GWL0 pages

ORTEC®
GWL Series Coaxial HPGe Detector
Product Configuration Guide
For Analysis of Small, Low-Activity Samples
• High absolute counting efficiency for small samples
• Active Volumes to 400 cc
• Unique ion-implanted blind well
• Resolution specified with source inside the well
• Spectroscopy from 10 keV to 10 MeV
• Near 4 ð geometry
• Extra-large well (1.55 x 4.0 cm) standard
ORTEC’s High-Purity Germanium (HPGe) Well Detectors offer
high absolute counting efficiency for radiochemical analysis and
low-level gamma-ray spectroscopy. The unique ion-implanted
detector well has an ultra-thin dead layer (only 0.3 ìm thick), and
therefore provides the most extensive useful energy range (10
keV to 10 MeV). Unlike other Well detectors that have a hole all
the way through the germanium crystal, ORTEC’s Well Detectors
have a “blind hole” with at least 5 mm of active germanium at the
bottom of the hole (Fig. 1). This near 4 ð geometry provides the
maximum absolute counting efficiency available. The large well
(1.55-cm-diameter and 4.0-cm-long) accommodates an extensive
range of sample sizes. Like all of ORTEC’s HPGe photon
detectors, the HPGe Well detector may be stored or cycled
repeatedly to room temperature without performance degradation.
As specified in ANSI/IEEE Std. 325-1996, the resolution is
measured with a point source inside the well, 1 cm from the
bottom. Measurements of resolution outside the well can be
deceiving.
A typical curve of absolute efficiency in the well vs. photon energy
is shown in Fig. 2.
The Following Specifications are Provided for Each
Model GWL Detector
• Energy resolution at 1.33-MeV photons from 60Co at optimum
shaping time.
• Acitve Ge volume and well tube diameter.
• Energy resolution at 122 keV photons from 57Co at optimum
shaping time.
Fig. 1. Simplified Isometric View of
HPGe Well Detector Cryostat.
Fig. 2. Absolute Detection Efficiency in the Well vs. Photon Energy.
[If a well detector is used as a general-purpose coaxial detector (a use
not recommended by ORTEC), its relative efficiency at 25 cm can be
determined from the equation on page 58.]