Measurement of prompt gamma ray lifetimes of fission fragments of $sup 252$Cf Page: 3 of 14
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variable gain amplifier and zero intercept units are controlled by the computer.
The output from the linear circuitry feeds dimensions 1 to 4 of the analogue
multiplexer and are defined as: dimension 1 fragment detector 1, dimension 2
fragment detector 2, dimension 3 low energy gamma rays (< 400 keV) and dimension
4 high energy gamma rays (< 1.2 Mev). The remaining two inputs to the analogue
multiplexer are derived from the timing and logic sections. Dimension 5 is a
marker which tells the computer what kind of event is being processed. Three
different types of events can be processed: double coincidences between frag-
ment detectors 1 and 2, triple coincidences between the two fragments and the
gamma ray detectors, and gamma stabilization events. One out of ever twenty
double coincidence events is used for digital gain stabilization and zero inter-
cept correction of the fission fragment pulse height distribution.
The timing and logic circuitry that provides dimension 5 and the coinci-
dence signal to the analogue multiplexer is fed by all 5 detectors and performs
the normal coincidence (2r = 100 nsec) and logic functions. The sum of the
fission stabilization events is used to give the number of fissions recorded
during the dtta acquisition process and is ueed to determine the yields of the
gamma lines per fission. The event by event data obtained from the analogue-to-
digital converter are accepted by the computer and recorded on magnetic tape to
be used for additional off-line sorting of the data, if necessary. In addition,
the computer makes an on-line mass sort to obtain gamma-ray distributions as a
function of mass. There are 32 such distributions, 4096 channels long, cor-
responding to adjacent mass windows of 2 amu. The gamma distributions are
analyzed in a larger computer at the end of the experiment to obtain the gamma-
The mass calculation is performed by means of a table look-up procedure.
An array containing masses indexed by the two fragments pulse height F1, F2 is
precalculated and used as the table. The mass calculation is similar to that
described by Watson et a. . We differ in that we are using the neutron
data from N'enecker et al. . Possible grid effects were removed by recording
fission fragments pulse heights with 4096 channels.
The gamma-ray spectrum associated with each mass window is analyzed with
the photopeak analysis code developed by Routti and Prussin  to obtain the
gamma line intensities. Since the mass resolution ( = 2-4 amu) is much broader
than our mass windows (2 amu) it is necessary to fit the intensities of a
particular gamma line as a function of mass assuming the shape of a gaussian in
order (Fig. 3) to obtain the total yield at each position.
As mentioned above six positions with respect to distance were used in
the experiment: 0.008, 0.1250, G.2500, 0.5000, 1.000, and 2.000 cm. Figure 3
shows an example of the intensities obtained for the 2 + 0 transition in lo2Zn
From these distances, the acceptance angle of the fission detectors and the
velocities of the fission fragments the average velocity of the fragments that
produced a specific isotope after neutron emission was determined by first
taking the Z of that isotope and using the experimental data of Reisdorf
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Jared, R.C.; Nifenecker, H. & Thompson, S.G. Measurement of prompt gamma ray lifetimes of fission fragments of $sup 252$Cf, article, July 1, 1973; Berkeley, California. (https://digital.library.unt.edu/ark:/67531/metadc1031367/m1/3/: accessed April 25, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.