Relativistic Gold Research Articles

Dynamics of Charge States of Relativistic Gold Ion Beams Passing through Cu and Au Foils in the NICA Project

In order to study the properties of dense baryonic matter, an accelerator complex is under development at the Joint Institute for Nuclear Research (Dubna, Russia) within the new NICA project. The NICA project assumes the use of accelerated ion beams ranging from protons to gold ions with relativistic energies up to 4.5 GeV/nucleon. To design experiments, it is necessary to have information on the efficiency of the yield of bare gold nuclei formed at the passage of a gold ion beam with energies of about several hundreds of MeV per nucleon through a foil of a specialized stripping station at the output of the booster of the accelerator. In this work, the optimal conditions (material and thickness of the foil and the energy of the ion) for the formation of fractions of bare gold nuclei with a probability of 80–90% have been determined by calculating electron loss and capture cross sections, as well as the dynamics of charge states of gold ions colliding with copper and gold foils at energies of 400 and 600 MeV/nucleon,

Extended Analysis of the Trek Ultraheavy Collector

We have made a measurement of the elemental abundance of cosmic rays with atomic number 72 < Z < 83. We made this measurement as part of the Extended Analysis of the Trek Detector (hereafter Extended-Trek). The Trek detector consisted of 150 stacks, each of 16 sheets, of BP-1 glass exposed on the Russian space station Mir. In the original analysis of Trek, 245 cosmic-ray events were analyzed. The cosmic-ray elemental abundance pattern observed by Trek was strongly inconsistent with a popular model of the Galactic cosmic-ray source. For Extended-Trek, we reanalyzed 146 events in the ~100 stacks that were calibrated with relativistic gold ions at two zenith angles. These correspond to a collecting area of approximately 0.7 m2. The Extended-Trek analysis improved the resolution of cosmic-ray charge to 0.34e over 0.39e-0.45e in the original Trek analysis and confirmed the cosmic-ray abundance pattern observed by Trek.

Fragmentation of relativistic gold by various target nuclei

We have studied the interactions of gold nuclei ${}_{79}^{197}\mathrm{Au}$ at eight different energies between 0.9 and $4.0A\mathrm{GeV},$ in targets ranging in mass from hydrogen to lead. This paper combines the results of these studies with earlier measurements at higher and lower energies. We discuss the production of fragments with charges Z between 81 and 50. The systematic trends found have allowed us to improve previously developed empirical relations which predict the cross sections in any target or energy for the production of fragments with $77l~Zl~67.$ Fragments with single and double charge pickup are observed in all targets at all energies. Fragments which have lost a single charge represent a special case, due presumably to the effects of electromagnetic dissociation. The energy variations of the total cross sections and the approach with increasing energy to limiting fragmentation are studied.

Fragmentation of Relativistic Gold Nuclei with Energies between 0.92 and 4.0AGeV in Hydrogen

Modeling the propagation of ultraheavy (UH) cosmic-ray nuclei through the interstellar medium requires a knowledge of the fragmentation cross sections. The cross sections for the production of fragments from the interactions of relativistic gold nuclei in hydrogen have been measured from 0.56 to 10.6 A GeV, using the Lawrence Berkeley Laboratory (LBL) Bevalac and the Brookhaven alternating gradient synchrotron (AGS). The total charge-changing cross sections are found to be essentially independent of energy. The partial elemental cross sections vary significantly with energy but show a transition to energy independence at the highest energies. These cross sections can be scaled to apply to neighboring elements, corrected for the effects of radio active decay, and applied to propagation models to deduce source abundances of the heaviest UH elements from those observed near Earth. There are serious uncertainties involved in deducing the cross sections applicable in space from those measured on Earth. Hence calculations of propagation must be regarded with caution.

Fragmentation of relativistic gold nuclei in nuclear emulsion

Basic data are presented on the parameters of fragmentation, multiplicities and angular spectra of low energetic targed associated particles in the interction of 197Au nuclei of 10.7A GeV.

A study of the dependence of the bulk etch rate and the reduced etch rate on the concentration of etched products of Lexan

Measurements of the bulk etch rate, υ g, for etching solutions with concentrations of Lexan etched products, x, ranging from 0 to 7.8 g/l showed the existence of an initial region where υ g increases with x; and a second region, for concentrations above approximately 2.15 g/l, where υ g no longer depends on x. The division between these two regions (≅2.15 g/l) did not coincide with the concentration of solubility saturation, found to be at 1.51 g/l. Tracks from relativistic gold ions (with kinetic energies between 10.3 and 10.6 GeV/u) were used to measure the reduced etch rate ( S, the ratio between the track etch rate, υ t, and υ g) for three etching solutions with different concentrations of etched products (0.052, 1.81 and 7.8 g/l); the values obtained for the first two concentrations were compatible with each other (3.95 ± 0.16 and 3.85 ± 0.14), whereas the reduced etch rate corresponding to the concentration of 7.8 g/l of etched products was significantly different; 4.68 ± 0.14.

Measurement of the registration temperature effect in BP-1 glass

In order to determine its effect on mass measurements and charge measurements for the cosmic-ray experiments ANTIPODE and TREK, I have measured the change in detector response with temperature (the so-called registration temperature effect, or RTE) for BP-1 glass responding to relativistic gold ions and to stopping argon ions. I measure a small but finite RTE for relativistic gold, and conclude that thermal regulation is necessary for the large collector of TREK, which is being exposed outside of the Russian space station Mir. I set a small upper limit for the magnitude of RTE for stopping argon, and conclude that the thermal variations experienced by ANTIPODE in its balloon flight over Antarctica were not large enough to degrade its mass resolution; I further conclude that the thermal variations that we anticipate for the small collector of TREK, which is being exposed inside the Russian space station, will not degrade its mass resolution.

Measurement of cross section for charge pickup by 11.4 A GeV gold ions

We have studied nuclear charge pickup by relativistic gold ions with an energy of 11.4 AGeV in various targets at the Brookhaven AGS. The cross section is similar to that previously measured at ∼1 AGeV. The dependence of cross section on target mass follows A T 0.37, while that on projectile mass is much steeper than linear and not inconsistent with the A p 2 dependence established at ∼1 AGeV.

Lexan polycarbonate response to relativistic gold ions

Abstract A knowledge of the charge resolution power of polycarbonate detectors for ultra-heavy ions (Z ≥ 30) is essential to establish the cosmic ray spectrum in the UH region and to obtain useful information on nucleosynthesis and propagation mechanisms. In this paper, a systematic study of LEXAN polycarbonate response to relativistic (⋍ 1 GeV/N) gold ions (Z = 79) is presented. The influence on the detector sensitivity of etching conditions, such as NaOH concentration and bath temperature, is explored and the conclusion is reached that detector response is rather independent of them all, in agreement with the well known results at lower ionizations.