Summary: Initial results from the Dewar attenuation
tests look odd. They won’t be
conclusively odd until all the sources have been measured for the same counting
time. At the moment, the Cs 137 32 keV
line is less attenuated than the 22 keV Cd 109 line which is expected, but it
also appears to be less attenuated than the Cd 109 88 keV line which is not
expected. It seems like a higher energy
should have an easier time getting through the Dewar material.
To Do Today:
- . Calculate the count rate from the Cs 137 source and compare it to the expected flux from Hirsch’s theory
- . Run a simulation on a much smaller diameter coil looking into quenching the small YBCO superconductor.
- . Analyze the overnight run on Cs 137
Bias
|
1500 V
|
Gate Window
|
0.5 uS
|
Threshold
|
1.5mV
|
Attenuation
|
0 dB
|
Data set
|
HBC_00018
|
Source
|
Cs 137 Centered in liquid helium Dewar
|
Start Time
|
~ 7:15 PM
|
Stop Time
|
9:57 AM
|
Date
|
2014_08_20 – 2014_08_21
|
x-y scope V/div
|
1, 0.5
|
Shielded?
|
Yes
|
Tube
|
Harshaw B-
|
Here’s the attenuation calculation done for the raw data.
time in minutes
|
Peak Count
|
Rate
|
Dewar
|
||
642
|
1235
|
1.923676
|
Window
|
||
185
|
14188
|
76.69189
|
attenuation
|
|
16.00618
|
Background
Bias
|
1500 V
|
Gate Window
|
0.5 uS
|
Threshold
|
1.5mV
|
Attenuation
|
0 dB
|
Data set
|
HBC_00019
|
Source
|
background
|
Start Time
|
10:04 AM
|
Stop Time
|
1:54 PM
|
Date
|
2014_08_20 – 2014_08_21
|
x-y scope V/div
|
1, 0.5
|
Shielded?
|
Yes
|
Tube
|
Harshaw B-
|
Bias
|
1500 V
|
Gate Window
|
0.5 uS
|
Threshold
|
1.5mV
|
Attenuation
|
0 dB
|
Data set
|
HBC_00020
|
Source
|
Cd 109 in Dewar
|
Start Time
|
1:59 PM
|
Stop Time
|
|
Date
|
2014_08_20 – 2014_08_21
|
x-y scope V/div
|
1, 0.5
|
Shielded?
|
Yes
|
Tube
|
Harshaw B-
|
The peak at 88 keV is still visible, but it’s moved over a
bit to the left and sits at channel 406 instead of at channel 421.
With background subtracted, the peak is still barely
apparent.
The peak near 22 keV is completely obscured. The run here wasn’t as long as the Cs 137 run
earlier, so it will be repeated with more counting time.
The rough attenuation calculations for the Cd 109 run follow
time in minutes
|
Peak Count
|
Rate
|
Source in Dewar
|
||
339
|
81
|
0.238938053
|
Source Taped to Window
|
||
83
|
213243
|
2569.192771
|
attenuation
|
|
40.31511371
|
Predicted Background Count at Peak
Channel
|
||
Peak Channel
|
|
Noise Count
|
59
|
|
62.29487179
|
time in minutes
|
Peak Count
|
Rate
|
Source in Dewar
|
||
339
|
23
|
0.067846608
|
Source Taped to Window
|
||
83
|
14777
|
178.0361446
|
attenuation
|
|
34.18980043
|
Predicted Background Count at Peak
Channel
|
||
Peak Channel
|
|
Noise Count
|
421
|
|
10.14102564
|
Here’s a comparison of the peak counts to Cs 137. Data was taken without the Dewar.
Cadmium 22 to Cs 36 count ratio 0
dB
|
33.50018767
|
Cadmium 88 to Cs 36 count ratio 0
dB
|
2.321446768
|
Plans for experiments
Pulsed Current Supply
·
Noise in scintillator output during pulse
o
Gate the detector
o
Run with source
o
Run without source
·
schematic
·
diameter of existing coil
·
simulation with existing coil
·
simulation with smaller coil
Iron Magnet
·
Need assistance for first bring-up
·
Run to half max current and check field
o
get Hall probe
·
Check heat generated by coils
Simulations
·
Heat generated by coil
·
Heat generated by eddy currents in sample
·
Discuss eddy currents and field diffusion
Proposal
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