Table of Contents
2011/05/04
| 0030 | Filled LN2 cold trap. |
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| 0031 | Flashed detectors. |
| 1430 | Fill N2 cold trap full. |
| 1535 | Perhaps we can improve charge collection by increasing the bias voltage, and hence the electric field. Let's not go mad: +/-3 V is a good starting point. |
| Stop flashing detector. | |
| 1705 | Start data series: 07110504_1701; -3 V DIB1, +3 V DIB2; Ba-133 source 13“ below top of mu-metal shield; 40 ADC bins trigger threshold on all charge channels; charge-only. |
| 1820 | Stop data series 07110504_1701 on file 11. |
| Start flashing detector. |
Charge Collection & Neutralisation at +/-2 V Bias
| 2045 | Perhaps there is a Ba-133 peak. Looking at the oZIP data from run 10, the 356 keV peak lies at an energy ≈ 2.5x greater than the background peak. Looking at data series 07110502_2259 (Ba-133 source 13” below mu-metal shield; +/- 2V bias), the 356 keV peak should appear at Qsum ≈ 0.0005 units. It appears to exist here, at least on side 1 (-ve bias; collects holes), as illustrated in Figure 2. |
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| Of course, due to the larger volume, it makes sense for the background to be higher for iZIPs than oZIPs. Perhaps the cuts need to be fine-tuned. | |
| Rather worringly, the 60 keV peak is not present from the two Am-241 sources above side 1. The χ2 cut on side 2 in Figure 1 cuts out most of the low energy events and needs to be tuned. Nevertheless, the 60 keV peak should be visible in the Qsum histogram for side 1. |
| Figure 1: Qsum after low energy, Qpart & χ2 cuts : Am-241 : +/-2 V bias. |
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| Figure 2: Qsum after low energy, Qpart & χ2 cuts : Am-241 & Ba-133 : +/-2 V bias. |
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| 2100 | Unfortunately, no gamma peaks are visible in Qsum as a function of time scatter plots in Figures 3 & 4. |
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| However, looking at the background peak, it seems as though neutralisation should be rather good. The band does dip slightly. It's difficult to discern the magnitude of this effect as the background has a fairly wide spectrum. |
| Figure 3: Qsum as a function of time after low energy, Qpart & χ2 cuts : Am-241 : +/-2 V bias. |
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| Figure 4: Qsum as a function of time after low energy, Qpart & χ2 cuts : Am-241 & Ba-133 : +/-2 V bias. |
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Charge Collection & Neutralisation at +/-3 V Bias
| 2100 | The 356 keV peak is clearer when looking at side 1 (-ve bias; collects holes) in Figure 5. There is definitely something there. |
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| Maybe my eyes are playing tricks on me, but the 356 keV line seems to be present for side 1 in Figure 6. Neutralisation seems to dip a little. |
| Figure 5: Qsum after low energy, Qpart & χ2 cuts : Am-241 & Ba-133 : +/-3 V bias. |
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| Figure 6: Qsum as a function of time after low energy, Qpart & χ2 cuts : Am-241 & Ba-133 : +/-3 V bias. |
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| 2115 | Stop flashing detector. |
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| 2205 | Start data series: 07110504_2201; -3 V DIB1; +3 V DIB2; Ba-133 source 20“ below top of mu-metal shield; 40 ADC bins trigger threshold on all charge channels; charge-only. |
| 2325 | Stop data series 07110504_2201 on file 9. |
| Start flashing detector. |
Charge Collection & Neutralisation at +/-3 V Bias : Part 2
| 2355 | Placing the source closer to the detector seems to wash out the 356 keV peak. Maybe this is an issue with pile-up? |
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| Is it just my eyes, or is there some degredation in neutralisation? |
| Figure 7: Qsum after low energy, Qpart & χ2 cuts : Am-241 & Ba-133 : +/-3 V bias. |
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| Figure 8: Qsum as a function of time after low energy, Qpart & χ2 cuts : Am-241 & Ba-133 : +/-3 V bias. |
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