June, 7, 2007 Cf rate measurements using Photonics PMT
Cf source was placed 16.5 cm away from face of PHotonics PMT. The PMT output signal was descriminated by a Lecroy Model 821 descriminator set to pass any voltage below -0.5 mV. The descriminated output was then sent to a counter Model TC 531.
Configuration Definitions
1: Placed the Cf source 16.5 cm from face of Scintillator. neutrons passing through scintillator would also pass through PMT
2: Inserted a 2.5 cm thick steel shielding wall between Scintillator and Cf source. Right up against Scintillator
3: Replaced steel wall with 5 cm thick lead shielding brick
4: Replaced lead brick with 6.7 cm thick paraffin block ( Paraffin N.F. , Household wax made by Parowax. 4 cackes, total net weight 16 oz (454 g))
5: Increased thickness of paraffin block to 13.4 cm
6: No source backround
Measurements
Using Photonics PMT and BC
| Configuration | Rate (counts/min) | Statistical Error in Rate (Counts/min) |
|---|---|---|
| 1 | 2.7e3 | 0.09e3 |
| 2 | 2.2e3 | 0.01e3 |
| 3 | 0.8e3 | 0.02e3 |
| 4 | 2.2e3 | 0.08e3 |
| 5 | 1.8e3 | 0.02e3 |
| 6 |
Analysis
Properties of Materials used
Steel : Zeff = 26 and =8.02
Atomic composition for AISI 304) in %
| Element | % |
|---|---|
| Si | 1 |
| Cr | 19 |
| Mn | 2 |
| Fe | 68 |
| Ni | 10 |
Lead: Z =