser ion source, a laser power density must be carefully chosen. Above around 10 W/cm of laser power density, laser ablation plasma is emitted from the surface of solid material.

Evaluation of magnetic field error in ExtendedEBIS.

The upgrade of the EBIS, called ExtendedEBIS, is now in progress in Brookhaven National Laboratory. Two 5T-superconducting solenoids have been placed in series with 200 mm distance from each other for higher trap capacity and production of polarized He ions. Since the two superconducting solenoids are used, the field error is expected to be larger.

Zr beam production for isobar experiment in relativistic heavy ion collider.

To investigate the chiral magnetic effect, Zr and Ru beams were accelerated at the relativistic heavy ion collider (RHIC) during Run-18 at Brookhaven National Laboratory. The Zr beam was provided from the electron beam ion source (EBIS) injector, which consists of a laser ion source, an EBIS high charge state ion breeder, a 300 keV/u radio frequency quadrupole, and a 2 MeV/u interdigital H type drift tube linear accelerator (IH-DTL). The natural abundance of Zr is only 2.

Contribution of material's surface layer on charge state distribution in laser ablation plasma.

To generate laser ablation plasma, a pulse laser is focused onto a solid target making a crater on the surface. However, not all the evaporated material is efficiently converted to hot plasma. Some portion of the evaporated material could be turned to low temperature plasma or just vapor.

Laser ion source for isobaric heavy ion collider experiment.

Heavy-ion collider experiment in isobaric system is under investigation at Relativistic Heavy Ion Collider. For this experiment, ion source is required to maximize the abundance of the intended isotope. The candidate of the experiment is (96)Ru + (96)Zr.

Iron plasma generation using a Nd:YAG laser pulse of several hundred picoseconds.

We investigated the high intensity plasma generated by using a Nd:YAG laser to apply a laser-produced plasma to the direct plasma injection scheme. The capability of the source to generate high charge state ions strongly depends on the power density of the laser irradiation. Therefore, we focused on using a higher power laser with several hundred picoseconds of pulse width.

Low charge state heavy ion production with sub-nanosecond laser.

We have investigated laser ablation plasma of various species using nanosecond and sub-nanosecond lasers for both high and low charge state ion productions. We found that with sub-nanosecond laser, the generated plasma has a long tail which has low charge state ions determined by an electrostatic ion analyzer even under the laser irradiation condition for highly charged ion production. This can be caused by insufficient laser absorption in plasma plume.

Effect of the solenoid in various conditions of the laser ion source at Brookhaven National Laboratory.

In the laser ion source (LIS) at the Brookhaven National Laboratory (BNL), a solenoid is used to guide the laser ablation plasma and modulate the extracted beam current. Many types of ion species are guided. In some cases, the plasma plume is injected into the solenoid away from the solenoidal axis.

Proton beam production by a laser ion source with hydride target.

We studied proton beam production from a laser ion source using hydrogen rich target materials. In general, gas based species are not suitable for laser ion sources since formation of a dense laser target is difficult. In order to achieve reliable operation, we tested hydride targets using a sub nanosecond Q-switched Nd-YAG laser, which may help suppress target material consumption.

Calcium and lithium ion production for laser ion source.

Calcium and lithium ion beams are required by NASA Space Radiation Laboratory at Brookhaven National Laboratory to simulate the effects of cosmic radiation. To identify the difficulties in providing such highly reactive materials as laser targets, both species were experimentally tested. Plate shaped lithium and calcium targets were fabricated to create ablation plasmas with a 6 ns 1064 nm neodymium-doped yttrium aluminum garnet laser.

Analyses of the plasma generated by laser irradiation on sputtered target for determination of the thickness used for plasma generation.

In Brookhaven National Laboratory, laser ion source has been developed to provide heavy ion beams by using plasma generation with 1064 nm Nd:YAG laser irradiation onto solid targets. The laser energy is transferred to the target material and creates a crater on the surface. However, only the partial material can be turned into plasma state and the other portion is considered to be just vaporized.

Comparison of graphite materials for targets of laser ion source.

To investigate efficient graphite material for carbon ion production in laser ion source, the plasma properties produced from these materials are measured. Comparing acquired current profile and charge state distribution, the distributions of ions in laser induced plasma from isotropic graphite and single crystal of graphite are different. The produced quantity of C(6+) from isotropic materials is larger than that from single crystal.

Multiple species beam production on laser ion source for electron beam ion source in Brookhaven National Laboratory.

Extracted ion beams from the test laser ion source (LIS) were transported through a test beam transport line which is almost identical to the actual primary beam transport in the current electron beam ion source apparatus. The tested species were C, Al, Si, Cr, Fe, Cu, Ag, Ta, and Au. The all measured beam currents fulfilled the requirements.

Investigation of effect of solenoid magnet on emittances of ion beam from laser ablation plasma.

A magnetic field can increase an ion current of a laser ablation plasma and is expected to control the change of the plasma ion current. However, the magnetic field can also make some fluctuations of the plasma and the effect on the beam emittance and the emission surface is not clear. To investigate the effect of a magnetic field, we extracted the ion beams under three conditions where without magnetic field, with magnetic field, and without magnetic field with higher laser energy to measure the beam distribution in phase space.

Interaction of plasmas in laser ion source with double laser system.

Multiple laser shots could be used to elongate an ion beam pulse width or to intensify beam current from laser ion sources. In order to confirm the feasibility of the multiple shot scheme, we investigated the properties of plasmas produced by double laser shots. We found that when the interval of the laser shots is shorter than 10 μs, the ion current profile had a prominent peak, which is not observed in single laser experiments.

Creation of mixed beam from alloy target and couple of pure targets with laser.

To create mixed species ion beam with laser pulses, we investigated charge state distributions of plasma formed from both Al-Fe alloy targets and pure Al and Fe targets placed close together. With two targets, we observed that the two kinds of atoms were mixed when the interval of two laser pulses was large enough (40 μs). On the other hand, when the interval was 0.

Iron beam acceleration using direct plasma injection scheme.

A new set of vanes of radio frequency quadrupole (RFQ) accelerator was commissioned using highly charged iron beam. To supply high intensity heavy ion beams to the RFQ, direct plasma injection scheme (DPIS) with a confinement solenoid was adopted. One of the difficulties to utilize the combination of DPIS and a solenoid field is a complexity of electro magnetic field at the beam extraction region, since biasing high static electric field for ion extraction, RFQ focusing field, and the solenoid magnetic field fill the same space simultaneously.

Particle simulation for direct plasma injection in a radio frequency quadrupole matching section.

We have been investigating direct plasma injection scheme (DPIS) for high-intensity heavy-ion beam acceleration. In the DPIS, laser-produced plasma is directly injected into a radio frequency quadrupole (RFQ) linac. To study the beam dynamics of the ion injection in the DPIS, we tracked particle motions in the RFQ matching section using three-dimensional particle-in-cell method.