GEM Cosmic V792 Measurements

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11-07-08

The pulse coming from the strips is delayed and amplified using the Timing Filter Amplifier Model_474(X6). The amplified pulse is connected to the V792 QDC.
Run 550

Start Time: Nov 6 19:58:03; End Time: Nov 7 09:45:57

ADC measurement GEMDetector HV3800V ADC1 11-07-08.gifADC measurement GEMDetector HV3800V ADC1 11-07-08 Landau fit.gif

12-10-08

The signal below represents a measurement of the Trig out signal from a 10 cm x 10 cm ionization chamber with 3 GEM preamplifiers. The chamber gas a 90/10 % mixture of Arcon and CO2. The Drift HV was set to 3200 Volts and the GEM preamplifier HV distribution network was set to 2900 Volts. The V792 CAEN ADC channels have a gain of 100 fC/channel. The main signal peak appears at channel number 759 and represents an accumulation of [math]75.9 \pm 4[/math] pC of charge.


TrigOutSignal R607.gif

Electronics Settings:

TrigOut goes to Timing Filter Amplifier(Coarse Gain=X6, Fine GAin=7.5ns && Integrate=20ns) and after amplification to ADC
StripOut is used as a trigger and gate. The signal from the strip is amplified by the Timing Filter Amplifier (Coarse Gain=X20, Fine Gain=12.5ns && Integrate=500ns)
The Threshold on DIFF. CFD is set to 0.70 (ULD=9.9~10 && LLD=0.5)

12-10(11)-08

HV Settings: [math]V_{Drift}=3200[/math] Volts and [math]V_{GEM}=2900[/math] Volts.

Using again only TrigOut and the signal from the Strip.

Electronics Setup: done (might change CFD threshold)

12-11-08

HV Settings: [math]V_{Drift}=3200[/math] Volts and [math]V_{GEM}=2900[/math] Volts.
Gas type 90/10 ArCO2.

TrigOut electronics setup 12-11-08.pngStripPulse electronics setup 12-11-08.png

Electronics Setup

TrigOut and the stripsignal, both are used as a pulse and go to ADC.
The pulse from the Strips is used as a trigger and gate.

The pulse from the trigout is delayed, Amplified by the Timinig Filter Amplifier(Coarse_Gain=X20, Fine_Gain=8.5 && Integrate=20ns).
Signal from the Strips goes to the Timing Filter Amplifier(Coarse_Gain=X20, Fine_Gain=10.5 && Integrate=20ns). Amplified pulse is devided into two signals, One is sued as a trigger and gate and second as a pulse for ADC. The first one(gate && trigger) is amplified using the Timing Filter Amplifier(Coarse_Gain=X2, Fine_Gain=10 && Integrate=50ns) and used in DIFF. CFD for gate and trigger. Second output from the Amplified strips, goes to delay box(TENNELEC TC 215 DELAY AMPLIFIER) and putted to the ADC.

The results shown below are for different Diff. CFD values.

1). Threshold Values: Threshold=1.90, ULD=9.65 && LLD=2.10

Run Number is r613

Start time: Dec 11 16:31:42 End Time: Dec 11 17:32:23


2). Threshold Values: Threshold=3.10, ULD=9.65 && LLD=2.90

Run Number is r622

Start time: Dec 11 19:25:28 End Time: Dec 11 21:53:44

Charge leaving last GEM foil-12-11-08 r622.gifCharge collected by the strips GEM-1l-12-11-08 r622.gif


2). Threshold Values: Threshold=3.70, ULD=9.65 && LLD=3.50

Run Number is r624

Start time: Dec 11 21:58:37 End Time: Dec 12 12:19:53

GEM RUN Number r624 charge collected by the strips and charge leaving last GEM foil-12-12-08.gif

The result shown below is reasonable. The charge that left the last GEM foil is greater than the charge collected by the strips.

change the picture below so they have the same units and overlay them.  Then plot ADC1/ADC5.  This will tell you the charge collection efficiency if the gains are the same..
I will Dr. Forest

Charge leaving last GEM foil run number r624-12-12-08.gifCharge collected by the Strips number r624-12-12-08.gif

12-12-08

Finding out what is gain for each channel using the Stanford pulse generator.

Setting:

Run Number: r634 && r635

Amplified pulse for two channels.gifAmplified pulse for two channels swapped.gif

Original pulse from stanford pulse generator goes to the ADC: r636 && r637


Pulse for two channels.gifPulse for two channels swapped.gif

I used the attenuator for both channels and it was set to the same value: 12dB = 10.7918.

[math]X db = 20 log_{10}\frac{I_1}{I_2}[/math]
[math]\frac{I_1}{I_2} = 10^{12/20} = 3.98[/math]

Gain Calculation

Gain_for_Channel_1 = Gain_TrigOut = [math]\frac{175 \times 10.7918}{110} = 17.1688[/math]
Gain_for_Channel_5 = Gain_Strip = [math]\frac{650 \times 10.7918}{145} = 48.377[/math]

12-13-08

Gas type ArCO2(90/10)

New measurements. Setting the gain for Strip pulse and TrigOut the same.

Below Channel 1 represents StripOut and Channel 2 trigOut.


Noise level On GEM detector HV 3310 3010Volts 12-13-08.pngPulse On GEM detector HV 3310 3010Volts 12-13-08.png

Setting Gain the same using The Stanford Pulse Generator:

Pulse output from the Stanford Pulse Generator 12-13-08.pngAmplified Pulse the Stanford Pulse Generator 12-13-08.png
Pulse output from the Stanford Pulse Generator Noise level 12-13-08.pngAmplified Pulse the Stanford Pulse Generator Noise level 12-13-08.png

Amplified and delayed Pulse the Stanford Pulse Generator 12-13-08.png



Take scope pictures of the stanford pulse generator signal which goes into each amplifer.  
Then take scope pictures of the stanford pulse as it exits both amplifiers.  
Also take scope picture of the noise for all 4 channels.
Predict where the signal will appear in the ADC and what the width of the signal will be.
Take data if the pulses are sufficiently similar.  
You could try to gain match the amplifiers such that ADC1/ADC5 = 1.
After the ratio of the amplifier gains are measured you should measure the GEM detector 
output from cosmic rays again.

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