LC scintillator-based muon detector tail-catcher R&D Page: 3 of 5
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- beam position-srps Z438-38
306 Q ,s 800 pP
200 WLW ] 600 Fs UYL CO
206 -S~ oao VV a
-00 5+ 200 -b+a
0 250 0 750 10 0 1000 'ADC/Anpli 4- s+ strip + 38 cable 155
2 +b
0 25 500 750 1000ADC/Ampli 5- d4o sirrp +38 cable 152
400 tO
200 b-a
0 250 5 750 1000ADC/Ampli 6- d+b strip +3B cable 162 ADC/Ampli 1 6- d-a strip -3B cable 174
60 'Q 600 _ '
-~~ -9 Ea. 150
40,r c 400 QTLW 1167.
20- 200
b-b 5-
_ . . . . L . . . . .5-....-..L ....l... 1-sL......-.
6 0
0 250 500 750 1000 0 250 500 750 1000
ADC/Ampli 17- d-b sirip -38 cable 11 ADC/Ampli 18- s- strip -38 cable 171Another observation from
Fig. 2 is that the mean pulse
height for these six channels
is quite varied. This comes
primarily from the different
responses of the multi-
anode cells to light pulses.
Other factors that affect the
observed pulse-height distri-
butions from different PMT
channels, include the ADC
calibration (# of pC/ADC
count), variations in the X10
amplifiers, and the light
transmission through the
thermally-fused splice joint
between the clear and WLS
fibers. The latter, o80%,
has been measured for each
of the 384 fiber splices but
it has not been applied in
our analysis.Figure 2: Pulse height histograms for beam exposure of the
four strips centered on the four planes: +38 and -38.
4 Measurement of MAPMT Relative Response
There are various schemes that can be used to measure the response of each MAPMT channel. We
used a custom setup that mimics green light generated in strips. It is a piece of scintillator that has two
1.01 m long, 1.2 mm diameter Kuraray Y1 1 fibers embedded in it, with a 5 mCi Sr-90 source (with
housing) placed on top of it to produce light pulses. A precision-drilled template with 64 1.2mm
diameter holes was used to accurately position the free end of the WLS fiber adjacent to the
Hamamatsu 7546B MAPMT photocathode window. The assembled PMT with base voltage divider
circuit, cables, and light source were operated in a light-tight box. The output of the MAPMT channel
that was illuminated was carried from the light-tight box to a commercial electrometer connected via
commercial DAQ apparatus to a PC. One of the two WLS fibers was connected to a given channel for
monitoring purposes throughout the measurements [2].
Each of six MAPMTs had their relative response measured with the HV set to 800V. At this voltage
the typical current was ~1 A. We also measured cross-talk, i.e. the output of physically adjacent
channels when light was incident on one channel. The cross-talk varied from a maximum of 4.9% to
an average of 3.9% for the four nearest channels to 1% for the next nearest channels. There was no
saturation in the output of any channel as the voltage was varied between 600V and 970V as
evidenced by a linear dependence of the logarithm of the current as a function of the voltage. The
variation in response over six MAPMTs that were measured is substantial. For all tubes measured the
maximum to minimum output varied by a roughly a factor of 5. The mechanical structure of theLCWSILC 2007
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Abrams, R.; Blazey, G.; Driutti, A.; Dychkant, A.; Fisk, H.E.; Gutierrez, A. et al. LC scintillator-based muon detector tail-catcher R&D, article, November 1, 2007; Batavia, Illinois. (https://digital.library.unt.edu/ark:/67531/metadc900884/m1/3/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.