Progress in the following activities has been made: the analysis of the gamma ray spectra taken from samples flown in Spacelab 2; the search for and review of neutron and proton activation cross sections needed to analyze the results of the Long Duration Exposure Facility (LDEF) activation measurements; the consideration given to data analysis of the LDEF and Spacelab 2 samples; the plan to measure relevant cross sections with nuclear accelerator measurements; and the preparation of an extended gamma ray calibration sources continues through planning and direct measurement of gamma ray efficiency for a Ge(Li) as a function of position along the surface of the detector housing

Laird, C. E.

English

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https://ntrs.nasa.gov/search.jsp?R=19840023693 2020-03-20T20:56:01+00:00Z
r(NASA-CR-171113) STUDY OF FECTON AND
	 N84- 317C-
3
NEUTRON ACTIVATION OF METAI SAS?DLES IN LOW
EARTH ORBIT Quarterly Technicai Report
(University of Eastern Kentucky) b p	 Uuclas,
HC AU2/MF A01
	 CSCI, 08G G3/43 2122;
EASTERN KENTUCKY UNIVERSITY Z
Department of Physics and Astronomy	 !'
4	
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Study of Proton and Neutron Activation'
of Metal Samples in Low Earth Orbit
d	 i
331
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July 19,1984
Quarterly Technical Report
	
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Contract M NAS6-35190
1
(Principal Investigators C. E. Laird) t^
Prepared for
George C. Marshall Space Flight Center
Marshall Space Flight Center, Alabama 35812
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AUG 1984
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FACIUT.y
EASTERN KENTUCKY UNIVERSI TY 	 r	 DEPI`,
	
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Richmond, Kentucky 40475
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OF POOR QUALITY
P
QUARTERLY REPORT
During the last quarter of activity under NASA Contract
NA58-35180 1
 as extended, the following activities have been.
undertakeni
1. the analysis of the gamma
-ray spectra taken from
samples flown in Spacelab II has been completed.
3a
Z. the search for and review of neutron and proton
activation cross-sections needed to analyze the
"a	 3
results of the LDEF activation measurements has .	 i
been continued. CalcuiatiDns of neutron induced
activation for the LDEF samples have been done`'
with currently available Gros
_
 sections.
3. the data analysis plan for the LDEF and Spacelab II
samples has been given initial consideration.
	 '!
4. the plan to measure relevant cross -sections with
nuclear accelerator measurements have been continued
while awaiting the scheduling of beam time.
t,
5. the preparation of an extended gamma -ray calibration
sources continues through planning and direct
measurement of gamma ray efficiency for a Ge(Li) as a►
function of position along the surface of the dwt"ctor	 i
^^	 I
housing.	 i
... .::. ,..............__....^._^.._....._............... e....... ... 	.__.... .._	 ..	 _ .. .. _........ _:	 ^ _...^._.	 «.112_ __-	 ^	 _	 _^__..:..Y...__:___
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ORIGINAL PAGE W
OF POOH? QUALITY
Copies of the result tables of the analysis of the 8pacelab
II samples are being sent to Dr. G. Fishman at MSFC. Originally,
It was planned that the program HYPERMET Would be used to
analyze the gamma-ray spectra. However, since the conversion of
HYPERMET to the VAX 110780 has not yet been completed, a method
was found by which the program SAMPO on the University of
Kentucky IBM 3038 could be used. No further analysis of the
gamma-ray spectra is needed.
The search for neutron and proton activation cross section
has been continued. Three significant aspects of this search
are the acquisition (1) of a report by F. J. Haasbroek, et al.,
the National Physical Research Laboratory, Pretoua, South
Africa, (2) of an Indiana University dissertation by Michael
Sadler, and (3) of copies of ACTL82 and ECPL82 from Reactor
Safety Information Center, Oak Ridge. The report by Haasbroek,
at al. contains excitation functions for Co, Ni, and Ta up to
85MeV or above. These have been converted to cross-sections and
added to the list presently available. Further information from
the South African group will be sought.
The dissetation by Drr M. E. Sadler contains considerable
information about activation cross sections on Ni isotopes from
80 to 150 MeV. This information has been evaluated,
interpolated and extrapolated to obtain approximate cross
sections for natural nickel in this energy range.
ACTL82 and ECPL82 are tabulated reaction cross section for
energies up to and above 20 MeV incident energy. ACTL82 is a
E^	 compilation of neutron activation cross sections and ECPLG2 is a
i
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collection of charged particle reaction cross sections.	 These
41
are presently being studied for further Inclusion in the current
tabulation.
The data analysis plan for the future samples has been
given initial considerations partially in view of the results of
the analysis of the samples already counted.	 One problem that
should be given further study before the LDEF samples are
returned involves background.
	 There are many (approximately 60)
peaks seen In the background spectra for energies up to 2
M&V. *
 One of theme lines (at 846 KwV) coincides with one which
is potentially observable from activation of the'Ni and Co
samples.	 The Intensities of the background peaks varies from
sample to sample s
 partially due to the shielding of the
background source by the samples due to radiation originally ul
present in the samples, and due to possible fluctuations In the
background sources.	 In order to account for these "background"
problems a series of background spectra should be taken with a,
set of original samples placed in the same geometry as the
LDEF samples.	 Long counting times should be used for each
sample with spectra being recorded once a day for a period of
five to seven days.	 After initially being checked for gain
shifts and other problems, these spectra can be summed and
analyzed to allow for .a good determination of the background for
each sample.	 To more clearly identify background peaks, a
background spectrum similar to the ones above should be taken
both inside and outside the low background facility.	 These in
conjunction with those already taken for the Spacelab II samples
. . . . ........
57
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ORIGHNAa
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will help resolve some questions about the existence and 	 ?.
intensity of certain weak peaks in the background.
Presuming that SAMPO or another similar gamma-ray analywis-
program will be used to analyze the LDEF sample spectra,
periodic accumulation of gamma spectra with a weak gamma source
would greatly facilitate the analysis process. This could be
done with a weak EU-152 source having an activity of about 1-10
nC. A source stronger than this might cause summing in the
spectra while one smaller than this would require too long a
counting period to be practical. Note that a 2'1r geometry (50%
maximum.efficiency) would mean that about one.Eu-152 gamma/sec-
would enter the G* (Li) detector per decay or 37 counts/sec per
nanocurie. Ten nanocuries would mean 370 counts/sec so little
summing should occur. A weak source will be prepared with the
extended calibration source now being made.
The measurement of relevant cross-sections with a nuclear
zccelerator is awaiting the assignment of beam time at Indiana
University Cyclotron Facility. Dr. Tom Ward of IUCF has agreed
to collaborate on this effort and is presently seeking beam-time
in a parasitic mode. Mopef ul l y, activation of samples will
begin during August. In anticipation of this work was concluded
earlier in the summer on interfacing a Canberra ADC to an Apple
He Computer which will be used both at Eastern and at IUCF.
The Apple acts as a controller and data accumulation device with
rapid data storage on a 5 1/4 inch floppy disk. Software to
display the data using Apple graphics has been developed as
well as that which can be used to do some data analysis with the
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`.	 Apple.	 Procedures for transferring the data to the VAX for
detailed analysis are currently being developed. n'
a,
Thee development of an extended gamma-ray calibration
sources continues.	 The plan calls for drop evaporating
-	 2	 xt -four (64) one-quarter inch squares on a thinEu i5s. onto sa	 	 qY .
.aplastic material.	 Each drop will be counted in a shielded
geometry to ascertain the uniformity of activity. 	 If needed,
small corrections to the activity will be made. 	 A uniformity p
within about 10% should be readily obtainable. 	 As previously
I
mentioned, one nanocurie of activity is 37 gammas per second
entering the detector. 	 If it is planned to-keep the count rate
at 1000 cps or less to prevent summing and other effects, this
source should have less than 40 nc total activity. 	 Thus each !
drop will have about .6 nc activity.
During the next quarter activities will continue on s	 ^i
items 2-4 previously listed. 	 Further considerations of the
^I
results of item i will most surely be done although that ='I
analysis is complete.	 The most pressing problem is scheduling :t
of beam-time at IUCF.	 This delay will most probably require
that a no cost extension of the contract be requested in the
near future.
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Study of proton and neutron activation of metal samples in low Earth orbit

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