Profile - ORTEC - #1

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ORTEC® PROFILE Coaxial HPGe Photon Detector Product Configuration Guide • "Application-Matched" P-type HPGe Detectors, optimized for specific sample types, gamma energy ranges and measurement geometries. • Know how your new HPGe detector will perform before you buy it! • Best absolute efficiency for the given IEEE standard relative efficiency in your counting geometry. • Warranted Crystal Dimensions ensure measurement performance. • Reproducible dimensions mean reproducible performance. . . no surprises. • Full range of PopTop Cryostats and options. PROFILE GEM detectors are a first in germanium detectors; a range of detectors from which you can choose the best solution for your application from specified crystal dimensions. Nominal relative efficiency specifications are provided in order to help relate relative efficiency to terms of crystal dimensions. The resolution is measured according to the IEEE standard. If a particular PROFILE series detector is available from the ORTEC detector stocklist, then the ACTUAL MEASURED specifications may be inspected before purchase. F-Series PROFILE GEM Detectors F-Series PROFILE detectors employ "over-square" (diameter > length) coaxial structures. For a given relative (IEEE) efficiency, the F-Series represents the "best use" of the germanium material in terms of producing the maximum absolute counting efficiency for on-endcap or "close geometry" extended samples, such as: • Point sources on-endcap • Filter Paper Samples on-endcap • Samples presented in bottles and pots on-endcap • Bio-Assay applications (e.g., lung monitoring) • Waste Drum monitoring In addition, the over-square geometry helps improve low-energy resolution by reduced crystal capacitance. FX-Series PROFILE GEM Detectors • All the advantages of the F-Series PROFILE detector with an ULTRA-thin Entrance Window. • Excellent warranted performance specifications FX-Series PROFILE GEM detectors employ a proprietary thin entrance window in order to improve low energy efficiency. The FX-series can extend the useful energy range down to 10 keV and below, which maintains the excellent peak shape and resolution characteristics of the PROFILE series. Figure 2 shows absolute efficiency curves for a 70 mm diameter x 15 mm length source on endcap for an 85 mm diameter GEMFX8530, compared to a GEM80 76 mm diameter x 87 mm length.1 Note the much higher absolute efficiency of the FX85 at all energies below 160 keV. At 59 keV, the FX is SIX times more efficient, and below that the efficiency of the GEM80 falls off due to the thick (~700 ìm) contact. The FX detector has an ultra thin contact (~10 ìm Ge) allowing good transmission at 22 keV and below. Figure 3 shows similar spectra from the three detectors compared, in the energy range up to ~130 keV. The spectra are taken from a mixed isotope calibration source. In all cases, the cursor is centered on the 59 keV 241Am peak. To the right is the 88 keV peak from 109Cd. In both the GEM-FX and the GMX, the thin entrance window clearly transmits the low-energy gammas in the 22–24 keV region. These peaks are entirely absent from the spectrum of the GEM80, even though the 88 keV is visible. 1Data taken from “The Evaluation of True Coincidence Summing Effect on CTBTO-Type Sample Geometry,” R.M. Keyser, ORTEC. Presented at IEEE Nuclear Science Symposium, Portland, Oregon, October 19–25, 2003. Figure 2. Absolute Efficiency vs. Energy for a 15 mm thick x 70 mm dia. disk on endcap, FX85 and 80% coax compared. Figure 1. P-type HPGe crystal geometries.