10-31-08 GEM HRRL Photon Runs

The Goal today is to observe position dependence of photons on the GEM detector

A1 -> 13 A2 -> 11 A3 -> Trig A4 -> 2 A6 -> 16 A7 -> 8 A8 -> 5 A9 -> NaI -> B9

B1 -> ADC1A

Run 0

GEM Backgrnd.mpa

GEM HV : VDrif = 3850, VGem = 3550

HRRL : E = 14 MeV, I =0

5 minutes long

Run 1

Run1.mpa

GEM HV : VDrif = 3850, VGem = 3550

HRRL : E = 14 MeV, I =20mA

ADC 1D has clear second peak at channel 150 but ADC1 does not. Lets Observe ADC 1D as a function of position. This corresponds to GEM output strip 13.

5 minutes long

Run 2

Run2.mpa

GEM HV : VDrif = 3550, VGem = 3550

HRRL : E = 14 MeV, I =20mA

5 minutes long

I see a second peak on ADC1D but it is at channels 100 and not 150.

Run 3

Run3.mpa

GEM HV : VDrif = 3550, VGem = 3550

HRRL : E = 14 MeV, I =20mA

3 minutes long

Unplug NaI and peak resumes near 150 channels

Run 4

Run4.mpa

GEM HV : VDrif = 3850, VGem = 3550

HRRL : E = 14 MeV, I =20mA

Now turn the detector on with the beam current on and I see a peak around 150 channels again.

3 minutes long. OOOPPPs left DAQ running while we moved the detector. Only look at first 3 minutes.

Pin 13 was located 63 cm from the mounting bracket horizontal cross bar.

Run 5

Run5.mpa

GEM HV : VDrif = 3850, VGem = 3550

HRRL : E = 14 MeV, I =20mA

Now move the detector away from the photons.

Pin 13 is a distance of 22 cm from the mounting bar moved 41 cm from its original location at 63 cm

Run 6

Run6.mpa

GEM HV : VDrif = 3850, VGem = 3550

HRRL : E = 14 MeV, I =20mA

Now move the detector away from the photons.

Pin 13 is a distance of 43 cm from the mounting bar moved 20 cm from its original location at 63 cm

Start 4:36 End 4:39

Run 7

Run7.mpa

GEM HV : VDrif = 3850, VGem = 3550

HRRL : E = 14 MeV, I =20mA

Now move the detector away from the photons.

Pin 13 is a distance of 33 cm from the mounting bar moved 30 cm from its original location at 63 cm

Start 5:51 End 5:54

Run 8

Run8.mpa

GEM HV : VDrif = 3850, VGem = 3550

HRRL : E = 14 MeV, I =20mA

Now move the detector away from the photons.

Pin 13 is a distance of 54 cm from the mounting bar moved 9 cm from its original location at 63 cm

Start : 5.03 End : 5:07

Analysis

Background -vs -signal

The graph below shows the observed rate from strip 13 of the GEM detector when t beam current is changed from 20 mA to 0 mA.

The graph below shows the observed rate when the GEM drift HV is changed from 3850 to 3550 Volts. This change should prevent ionized electrons from traveling to the charge collector.

Position -vs Rate

Run Number	Distance From max Rate(cm)	Strip 13 Rate X 1000(per event [math]\times[/math])	Strip 13 Rate per minute	Histogram	Histogram(Zoomed In)
1	0	134.0	3678
2	0
3	0
4	0
5	41
6	20	143.3	4137
7	30	155.5	2805
8	9	183.1	5030

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