Intense Heavy Ion Beams Research Articles

High-energy-density physics experiments with intense heavy ion beams

In this paper we discuss physical and technical issues of high-energy-density physics (HEDP) experiments with intense heavy ion beams that are being performed at the Gesellschaft für Schwerionenforschung (GSI), Darmstadt. Special attention is given to a comparison of some recent results on expansion dynamics of evaporating lead that have been obtained in heavy ion beam driven HIHEX (Heavy-Ion Heating and Expansion) experiments at GSI-Darmstadt and in high-explosive driven shock wave loading and release experiments at IPCP–Chernogolovka.

Effects of finite pulse length, magnetic field, and gas ionization on ion beam pulse neutralization by background plasma

This paper presents a survey of the present theoretical understanding of plasma neutralization of intense heavy ion beams. Particular emphasis is placed on determining the degree of charge and current neutralization. We previously developed a reduced analytical model of beam charge and current neutralization for an ion beam pulse propagating in a cold background plasma. The model made use of the conservation of generalized fluid vorticity. The predictions of the analytical model agree very well with numerical simulation results. The model predicts very good charge neutralization during quasi-steady-state propagation, provided the beam pulse duration is much longer than the electron plasma period. In the opposite limit, the beam pulse excites large-amplitude plasma waves. If the beam density is larger than the background plasma density, the plasma waves break, which leads to electron heating. The reduced-fluid description provides an important benchmark for numerical codes and yields useful scaling relations for different beam and plasma parameters. This model has been extended to include the additional effects of a solenoidal magnetic field, gas ionization and the transition regions during beam pulse entry and exit from the plasma. Analytical studies show that a sufficiently large solenoidal magnetic field can increase the degree of current neutralization of the ion beam pulse. However, simulations also show that the self-magnetic field structure of the ion beam pulse propagating through background plasma can be complex and non-stationary. Plasma waves generated by the beam head are greatly modified, and whistler waves propagating ahead of the beam pulse are excited during beam entry into the plasma. Accounting for plasma production by gas ionization yields a larger self-magnetic field of the ion beam compared to the case without ionization, and a wake of the current density and self-magnetic field are generated behind the beam pulse. Beam propagation in a dipole magnetic field configuration and background plasma has also been studied.

Inertial fusion energy issues of intense heavy ion and laser beams interacting with ionized matter studied at GSI-Darmstadt

European activities on inertial fusion energy are coordinated by “keep in touch activities” of the European Fusion Programme coordinated by the European Commission. There is no general inertial fusion program in Europe. Instead, a number of activities relevant to inertial fusion are carried out by university groups and research centers. The Helmholtz-Research Center GSI-Darmstadt (Gesellschaft für Schwerionenforschung) operates accelerator facilities which provide the highest intensity for heavy ion beams and therefore key issues of ion beam driven fusion can be addressed. In addition to the accelerator facilities, one high-energy laser system is available (nhelix: nanosecond high-energy laser for ion experiments) and another one is under construction (PHELIX: petawatt high-energy laser for ion experiments). The heavy ion synchrotron facility, SIS18 (Schwer-Ionen-Synchrotron 18) recently delivered an intense uranium beam that deposits about 1 kJ/g specific energy in solid matter. Using this beam, experiments have been performed where solid Pb- and Ta-targets have been heated to the level of 1 eV. Experiments to study interaction mechanism of heavy ion beams with matter have been continued and are reported here.

Resonant coherent excitation of relativistic nuclei in aligned crystals: New experimental perspectives at FAIR

A short overview of the status of nuclear resonant coherent excitation (RCE) of relativistic nuclei in aligned crystals is presented. The planned GSI accelerator facility FAIR, which will provide intense relativistic heavy-ion beams, will offer new experimental perspectives to study nuclear RCE. Unique opportunities will arise from the availability of bare ions up to uranium with relativistic energies up to 30GeV/u. Synchrotron accelerators, which allow for fine-tuning of the extraction energy, provide ideal conditions for nuclear RCE experiments. Calculations of electromagnetic excitation cross-sections of projectile nuclei in relativistic collisions with individual target atoms are presented, estimates of the nuclear RCE probability in a crystal, a list of candidate nuclei for nuclear RCE experiments, as well as possible experimental schemes at FAIR.

Charge change-induced beam losses under dynamic vacuum conditions in ring accelerators

Intense heavy ion beams from the Gesellschaft für Schwerionenforschung (GSI-Darmstadt) accelerator facilities are investigated for their potential to drive inertial fusion targets and are currently used to generate and probe high-energy-density (HED) matter. The existing heavy ion synchrotron facility SIS-18 delivers intense uranium beam pulses for experiments with up to 4× 109 ions per bunch at a charge state of q = 73+. Higher intensities are potentially available at lower charge states, when related loss mechanisms can be overcome. We have observed intensity-dependent beam losses in SIS-18. The origin of these beam losses is attributed to processes changing the charge state of ions, which is predominantly due to collisions with rest gas atoms. The resulting change in the mass over charge ratio m/q leads to modified trajectories in dispersive beam transport elements, and finally to the loss of the particle at the vacuum tube wall. At the impact position secondary particles are produced by ion-induced desorption and as a result the pressure in the vacuum tube is increased locally. This local rise in pressure in turn leads to increased charge changing processes starting an avalanche process that may eventually lead to a complete loss of the beam during a few turns in the synchrotron. In this paper, we discuss a method to control the problem of desorbed gases with specifically designed beam catchers at critical positions. We have further developed a program package to calculate the most important beam loss mechanisms and to couple them to the dynamic vacuum problem. The basis of this simulation is an ion–optics routine where relevant atomic processes and the effects of dynamic vacuum are implemented.

Rotating charge strippers for acceleration of intense heavy-ion beams at RIKEN

Two types of rotating charge strippers were constructed for the acceleration of intense heavy-ion beams at the RIKEN RI-beam factory. One charge stripper rotates a carbon disk using a rotating shaft. The other rotates a carbon foil attached onto the end of a rotating cylinder that is connected to hollow-shaft rotary-motion feedthroughs.

Design, development, and testing of non-intercepting profile diagnostics for intense heavy ion beams using a capacitive pickup and beam induced gas fluorescence monitors

An intense and focused heavy ion beam is a suitable tool to generate high energy density in matter. To compare results with simulations it is essential to know beam parameters as intensity, longitudinal, and transversal profile at the focal plane. Since the beam's energy deposition will melt and evaporate even tungsten, non-intercepting diagnostics are required. Therefore a capacitive pickup with high resolution in both time and space was designed, built and tested at the high temperature experimental area at GSI. Additionally a beam induced fluorescence monitor was investigated for the synchrotron's (SIS-18) energy-regime (60–750 AMeV) and successfully tested in a beam-transfer-line.

Requirements for the Silicon Tracking System of CBM at FAIR

The Compressed Baryonic Matter (CBM) experiment at the future Facility for Antiproton and Ion Research (FAIR) in Darmstadt will systematically study dense baryonic matter created in collisions of intense heavy-ion beams with nuclear targets. The research addresses current questions of strong-interaction physics as confinement in normal nuclear matter, chiral symmetry restoration in deconfined matter at high temperatures and densities, and the search for the critical end-point of the phase boundary. With beams of ions as heavy as Au and U, energies up to 45 GeV/nucleon and intensities up to 10 12 ions per pulse, FAIR will enable CBM to probe the phase diagram of quantum chromo dynamics (QCD) in a region poorly known, while being complementary to current and future research programmes at RHIC and LHC. The CBM experiment is planned as a fixed-target spectrometer optimized for the detection of rare probes. Among these are open charm and low-mass vector mesons, important observables for the initial energetic and dense phase of the collisions. The experimental concept and challenge is to accomplish charged particle tracking in the high-multiplicity, high-radiation collision environment. This will be realized exclusively with a silicon tracking detector system installed in a strong magnetic dipole field directly behind the target. Key to the physics of CBM and benchmark for the tracking is the reconstruction of short-lived charmed mesons that puts high demands on the silicon detectors. The article presents a conceptual design of the CBM experiment with emphasis on the silicon tracking system. Requirements for silicon microstrip and pixel detectors and their arrangement in the tracker are discussed in relation to important physics observables addressed by CBM.

Pulse line ion accelerator concept

April 3, 2006 LBNL-59492 The pulse line ion accelerator concept Richard J. Briggs Science Applications International Corporation, Alamo, California, 94507 The Pulse Line Ion Accelerator concept was motivated by the desire for an inexpensive way to accelerate intense short pulse heavy ion beams to regimes of interest for studies of High Energy Density Physics and Warm Dense Matter. A pulse power driver applied at one end of a helical pulse line creates a traveling wave pulse that accelerates and axially confines the heavy ion beam pulse. Acceleration scenarios with constant parameter helical lines are described which result in output energies of a single stage much larger than the several hundred kilovolt peak voltages on the line, with a goal of 3-5 MeV/meter acceleration gradients. The concept might be described crudely as an “air core” induction linac where the PFN is integrated into the beam line so the accelerating voltage pulse can move along with the ions to get voltage multiplication. 1. Introduction In the “Pulse Line Ion Accelerator” (PLIA) concept described in this paper a ramped high voltage pulse is applied at the input end of a helical pulse line structure. The resulting traveling wave pulse on the line can accelerate an ion bunch to energies much greater than the peak voltage applied to the line. It should also be possible to achieve an axial acceleration gradient of several MeV per meter with realistic helix parameters. The development of this concept was originally motivated by a proposal to use moderate energy intense ion beams to heat matter to regimes of interest for studies of High Energy Density Physics (HEDP) and Warm Dense Matter (WDM) [ 1 ] . In this approach, very short pulses (~ a nanosecond or less) of “medium mass” ions with energies slightly above the Bragg peak are focused to mm scale spot sizes onto thin target “foils”, which may in fact be foams with mean densities of order 10% solid density or less. The high degree of uniformity and efficiency with volumetric and shock-less heating of the target to temperatures of order 1 to 10 eV are attractive features in this approach. The concept presented in this paper is an excellent fit to the accelerator requirements for this HEDP/WDM application. A helical pulse line inserted into a large bore 5 - 10T superconducting solenoid can transport and accelerate a singly charged Ne or Na ion bunch with a total charge of order 0.1 to 1 micro-coulombs, an axial bunch length of 10’s of cm, and a radius of a few cm. The required axial compression to bunch lengths of order one cm in a neutralized drift compression region following the accelerator is then only a factor of 10-30, which greatly eases the requirements on longitudinal emittance, velocity tilt, and drift distance.

Emittance growth and instability induced by space charge effect during final beam bunching in HIF accelerator system

Beam dynamics and emittance growth are investigated by using particle-in-cell simulations during a final beam bunching for a driver system of inertial fusion driven by intense heavy ion beams. Space-charge-dominated beams are transported by a transverse confinement lattice with longitudinal compression, and the emittance increases along the longitudinal beam bunching. Dipole oscillations are excited due to the initial displacement of the beam center. The displacement causes the additional emittance growth during the final beam bunching.

Pyrometric system for temperature measurements of HED matter generated by intense heavy ion beams

Recent experiments performed on heating of matter using intense uranium beams generated by the heavy ion synchrotron, SIS18, at the Gesellschaft fur Schwerionenforschung (GSI) Darmstadt, have shown that using the present beam parameters, one can achieve near critical states of lead. The beam intensity was 4 10 9 ions per bunch that was 130 ns long while the particle energy was 350 AMeV. A fast 6-channel pyrometer has been developed at the GSI in collaboration with scientists from the Institute of Problems of Chemical Physics (IPCP), Chernogolovka, to measure the temperature of the heated material. Temperatures from 1500 K to 5000 K were recorded for metallic targets.

Studies of thermophysical properties of high-energy-density states in matter using intense heavy ion beams at the future FAIR accelerator facilities: The HEDgeHOB collaboration

Intense beams of energetic heavy ions are believed to be a very efficient and novel tool to create states of High-Energy-Density (HED) in matter. This paper shows with the help of numerical simulations that the heavy ion beams that will be generated at the future Facility for Antiprotons and Ion Research (FAIR)[W.F. Henning, Nucl. Instr. Meth. B 214, 211 (2004)] will allow one to use two different experimental schemes to study HED states in matter. First scheme named HIHEX (Heavy Ion Heating and EXpansion), will generate high-pressure, high-entropy states in matter by volumetric isochoric heating. The heated material will then be allowed to expand isentropically. Using this scheme, it will be possible to study important regions of the phase diagram that are either difficult to access or are even unaccessible using traditional methods of shock compression. The second scheme would allow one to achieve low-entropy compression of a sample material like hydrogen or water to produce conditions that are believed to exist in the interiors of the giant planets. This scheme is named LAPLAS (LAboratory PLAnetary Sciences).

Electrical resistivity of high energy density matter generated by high intensity heavy ion beams

Development of new diagnostic techniques allowed, during the past few years, for a first series of measurements on the electrical resistivity of heavy ion beam generated high energy density (HED) matter. The experimental investigations have been carried out at the HHT laboratory of the Plasma Physics Department of the Gesellschaft fur Schwerionenforschung in Darmstadt. In this report we review the results of these experiments and discuss future experimental and theoretical work planned to be carried out within the framework of the HEDgeHOB collaboration for precise determination of the electrical resistivity of HED matter.

Proposed studies of strongly coupled plasmas at the future FAIR and LHC facilities: the HEDgeHOB collaboration

Detailed theoretical studies have shown that intense heavy-ion beams that will be generated at the future Facility for Antiprotons and Ion Research (FAIR) (Henning 2004 Nucl. Instrum. Methods B 214 211) at Darmstadt will be a very efficient tool to create high-energy-density (HED) states in matter including strongly coupled plasmas. In this paper we show, with the help of two-dimensional numerical simulations, the interesting physical states that can be achieved considering different beam intensities using zinc as a test material. Another very interesting experiment that can be performed using the intense heavy-ion beam at FAIR will be generation of low-entropy compression of a test material such as hydrogen that is enclosed in a cylindrical shell of a high-Z material such as lead or gold. In such an experiment, one can study the problem of hydrogen metallization and the interiors of giant planets. Moreover, we discuss an interesting method to diagnose the HED matter that is at the centre of the Sun. We have also carried out simulations to study the damage caused by the full impact of the Large Hadron Collider (LHC) beam on a superconducting magnet. An interesting outcome of this study is that the LHC beam can induce HED states in matter.

Electrical resistivity measurements of heavy ion beam generated high energy density aluminium

The high intensity heavy ion beams provided by the accelerator facilities of the Gesellschaft fur 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. In this paper we present the most recent results on electrical resistivity of HED matter obtained at the High Temperature Laboratory of the Plasma Physics Department of GSI. The targets under investigation consisted of 5 mm long and 0.25 mm diameter aluminium wires. Uranium beam pulses with durations of approximately 200 ns, intensities of about 2 × 109 ions/bunch and an initial ion energy of 350 A MeV have been used as a driver. An energy density deposition of about 1 kJ g−1 has been achieved by focussing the ion beam to less than 1 mm FWHM. Under these conditions, resistivities of up to 1.5 × 10−6 Ω m have been observed within 1 µs after irradiation.

Numerical simulations and theoretical analysis of High Energy Density experiments at the next generation of ion beam facilities at Darmstadt: The HEDgeHOB collaboration

This paper presents detailed numerical simulations and theoretical analysis of different possible experimental schemes to study the thermophysical and transport properties of High Energy Density ( HED) matter generated by the interaction of intense heavy ion beams. The considered beam parameters are those which will be available at the future Facility for Antiprotons and Ion Research ( FAIR) at Darmstadt [W.F. Henneing, Nucl. Instrum. Methods, B214, (2004) 211]. This work has shown that an intense heavy ion beam can be used employing two very different configurations to study HED states in matter. In the first scheme, a sample material is uniformly and isochorically heated by the beam and the heated material is subsequently allowed to expand isentropically. Depending on the specific energy deposited in the material, one may access all the interesting physical states, including that of an expanded hot liquid ( EHL), two-phase liquid–gas ( 2PLG) region, critical point ( CP) parameters as well as strongly coupled plasma ( SCP) states during the expansion. This scheme is named HIHEX ( Heavy Ion Heating and EXpansion). We have considered a 1 GeV/u uranium beam with an intensity, N = 10 10–10 12 ions that are delivered in a single bunch, 50 ns long. The particle intensity distribution in the transverse direction is assumed to be Gaussian with a full width at half maximum (FWHM) in the range of 1–4 mm. We note that the estimated critical temperatures for many metals are very high which are very difficult to access using traditional techniques of shock compression of matter. Employing the proposed HIHEX scheme, one can easily achieve the required temperature by depositing corresponding specific energy in the sample. Solid as well as porous targets have been used in our study. In the second scheme, a sample material like frozen hydrogen that is enclosed in a cylindrical shell of a high- Z material like gold or lead, is imploded by the ion beam. This scheme is specially designed to generate multiple reflection of shocks in the target that leads to a low-entropy compression of the sample material. As a result of this, one achieves super-high densities (up to 30 times solid density) and ultrahigh pressures (3–30 Mbar) in the hydrogen. If one uses a hollow beam with an annular focal spot, hydrogen is not directly heated by the ion beam that leads to a low final temperature (of the order of a few thousand K). This scheme is therefore suitable to study the problem of hydrogen metallization. In case one uses a circular focal spot, although the hydrogen is strongly heated by the beam, one still achieves a very high compression because the pressure in the surrounding shell is orders of magnitude higher than that in hydrogen. However, in this case the final hydrogen temperature is much higher (of the order of a few eV) than in the previous case. This configuration is thus suitable to study the interiors of the giant planets and is named LAPLAS ( LAboratory PLAnetary Science). We have also analyzed the hydrodynamic stability of the LAPLAS target and we find that the Rayleigh–Taylor (RT) and Richtmeyer–Meshkov (RM) instabilities will not pose any serious problems to this scheme.

Laser Accelerated, High Quality Ion Beams

Intense beams of protons and heavy ions have been observed in ultra-intense laser-solid interaction experiments. Thereby, a considerable fraction of the laser energy is transferred to collimated beams of energetic ions (e.g. up to 50 MeV protons; 100 MeV fluorine), which makes these beams highly interesting for various applications. Experimental results indicate very short pulse duration and an excellent beam quality, leading to beam intensities in the TW range. To characterize the beam quality and its dependence on laser parameters and target conditions we performed experiments at several high-power laser systems. We found a strong dependence on the target rear surface conditions allowing to tailor the ion beam by an appropriate target design. We also succeeded in the generation of heavy ion beams by suppressing the proton amount at the target surface.

Studies of equation of state properties of high-energy density matter using intense heavy ion beams at the future FAIR facility: The HEDgeHOB collaboration

This paper shows with the help of numerical simulations the capabilities of intense heavy ion beams to induce states of high-energy density (HED) in matter. Two different experimental schemes are considered, namely, HIHEX (heavy ion heating and expansion) and LAPLAS (laboratory planetary sciences). The first scheme considers isochoric heating and subsequent isentropic expansion of matter while the latter deals with low entropy compression of matter using multiple shock reflection technique. This work has been done within the framework of the HEDgeHOB (high-energy density matter generated by heavy ion beams) collaboration that has been formed to organize and facilitate construction of experimental facilities and later to perform experimental work in the field of HED matter at the future FAIR (facility for antiprotons and ion research) facility.

Production and accumulation of a mA-DC bismuth ion beam

At our Institute an experiment for the direct measurement of the atomic mass unit is under way by accumulating ions from an ion beam up to a ponderable mass. The aim of this experiment is to find an alternative approach for the redefinition of the SI unit kilogram via the atomic mass unit. This paper discus two important aspects of the experiment, namely the production of a DC intense heavy ion beam and the collection process of such a beam. Until now a bismuth ion beam of ≈5mA can be extracted out of a CHORDIS ion source. Suitable geometries of an ion-collector are shown based on SIMION-3D simulations.

Present and future perspectives for high energy density physics with intense heavy ion and laser beams

Present and future perspectives for high energy density physics with intense heavy ion and laser beams