IAC data analysis for GEM
- Electronics Setup
PS-ADC, QDC and TDC were used for this experiment. The collected data for GEM was discriminated by CFD and its output was in coincidence with beam gun signal, which became an input for gate generator for QDC and PS-ADC and stop for the for the TDC. (TDC setup was in a common start and beam gun signal was the starter).
The picture above shows the time frame of the pulses relative to each other. The beam gun RF signal was earliest in time, then the beam electron's signal came after 200 ns, and finally GEM's analog signal, with a rise time of about 200 ns, as it was in time with the TDC stop pulse that had a pulse width of about 50 ns.
GEM had a cathode voltage of V=3.5 kV, and 2.8 kV for the potential divider circuit for a triple GEM preamplification.
- data Analysis
8851 qdc channel 4, TDC 23 before run8859 switch to 29 , PDC 13.
runs expected to have good in info :8850 8858 8875, 8876,
shutter closed: 8877 (without target).8878
all the runs had an open shutter (Green) , then they were all compared to a closed shutter run number 8878 (red), and a without target run which was run number 8877 (blue). The QDC's charge spectrum figures had a 160 fC per channel, and 0.6 ns for the TDC's time spectra.
the figures above shows the charge spectra for the QDC and PS-ADC in time cut of 230ns and 500ns. When the shutter was open, both spectra showed a difference as open shutter spectrum compared with closed shutter and no target spectrum. Based on the previous behaviour of the detector, when the detector was tested with alpha particles that were emitted from U-233, closing the shutter stopped the alpha particles as shown in the figure below. when U-233 exposed to neutrons, a fission event happened and the shutter stopped the fission fragments, those fragments ionized the gas in case of open shutter with a charge in range of 475pC to 575 pC after preamplification and postamplification.
tdc is ch.26.
run 8880 and 8881 show the tdc hit for gun gate of width of 9 us, the hits are from the source up to 90 percent of the pulses detected by the oscilloscope.
pulse shape disc. in use for run 8886 (20 min.),
QDC input attenuated 4 db starting from 8887,8889
run 8891 (from 1:46 to 5:00pm) PDC gate was connected 50 min. after the run started
QDC: filter amp ortec x1, int. 20 , atten. 3 db. , int. gate 1.7 us. PDC : filter amp ortec x1, int. 20 , filter amp ortec 474 x20 fine max., gate 1.7 us
|8904||open||high noise level 5 min.|
|8906||open||power supply was turned off|
03/31/15 Source measurements (shutter open and closed)
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