Difference between revisions of "ASIC design optimizations"
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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). | 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: | The result: | ||
− | [[Image:hvplateau_ch15.jpg|thumb|none|400px|HV-curve,the count is normalized to 100s measurements.]] | + | {| border="1" cellpadding="2" |
− | So things start to show up (above threshold, the threshold was set just above noise) at | + | |- |
+ | |width="415pt"|[[Image:hvplateau_ch15.jpg|thumb|none|400px|HV-curve,the count is normalized to 100s measurements.]] | ||
+ | |width="415pt"|[[Image:hvplateau2_ch4.jpg|thumb|none|400px|HV-curve-plateau, tracked events, normalized to a 40' measurement.]] | ||
+ | |- | ||
+ | |} | ||
+ | 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. | ||
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== Chamber at 60 degrees == | == Chamber at 60 degrees == |
Revision as of 10:00, 20 May 2008
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:
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.
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.
- The noise
Noise before preAmp is dominated by the noise pickup of the probe. |
- 1600V
N/A because of noisy probe. |
- 1700V
N/A because of noisy probe. |
- 1750V
- 1800V
- 1900V
- 1950V
- 2000V
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) )
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):
- 1600 V
- 1650 V
- 1700 V
- 1750 V
- 1800 V
- 1850 V
- 1900 V
- 1950 V
- 2000 V
Chamber at 60 degrees
Below you can find some pulse galleries and amplitude spectra (low statistics)
- 1600 V
- 1650 V
- 1700 V
- 1750 V
- 1800 V
- 1850 V
- 1900 V
- 1950 V
- 2000 V
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: