Design optimization of liquid scintillator cosmic-ray veto detector with BBQ shifter Page: 3 of 4
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A 6 mm 00Q/
Fig. 3. Normalized emission spectre of two liquid
scint 111 atom . produced by ^Co gamma radiation, In
comparison with stimulated emission from BBQ acrylic.
Absorption In BBS
Light was created In liquid scintillator (p-xylene
with 5 g/£ p-terphenyl and O.k g/Jt POPOP) by ^Co
gaima radiation. Such light was directed normal to
the BBQ (90 mg/i BBQ'’ in acrylic) surface illustrated
in Fig, 2. Transmission and spectra of light were
measured with the Tracor horthern TN — 1710 Multi-
Channel Analyzer. This system utilizes the TN — T 150
Holographic Rating Monocrometer and the TN-1223-21512
element intensified reticun array. A 100 micron silt
was used for these measurements. Therefore, the
resolution of the spectra measurements are l3 nm. The
transmission for various wavelengths Is Indicated in
Fig. k. At wavelengths shorter than about kiio nm. the
absorption la strong with attenuation length of
4 5 0 PIT
4 40 N"
Tig. k. Optical transmission at various wavelengths
for differing thicknesses of BPJ In acrylic.
The scintillator light Just described was also
directed normal to the BBQ of various thicknesses,
while we observed the corresponding current from a
photodiode (S20 response) at the end of the shifte-
bsr, a distance of 10 cm from the location of the
scintillator light source passing through the BB0.
Figure 5 indicates thlu dependence for scintillators
with POPOP Bnd with butyl-PBD.
Inconsistencies in the data of Fig. 5 make a
detailed conclusion difficult, possibly due to
differences in the scintillator efficiencies (our
samples were not of the same batch). These data
suggest nearly linear dependence of light output on
BBQ thickness up to -15 mm. for the POPOP case.
Output for the case of butlyl-PBD appears to be linear
up to -5 mm, This seems consistent with the data
presented In Fig. k. That is. butyl-PBD spectrum is
mostly comprised of light below »20 nm where tne
absorption length Is less than -2 ran, as Indicated In
Fig. k. The POPOP/terpheriyl spectrum, however,
contains significant fraction or light near kko •
where the absorption length is near 9 mn.
The scintillator light was directed normal to the
BBQ surface illustrated in Fig. 2, at various points
along the length of the BBQ shifter bar. The relative
currents from a detector at the end of the BBQ are
contained In Fig. 6.
An absorption length of ?.0 m (1/e value) is
Indicated from these measurements for the BBQ
stimulated emission spectrum, a value which contains
the effects of bulk absorption as well as attenuation
due to geometry and surface imperfections. Variation
of the detector response from S20 to S11 did not alter
the absorption length observed.
Fig. 5. Relative light collected at end if PPQ
• rrylln of various thicknesses, for two dl'fer''nt
incident light spectra from liquid scintillators. In
both cases, the Co gamma Irradiation was hi Id
Comparison of POPOP with hutyl-PHD
For the same givmet r 1 cal conditions, butyl-Pi®
gave more light output for the detector at the enc of
tlie BBQ than POPOT by u factor of t, 3 '/. Tills rer.u.t.
however, wns obtained with a glass window between ‘ie
liquid scintillator and the RPO. Our detector
configuration entails a window of 5 ran acrylic wttli
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Kruse, H.W.; Egdorf, S.S. & Simmons, D.F. Design optimization of liquid scintillator cosmic-ray veto detector with BBQ shifter, article, October 1, 1981; New Mexico. (https://digital.library.unt.edu/ark:/67531/metadc1099399/m1/3/: accessed March 25, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.