Lithium-Drifted Germanium for Charged Particle Spectroscopy

The Michigan State University Cyclotron Laboratory has undertaken a program of develoning lithium-drifted germanium for hiphresolution charged particle soectroscopy. The charged particle spnectroscopy has been concerned with reactions leading to protons, deuterons, and tritons in the energy range of 25 to 90 MeV. The emphasis of this program has been two-fold in that both the response of the detector and the packaging of the detector are considered. The side-entrv geometry Ge(Li) detector was shown to be capable of 60 keV (FWHM) with 40-MeV protons. The major limitation in the resolution for this geometry is attributed to a non-uniform window (3-12¿) on the surface of the detector. The electrodes of a side entry detector were segmented and a single crystal ¿E - E counter telescope was achieved. The best resolution was achieved with a thin-window surface barrier Ge(Li) detector and measured to be 34 keV (FWHM) for 40 MeV protons. A "thin" slit was used and shown to give cleaner spectra over a limited range in excitation energy. A peak to valley ratio of 5000:1 was obtained using this thin slit. The proton radiation damage of Ge(Li) was studied at 40 MeV and shown to be an appreciable problem bv 1010 protons/cm2.