Recognizing and Documenting an A0 Abort Kicker Pre-fire
CDF's SVX is very vulnerable to A0 abort kicker pre-fires, so we need to take special care in understanding these events. The first step is to identify an event that is potentially a kicker pre-fire, and the next step is to document the conditions and results. There are 4 tell tale signs that a Kicker pre-fire has occurred:
1) Losses through A-sector, and possibly F4 if there are Pbars in the machine, that rise up in one update of the BLMs. If there are 36 bunches in the machine, there will almost always be a quench at B0 (BA and BB) and probably some other Tevatron cells between A0 and B1.
2) There will be three anomalous features on the traces of abort kicker scopes. There will be an abnormal waveform at the start of the kicker rise. Also, the marker will not be in the correct place, and there will be evidence on the BPM signal that the kicker has swept through the bunch train.
3) The A4 scintillator will trigger with the marker and beam in an abnormal time.
4) One of the A0 kickers will have a Pre-fire/Fail to fire bit bad on its digital status.
If there is an abort pre-fire, there will be no evidence that anything else is wrong before the sudden beam loss. The circular buffer on B0 triplet QPM will show the quench as the first event. The abort loop going down will be within one line cycle of this quench. The orbits will not have changed from snapshot frame 511 to the smallest number where beam is still in the machine (individual BPMs may show a difference, but there will be nothing that resembles a real, physical orbit distortion).
If any one of above 4 things happen, we should treat the event like a kicker pre-fire as far as documentation goes. All of the following things should be placed in the Tevatron Logbook.
T40 snapshot frame 0
T39 snapshot frame 20
T44 plot from frame 511 to 0 (scale 0 to 200 r/sec) for T:LMB1SD, T:LMA4QU, T:LEXCHU
A0 scope trace for Proton and Pbar kickers (from page T106).
Was there a CDF SVX abort? Was there a D0 SVX abort?
A list of every cell that quenched (don't forget to archive as well).
Proton and Pbar intensities at the time.
The voltage that the A0 kickers were running at. The settings can be determined by the table values C:PAK1[15] if the Tevatron was at flattop energy. Slot 15 should be checked for all 10 kicker power supplies.
Any status bit that is not normal on all 10 abort kickers (nominal status is shown below).
The A4 scintillator trace (found on the web at http://tevtek01/).
Position of the A11 collimator (T:A01UH, T:A01DH, T:A01UV, T:A01DV)
Collect CDF SVX data
Collect D0 SVX data - Follow the same instructions as for the CDF SVX data except page E35 is used.
Below is a set of nominal pictures for some of the signals we will want to record.
Nominal A4 Scintillator trace. This picture is during a clean abort.
Nominal Proton abort kicker trace from page T106.
Nominal Pbar abort kicker trace from page T106. Note that the waveform trace is noisier than the Proton kicker waveform.
This is nominal kicker status. This should be checked for all 10 kickers. Document any bit for any kicker that does not show this status.
Below are traces showing a prefire.
This shows a prefire on the Proton kicker. Note the shoulder at the beginning of the kicker waveform. Also, the marker is not in the same place as on the nominal trace, and you can see the BPM signal disturbed above the abnormal portion of the kicker waveform.
This is the scope trace for a Pbar kicker pre-fire. Again notice the shoulder at the start of the kicker waveform. Also, the marker is not in the same place as on the nominal trace.
This is an example of the CDF SVX plot made from the pre-fire Nov 22, 2002.
After documenting all required data in the Tevatron log, please send e-mail to Jerry Annala to notify him that this data has been collected.
Link to a History of previous pre fires.