ASIC meeting June 14, 2010

Meeting Time and Place

Monday June 11, 2010 at 10:00am At Jefferson Lab, the meeting will be held in room F326-327

Connections

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then enter participant code: 77438230# (remember the "#")

Agenda

Performance Plots for the ASIC

The following links go to pages that compare the performance of the older preamplifier to the newest version of the ASIC. We note that the interposer board was not used for the older preamplifier and that the Struck FADCs we have at CMU are set to a scale such that 1 volt coresponds to about 4000 channels. We note that the new preamplifier does not exceed ~2000 channles here because the output voltage is now (apparently) limited to 0.5V.

Preamp 4 : Comparison of scope traces with earlier preamps

The following sets of plots were taken simply by swapping the old and new preamplifier on the CDC. The high volatge settings were the same and the gas mixture were the same for both. For the case of the cosmics with a reduced gain in the new ASIC, we would expect the location of the minimum ionizing peak for cosmics to go down by about a factor of three. Oddly, by just about any reasonable measure, it has moved up. We find this extremely confusing.

Efficiency Plots for the CDC

The following plot is taken from our NIM article that shows the chamber efficiency as a function of the high voltage setting for various gas mixtures. As can be seen, for the optimal gas mixture (around 50/50), the plateau starts at about 2100 V and there is no efficiency below around 1900V.