Transcript ppt
TKR Noise Flares observed in TKR #11 and #8 Mutsumi Sugizaki, Hiro Tajima, and TKR team 10/21/2005 Inst Ana Meeting TKR Noise Flares 1 Noise flares observed in TKR #11 • Test of noise occupancy monitor for TKR #11 in the acceptance test at SLAC X11 X16 ~ 2 hours Y10 10/21/2005 Inst Ana Meeting The strip occupancy occasionally exceeds10-4 in the layer average during some short terms (~10 min). These noise flares do not always appear. It is rather rare. The noise flares appeared only in these three layers on TKR #11. The flares were not synchronized layerto-layer. TKR Noise Flares 2 Strip profile of noise flares in TKR#11 X11 X16 Single strip flare. It can be disabled by data and trigger masks. >> Solved. Y10 Multi-strip noise flare? It looks very strange. Noisy strips are gathering on the layer edge. 10/21/2005 Inst Ana Meeting TKR Noise Flares 3 Noise flares observed in TKR #8 • The next noise flare was found during noise occupancy monitor for TKR #8 in the TKR acceptance test at SLAC Time profile Strip profile TKR #8 Y0 Ladder edge Questions How can these multi-strip noise flare occur? Does it have a serious impact on the LAT performance? Flare strips seem to be confined by ladder boundary. Is it true? Are they also bunched by front-end chip (64 channels)? Why did it appear only in TKR #11 and #8? 10/21/2005 Inst Ana Meeting TKR Noise Flares 4 Strip multiplicity of noise flare TKR#11 X11 TKR#11 Y10 GTRC event buffer overflow TKR #8 Y0 GTRC event buffer overflow Reference: normal layer GTRC event buffer overflow In the layers with noise flares, large-multiplicity events are increased. The gathering of the noisy strips on the layer edge can be explained by the GTRC event-buffer overflow. 10/21/2005 Inst Ana Meeting TKR Noise Flares 5 Event selection with multiplicity TKR #8 Y0 Time profile Strip profile Ladder edge TOT distribution 0 Selection condition: (20<=Multiplicity<64) The noise flare can be mostly explained by these large-multiplicity events. TOTs of the noise flare events are longer than a few ms. 10 20 30 40 50us 10/21/2005 Inst Ana Meeting TKR Noise Flares 6 Layer (trigger) occupancy of noise flares TKR#11 X11 TKR #8 Y0 10/21/2005 Inst Ana Meeting TKR#11 Y0 Layer Occupancy is < 0.1, which corresponds to the single-layer trigger rate < 50 kHz. (0.1/2ms=50 kHz in the worst case). This still meets trigger specification at GTRC OR_STRECH=31. The relation between strip and layer occupancies in noise flare can be explained by the large hit-strip multiplicity. TKR Noise Flares 7 Other info. we have known about the noise flare • According to the TKR group in Italy, similar noise flares were observed in Towers A, #1, #4, #7, #8, #11, too, during the TVAC test (L. Latronico NCR/FM/INFN/PI-592). They were considered to be due to pickup of external noise because it seemed to be synchronized with the time of the temperature change. • The bias-voltage dependence of the noise flares is not clear, so far. If it is caused by discharge on the detector, it should have some bias-voltage dependence. • I personally think that we cannot abandon the scenario of pickup of external noise because we could not find any noise flare from the data taken on last Sunday. 10/21/2005 Inst Ana Meeting TKR Noise Flares 8 Summary • Current understanding about the noise flare – Impact on the LAT performance is small. • Frequency is very low. • Single layer trigger rate still meets the requirement even during the intense noise flare. • The effect on the TKR 6-in-a-row trigger is negligible. – We did not know the root cause. • Analysis tools to monitor flare activities during normal data taking are under development. We plan to involve them in the regular data processing. • TKR #8 is supposed to go to a beam-test tower. We are thinking more tests using TKR #8 to reveal the root cause. 10/21/2005 Inst Ana Meeting TKR Noise Flares 9