Gamma-X N-type HPGe Coaxial Radiation Detector (GMX)
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GMX Series Coaxial HPGe Detector Product Configuration Guide GAMMA-X: N-type Coaxial HPGe Detectors for High-Performance Gamma Spectroscopy in the Energy Range of ~3 keV and Upward The GAMMA-X detector is a coaxial Germanium (Ge) detector with an ultra-thin entrance window. While most coaxial detectors have entrance windows from 500to 1000-µm thick, the entrance window of the GAMMA-X detector is a 0.3-µm-thick, ion-implanted contact, extending the lower range of useful energies to around 3 keV. Ion implantation results in a totally stable contact which will not deteriorate with repeated cycling. Moreover, N-type HPGe detectors have been shown to be resistant to damage by fast neutrons. All GAMMA-X Series detectors feature: • • • • • • • • Efficiencies to 100%, higher on request. Spectroscopy from 3 keV to 10 MeV. ULTRA thin boron ion implanted radiation window, ideal for Compton Suppression systems. Neutron damage resistant; user self-repair neutron damage option. Excellent energy resoluton and peak symmetry. SMART bias option. Harsh Environment (-HE) option. Be window supplied with protective cover; Al or carbon fiber window option available at no additional charge. • Low-background carbon fiber endcap option. • PLUS preamplifier option for ultra-high-rate applications. • Huge configuration flexibility, PopTop, Streamline, and mechanically cooled options. GAMMA-X Series detectors are manufactured from ORTEC-grown germanium crystals processed in our advanced manufacturing facility in Oak Ridge, TN. The detectors are fabricated from N-type germanium with an inner contact of diffused Li and an outer, ultra thin, contact of ion-implanted boron. The wide energy range of application of the GAMMA-X detector is illustrated in Figure 1 which compares the relative efficiencies of a GAMMA-X, a GEM (P-type coaxial), and a GLP planar detector. The GAMMA-X detector, uniquely, demonstrates excellent efficiency at both high and low energies. Fig. 1. Comparison of the Efficiency-Energy Curve of the LEPS, HPGe Coaxial, and GAMMA-X Detectors. ORTEC offers GMX Series HPGe detectors with relative efficiencies from 10% to 100% and beyond. ORTEC maintains a large stocklist of HPGe detectors. Some of these have "super specifications," that is, a warranted energy resolution better than the usual warranted specifications. High- and Low-Energy Performance of the GAMMA-X Detector The high-energy performance of a GAMMA-X detector is defined by its relative efficiency, resolution, and peak-to-Compton ratio at 60Co. The low-energy performance of this detector is defined by its resolution at 5.9 keV, its active surface area, and the detector window thickness. Fig. 2. Configuration of GMX Coaxial Germanium Crystal. The thickness of the entrance contact of the GAMMA-X detector is described by the ratio of the areas of two peaks of a readily available source. The peaks chosen are those of the 88-keV gamma rays from the 109Cd and of the 22.16-keV Ag K x rays from the same source. The warranted window attenuation ratio is 20. WE = peak area at 22.16 keV peak area at 88 keV This specification quantifies the thinness of the entrance window in GAMMA-X detectors. The natural ratio of gamma rays from the 22-keV and 88-keV lines of a 109 Cd source is ~21:1. A GAMMA-X detector typically dis

GMX Series Coaxial HPGe Detector Product Configuration Guide Beryllium Window GMX detectors in 70-mm (2.75-in.) or 76-mm (3-in.) diameter endcaps (10 to ~35%) are supplied with 51-mm (2-in.) diameter Be windows. GMX detectors in 83-mm (3.25-in.) diameter endcaps (~30 to 65%) are supplied with 64-mm (2.5-in.) diameter Be windows. These windows are 0.020-in. thick and have a transmission coefficient of ~95% at 5.9-keV. Detectors in 95-mm (3.75-in.) diameter endcaps (~60 to 100%) receive a 84-mm (3.3-in.) diameter Be window that is 0.030-in. thick. High-Voltage Shutdown and High-Rate Indicator...

Configuration Guidelines GMX Series Coaxial HPGe Detector Product Configuration Guide PopTop or Streamline (non-PopTop) Configuration The essence of a PopTop detector system is that the HPGe detector element cryostat, preamplifier, and high voltage filter are housed in a detector “capsule” which is then attached to an appropriate cryostat (Figure 4.) In Streamline systems, the detector capsule is NOT demountable. Detector capsule and cryostat share the same vacuum. In configuration terms, this requires a cryostat or cryostat/dewar selection with the cryostat having a matching diameter to...

Detector Options Integrated Cryocooling System Option (-ICS-E) The Integrated Cryocooling System (ICS) cryostat is sealed with a cryocooler and is immune to thermal short cycling. Unlike the typical three day loss of use of the detector with a standard type cryostat, the ICS can be re-cooled immediately, minimizing any time lost for temporary warm up. Aluminum Window Option (-A) An all aluminum endcap can be chosen if the energies of interest exceed 20 keV. See Table 1 for the transmission data for Al. Ultra-High Count-Rate Preamplifier Option (-PL) The Ultra-High Count-Rate Preamplifier...

Low-Background Carbon Fiber Endcap Options (-RB, -LB-C, and -XLB-C) Carbon Fiber is as strong as Al, Mg, and Cu, creates less background, does not corrode, and can detect energies less than 10 keV. This lower background material allows for lower Minimum Detectable Activity (MDA) for a specific counting time, which provides another step in increasing sample throughput in low-background counting applications. The lower Z of Carbon Fiber provides a low-energy window without the additional background found in most alloys. See Figures 8 and 9 for transmission characteristics of the Be and carbon...

GMX Series Coaxial HPGe Detector Product Configuration Guide PopTop Detector Capsule Preamplifier default is Resistive Feedback -PL changes to Transistor Reset -SMN changes to SMART DIM with HV Preamplifier Outside Vacuum PopTop Cold Finger Coupling Window default is Be -A changes to Al -CW, -RB and -HE change to Carbon Fiber -RB-B changes to lowbackground Be High Voltage Filter Electronic Shroud -HE changes to a sealed chamber with additional .25” dia and .4” length, and adds a replaceable desiccant. Mount default is Al -RB and -RB-B change to Cu Endcap default is Al -RB and -HE change to...