In a study of the transport of radiation in matter, the response parameters of monoenergetic gamma rays incident on various materials with finite geometries were calculated on a CDC 3600 computer. The report includes results for gamma rays normal to cyclindrical germanium and silicon detectors

Snow, W. J.

English

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March 1969	 Brief 69-10080 
,Icy co..
AEC-NASA TECH BRIEF 
TES
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. 
The Response of Monoenergetic Gamma Rays 
in Finite Media Are Investigated 
The transport of radiation in matter, a phenomenon 
useful in the field of gamma-ray spectroscopy, has 
been studied. The response parameters of monoener-
getic gamma rays incident on various materials with 
finite geometries were calculated on a CDC-3600 com-
puter. The Monte Carlo technique was used in obtain-
ing the solution to this gamma-ray transport problem. 
The program permits calculations of various source 
geometries and detector shapes for incident gamma 
rays varying in energy from 5 keV to 12 MeV. The re-
port includes results for gamma rays normal to 
cylindrical germanium and silicon detectors. Also pre-
sented are data representing the double and single es-
capes subsequent to positron annihilation occurring 
uniformly throughout the volume of the detector. 
The theoretical energy-loss spectra and other de-
tector—response-parameters for gamma rays are use-
ful in the design of counter systems and in the anal-
ysis of complex spectra. 
In the radiation transport process, gamma rays con-
stitute the source. These rays enter the detector at 
some boundary and are diffused by the material. The 
radiation may be totally or partially absorbed by the 
medium. Primary and secondary radiations, created 
by the interaction collision of gamma rays with the de-
tector material, are traced within the boundary of the 
detector to determine the amount of energy that es-
capes. This escape quantity leads to the solution of the 
transport problem. By generating numerous incident 
photons, a histogram representing the energy loss to 
the medium can be produced in the form of a spec-
trum. 
The collision processes, both primary and secon-
dary, that affect the transport of gamma rays are 
Rayleigh and Compton scattering, pair production,
and photoelectric effect. During these processes, sec-
ondary electrons, positrons, and photons are created. 
The secondary photons considered are the scattered 
gammas in Rayleigh and Compton scattering, the flu-
orescent radiation subsequent to the photoelectric ef-
fect, and photons created from positron annihilation. 
Charged particles accounted for are Compton-scat-
tered electrons, photoelectrons, and positrons and 
electrons resulting from pair production. The charged 
particles are slowed by two processes, namely, radia-
tive collisions with the fields of the nuclei, and inelas-
tic collisions with bound electrons. The radiative 
loses are considered to be energy imparted as brems-
strahlung photons. 
The materials relevant to this investigation may be 
specified as single elements or organic or inorganic 
compounds by employing the appropriate gamma ray 
attenuation coefficients and various numerical con-
stants, such as binding energies, density, etc., which 
are peculiar to the material under consideration. Five 
materials are currently used: sodium iodide, PILOT 
"B", cesium iodide, germanium and silicon. The first 
three substances are relevant to scintillation counters; 
germanium and silicon are elements of solid-state de-
tectors. The type of detector is of no consequence in 
the theoretical calculation because the physical proc-
esses simulated are the same for all substances. 
Notes: 
I. The report is entitled "The Response of Monoen-
ergetic Gamma Rays in Finite Media," ANL-73 14, 
Argonne National Laboratory, April 1967. This re-
port is available from the Clearinghouse for Fed-
eral Scientific and Technical Information, Spring-
field, Va. 22151; price: $3.00 (microfiche copies, 
$0.65).
(continued overleat) 
This document was prepared under the sponsorship of the Atomic	 liability resulting from the use of the information contained in this 
Energy Commission and/or the National Aeronautics and Space document, or warrants that the use of any information, apparatus, 
Administration. Neither the United States Government nor any per-	 method, or process disclosed in this document may not infringe pri-
son acting on behalf of the United States Government assumes any vately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19690000080 2020-03-16T17:53:04+00:00Z
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: B69-10080
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 
Argonne, Illinois 60439
Source: W. J. Snow
Applied Mathematics Division
(ARG-10295)
. 
. 
Brief 69-10080	 Category 02


The response of monoenergetic gamma rays in finite media are investigated

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