High-Purity Germanium (HPGe)

Princeton Gamma-Tech has been a leader in the field of semiconductor gamma- and Xray detectors for over 30 years. In the early days, this meant lithium-compensated germanium. Then, when General Electric first produced high-purity (intrinsic) germanium crystals in 1972-73, PGT manufactured the first commercial HPGe planar detectors, soon followed by the first HPGe coaxials.

Since that time, PGT HPGe detectors have explored outer space, gone to the depths of mines in search of b b decay in enriched germanium, and found uses throughout the world in nuclear power plants, environmental measurements, and aerospace studies. High Purity Germanium has an impurity level of ~1010 impurities per cubic centimeter and is designated either P-type or N-type, based on the type of impurity. One surface of the crystal has a lithium-diffusion N+ layer, ~0.5 mm thick; the other surface has a thinner P+ layer formed by boron ion implantation or gold metallization.
When a bias voltage is applied to the crystal, incident ionizing radiation creates charge carriers that are swept toward oppositely charged contacts. In P-type coaxial (IGC series) and well detectors (IGW series), the applied voltage is positive, and holes are the primary charge carriers. In N-type coaxial (NIGC series) and planar crystals (IGP or NIGP detectors), the outer face is the thin P+ layer and the applied bias is negative. Electrons are the main carriers. These detectors have lower trapping levels and are less sensitive to neutron damage. PGT also manufactures lithium-drifted silicon, Si(Li), detectors for X-ray spectroscopy. Selecting a Detector ll PGT HPGe and Si(Li) detectors can be temperature cycled and stored indefinitely at room temperature. Several parameters are useful in the selection of a detector for a particular application.

A variety of liquid-nitrogen cooled cryostats, including dipstick, unitary, and portable styles, along with the JT Cool cryocooler, can be selected. The PGT QUIET ONE™ ultralow microphonics mounting system assures the best possible resolution even in the noisiest field deployment situations. Beryllium and low-Z organic windows and well inserts are needed for lower energy ranges. Low-background materials, as well as lead shields, can be specified if needed. PGT can design a system best suited to your nuclear spectroscopy needs.