Measurements of possible type inversion in silicon junction detectors by fast neutron irradiation

The successful application of silicon position sensitive detectors in experiments at the SSC or LHC depends on an accurate assessment of the radiation tolerance of this detector species. In particular, fast neutrons (E{sub av} = 1 MeV) produce bulk displacement damage that is projected, from estimated fluences, to cause increased generation (leakage) current, charge collection deficiencies, resistivity changes and possibly semiconductor type change or inversion. Whereas the leakage current increase was believed to be the major concern for estimated fluences of 10{sup 12} n/cm{sup 2} experiment year at the initial SSC luminosity of 10{sup 33}/cm{sup 2}-sec, increased luminosity and exposure time has raised the possible exposure to 10{sup 14} n/cm{sup 2}, which opens the door for the several other radiation effects suggested above to play observable and significant roles in detector degradation or change. 17 refs., 19 figs

Determination of surface oxide compositions on Alloy 600 using Rutherford backscattering

The surface composition of oxides formed on Alloy 600 under conditions similar to those in the primary side of PWR heat exchangers has been studied as a function of potential using Rutherford backscattering and proton inelastic scattering. Electropolished samples of Alloy 600 were exposed at several potentials to a solution of 0.18M H/sub 3/BO/sub 3/(2000 ppM B) with 0.28M LiOH (1.4 ppM Li) at 300/sup 0/C for 450 hours. The potentials relative to an internal hydrogen electrode ranged from -.09 to 750 mV. RBS analysis showed little or no oxide formation on samples exposed at 0 mV. Above 0 mV oxide layers formed whose thicknesses increased with potential. In addition the RBS showed a significantly enhanced concentration of aluminum and silicon in oxide. Both the oxygen and the sum of the aluminum and silicon content appeared to maintain a fixed surface concentration independent of the oxide thickness. Boron and lithium concentration were analyzed with proton inelastic scattering. No lithium was found in any sample. The boron concentration was found to follow the thickness of the oxide

Determination of light elements in amalgam restorations. [Dental amalgam]

Rutherford backscattering has been used to measure the major elemental compositions in the near-surface regions of freshly prepared and used samples of dental amalgam. A depletion from bulk stoichiometry of the major elements, which indicates an accumulation of lighter elements on the surface of the materials, has been observed. Increases in the F, Na, Cl, P, O, C, and N concentrations between freshly prepared samples and used samples were measured by observation of gamma rays produced by proton and deuteron induced reactions

Transmission scanning II

From nuclear science symposium; San Francisco, California, USA (14 Nov 1973). Work has been continued on the development of techniques for imaging spatial elemental distributions by means of differential absorption about the K- absorption edge of the particular element Z. A method to correct for spurious effects due to differential absorption in overlying absorber is described. Initial clinical studies of thyroid iodine images on patierts are presented. Application of absorption edge transmission scanning to measurements of Ca cortent in thin in-vitro samples of rat bone is also discussed. An x-ray source with a broad energy spectrum was used. (CH

Silicon Detectors System for High Rate EXAFS Applications

A multichannel silicon pad detector for EXAFS (Extended X-ray Absorption Fine Structure) applications has been designed and built. The X-ray spectroscopic measurements demonstrate that an adequate energy resolution of 230 eV FWHM (corresponding to 27 rms electrons in silicon) can be achieved reliably at -35\ub0C. A resolution of 190 eV FWHM (corresponding to 22 rms electrons) has been obtained from individual pads at -35\ub0C. At room temperature (25\ub0C) an average energy resolution of 380 eV FWHM is achieved and a resolution of 350 eV FWHM (41 rms electrons) is the best performance. A simple cooling system constituted of Peltier cells is sufficient to reduce the reverse currents of the pads and their related shot noise contribution, in order to achieve resolutions better than 300 eV FWHM which is adequate for the EXAFS applications