A Low Energy Van de Graaff Accelerator for the Study of Semiconductor Detector Surfaces and of the Stopping Power of Biological Materials

A proton beam stable at energies upto 400 KeV has been obtained by attenuation due to back-scattering from a gold layer on a Be substrate and by collimation. The beam has been used to measure the window thicknesses of silicon surface barrier detectors and the stopping power of tissue - equivalent materials. The window thickness measurements are part of an investigation of dead layer characteristics; in addition, this is an important correction to energy loss measurements for the stopping power work. Silicon detectors are fabricated as part of a study of the effect of surface treatments on detector characteristics. Three different processes of oxidation are being employed on Si surface after polishing and etching. The stopping power work is part of a study of the effect of phase of tissue-equivalent materials with regard to the dosimetry of fast neutrons.