Chamber at 0 degrees
- High Voltage plateau === done
Gas: Ar-CO2 87%-13% gas mixture.
Setup: the signal after the shaper was inverted and fed to a discriminator. The HV was changed and the signals above threshold where counted (normalized to 100s measure time).
The result:
HV-curve,the count is normalized to 100s measurements.
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HV-curve-plateau, tracked events, normalized to a 40' measurement.
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So things start to show up (above threshold, the threshold was set just above noise) at 1500 V and start to break down at +2000V. We see a plateau starting at 1750V.
Next the scope traces of the (maximum) noise level after the shaper is shown on the left side. This pickup happens mostly on a different time then a signal. The right side shows a signal at 1800V, also after the shaper. To trigger on the signal I set the threshold to 350 mV.
Trace of maximum noise after shaper.
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Trace of a signal at 1800 V after the shaper.
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Let's compare signals at different stages in the electronics chain. Left plot is the signal right BEFORE the pre-amplifier, middle plot is the signal AFTER the pre-amplifier (0.366 times attenuated because of the differential probe), right plot is AFTER the shaper.
Noise before preAmp is dominated by the noise pickup of the probe.
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N/A because of noisy probe.
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Trace of signal after preAmp of channel 2.
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Gallery of pulses of channel 2.
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N/A because of noisy probe.
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Trace of signal after preAmp of channel 2.
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Gallery of pulses of channel 2.
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Trace of signal before preAmp of channel 2.
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Trace of signal after preAmp of channel 2.
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Gallery of pulses of channel 2.
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Trace of signal before preAmp of channel 2.
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Trace of signal after preAmp of channel 2.
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Gallery of pulses of channel 2.
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Trace of signal before preAmp of channel 2.
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Trace of signal after preAmp of channel 2.
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Gallery of pulses of channel 2.
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Trace of signal before preAmp of channel 2.
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Trace of signal after preAmp of channel 2.
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Gallery of pulses of channel 2.
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Trace of signal before preAmp of channel 2.
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Trace of signal after preAmp of channel 2.
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Gallery of pulses of channel 2.
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What exactly does the shaper? Well you can see this in following traces: from left to right: three signals before/after (green/red) the shaper @ 1800 V:
(remember that the signal before the shaper is attenuated (0.336x) )
Trace of signal before/after (green/red) shaper.
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Trace of signal before/after (green/red) shaper.
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Trace of signal before/after (green/red) shaper.
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Below galleries of pulses are shown for different HV (on the left channel 2, in the middle channel 15) -- remember everything above 1V is an overflow on the fADC, also the b/w traces are taken with infinite persistence, the colored ones with 10 s persistence. The amplitude spectra are also shown: notice the growing overflow peak around channel 3000 (they are pedestal subtracted):
Gallery of pulses of channel 2.
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Gallery of pulses of channel 15.
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Amplitude spectrum of ch 15 (counts versus amplitude in ADC channels, with shaper).
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Gallery of pulses of channel 2.
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Gallery of pulses of channel 15.
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Amplitude spectrum of ch 15 (counts versus amplitude in ADC channels, with shaper).
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Gallery of pulses of channel 2.
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Gallery of pulses of channel 15.
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Amplitude spectrum of ch 15 (counts versus amplitude in ADC channels, with shaper).
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Gallery of pulses of channel 2.
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Gallery of pulses of channel 15.
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Amplitude spectrum of ch 15 (counts versus amplitude in ADC channels, with shaper).
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Gallery of pulses of channel 2.
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Gallery of pulses of channel 15.
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Amplitude spectrum of ch 15 (counts versus amplitude in ADC channels, with shaper).
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Gallery of pulses of channel 2.
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Gallery of pulses of channel 15.
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Amplitude spectrum of ch 15 (counts versus amplitude in ADC channels, with shaper).
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Gallery of pulses of channel 2.
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Gallery of pulses of channel 15.
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Amplitude spectrum of ch 15 (counts versus amplitude in ADC channels, with shaper).
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Gallery of pulses of channel 2.
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Gallery of pulses of channel 15.
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Amplitude spectrum of ch 15 (counts versus amplitude in ADC channels, with shaper).
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Gallery of pulses of channel 2.
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Gallery of pulses of channel 15.
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Amplitude spectrum of ch 15 (counts versus amplitude in ADC channels, with shaper).
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Chamber at 60 degrees
Below you can find some pulse galleries and amplitude spectra (low statistics)
Gallery of pulses of channel 2.
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Gallery of pulses of channel 15.
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Amplitude spectrum of ch 15 (counts versus amplitude in ADC channels, with shaper).
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Gallery of pulses of channel 2.
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Gallery of pulses of channel 15.
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Amplitude spectrum of ch 15 (counts versus amplitude in ADC channels, with shaper).
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Gallery of pulses of channel 2.
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Gallery of pulses of channel 15.
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Amplitude spectrum of ch 15 (counts versus amplitude in ADC channels, with shaper).
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Gallery of pulses of channel 2.
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Gallery of pulses of channel 15.
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Amplitude spectrum of ch 15 (counts versus amplitude in ADC channels, with shaper).
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Gallery of pulses of channel 2.
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Gallery of pulses of channel 15.
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Amplitude spectrum of ch 15 (counts versus amplitude in ADC channels, with shaper).
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Gallery of pulses of channel 2.
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Gallery of pulses of channel 15.
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Amplitude spectrum of ch 15 (counts versus amplitude in ADC channels, with shaper).
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Gallery of pulses of channel 2.
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Gallery of pulses of channel 15.
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Amplitude spectrum of ch 15 (counts versus amplitude in ADC channels, with shaper).
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Gallery of pulses of channel 2.
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Gallery of pulses of channel 15.
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Amplitude spectrum of ch 15 (counts versus amplitude in ADC channels, with shaper).
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Gallery of pulses of channel 2.
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Gallery of pulses of channel 15.
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Amplitude spectrum of ch 15 (counts versus amplitude in ADC channels, with shaper).
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To Do
- (absolute) Gas gain as a function of High Voltage
Source measurement using Sr-90 (e-) or 55-Fe (X-rays) (if we have it) / or using cosmic rays?
-- Estimated time: 1 day -- if we have a good source
- amplitude distributions of tilted chamber
1 week measure with tilted chamber => In progress
- Collection of gallery of pulses
I found 4 pulse galleries, measured directly after the pre-amplifier made by Gerard when he was here, they are shown below:
Gallery of pulses measured after the pre-amplifier
Gallery of pulses measured after the pre-amplifier
Gallery of pulses measured after the pre-amplifier
Gallery of pulses measured after the pre-amplifier