Preshower tile test, December 2013
The scintillator tile we got is a 12x12x1.5cm LHCb-type tile, wrapped
in TYVEk paper. There is a WLS fiber embedded inside, making 3.5 turns
in a circular groove then come out through straight grooves. The length
of the fiber outside the scintillator is about 30cm on each side (see
picture setup_20131219.JPG).
According to Vladimir, "this scintillator from preshower module which
was demage during transportation", and thus has not seen beam. I can't
tell where the damage is, perhaps on the LED attached to it?
PMTs: Philips (now Photonis) XP2262 with a CERN-type "P.M." base, with H.V. about -2000V. (see XP2262.pdf for PMT specs.)
December 18-19, 2013
Cosmic test. Two PMTs were setup to read the tile. One placed directly
on the side of the tile, the other read out the two fibers. HVs were
adjusted so the single ph.e. peak of both PMTs were at about 5-10mV.
Setup: see picture setup_20131219.JPG;
Scope readout: See IMG_1293_screenshot.png or IMG_1293.MOV (the movie is upside down, so you need to either flip your screen or yourself, sorry!)
Channel 2 (blue, 1.00V/div) is direct readout by positioning a 2"-diameter PMT next to the side of the scintillator
Channel 1 (yellow, 20mV/div) is WLS fiber readout by another 2"-diameter PMT
Fiber readout seems to be 10% of direct readout.
December 20, 2013
Took some QDC spectrum of both direct readout and fiber readout. The
direct readout was used as the trigger, with the threshold set just
above the single ph.e. HV were adjusted such that the single
ph.e. on scope are roughly the same for both direct and fiber readouts.
One can see a clear correlation (sorry no plot) with a slope of roughly direct:fiber=20:1.
Unfortunately we couldn't see MIP peaks in either readout. The single
ph.e. peak was very high. In addition there is a signal around 2-3
ph.e. that triggers both fiber and direct readout, in the rate of
roughly 60 Hz. This is so high that, even if there is a MIP peak, it
probably is washed out by this background.
December 21, 2013
Continued the test today. Totally changed the setup to make it the same as in the LHCb paper. See file MIP-Trigger.png.
Setup: Used two CsI blocks left over from some tests for Dinko years
ago, and set them up as a crossed hodoscope and put them in coincidence
with the LHCb tile between them. The rate is about 0.2Hz which is about
right for the vertical solid angle they define.
With this setup the MIP is much cleaner and is about right with respect
to the single p.e based on the (LHCb) NIM article. The plot at
bottom right in MIP-Trigger.png. shows both s.p.e and MIP peaks on the same graph using a log x scale.
Unfortunately the DAQ computer is very unstable and dropped the network
connection right after this run, so we'll have to wait until January.