High-intensity Ion Beam Research Articles

Stability of an ion beam in synchrotrons with digital filters in the feedback loop of a transverse damper

The stability of an ion beam in synchrotrons with digital filters in the feedback loop of a transverse damper is treated. A transverse feedback system (TFS) is required in synchrotrons to stabilize the high intensity ion beams against transverse instabilities and to damp the beam injection errors. The TFS damper kicker (DK) corrects the transverse momentum of a bunch in proportion to its displacement from the closed orbit at the location of the beam position monitor (BPM). The digital signal processing unit in the feedback loop between BPM and DK ensures a condition to achieve optimal damping. Damping rates of the feedback systems with digital filters are analysed in comparison with those in an ideal feedback system.

ITEP MEVVA ion beam for rhenium silicide production

The rhenium silicides are very attractive materials for semiconductor industry. In the Institute for Theoretical and Experimental Physics (ITEP) at the ion source test bench the research program of rhenium silicide production by ion beam implantation are going on. The investigation of silicon wafer after implantation of rhenium ion beam with different energy and with different total dose were carried out by secondary ions mass spectrometry, energy-dispersive x-ray microanalysis, and x-ray diffraction analysis. The first promising results of rhenium silicide film production by high intensity ion beam implantation are presented.

Low emittance plasma ions beam by a new double accelerating configuration

High intensity ion beams can be obtained by laser plasma or applying high electric fields or utilising large acceleration gaps. We get it developing a double acceleration gap system supplied by two power generators of different bias voltages. In this way we realized a new LIS accelerator configuration in order to produce and to accelerate ions of different elements. The LIS consists of a laser-induced plasma from solid targets, where the plume freely expands before the action of the accelerating fields. Our system provides ion beams of maximum energy up to 160 keV per charge state. We extracted charge from a Cu plasma as a function of the accelerating voltage at laser fluence values of 1.8, 2.2 and 3.4 J/cm 2. At 60 kV of total accelerating voltage, the peak currents were 3.9 and 5.3 mA corresponding to 1.8 and 2.2 J/cm 2 laser fluences, respectively. At the highest laser fluence, the maximum output current was 11.7 mA with an accelerating voltage of 50 kV and a corresponding ion flux of 10 12 ions/cm 2. Under the condition of 60 kV accelerating voltage and 5.3 mA output current (ion flux 3.4×10 11 ions/cm 2) the normalized emittance of the beam measured by pepper pot method resulted of 0.22π mm mrad. Under the condition of 160 kV accelerating voltage the ion flux was higher than 1.0×10 11 ions/cm 2.

Anisotropies in a charged particle beam

AbstractThis paper examines the anisotropies of a charged particle beam moving into a linear focusing channel. Considering a high-intensity ion beam in space-charge-dominated regime and large mismatched root mean square (RMS) initial beam size, a fast increase in spatial beam anisotropy is observed. Calculations presented here are strong evidence that this anisotropy is responsible for the beam's equipartition. It is shown that particle–particle resonances and wave-particle resonances lead to anisotropization of the beam, i.e. both the envelope and emittance ratios different from unity. It indicates that this anisotropy is responsible for the beam's equipartitioning and suggest that the beam remains equipartitioned even when exhibiting a macroscopic anisotropy, which is characterized by the following properties: the development of an elliptical shape with increasing size along one axis, the presence of a coupling between transversal emittances and halo formation along a preferential direction.

Design of two-beam-type IH-RFQ linac

In order to obtain high-intensity ion beams from a linear accelerator (linac) in a stable manner, it is necessary to suppress the defocusing force due to the space charge effect. The defocusing force is extremely strong in low-energy and high-intensity beams. Therefore, high-intensity ion beam acceleration in the low-energy region is one of the most difficult conditions to achieve. One solution is to suppress the defocusing force by dividing the high-intensity beam into several beams. Thus, a multibeam Interdigital-H (IH)-type Radio Frequency Quadrupole (IH-RFQ) linac has been proposed for a heavy ion inertial fusion (HIF) injector system. In particular, we have been developing a two-beam-type IH-RFQ cavity as a prototype of the multibeam-type IH-RFQ. This prototype has the capability of accelerating charged particles to a mass ratio ( q/ A) greater than 1 6 from 5 up to 60 keV/u. In the design, the expected total output current is about 87 mA for the total input beam current of 120 mA.

Advanced numerical simulations of temperature anisotropy instabilities and collective interaction processes in high-intensity bunched ion beams

The δ f particle-in-cell simulation method has been extended to allow the perturbation to be defined relative to any reference state, and a switching algorithm that can smoothly switch between the δ f and total- f methods has been developed. The improved δ f method has been successfully applied to simulate the collective dynamics of high-intensity bunched beams. Systematic studies of the influence of finite bunch length on the spectra of collective excitations in high-intensity ion beams, and the linear and nonlinear evolution of the temperature anisotropy instability has been carried out.

Coating deposition using vacuum arc and ablation metal plasma

An innovative concept in the development of advanced coating deposition and ion implantation method including an application of filtered DC metal plasma or ablation plasma and high-frequency short-pulsed negative bias voltage with a duty factor in the range 10–99% is considered. The regularities of metal ion implantation and vacuum arc metal plasma or ablation plasma deposition for conducting and insulating materials are considered. It was shown that plasma based ion implantation as well as high-concentration plasma ion implantation with compensation of ion surface sputtering by plasma deposition as well as ion-assisted coating deposition may be realized for metal and dielectric samples by variation of negative bias potential in the range of 0–4·10 3 V, pulse repetition rate smoothly adjusted in the range of (2–4.4) × 10 5 pps and pulse duration in the range of 0.5–2 µs. It was experimentally shown that at coating deposition from ablation plasma obtained by high intensity ion beam ( j = 300 A/cm 2, E = 350 keV, τ = 90 ns) influence on the target, the breakdown of the plasma sheet occurred at dc negative bias potential on a substrate more than 60 V. The transfer to 0.5 µs duration pulses allowed us to increase the bias potential up to − 4 kV. The possibility of high-frequency, short-pulsed plasma-immersion ion implantation and deposition method application for coating deposition from vacuum arc and ablation plasma with high adhesive strength and improved exploitation characteristics is discussed in the paper.

Publisher’s Note: High intensity ion beams in rf undulator linac [Phys. Rev. ST Accel. Beams11, 074201 (2008)

Publisher’s Note: High intensity ion beams in rf undulator linac [Phys. Rev. ST Accel. Beams<b>11</b>, 074201 (2008)

High intensity ion beams in rf undulator linac

High intensity ion beams in rf undulator linac

Localization of volatile isotopes on a cryotrap

Neutron-induced fission of uranium allows for the production of high-intensity neutron-rich radioactive ion beams. However, also large quantities of unwanted volatile radioactive species are produced that have to be hindered from contaminating the beamline and vacuum system of the facility. In the framework of radioprotection studies within the MAFF project at the FRM II in Garching with 1014fission events/s [D. Habs et al., The Munich accelerator for fission fragments MAFF, Nucl. Instr. and Meth. B 204 (2003) 739], the performance of a cryotrap system has been studied, designed to localize gaseous radioactivity close to its origin. These studies provide important radioprotection information for the planned EURISOL facility with 1015fission events/s. Design considerations of a compact cryotrap operated with cold helium gas at a saturation temperature around 18K will be presented. Activity distribution calculations of the fission source, the cryotrap and the subsequent vacuum system result in a prediction of the retention capability of the cryotrap system of 99.98%. These design calculations have been experimentally verified with three cryotrap prototypes differing in cold surface area as well as in their internal helium gas flow characteristics. Retention capabilities have been measured with and without passive shielding of the external thermal load (300K) using different tracer gases and an inclusive pressure-related diagnostics as well as mass-spectroscopic measurements.

Heavy-Ion Beam Pumped UV Laser

Accelerators are mainly built to study collisions between the projectiles and individual particles in the target. There is, however, also an application of heavy ion accelerators where collective effects in the target such as heating, heat induced expansion, and compression of the target material is studied. Such experiments are for example performed by the plasma physics group at the Gesellschaft für Schwerionenforschung (GSI) in Darmstadt, Germany [1]. The experiment described here is closely related to these experiments and aims at the production of high population densities of electronically excited species in gas targets. It benefits from the efforts to produce high energy density in matter because it also requires pulsed high intensity ion beams with excellent beam quality. One particular goal is to study conditions where the target is not in thermodynamic equilibrium, and a clear indication that such a situation is obtained is the observation of laser effect from the target.

Development of a cryogenic gas target for intense RI beam production at CRIB

Nuclear reactions of astrophysical interest, especially those under high-temperature and high-density conditions, require high-intensity low-energy radioactive ion beams, because the cross-sections are very small for the direct method study. Production of high-intensity radioactive ion beams is, therefore, one of the key developments for RI beam facilities. We report the development of a new cryogenic RI beam production gas target, along with its characteristics and performance. Some of its advantages are the increased stability against high-current primary beams and the increased thickness due to the cooling by liquid nitrogen. The target is being tested with heavy-ion beams. Measures by energy loss of the beam indicate that a thickness of about 2.4 mg/cm 2 of H 2 gas has been attained and a secondary beam of 7Be 4+ at 4.0 MeV/ u of more than 2×10 8 pps was produced.

Improvement of thickness and uniformity of isotopically enriched 12C targets on backings by the HIVIPP method

We have made enriched 12C targets to accurately measure the cross-section of the 12C( α, γ) 16O reaction, which is very important in nuclear astrophysics. Isotopically enriched 12C targets for studying this small cross-section, especially for use with an intense pulsed α beam was desired to meet the following requirements: (1) use of impurity-free enriched 12C, (2) stability for a long time measurement and (3) uniform thickness in the range 200–300 μg/cm 2. To meet these experimental requirements, isotopically enriched amorphous 12C powder was converted into graphite powder in an electric furnace at a temperature of 3000 K and subsequently the graphite powder was deposited on a thick Au backing via the HIVIPP method. Targets thus prepared could be made thicker than 200 μg/cm 2. They had a good uniformity and a very high stability against irradiation with high intensity ion beams.

Design study of a multibeam type IH-RFQ linac to accelerate high intensity and low energy heavy ion beams

A multibeam Radio Frequency Quadrupole (RFQ) linac with an Interdigital H-mode (IH) structure has been developed for high intensity heavy-ion beam acceleration. The defocusing force of space charge effect is proportional to the beam current and to the inverse square of the beam velocity. Therefore, multibeam acceleration is an attractive scheme to suppress this in the low energy region. The electromagnetic field distribution and the beam dynamics were studied for a prototype. We discuss the configuration of the multibeam IH-RFQ linac and the results of these simulations.

Control of beam halo-chaos by the number of ions in small fixed regions

Exploiting the information provided by the number of ions in some fixed regions outside the matched radius boundary, the simulation of controlling the beam halo-chaos of a high intensity ion beam has been studied by applying the logarithm-function controller. Control results show that the halo-chaos and its regeneration can be eliminated effectively for five different initial distributions, respectively. The controlling method is easy to realize in experiment because it only needs to probe the control information in small and fixed regions.

Multibeam cavity for low energy beam acceleration

In order to accelerate high intensity ion beams, it is necessary to suppress a defocusing force by the space charge effect. The function of the defocusing force is extremely strong in the low energy region. One of the solutions is the relaxation of the defocusing force by dividing the high intensity beam into several beams. We then propose a high intensity injector system with a multibeam IH type radio frequency quadrupole (IH–RFQ) linac, and simulated the resonance frequency and the electromagnetic field distributions in the multibeam type IH–RFQ linac. We report the design of the multibeam type IH–RFQ linac.

Neutralized drift compression experiments with a high-intensity ion beam

To create high-energy density matter and fusion conditions, high-power drivers, such as lasers, ion beams, and X-ray drivers, may be employed to heat targets with short pulses compared to hydro-motion. Both high-energy density physics and ion-driven inertial fusion require the simultaneous transverse and longitudinal compression of an ion beam to achieve high intensities. We have previously studied the effects of plasma neutralization for transverse beam compression. The scaled experiment, the Neutralized Transport Experiment (NTX), demonstrated that an initially un-neutralized beam can be compressed transversely to ∼1 mm radius when charge neutralization by background plasma electrons is provided. Here, we report longitudinal compression of a velocity-tailored, intense, neutralized 25 mA K + beam at 300 keV. The compression takes place in a 1–2 m drift section filled with plasma to provide space-charge neutralization. An induction cell produces a head-to-tail velocity ramp that longitudinally compresses the neutralized beam, enhances the beam peak current by a factor of 50 and produces a pulse duration of about 3 ns. The physics of longitudinal compression, experimental procedure, and the results of the compression experiments are presented.

Measurements of electrical resistivity of heavy ion beam produced high energy density matter: Latest results for lead and tungsten

The high-intensity heavy ion beams provided by the accelerator facilities of the Gesellschaft für Schwerionenforschung (GSI) Darmstadt are an excellent tool to produce large volumes of high energy density (HED) matter. Thermophysical and transport properties of HED matter states are of interest for fundamental as well as for applied research. During the last few years development of new diagnostic techniques allowed for a series of measurements of the electrical resistivity of heavy ion beam generated HED matter. In this report we present the most recent results on electrical resistivity of HED matter at GSI. The experiments on which we report have been performed with targets consisting of tungsten wires and lead foils, respectively. Uranium and argon beam pulses with durations of a few hundred ns, intensities of about 2 × 10 9 and 1 × 10 11 ions / bunch , respectively, and an initial ion energy of 300–350 A MeV have been used as a driver. An energy density deposition of about 1 kJ/g has been achieved by focusing the ion beam down to 1 mm FWHM or less.

Prospects of nuclear structure at the future GSI accelerators

The accelerator complex FAIR (International Facility for Antiproton and Ion Research) will provide a unique combination of accelerators and storage rings for a multidisciplinary scientific program. The FAIR accelerator complex constitutes a substantial extension of the present GSI systems and will use the existing accelerators after several upgrades as an injector. This new facility comprises as an integral part a next-generation rare-isotope beam facility based on the production and separation of secondary beams produced by fragmentation or fission of energetic high-intensity primary ion beams. An advanced experimental program including new and unique concepts promises a new quality in investigations of nuclei far away from stability. A brief overview on the facility is presented with emphasis on the radioactive-beam facility. The experimental program and its related instrumentation is discussed briefly.

Effect of ultrasonic surface treatment of steel 40Kh13 on the microstructure of nitrided layer formed by high-intensity low-energy implantation with nitrogen ions

X-ray diffraction and transmission electron microscopy were used to study the microstructure and phase composition of surface layers of steel 40Kh13 subjected to irradiation with high-intensity low-energy ion beams, ultrasonic surface modification, and combined treatment including ultrasonic surface modification and ion implantation. It was found that the ultrasonic modification of steel surface leads to changes in the structure of tempered martensite and the formation of grain structure with a grain size of 0.3 μm and nanosized special carbides Cr23C6 in the martensite lamellae. The ion implantation into this steel results in the formation of a nitrided layer consisting of a nitride region, which represents a mixture of several phases (α-, γ′-, ɛ, and ultrafine chromium nitrides), and a zone of internal nitriding (α″ and nitrogen-containing martensite αN). The preliminary ultrasonic modification causes an increase in the nanohardness and in the thickness of the nitrided layer, which is due to the more intense penetration of nitrogen atoms into the surface layer and an increase in the volume fraction of iron nitrides and density of ultrafine chromium nitrides in this layer.