Difference between revisions of "22 February 2008"

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[[Image:trigger.jpg|thumb|none|400px|figure 3.1: Histogram of trigger zero crossing time.]]
 
[[Image:trigger.jpg|thumb|none|400px|figure 3.1: Histogram of trigger zero crossing time.]]
 
One can see too peaks that are 20 ns away from each other. The early peak contains almost 1/3 of the events. For now we do not worry too much because we have other problems.
 
One can see too peaks that are 20 ns away from each other. The early peak contains almost 1/3 of the events. For now we do not worry too much because we have other problems.
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== Drift time spectra ==

Revision as of 16:10, 21 February 2008

Shaper board

As mentioned before there is a problem with three channels on the shaper board - they show a 10x lower gain. Although it is not clear what is causing this Gerard will send a new board with a slightly different gain.

Clock

Kim told us she will send a 125 MHz clock to CMU earliest in the first week of March.

Trigger

In this setup we will are reading out the trigger using one channel of the fADCs. The block pulse coming out of the coincidence unit is attenuated and shaped (against jitter) using a device Gerard gave us. Out of this signal a differential signal is made using another device (also from Gerard). This signal is injected in the shaper board and then read out by the fADC. The real trigger (a NIM signal going to the STOP input on the fADC) is basically the delayed output from the coincidence unit.

A straight line is fit to the rising edge of the trigger signal and the zero crossing (in ns) is dumped into the histogram shown in figure 3.1.

figure 3.1: Histogram of trigger zero crossing time.

One can see too peaks that are 20 ns away from each other. The early peak contains almost 1/3 of the events. For now we do not worry too much because we have other problems.

Drift time spectra