The coincident measurement of neutron-proton pairs from the photodisintegration of lithium-6
Wade, Michael William
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Permalink
https://hdl.handle.net/2142/25318
Description
Title
The coincident measurement of neutron-proton pairs from the photodisintegration of lithium-6
Author(s)
Wade, Michael William
Issue Date
1984
Doctoral Committee Chair(s)
Koester, L.J.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Date of Ingest
2011-06-07T15:22:02Z
Keyword(s)
coincident measurement
neutron-proton pairs
photodisintegration
lithium-6
bremsstrahlung photon beam
quasideuteron correlations
Language
en
Abstract
A 100 % duty cycle bremsstrahlung beam with a 67 Mev endpoint energy was used to produce neutron-proton coincidences from the photodisintegration of 6Li. The proton energy was measured with a 6E-E
scintillator telescope; the neutron energy was determined by measuring its time of flight across two meters. The energy and angle of the np pair were used to determine the photon energy for each event through the use of 6Li(y,np)a kinematics. A 2H target was used to calibrate the detector system and to normalize the 6Li data.
Quasideuteron correlations between the neutron and proton momenta (direction and magnitude) were observed. The ratio of the quasideuteron photodisintegration cross section for 6Li , daqd/dO' to that of 2H,
p dad/dOp' was found to have the values .084 ± .009, .17 ± .01, .31 ± .02 and .43 ± .04 at photon energies of 30, 40, 50 and 60 Mev, respectively (at 90° in the center of mass systems of both the deuteron and quasideuteron). A 2S harmonic oscillator momentum distribution of the
np pair momentum transverse to the photon beam, which was assumed to be
equal to the transverse momentum of the quasideuteron inside the
nucleus. A value of qo = 84.5 ± 5.3 Mev/c was obtained, which corresponds
to a FWHM of 89.4 ± 5.6 Mev/c. This was in good agreement with
values obtained in 6Li(n-,np) and 6Li(p,p'd) experiments. The same momentum distribution used to calculate np angular correlations predicted widths greater than those observed at photon energies less than 45 Mev.
Events consistent with the two-body photodisintegration of 6Li into a proton and SHe were also observed (SHe decays to an alpha and a neutron). The ratio of the cross section for this two-body break up of 6Li , dG2/dQp' to that of 2H was found to have the values 1.18 ± .26,
1.00 ± .23, 0.87 ± .22 and 0.19 ± .07 at photon energies of 30, 40, 50 and 60 Mev, respectively (at 84 degrees in the laboratory).
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