E. P. Steinberg

A calibration procedure for the response of silicon surface-barrier detectors to heavy ions

Abstract The response of silicon surface-barrier and other semiconductor detectors to heavy ions is complicated by the presence of a pulse-height defect, such that heavy ions produce a smaller pulse height than lighter ions of the same kinetic energy. Based on the results of measurements of this phenomenon with a variety of ions, a new calibration technique for such detectors is proposed. Unlike the widely used calibration technique proposed by Schmitt and co-workers, which assumes the pulse-height response to be linear in both mass and kinetic energy, the present procedure reproduces the observed non-linearities. It is based on separating the energy of the ion into two terms, one of which is strictly proportional to the pulse height and is, in fact, the energy which a light ion, such as an alpha particle, must have to give the same pulse height. The second term is the energy defect of the ion, and is a function of its kinetic energy, mass and atomic number. Applications of the technique to experimental data are presented, including energy and time-of-flight mass measurements of energy-degraded fission fragments, and double-energy measurements of the fissioning systems 235U(n,f) and 252Cf(sf).

PULSE-HEIGHT DEFECTS FOR HEAVY IONS IN A SILICON SURFACE-BARRIER DETECTOR.

Abstract The pulse-height vs energy response of a surface-barrier detector was measured for the ions He, C, O, Al, S, Ni, Cu, Ag, Au and U. The detector was a “heavy-ion” type, with high field strength. The ions were obtained by elastically scattering oxygen and sulfur beams on the appropriate targets. The lighter ions (up to sulfur) showed little or no pulse-height defect (PHD). Heavier ions had a significant PHD which increased with increasing energy, and their response curves were non-linear at low energies. The highest energies at which the PHD was measured were: Ni, 58 MeV; Cu, 18 MeV; Ag, 45 MeV; Au, 31 MeV; and U, 26 MeV. The total PHD is described in terms of three contributing parts: a window defect, a nuclear-stopping defect, and a residual defect, which is attributed to charge recombination. The residual defect is shown to be proportional to the difference between the electronic stopping power of the ion in silicon and a constant, in agreement with a simple model of the recombination defect. The constant is the critical value of the stopping power, below which no recombination occurs. Although there is insufficient data on which to base a practical scheme for calibrating detectors for heavy ions at the present time, some features which appear necessary to such a scheme are pointed out.

PULSE HEIGHT RESPONSE CHARACTERISTICS FOR HEAVY IONS IN SILICON SURFACE- BARRIER DETECTORS.

Abstract A previous study of the pulse-height defect (PHD) for heavy ions (Ni, Cu, Ag, Au and U) in a silicon surface-barrier detector has been extended to include 10 different detectors and higher energy ions. Iodine was also added to the list of ions studied. All of the low-resistivity, heavy-ion type detectors showed nearly identical response characteristics. The PHD for these detectors appears to be a general phenomenon that can be described as the sum of a simple energy loss in the gold surface layer, a calculated nuclear-stopping defect, and a residual defect expressed as a linear dependence on the difference between the electronic stopping power of the ion in silicon and a constant critical value. High resistivity detectors exhibited larger residual defects, but qualitatively similar behavior.

Nuclear reactions of Au 197 with 11.5- and 300-GeV protons

The formation cross sections of more than 60 nuclides produced in the reaction of 11.5- and 300-GeV protons with

Cross section for 7Be production from 12C with protons of 3 – 12.5 GeV

^{197}\mathrm{Au}

Secondary nuclear reactions of 11.5 GeV protons on uranium: A search for the production of transcurium actinide elements

were measured. Most of the measurements were done by direct counting of the target with calibrated Ge(Li)

Nuclear reactions of /sup 197/Au with 11. 5- and 300-GeV protons. [Formation cross sections of >60 nuclides]

\ensuremath{\gamma}

Nuclear Reactions of Au-197 with 11.5-GeV and 300-GeV Protons.

-ray spectrometers and spectral analysis with computer programs. In addition, chemical separations of osmium and gold fractions permitted the assay of nuclides which could not be resolved in the unseparated targets. The cross-section ratio at the two energies

Scission-point model of nuclear fission based on deformed-shell effects

\frac{{\ensuremath{\sigma}}_{300}}{{\ensuremath{\sigma}}_{11.5}}

Cross-section measurements of nuclides formed by the reaction of 0. 20 -- 6. 0 GeV protons with /sup 197/Au

was within 20% of unity for all nuclides studied, which ranged in mass from