Charge States Of Heavy Ions Research Articles

Interaction of heavy ions with plasma

Abstract The accelerator facilities at GSI, consisting of a high current radio frequency quadrupole (RFQ) accelerator, a rf-linac (UNILAC), a heavy ion synchrotron (SIS), and an experimental storage ring (ESR) provide the unique opportunity to study beam-target interaction phenomena over a wide range of beam energy. This range extends from 45 keV/u up to, and above 1 GeV/u. Thus rf accelerator and beam-target interaction physics issues for heavy-ion-beam driven inertial confinement fusion can be studied. Recent results of the experimental program such as the enhanced energy loss and the increased effective charge state of heavy ions in ionized matter, the generation of dense plasma by intense heavy ion beams, and new advanced focussing methods for intense beams are discussed.

Charge states of heavy ions in an electron gas

Abstract This work presents a study of the electron states generated by a travelling projectile and makes a comparison with the traditional theories of the effective charge.

Energy loss and straggling of heavy ions in matter

By using the Lindhard theory and the wave-packet theory, the electron energy loss and straggling are studied for heavy ions penetrating through matter. The charge state of heavy ions in matter is considered by a simple empirical formula. The energy dependences of the stopping power and the straggling are discussed. The theoretical results are qualitatively in good agreement with experimental data.

Charge States of Heavy Ions with Energy in the MeV Range in Crystalline Semiconductor Targets

ABSTRACTIn this work a formalism for the evaluation of electronic losses of heavy ions with energy of few MeV in crystalline semiconductor targets is presented. The stopping values are used in a Monte Carlo simulation to calculate the ion range in silicon and in gallium arsenide for a random orientation of the target and under channelling conditions.

Equilibrium charge fractions of 1 MeV/u Fe and Ni ions after passage through a carbon foil

Equilibrium charge fractions have been measured for 56 MeV 56Fe and 58Ni ions passing through a carbon foil to investigate the Z 1-dependence of heavy ion charge states at 1 MeV/u.

Charge states of fast heavy ions in solids — target atomic number dependence

Z 2 (target atomic number) dependence of equilibrium charge states of heavy ions has been investigated for 29 and 59 MeV F, 29–109 MeV Si, 24–109 MeV Cl, and 117 MeV Cu ions after passage through 20 kinds of thin foils with different Z 2. Except for the F ions, mean charge states ītq exhibit oscillations of Z 2 for a given collision energy. Such oscillations are closely related to the Z 2 oscillation of electron capture cross sections into the projectile inner shell vacancies. The relationship of the Z 2dependence of ītq and the stopping power is discussed for heavy ions of a few MeV/u.

First composition measurement of the bulk of the storm-time ring current (1 to 300 keV/e) with AMPTE-CCE

Mass and charge-state measurements of major ion species have been made for the first time in the bulk of the ring current preceding and during the strongly asymmetric geomagnetic storm of Sept. 4-7, 1984. Using data from the Charge-Energy-Mass (CHEM) Spectrometer on the CCE spacecraft we derive the differential energy spectra, energy densities (u) and number densities (n) in the energy range ∼1 to 315 keV/e for H+, O+, He+, He2+, O2+ and [C+N+O] with charge states above 3. We find that the prestorm, quiet-time ring current consists primarily of ions of solar wind origin (nHe2+/nH+ = 0.017) with O+ contributing only 2.7% to the total energy density of ∼4·10−8 ergs/cm³ at L ∼3 to ∼8. In contrast, O+ supplies a substantial fraction (29%) of the total storm-time ring current energy density (2.9·10−7 ergs/cm³), with O2+, He+, He2+ and [CNO] ≥3+ contributing 2.4, 1.6, 0.96 and ∼0.04% respectively. The storm-time differential energy spectra, number and energy densities are best organized in terms of energy per charge with typical average energies (E ≡ u/n) ranging from ∼41 keV/e for O+ to 64 keV for protons. We observe 1-300 keV/e, high charge state heavy ions (CNO, Si, Fe) with abundances similar to solar wind ions, implying that their entry and acceleration does not depend strongly on the mass or charge state of the ions. We conclude that while the storm-time increases in the number densities of ring current H+ and He2+ may be roughly accounted for by the decreased volume of the compressed magnetosphere, the large jumps in the number and energy densities of O+ require injection of energetic ionospheric ions.

Charge transfer in solids

Charge states of heavy ions moving in solids at intermediate velocity (0.2 v 0≲ v ≲ v 0, v 0: Bohr velocity) are investigated. The solid is treated as a non-interacting Fermi gas. The charge fraction of the ion is determined by the equilibrium charge state value, in which the velocity-dependent lifetime broadening due to both the interaction of the discrete level of an ion with the conduction band in a solid and the electron loss probability per unit time plays a dominant role. Numerical calculations for Li ions moving in Al, Zn and Au are compared with the experimental data.

External ion injection into CRYEBIS

CRYEBIS, a source of high charge state heavy ions, has been successfully operated with the use of an external low charge state ion source. Injection of ions in this manner makes CRYEBIS operation independent of the working material. The use of an external source opens up the possibilities of producing high charge states of solid materials, as well as the possibility of changing materials on a shot to shot basis.

A determination of the charge state of energetic magnetospheric ions by the observation of drift echoes

The mean charge states of heavy ions trapped in the earth's magnetosphere are important parameters for distinguishing among magnetospheric theories. No direct measurements have been made at energies greater than ∼ 50 keV. A technique, which uses the E/q dependence of ion drift velocity, is described in this letter. A drift‐echo event, which followed a substorm that occurred at 2100‐2200 UT on 25 February 1979, is discussed to illustrate the application of this technique. In this event the charge state of helium ions was +2 and CNO ions was > +2 and probably ≥ +5. This result implies that the drift‐echo particles were from freshly injected solar‐wind plasma.

An ECR Heavy Ion Source for the LBL 88-Inch Cyclotron

An Electron Cyclotron Resonance (ECR) heavy-ion source is under construction at the LBL 88-Inch Cyclotron. This source will produce very high charge state heavy ions, such as o8+ and Ar12+, which will increase cyclotron energies by a factor of 2-4, up to A = 80. It is a two-stage source using room temperature coils, a permanent magnet sextuipole, and a 6-9 GHz microwave system. Desiqn features include adjustable first to second staqe plasma coupling, a variable second stage mirror ratio, high conductance radial pumpino of the second stage, and a beam diagnostic system. A remotely movable extraction electrode will optimize extraction efficiency. The project includes construction of a transport line and improvernents to the cyclotron axial injection system. The construction period is expected to be two years.

Ionization states of heavy elements observed in the 1974 May 14-15 anomalous solar particle event

The charge states of heavy ions accelerated in the (3)He-Fe rich solar particle event of 1974 May 14-15 are determined using data from the Interplanetary Monitoring Platform-8. In addition to Fe(+11,12) both 0(+5) and Fe(+16,17,18) are also present suggesting variations in coronal temperatures over a range from approximately 400,000 to 5,000,000 K. The presence of 0(+5) and Fe(+16-18) may be explained by a resonant plasma heating mechanism proposed to account for the enhancements of (3)He and Fe.

Final Charge States of Ions Scattered to Large Angles by Single Collisions

Measurements of the charge states of ions following ion or atom excitation, have been used as probes of atomic structure since the early 1900's. More recently, the investigation of the final charge states of heavy ions scattered from heavy atoms has led to the realization that much of the ionization results from the production and subsequent cascade filling of inner-shell vacancies. The development, by Fano and Lichten, of the molecular orbital model for heavy ion-atom collisions has made our present understanding of these collisions possible. Today charge state measurements are made not only because of their intrinsic interest, but because they shed light on the molecular dynamics of collisions over a wide range of collision energies. It is found that collisions from 100 ev to 100 Mev can have features in common, and that an effective way of testing the molecular orbital model over this wide range of energies is to measure charge states as a function of scattering angles for single collisions.

Recent Developments in High Charge State Heavy Ion Beams at the LBL 88-Inch Cyclotron

Recent advances in design and operation of the internal PIG sources at the LBL 88-Inch Cyclotron have led to the development of high charge state (0.4 ≾ Q/A ≾ 0.5) heavy ion beams between lithium and neon with energies 20 ≾ E/ A ≾ 32 MeV ger nucleon, including fully stripped ions up to l6o8+. Total external intensities of these beams range from 1012 particles/s for 6Li3+ to 0.1 particles/s for 16o8+. Techniques have been developed for routine tune-out of the low intensity beams. These include use of model beams and reliance on the large systematic data base of cyclotron parameters which has been developed over many years of operation. Techniques for delivery of these weak beams to the experimental target areas are presented. Source design and operation, including special problems associated with Li, Be and B beams, are discussed.

Recent Progress in Heavy Ion Sources

This paper summarizes the progress during the last several years in the technology of sources of high charge state positive heavy ions and negative heavy ions. Subjects covered include recent results in ECR and EBIS source development and comparison of various source types for high charge state heavy ions.

High Charge State Heavy Ion Production from a PIG Source

The comparison of pulsed vs. dc arc operation for nitrogen and argon shows a shift in charge distribution toward the higher charge states for the pulsed case. Tests with various magnetic field shapes along the arc column show a significant increase in high charge state output for a uniform field compared to the case with a field low at the cathodes.

High Charge State Heavy Ion Sources

A review is given of existing sources of highly charged heavy ions. The performance of the sources, predominantly of the P.I.G. type, are summarized and compared. Some mechanisms for the production of high charge states are described. There is a brief description of new developments, particularly of devices using ion trapping.