Improved sensitivity X-ray detectors for field applications

Thermoelectrically cooled X-ray detectors based on Si-PIN and Cd_1-xZn_xTe (CZT) devices are now widely used in field portable XRF instrumentation. The current generation of Si-PIN detectors provides an energy resolution of 160 eV FWHM, comparable to that of cryogenic detectors, but at much reduced sensitivity. The sensitivity of the CZT detectors is limited due to poor charge collection. Recent research at Amptek, Inc. has explored several approaches to improving the sensitivity of the detectors for higher energy X-rays. First, larger volume Si-PIN detectors have been integrated with two-stage coolers and Amptek\´s low noise electronics. Second, CdTe M-π-n detectors have been successfully integrated with the thermoelectric cooler hybrid. These diodes reduce the leakage current to levels comparable to that of CZT, with equivalent electronic noise, but with much better hole transport as expected from CdTe. Moreover, these diodes can be used at lower temperatures than either CZT or conventional CdTe. Third, a "dual" detector has been developed, consisting of a Si-PIN for high resolution at the lowest energies stacked on a high-Z semiconductor detector for higher sensitivity at the higher energies. The design and performance of these sensors will be presented and the results compared with theoretical expectations. All of these detectors are now commercially available and used in commercial products.