Crystal-diffraction spectrometer, combined with a lithium-drifted Ge-diode detector, performs high-resolution gamma ray spectroscopy on the complicated neutron-capture gamma ray spectra. The system is most useful in the 1-3 MeV energy range and improves the signal to background ratio

Namenson, A. I.

Smither, R. K.

English

NASA Technical Reports Server

Multislit 
Collimator 
Ge- Diode 
Detector
I- .7 
L	 ..-I 
- Nal Detector 
Constant 
Gamma Energy=
Sin 0
January 1969	 Brief 69-10005 
AEC-NASA TECH BRIEF 
AEC-NASA Tech Briefs describe innovations resulting from the research and development program 
of the U.S. AEC or from AEC-NASA interagency efforts. They are issued to encourage commercial 
application. Tech Briefs are published by NASA and may be purchased, at 15 cents each, from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Ge-Diode Detector Combined With Crystal-Diffraction 
Spectrometer Permits High-Resolution Gamma Ray Spectroscopy 
Sample	 Collimator
The problem: 
To perform high-resolution gamma-ray spectro-
scopy on complicated neutron-capture gamma-ray 
spectra. The most difficult region to analyze is the 
intermediate range (1-4MeV) where the (n, y) spec-
trum is very complicated and the peak-to-background 
ratios are generally low. This is especially true in the 
1-2 MeV range, where the photoelectric cross section 
is comparable to the pair-production cross section 
and both are very much less than the Compton cross 
section. 
The solution: 
The Argonne 7.7-rn bent-crystal gamma-ray spec-
trometer, combined with a lithium-drifted Ge-diode 
detector, performs high-resolution gamma-ray spec-
troscopy on the complicated (n, y) spectra with sig-
nificant improvements in resolution, energy precision, 
and overall sensitivity. The system combines the 
energy precision of the bent-crystal spectrometer with 
the high resolution of the Ge diode. 
The system is most useful in the 1-3 MeV energy 
range where both the precision and energy resolu-
tion are from 3 to 10 times those of either the bent
crystal or the Ge diode used individually. A 50-fold 
improvement in the signal-to-background ratio is ob-
tained through the use of the combined system. 
How it's done: 
The Ge-diode gamma detector can be combined 
with a crystal-diffraction spectrometer in four basic 
ways, depending upon the type of experiment per-
formed. The general approach is the same in all four 
configurations. The crystal diffraction process separ-
ates out a limited energy region of the -y spectrum 
and projects it on the Ge-diode gamma detector. The 
high resolution of the Ge diode then further resolves 
this narrow region of the y spectrum into its com-
ponent parts. 
Three important things occur in this process: (I) 
The gamma rays incident on the detector are limited 
to the small region under investigation, and the total 
counting rate in the detector system can be kept quite 
low without losing sensitivity. This allows the use of 
amplifiers with a slow response function and therefore 
the best possible energy resolution. (2) The large back-
ground of Compton events from the higher energy 
gammas in the full spectrum is eliminated, allowing a 
(continued overleaf) 
This document was prepared under the sponsorship of the Atomic 
Energy Commission and/or the National Aeronautics and Space 
Administration. Neither the United States Government nor any per-
son acting on behalf of the United States Government assumes any
liability resulting from the use of the information contained in this 
document, or warrants that the use of any information, apparatus, 
method, or process disclosed in this document may not infringe pri-
vately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19690000005 2020-03-16T17:30:16+00:00Z
marked improvement in the peak-to-background ratio 
in the Ge detectors. (3) The relative intensity of the 
individual components of the close doublet or com-
plex structure can be controlled by adjusting the set-
ting of the bent-crystal spectrometer. By recording a 
set of gamma-ray spectra taken with the Ge-diode de-
tector at different settings of the bent-crystal spec-
trometer, new additional information about the com-
plex structure can be obtained. For example, one can 
enhance the weaker member of a close doublet there 
by making it much more visible (see exam p le) and 
easier to resolve. It is, in fact, this type of additional 
information that leads to the improvement in energy 
resolution over what can be obtained with either system 
used individually. 
Ao mtt 
NATURAL SPECTRUM SPECTRUM 
AFTER DIFFRACTION
Notes: 
I. Additional details may be found in Review of 
Scientific Instruments, vol. 38, no. I, p. 52-65 (January 1967). 
2. Inquiries concerning this innovation may be di-
rected to:
Office of Industrial Cooperation 
Argonne National Laboratory 
9700 South Cass Avenue 
Argonne, Illinois 60439 
Reference: B69-10005 
Source: R. K. Smither and A. I. Namenson

Physics Division
Argonne National Laboratory 
(ARG-10190) 
Patent status: 
Inquiries about obtaining rights for commercial use 
of this innovation may be made to: 
Mr. George H. Lee, Chief 
Chicago Patent Group 
U.S. Atomic Energy Commission 
Chicago Operations Office 
9800 South Cass Avenue 
Argnne, Illinois 60439 
Brief 69-10005 Category 02


Ge-diode detector combined with crystal-diffraction spectrometer permits high-resolution gamma ray spectroscopy

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