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| Nuclear hyperfine mixing in 229Th89+ |
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Message ID: 60
Entry time: Fri Apr 1 23:47:45 2022
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| Author: |
Carsten |
| Category: |
Detectors |
| Subject: |
PMT thresholds / PMT north does not allow voltage abow ~ -1kV |
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Checked thresholds of PMT with beam and without beam.
The PMT "south" which is now at the gas-jet target has burst-like pulses with a train of many short pulses of duration of about 1us. The signals are taken out of the ADC of the 2nd DAQ (but are still in the VUPROM TDC).
The PMT "middle" (broad-band VUV) has a quite high count rate of about 4-kHz at a few 10e7;; ions in the ring. The rate is very low without ions in the ring but it does not fully scale to low intensities.
At low intensities of a few 10e5;; we still have more than 100 Hz.
For a PMT voltage of -1800V a threshold of 20mV was set which is ok an d we leave it
Note: We see a noise beat of 6ns and 55ns with amplitude of about 15mV to 20mV. The high frequency disappears if we use a battery scope.
PMT "north" small-band VUV
We tried to put the voltage to the wanted level of -2500V. It was not possible to set a voltage higher than about -1000V. WIth this voltage the PMT draw a current of about 200uA and at a voltage above this value it dropped to zero and switched off.
We need to have a closer look at the PMT in the ESR tomorrow with some specialist knowledge. |