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A Primer Course of Experimental Particle and Nuclear Physics
Advanced Technology Training Program for Radiation Measurements
LOGO
6th March 2009, Osaka University, Japan
Geiger Muller ( GM ) Counter
Experiments
Nguyen Thi Duyen An
Institute of Nuclear for Science and Technology
Contents
I
Purpose
II
III
Distance dependence of counting rate
Determination of Оі -ray absorption constants
(1/)
I. Purpose
1. Study of GM counter operation mechanism through measurement
distance dependence of counting rate
2. Studying of γ – ray interaction with material by measuring γ- absorption
constants in material
(2/)
II. Distance dependence of counting rates
1. Apparatus: Basic scale, GM counter, Оі source 137Cs, lead shielding.
(3/)
II. Distance dependence of counting rates
2. Practice
Step 1: Set up system at 1325 HV, 0.5 minute measurement time
Step 2: Changing the distance between the source and GM counter (1cm/time)
Step 3: Recording the count in the Basic scale
(4/)
II. Distance dependence of counting rates
3. Result
Count (N)
Distance
(cm)
L1
L2
L3
Average (N)
CR
Error
1
3220
3406
3693
3439.67
114.66
3.57
2
3002
2922
2792
2905.33
96.84
3.28
3
2357
2344
2404
2368.33
78.94
2.96
4
1885
1846
1860
1863.67
62.12
2.63
5
1361
1327
1330
1339.33
44.64
2.23
6
1005
1053
1044
1034.00
34.47
1.96
7
771
872
812
818.33
27.28
1.74
8
631
708
652
663.67
22.12
1.57
9
525
516
538
526.33
17.54
1.40
(5/5)
II. Distance dependence of counting rates
Background (3 march 2009)
221counts/15minute
(1/)
III. Determination of Оі -ray absorption constants
1. Apparatus: Basic scale, GM counter, Оі source 137Cs, Aluminum, Iron, Lead shielding.
(1/)
III. Determination of Оі -ray absorption constants
2. Practice
Step 1: Set up system at 1325 HV, 1.5 minute measurement time
Step 2: Collimating beam before striking the absorber by shielding the γ – ray source
and the GM
Step 2: Changing the material
Step 3: Recording the count in the Basic scale
(1/)
III. Determination of Оі -ray absorption constants
3. Result
Count
Al (cm)
Average
CR
Error
1043
1028.33
11.43
1.13
926
943
931.33
10.35
1.07
856
879
868
867.67
9.64
1.03
0.9
822
836
812
823.33
9.15
1.01
1.2
794
804
799
799.00
8.88
0.99
1.5
756
749
769
758.00
8.42
0.97
1.8
725
729
744
732.67
8.14
0.95
L1
L2
L3
0
1046
996
0.3
925
0.6
(1/)
III. Determination of Оі -ray absorption constants
3. Result
(1/)
III. Determination of Оі -ray absorption constants
Count
Fe(cm)
Average
CR
Error
1043
1028.33
11.43
1.13
870
858
874.33
9.71
1.04
739
736
736
737.00
8.19
0.95
1.26
570
602
569
580.33
6.45
0.85
2.14
412
440
413
421.67
4.69
0.72
3.02
318
281
302
300.33
3.34
0.61
4.9
149
157
146
150.67
1.67
0.43
L1
L2
L3
0
1046
996
0.22
895
0.67
(1/)
III. Determination of Оі -ray absorption constants
(1/)
III. Determination of Оі -ray absorption constants
Count
Pb (cm)
Average
CR
Error
1043
1028.33
11.43
1.13
816
815
813.67
9.04
1.00
510
477
510
499.00
5.54
0.78
1.225
301
316
288
301.67
3.35
0.61
1.725
207
179
186
190.67
2.12
0.49
L1
L2
L3
0
1046
996
0.225
810
0.725
(1/)
III. Determination of Оі -ray absorption constants
(1/)
III. Determination of Оі -ray absorption constants
Total cross section of absorption materials
Пѓ Al = 2.44 (cm-1)
Пѓ Fe = 3.46 (cm-1)
Пѓ Pb = 18.25(cm-1)
I = I0 e - Ој x
Пѓ =Ој / n
LOGO
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