THGEM

THGEM#9 counting experiment

The same setup above for THGEM#9 is used for a counting experiment.

The aim is to compare the number of counts in an hour for three different cases:

case 1-The alpha source's shutter is closed.

case 2- The alpha source's shutter is closed and a gamma source (Co-60) placed on the detector's entrance window.

case 3-The alpha source's shutter is open the gamma source is removed

case 4-The alpha source's shutter is open and a gamma source (Co-60) is placed on the detector's entrance window.

V_cathode	THGEM_1T	THGEM_1B	[math]\Delta V1 [/math]	THGEM_2T	THGEM_2B	[math]\Delta V2 [/math]	THGEM_3T	THGEM_3B	[math]\Delta V3 [/math]
4200	2950	2450	500	1950	1200	750	950	100	850

Experimental Setup

Trigout-> 474 ortec timing filter amp. -> EGG&G ESN CF4000-01 discriminator (5 mV threshold) -> tennelec TC534 counter and timer.

case #	case 1	case 2	case 3
counts/hr	462	2400	2759

According to the number of counts in each case:

1- The detector detects cosmic rays (noise). (assuming the shutter stops all the alpha particles without any ionization)

2- The detector is sensitive to gamma rays (2400-462 = 1938)

3- The detector is sensitive to alpha particles (2759-462 = 2297) considering the same assumption above.

Discriminator level-count level relationship

V_cathode	THGEM_1T	THGEM_1B	[math]\Delta V1 [/math]	THGEM_2T	THGEM_2B	[math]\Delta V2 [/math]	THGEM_3T	THGEM_3B	[math]\Delta V3 [/math]
4359	2950	2450	500	1950	1200	750	985	100	850

The following table represent the discriminator level and the count rate that is measured in 10 minute time interval with the shutter OPEN and 474 ortec timing filter amp. amplification is x6.

discriminator level	Counts/min
(mv)	Trial 1	trial 2	Trial 3	Trial 4	trial 5	Ave [math]\pm[/math] err
5	80.7	104.2	67.4	64.5	72.8
7	96.6
8
9	36.8
10
12	11.2
13
15	5.1
18	3.7
20	3.2
50	0
75	0.1
100	0

Counting Experiment using Leading Edge discriminator (Lecroy 623b)

The same setup above for THGEM#9 is used for a counting experiment.

The aim is to compare the number of counts for three different cases:

case 1-The alpha source's shutter is closed.

case 2- The alpha source's shutter is closed and a gamma source (Co-60) placed on the detector's entrance window.

case 3-The alpha source's shutter is open the gamma source is removed

case 4-The alpha source's shutter is open and a gamma source (Co-60) is placed on the detector's entrance window.

V_cathode	THGEM_1T	THGEM_1B	[math]\Delta V1 [/math]	THGEM_2T	THGEM_2B	[math]\Delta V2 [/math]	THGEM_3T	THGEM_3B	[math]\Delta V3 [/math]
4200	2950	2450	500	1950	1200	750	950	100	850

The amplifier amplification affect the count rate, the follwing table shows the effect as the discrimination level is 1.19V :

Amplification	Count rate (Count/min)
x10	1.37x10^7
X6	1151
x4	9
x2	1
x1	1

based on the above table, the amplification is chosen to be x6 for the measurement below.

case #	case 1	case 2	case 3	case 4	Notes
counts/min	1.55 x 10^7				disc. level = 0.30V (700 mV sq.p-p)
counts/min	2.08 x10^6				disc. level = 0.53 mV (1.8V sq.p-p)
counts/min	6902				disc. level = 1.1 V (3V sq.p-p)
counts/min	3222				disc. level = 1.2 V
counts/min	1469				disc. level = 1.3 V
counts/min	680				disc. level = 1.4 V
counts/min	113				disc. level = 1.5 V
counts/min	64	84			disc. level = 1.62 V (4V sq.p-p)
counts/min	10	11			disc. level = 1.7 V
counts/min					disc. level = 1.8 V
counts/min	10	9			disc. level = 1.9 V
counts/min	7	9			disc. level = 2 V

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