Difference between revisions of "March 2013"
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5. Add both TI and FADC trigger match into the decoder and provide deadtime calculation | 5. Add both TI and FADC trigger match into the decoder and provide deadtime calculation | ||
</pre> | </pre> | ||
| + | |||
| + | '''Date : 1st March 2013''' (R. Michaels) | ||
| + | |||
| + | Scan of Deadtime and Asymmetry. | ||
| + | |||
| + | Using Kalyan's deadtime calculation, now embedded in my version of the code, I made a rate scan to see how | ||
| + | the deadtime changed and what happened to the asymmetry. | ||
| + | |||
| + | <pre> | ||
| + | Definitions | ||
| + | F+ = rate when helicity bit is true | ||
| + | F- = rate when helicity bit is false | ||
| + | Favg = DAQ rate (should be average of F+ and F-) | ||
| + | A_pred = (F+ - F-)/(F+ + F-) = predicted asymmetry | ||
| + | A_obs = observed helicity in data | ||
| + | DT = deadtime reported by Kalyan's algorithm | ||
| + | DNR? = if "Y", there were "Data Not Ready" printouts by the event list. If "N" there were none. | ||
| + | |||
| + | Run ... avg F ... F+ ... F- ..... A_pred .... A_obs ..... DT ..... DNR? | ||
| + | .......... kHz ..... kHz ........... % ....... % ......... % | ||
| + | 2056 ... 280 ... 276.2 .. 285.9 .. 1.73 .... 1.01 ..... 0 ..... N | ||
| + | 2060 ... 239 ... 236.8 .. 246.3 .. 1.97 .... 2.35 ..... 0 ..... N | ||
| + | 2063 ... 311 ... 306.8 .. 316.2 .. 1.51 .... 0.03 ..... 47.7 .. Y | ||
| + | 2066 ... 330 ... 323.1 .. 332.3 .. 1.40 .... 0.01 ..... 53.3 .. Y | ||
| + | 2068 ... 421 ... 418.3 .. 427.6 .. 1.10 .... 0 ........ 78.7 .. Y | ||
| + | 2071 ... 218 ... 216.4 .. 226.1 .. 2.19 .... 1.22 ..... 0 ..... N | ||
| + | 2073 ... 138 ... 135.8 .. 145.9 .. 3.58 .... 1.53 ..... 0 ..... N | ||
| + | </pre> | ||
| + | |||
| + | Comments | ||
| + | |||
| + | The deadtime (DT) skyrockets at a critical frequency. I don't think I could get a small nonzero | ||
| + | deadtime (e.g. 5%). | ||
| + | |||
| + | The presence of nonzero DT causes the Asymmetry to be completely diluted, by a far larger factor | ||
| + | than you'd expect. Expect a dilution factor of 1-DT | ||
| + | |||
| + | A_obs often does not agree with A_pred. The other day (late Feb entry) this was also true, | ||
| + | though one is sometimes greater and sometimes less than the other. Not clear why. | ||
| + | |||
| + | I am not convinced we are measuring the DT correctly. Need a second, redundant method. | ||
Revision as of 14:51, 1 March 2013
Date : 1st March 2013 (K.Allada)
For an accurate deadtime calculation we need to turn on TI readout. It will tell us how many triggers are received.
Things to do:
1. Turn on TI readout 2. Learn to access trigger counts from TI readout (Bryan said he maybe able to provide a routine to access trigger counts..check with him again) 3. Also check tiStatus() routine if it has anything useful in terms of trigger counts 4. After 1-3 is finished, check to see if FADC trigger counts match-up with TI counts. Otherwise we have problem? 5. Add both TI and FADC trigger match into the decoder and provide deadtime calculation
Date : 1st March 2013 (R. Michaels)
Scan of Deadtime and Asymmetry.
Using Kalyan's deadtime calculation, now embedded in my version of the code, I made a rate scan to see how the deadtime changed and what happened to the asymmetry.
Definitions F+ = rate when helicity bit is true F- = rate when helicity bit is false Favg = DAQ rate (should be average of F+ and F-) A_pred = (F+ - F-)/(F+ + F-) = predicted asymmetry A_obs = observed helicity in data DT = deadtime reported by Kalyan's algorithm DNR? = if "Y", there were "Data Not Ready" printouts by the event list. If "N" there were none. Run ... avg F ... F+ ... F- ..... A_pred .... A_obs ..... DT ..... DNR? .......... kHz ..... kHz ........... % ....... % ......... % 2056 ... 280 ... 276.2 .. 285.9 .. 1.73 .... 1.01 ..... 0 ..... N 2060 ... 239 ... 236.8 .. 246.3 .. 1.97 .... 2.35 ..... 0 ..... N 2063 ... 311 ... 306.8 .. 316.2 .. 1.51 .... 0.03 ..... 47.7 .. Y 2066 ... 330 ... 323.1 .. 332.3 .. 1.40 .... 0.01 ..... 53.3 .. Y 2068 ... 421 ... 418.3 .. 427.6 .. 1.10 .... 0 ........ 78.7 .. Y 2071 ... 218 ... 216.4 .. 226.1 .. 2.19 .... 1.22 ..... 0 ..... N 2073 ... 138 ... 135.8 .. 145.9 .. 3.58 .... 1.53 ..... 0 ..... N
Comments
The deadtime (DT) skyrockets at a critical frequency. I don't think I could get a small nonzero deadtime (e.g. 5%).
The presence of nonzero DT causes the Asymmetry to be completely diluted, by a far larger factor than you'd expect. Expect a dilution factor of 1-DT
A_obs often does not agree with A_pred. The other day (late Feb entry) this was also true, though one is sometimes greater and sometimes less than the other. Not clear why.
I am not convinced we are measuring the DT correctly. Need a second, redundant method.
