LO-AX Germanium (HPGe) Low-Energy Photon Detector

LO-AX^™ Germanium (HPGe) Low-Energy Photon Detector

The LO-AX provides optimum peak-to-background ratio from 10 to 400 keV on large-area samples. It is also ideal for in vivo actinide monitoring using L x rays.

Large active area
36-, 51-, 60-, and 70-mm diameter available
Ideal for in vivo actinide monitoring
Excellent for uranium monitoring
PopTop flexibility
ULTRA-thin rugged Ion-implanted pointer contact sensitive at front and sides

The LO-AX is a large active area, "short" coaxial detector which supplies the best possible energy resolution for the energy range from 3 to 400 keV.

A typical application for the LO-AX is in vivo quantitative actinide monitoring. This measurement, frequently performed in the past using phoswich scintillation counters, is now routinely performed using a LO-AX, usually in a low-background cryostat.

Figure 21. Dimensional Drawing of the 51-mm-Diameter LO-AX Detector Element.

Figure 22. Low Energy Gamma and X-Ray Transmission of Be and Carbon Fiber Windows.

The LO-AX detector element length, about one-half that of the diameter (Fig. 21), provides a special, low-capacitance coaxial geometry. The result is 370-eV energy resolution at 5.9 keV for the 51-mm diameter LO-AX detector. Typical measured resolution for 13- to 17-keV x rays is ~400 eV. Higher efficiency is available with the 60-mm and 70-mm-diameter LO-AX detectors.

Because of their good energy resolution at low energies LO-AX detectors, particularly in low-background cryostats, are ideal for quantifying plutonium. In most laboratories 70-mm diameter LO-AX have become the detector of choice because of their higher efficiency and sensitivity. An additional benefit of the 70-mm detector is a net reduction in Compton background due to the increased probability that a high energy event will experience a multiple interaction in the larger detector, and thus generate a count in a channel well above the Pu peak.

The LO-AX detector’s wide energy range results in high efficiency for the quantification of uranium.

The LO-AX is equipped with an automatic, high-voltage shutdown capability.

LO-AX detectors are available with a choice of Be or carbon fiber window. Transmission data is shown in Fig. 22.

Ordering Information

LO-AX Germanium (HPGe) Coaxial Low-Energy Photon Spectrometer in PopTop Capsule*
A complete detector assembly requires a cryostat and a dewar.

Model No.	Detector Diameter (mm)	Area (mm²)	Dimensions Depth (mm)	Energy Resolution FWHM **
Model No.	Detector Diameter (mm)	Area (mm²)	Dimensions Depth (mm)	@ 5.9 keV	@ 122 keV
LX-36300-15P4	36	1000	15	300	550
LX-51370-20P4	51	2000	20	370	625
LX-60450-30P4	60	2800	30	450	700
LX-70450-30P4	70	3850	30	450	725
Options
-C	Carbon Fiber Window, add-C to the model number
-RB	Reduced background PopTop capsule with Carbon Fiber Endcap, add “-RB” to the model number [e.g., LX-36300-15P4-RB]
-RB-B	Reduced background PopTop capsule with Be Window in Cu Endcap, add “-RB-B” to the model number [e.g., LX-36300-15P4-RB-B]
SMART-1-N	SMART-1 detector option for negative bias detector. To order, add SMART-1-N as a separate line item.

* All LO-AX PopTop detector capsules include sealed detector element, preamplifier, high-voltage filter, and a 0.02 inch thick Be window with diameter ≥ that of the detector.

** FWHM = Full Width at Half Maximum; total system resolution for a source at 1000 counts/s measured in accordance with ANSI/IEEE Std. 325-1996, using ORTEC standard electronics.