Transcript 2007/12/18 reports

12.18 report
LIU Qian
Moon box test
Purpose: Try to find the reason why the Q resolution is about 10%.
Test:
• The stability of Ref-PMT test
• Ref-PMT voltage test
• We use the LECROY 7100 oscilloscope, which can fill a
histogram using measured value (such as peak to peak).
• We saved the histogram to a data file, and used root to
analysis it.
• The luminosity is set as 3.5, and the voltages of Ch1 and
Ch2 Ref-PMT are 460 mV and 486 mV respectively.
• The trigger for laser is 3V, 1K Hz, and the width of pulse is
2 us.
The pkpk histogram of Ref-PMT signal
Using the LECROY 7100 oscilloscope, we measured the peak to peak, filled a
histogram and fitted with Gaussian in ROOT.
Entries
pkpk
The stability of Ref-PMT
Pkpk (V)
After fitted with Gaussian, the mean value and the sigma are plotted.
Plot
Date
Time
CH1 (mV)
CH2(mV)
0
Dec. 18
6:00 pm
266.4±7.6
342.3±10.8
1
Dec. 19
9:00 am
244.7±8.0
312.6±10.5
2
Dec. 19
..
237.8±8.1
304.4±10.2
3
Dec. 19
..
234.6±8.2
300.9±10.4
4
Dec. 19
..
233.0±8.5
306.8±10.3
5
Dec. 19
..
234.4±8.3
303.8±10.4
6
Dec. 19
..
234.7±8.4
302.8±10.1
7
Dec. 19
11:00 am
246.2±8.3
307.5±9.7
We can see that the sigma of both channel doesn’t change much, but the mean
value changes a lot. For channel 1, it changed about 33.4 mV , While for
channel 2, it changed about 39.5 mV.
1.
2.
3.
4.
After we installed the moon box into the rack, we did measure the
Ch1 and Ch2’s pkpk, they were: 187 mV and 196 mV, but now
they’ve changed to 240 mV and 302 mV.
I’ve opened the box again and checked the prisons, they’re clean and
stable.
The temperature in the rack is about 30 degree (or even higher).
Maybe this is the reason. They’re working on how to cool the rack
now.
The resolution is small, about 2% ~ 3% which is much less than
10%.
Ref-PMT voltage test
Pkpk (V)
Pkpk (V)
mV
Almost linear
X is the voltage of Ref-PMT, Y is mean, the error of Y is sigma.
mV
Percent (%)
Percent (%)
mV
X is the voltage of Ref-PMT, Y is sigma/mean (%)
We can see the sigma/mean doesn’t change with the voltage of Ref-PMT.
mV
• The sigma/mean don’t change with Ref-PMT voltage, and they are
about 2% ~ 3%. Now we choose the voltages of Ref-PMT are 447 mV
and 455 mV, the pkpk of these two Ref-PMT are both 200 mV.
• From these test results, I think our laser is stable. But the mean value
did change a lot.
• Tomorrow we’ll pulse the laser and read the data from USTC DAQ
(including the barrel TOF).
LIU Qian