Charge State Measurements Research Articles

Fermi acceleration of suprathermal solar wind oxygen ions

The Wind spacecraft has observed numerous sunward bursts of ≈2 MeV ions upstream of the Earth's bow shock. These energetic particles are not protons or alpha particles and are probably oxygen ions. The bursts typically last several minutes at the highest energies, but they can last for tens of minutes at intermediate energies (tens to hundreds of keV). In this paper, Wind observations of the November 30, 1994, bursts and numerical particle simulations are presented that demonstrate that suprathermal solar wind O6+ ions, which have undergone Fermi acceleration between the bow shock and interplanetary magnetic field (IMF) rotations, are the most likely source of these bursts. Each burst either coincides with or is closely followed by a large IMF rotation. By using measured magnetic field data the timing of the bursts detected by Wind is reproduced in the simulation. Simulated spectra of H+, He2+, and O6+ fluxes fit the observed spectra, assuming an increase of ∼2 orders of magnitude in the high‐energy tail of the solar wind oxygen distribution, relative to the average solar wind abundance of oxygen. Such enhancements in CNO group ions above 40 keV/nucleon were measured by the Suprathermal and Energetic Particle (STEP) instrument during this interval. This study concludes by predicting that ion composition and charge state measurements will show these bursts to be solar wind oxygen ions in high charge states.

Plasma physics with intense laser and ion beams

The unique combination of an intense heavy ion beam and a high-energy Nd:glass laser system at Gesellschaft für Schwerionenforschung (GSI-Darmstadt) facilitates pioneering beam-plasma interaction experiments and thus allows to address basic physics issues associated with heavy ion-driven inertial fusion. The deposition power of the intense heavy ion beam from the synchrotron has recently been increased to 1 kJ/g. The hydrodynamic response of solid targets was measured. A comparison with detailed numerical simulations attributes the target response to a pressure pulse of 3 GPa at a maximum temperature of 2500 K. Beam plasma interaction experiments to measure the stopping power of laser plasmas for heavy ion beams have been performed and show an increased energy loss for Ni ions in a 60 eV dense carbon plasma. Subsequently performed time-resolved charge-state measurements indicate that the increased stopping power can partially be attributed to a high charge state of the beam ions traversing the plasma. Improved plasma diagnostic by high-resolution spectroscopy revealed the unexpected existence of He-like resonance and intercombination lines (He α = 1s2p 3P 1–1s 2 and Y α = 1s2p 3P 1–1s 2) of fluorine even for a modest laser intensity of 5 × 10 11 W/cm 2.

Experiments on the interaction of heavy ions with dense plasma at GSI-Darmstadt

One of the main objectives of the experimental plasma physics activities at the Gesellschaft für Schwerionenforschung (GSI) are the interaction processes of heavy ions with dense ionized matter. Gas-discharge plasma targets were used for energy loss and charge state measurements in a regime of electron density and temperature up to 10 19 cm −3 and 20 eV, respectively. An improved model of the charge exchange processes in fully ionized hydrogen plasma, taking into account multiple excited electronic configurations which subsequently ionize, has removed the discrepancies of previous theoretical descriptions. The energy loss of the ion beam in partially ionized plasmas such as argon was found to agree very well with our simple theoretical model based on the modified Bethe–Bloch theory. A new setup with a 100 J/5 GW Nd–glass laser now provides access to density ranges up to 10 21 cm −3 and temperatures of up to 100 eV. First results of interaction experiments with laser-produced plasma are presented. To fully exploit the experimental possibilities of the new laser-plasma setup both improved charge state detection systems and better plasma diagnostics are indispensable. Present developments and future possibilities in these fields are presented. This paper summarizes the following contributions: • Interaction of heavy-ion beams with laser plasma by C. Stöckl et al. • Energy Loss of Heavy Ions in a laser-produced plasma by M. Roth et al. • Charge state measurements of heavy ions passing a laser produced plasma with high time resolution by W. Süß et al. • Plasma diagnostics for laser-produced plasma by O. Iwase et al. • Future possibilities of plasma diagnostics at GSI by M. Geißel et al.

Inversion relations for exclusive and inclusive cross sections within the independent electron approximation

Inversion relations expressing inclusive cross sections as linear combinations of exclusive cross sections are derived within the independent electron approximation without exchange. Both binomial and multinomial probability distributions are used. No particular model is used for $P(\stackrel{\ensuremath{\rightarrow}}{b}).$ A criterion for applicability of the multinomial probability distribution to describe second-order transitions for the different collision channels, also independent of $P(\stackrel{\ensuremath{\rightarrow}}{b}),$ is presented. The coupling of ionization and capture of outer-shell electrons is discussed and the inversion relations derived are applied to the analysis of coincidence measurements of projectile and target charge states. Parametrization and scaling laws for single and double ionization of outer-shell electrons of many-electron atoms are considered by studying the influence of the electron capture channel.

Experiments on the Interaction of Heavy-Ion Beams with Dense Plasmas

Gas discharge plasma targets were used for energy loss and charge state measurements of fast heavy ions 5 MeV/u ≤ Ekin ≤ 10 MeV/u in a regime of electron density and temperature up to 1019 cm−3 and 20 eV, respectively. Progress has been achieved in the understanding of charge exchange processes in fully ionized hydrogen plasma. An improved model that has taken excitation-autoionization processes into account has removed some of the discrepancies of previous theoretical descriptions. Furthermore, the energy loss of the ion beam serves as an excellent diagnostic tool for measuring the electron density in partially ionized plasmas such as argon. The experience with these methods will be used in the future to diagnose dense laser-produced plasmas. A setup with a 5-GW neodymium-glass laser, currently under construction, will provide access to density ranges up to 1021 cm−3 and temperatures > 100 eV.

Interaction of heavy ion beams with dense plasmas

The main objective of the experimental plasma physics activities at the Gesellschaft für Schwerionenforschung (GSI) is the interaction processes of heavy ions with dense ionized matter. Gas discharge plasma targets were used for energy loss and charge state measurements in a regime of electron density and temperature up to 1019 cm-3 and 20 eV, respectively. Progress has been achieved in the understanding of charge-exchange processes in fully ionized hydrogen plasma. An improved model taking excitation-autoionization processes into account has removed most of the discrepancies of previous theoretical descriptions. Furthermore, it was found that the energy loss of the ion beam serves as an excellent diagnostic tool for measuring the electron density in partially ionized plasmas such as argon. The experience with these methods will be used in the future to diagnose dense laser produced plasmas. A setup with a 100 J/5 GW Nd:glass laser, currently under construction, will provide access to density range up to 1021 cm-3 and temperatures of more than 100 eV. To reach electron densities near solid-state density (1023 cm-3), heavy ion heated frozen rare gas crystals were used. The first hydrodynamic motion of ion heated solid material was observed. Vacuum-ultraviolet (VUV) spectroscopy was applied to diagnose these strongly coupled nonideal plasmas.

Solar Energetic Fe Charge State Measurements: Implications for Acceleration by Coronal Mass Ejection–driven Shocks

A variety of studies have demonstrated that large (gradual) solar energetic particle (SEP) events are produced by shocks driven by fast mass ejections (CMEs). As the CME-driven shocks propagate through the corona and interplanetary space, they accelerate energetic particles from ambient plasma. A key piece of evidence supporting the CME-driven shock acceleration scenario is the SEP Fe mean charge state measurements from ~1 MeV nucleon-1 to 200-600 MeV nucleon-1, which are consistent with each other and imply acceleration in either the high corona or interplanetary space. However, the SEP Fe mean ionic charge state measurements are generally inconsistent with typical quasi-stationary interstream or hole solar wind Fe charge state measurements, despite the fact that gradual SEP time profiles indicate that shock acceleration subsequent to departure from the corona dominates the SEP observations. These Fe results indicate that neither overtaken solar wind nor charge state biasing of the solar wind as it is swept up and accelerated by the shock are the dominant component accelerated by the CME-driven shock. We suggest that the dominant component for both the plasma and SEP populations appears to be expelled coronal plasma stored in the so-called sheath region (between the CME and the shock front), and that swept-up solar wind generally makes only a minor contribution to the SEPs. The only concurrent observation of SEP and solar wind charge states made to date (by instruments on board ISEE 3 in 1978 September) supports this view. We suggest that coordinated SEP and solar wind charge state observations should be given high priority by state-of-the-art instruments currently deployed on board the Solar Anomalous Magnetospheric Particle Explorer, Wind, and the Solar and Heliospheric Observatory.

Dielectronic recombination and energy loss for He-like 79Br ions channeled in a thin single crystal of Si.

Dielectronic recombination of He-like {sup 79}Br ions channeled along the {l_angle}110{r_angle} axis of a thin Si crystal has been studied by the measurement of the charge-state distribution and x-ray production. The results of the charge-state measurements confirm that the probability of resonance capture is proportional to the valence electron density sampled by the ion. The energy-loss distributions of channeled ions are also in good agreement with theoretical estimates. {copyright} {ital 1996 The American Physical Society.}

Payload requirements for the Solar Probe

The scientific goals and objectives for a Solar Probe determine the requirements for a model payload and concepts for the instruments. To accomplish the main aim, which is to make in-situ measurements of particles and fields in the solar corona and wind, the strawman payload must include a magnetometer and plasma wave instrument, fast three-dimensional plasma anlyzers to measure ions and electrons, and detectors for suprathermal and solar energetic particles. In addition a light-weight dust detector is required to probe the dust environment in the outer corona. Tight constraints are to be placed on all instruments concerning mass, power and telemetry in order to keep the expected costs and complexity to a bare minimum. This will require further developments of existing instruments or innovative concepts, allowing the objectives to be met with a payload of only 20 to 25 kg. All instruments have to be acommodated on a three-axis stabilized probe and should be capable of measuring particle fluxes that might vary by many orders of magnitude. The plasma experiments are central to the mission and very demanding because of the wide dynamic ranges required for the spatial, temporal, and particle-species energy, mass and charge state measurements. Furthermore, ion velocity distributions are expected to range from subsonic to supersonic in the Sun's frame of reference and are to be measured from a spacecraft with speed of about 300 km/s near perihelion at 4 R ⊙. Also shapes and heat flux tails of the distributions must be resolved, as they carry information crucial to the determination of coronal heating and solar wind acceleration mechanisms. The wave experiments must identify the wave modes and spectral intensities, which are essential for quantifying the wave effects on particles and their energization.

Measurements of the Ionic Charge States of Solar Energetic Particles Using the Geomagnetic Field

The mean charge states of C, N, O, Ne, Na, Mg, Al, Si, S, Ar, Ca, Fe, and Ni ions with ~15-70 MeV nucleon^(-1) in the two large solar energetic particle (SEP) events of 1992 October 30 and November 2 have been determined using measurements of the invariant latitude of the cosmic-ray cutoffs of these elements from the Mass Spectrometer Telescope on the polar-orbiting SAMPEX satellite. The deduced charge state values are in good agreement with the mean values measured directly in previous SEP events at much lower energies of ~1 MeV nucleon^(-1). The inferred equilibrium source temperatures are confirmed to be typically 2 × 10^6 K, which provides additional evidence that SEPs in gradual-type events are accelerated coronal material.

Charge State Measurements of Solar Energetic Particles Observed with SAMPEX

view Abstract Citations (64) References (32) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Charge State Measurements of Solar Energetic Particles Observed with SAMPEX Mason, G. M. ; Mazur, J. E. ; Looper, M. D. ; Mewaldt, R. A. Abstract We have measured the ionization states of major elements accelerated in two large solar energetic particle events by use of the geomagnetic cutoff technique. The observations were made in 1992 October/November using instrumentation on the SAMPEX satellite, which is in an 820 inclination low Earth orbit. We calibrate the geomagnetic cutoff rigidity by assuming that protons and He observed on SAMPEX are fully stripped. The mean charge states of the heavier elements are then determined from their measured cutoffs, along with this calibrated scale. Our results cover the energy range ∼0.5-5 MeV nucleon-1 and are in good agreement with earlier studies by Luhn et al. (1985) near ∼1 MeV nucleon-1 in all cases except for Fe. We find a mean charge state of 11.04±0.22 for Fe, while the average from Luhn is 14.09±0.09. The lower ionization state of Fe reported here appears to be consistent with the general range of values recently measured in solar wind Fe on the Ulysses deep space probe. Although the observational picture is still incomplete, overall the present results confirm and extend previous evidence that the solar energetic particles in large events are accelerated from the coronal or solar wind material. Publication: The Astrophysical Journal Pub Date: October 1995 DOI: 10.1086/176358 Bibcode: 1995ApJ...452..901M Keywords: SUN: ABUNDANCES; SUN: FLARES; ISM: COSMIC RAYS; SUN: PARTICLE EMISSION full text sources ADS |

The southern high-speed stream: results from the SWICS instrument on Ulysses

The high-speed solar wind streaming from the southern coronal hole was remarkably uniform and steady and was confined by a sharp boundary that extended to the corona and chromosphere. Charge state measurements indicate that the electron temperature in this coronal hole reached a maximum of about 1.5 million kelvin within 3 solar radii of the sun. This result, combined with the observed lack of depletion of heavy elements, suggests that an additional source of momentum is required to accelerate the polar wind.

Charge state of fast heavy ions in a hydrogen plasma.

We report the first charge-state measurements of fast heavy ions passing through a plasma target. The projectiles were $^{40}\mathrm{Ar}$ ions at an energy of 4.8 MeV/amu and $^{129}\mathrm{Xe}$ ions at an energy of 5.9 MeV/amu. The target was a 20-cm-long Z pinch discharge which provided fully ionized hydrogen plasma with free electron densities up to 1.5\ifmmode\times\else\texttimes\fi{}${10}^{19}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$. The measured charge-state distributions are in excellent agreement with theoretical calculations. For Xe ions an increase of the ion charge state in plasma over the charge state in cold gas was observed.

RTE measurement with Xe 52+ ions channeled in a Si crystal

KLL resonant transfer and excitation (RTE) of 33–43 MeV/nucleon He-like Xe ions channeled along the 〈110〉 axis of a thin Si crystal has been investigated in measurements of charge state distributions and of the resulting X-ray production. The resonance peaks obtained by the two methods are quite similar. The charge state measurements show that RTE appears, for well channeled ions, to be rather independent of the electron density they sample. Resonance energy, width and intensity are compared with theoretical estimates.

Charge-state measurements for 63Cu, 90Zr, 107Ag, 115In, 127I and 197Au in carbon for energies below 1 MeV/u

Equilibrium charge-state distributions have been measured for ∼0.2–1.0 MeV/u 63Cu, 90Zr, 107Ag, 115In, 127I and 197 emerging from thin (10–30 μg/cm2) carbon foils. In many cases, values deduced for the mean charge were found to deviate substantially (from 1 to 3 charge states) from those predicted by semi-empirical formulae. Highly asymmetric charge-state distributions were observed for 107Ag and 115In near 30 MeV, which are attributed to a shell effect at the boundary between the N- and M-shell electrons. The present results will be used to select the optimum charge-state combinations for heavy-ion beams from the tandem accelerator superconducting cyclotron (TASCC) at Chalk River.

Charge-state measurements of backscattered ions from Au films.

A small electrostatic accelerator (65 kV) was built as a postaccelerator for measuring the charge-state fractions of ions backscattered from solid or gas targets. A new method is described in which the charge-state fractions of $^{3}\mathrm{He}$, $^{4}\mathrm{He}$, $^{12}\mathrm{C}$, $^{14}\mathrm{N}$, and $^{16}\mathrm{O}$ ions backscattered from gold films are determined simultaneously. The added features in this work are the facts that the method can be efficiently used for low-energy incident ions and that spectra could be measured, compared, and analyzed by minimizing uncertainties inherent in experimental parameters. The energy dependence of the charge-state fractions of $^{3}\mathrm{He}$, $^{4}\mathrm{He}$, and $^{12}\mathrm{C}$ ions are measured between 3 MeV and 150 keV. The $^{12}\mathrm{C}$ charge-state-fraction data nicely fit the Gaussian model but none of the ${\ensuremath{\chi}}^{2}$ models. The mean ion charge ${i}_{m}$ and the standard deviation s are also measured. Preliminary measurements of the dependence of the charge-state fractions on target thickness are also discussed.

Observation of radiative electron capture into K,L,M shells of 25-MeV/u Xe53+ ions channeled in silicon.

We present experimental results showing that channeling measurements with fast stripped heavy ions incident on thin crystals can allow a detailed study of radiative electron capture. Charge-state measurements and photon-energy spectra have been used to deduce cross sections of radiative capture into the K, L, and M shells of 25-MeV/u ${\mathrm{Xe}}^{53+}$ ions. The orientation dependence of the positions and shapes of associated photon lines has been observed.

Solar wind iron charge states preceding a driver plasma

During September 28 and 29, 1978, the ISEE 3 spacecraft observed several distinct types of high‐speed solar wind flows when a coronal hole‐associated high‐speed stream was followed by two interplanetary shocks, one of which was driven by flare ejecta contained in a “magnetic cloud” or interplanetary “plasmoid.” Using the University of Maryland/Max‐Planck‐Institut ultralow energy charge analyzer (ULECA) on ISEE 3, we present solar wind Fe and Si/S charge state and Fe density measurements for the different plasma regimes associated with the flare‐related shock and combine these measurements with the Los Alamos National Laboratory proton observations to obtain iron/hydrogen density ratios and iron/hydrogen velocity differences. We place special emphasis on the postshock shell of turbulent and compressed ambient solar wind and interplanetary magnetic fields constituting the “sheath region” preceding the driver plasma. It is generally expected that the abundance ratios and charge states of the solar wind ions in the driver plasma and the sheath remain distinct, reflecting their different origins in the solar corona. However, while the Fe/H abundance ratios observed in the sheath are consistent with the preshock solar wind values (and a factor of 2 to 6 times less than the values obtained in the driver plasma), the iron charge states observed in the sheath appear to indicate a transition between the lower charge states observed in the ambient (coronal hole associated) solar wind and the higher charge states observed in the driver plasma. These results may reflect X ray ionization of the solar wind plasma near the flare site, although other explanations are possible.

Effects of non‐Maxwellian electron velocity distribution functions and nonspherical geometry on minor ions in the solar wind

A previous model has shown that in order to account for the charge state distribution in the low‐speed solar wind a high coronal temperature is necessary and that this temperature peak goes together with a peak of nα/np in the corona. In the present paper, one of the assumptions made previously, i.e., that coronal electrons are Maxwellian, is relaxed, and a much cooler model is presented, which could account for the same oxygen charge states in the solar wind due to the inclusion of non‐Maxwellian electrons. Also, due to a different choice of the coronal magnetic field geometry, this model would show no enhancement of the coronal nα/np. Results of the two models are then compared, and observational tests to distinguish between the two scenarios are proposed: comparison of directly measured coronal Te to charge state measurements in the solar wind, determination of the coronal nα/np, measurement of ion speeds in the acceleration region of the solar wind, and measurement of the frozen‐in silicon charge state distribution.

Solar wind Fe and CNO measurements in high‐speed flows

We present solar wind Fe charge state and density measurements from two time periods of high‐speed solar wind occurring during a flare‐associated driver plasma and two time periods during coronal hole‐associated high‐speed streams. This constitutes the first reported measurements of Fe charge states in coronal hole‐associated high‐speed streams. The observations, made with the ultralow energy charge analyzer (ULECA) sensor on ISEE 3, indicate that the iron in the driver plasma solar wind was predominately of charge state 15 or 16, indicative of an unusually high coronal temperature (∼4×106 K). In contrast, the Fe charge state distributions in the coronal hole‐associated high‐speed streams peak at 9 or 10, indicating a much lower coronal temperature (∼1.4×106 K). We also present the charge state distribution of the CNO group in one coronal hole‐associated stream and find an ionization temperature of (1.3±0.3) × 106 K. Combining the ULECA measurements with proton observations made with the Los Alamos National Laboratory solar wind instrument on ISEE 3, we find that the speed of solar wind iron is equal to that of hydrogen in the driver plasma but is substantially higher (by about the Alfvén speed) in the coronal hole flows. Both the iron‐hydrogen velocity difference and the calculated temperature gradient from the corona to 1 AU suggest that although the driver plasma expansion was nearly adiabatic, an extended energy input existed for the coronal hole flows. The abundance ratio Fe/H, relative to the nominal interstream value, is found to be enhanced by a factor of ∼2 in the driver plasma and depressed by a factor of ∼2 in the coronal hole‐associated solar wind.