<p>Summary at start of run</p>
<p>Read through the runbook and end of run summar and the situation appears to be:</p>
<p>1. The check of the tune showed it was OK, although a bit of beam (or halo) clipping 4mm collimator</p>
<p>2. There are some changes to the gas filling scheme - Jamie should be present for the next one.</p>
<p>3. Evidence that the gas pressure is dropping slowly - need to watch this</p>
<p>4. Trigger is Coinc.OR.SS_2.OR.PD. Rate at this is 200/s at 4epA (50/50 Coinc and S2_2)</p>
<p>5. Suggestion we could increase the beam a factor of two to get back to the same coinc rate.</p>
<p> </p>
<p>Analysis. Looking at the rates I see:</p>
<p>Running at 66 pnA and see about 4,000/s triggers and 3,200/s accepts. Scaler 9 over 40,000/s.</p>
<p>Looking back in run book the max trigger accept rate we see is about 3,800/s. Could double beam and gain only</p>
<p>modest increase on accepted rate, but at cost of faster damage of detector. Suggest we run</p>
<p>like this for a bit and make sure all is well.</p>
<p> </p>
<p>Took a look through the spectra. All ADCs OK, but no TDC signals. Checked past saved runs. There up</p>
<p>to run 98. The next saved on disc is run 104 and they aren't there. Nor in any saved runs after this.</p>
<p>Looked at electronics and reason clear as the module providing the TDC trigger (lower section of a</p>
<p>429 unit) has no input. Eventually determined that it would make sense if this unit was operating</p>
<p>in 2 x 8 mode rather than what it is currently set on (4x4). Switched this over and now working OK.</p>
<p>Assume this was changed inadvertently during all the work on the chamber yesterday.</p>
<p> </p>
<p>0300. Running again and all ADC and TDC spectra make sense. Off for a cup of tea.</p> |