1. 1 Beetle xtalk measurements with test pulse at NIKHEF, B1.4 and B1.5 Aras Papadelis

2. 2 Outline Xtalk measurements with testpulse were done at NIKHEF April 5-6th, 2005. This document treats: –Experimental setup –Odd/Even xtalk –Xtalk vs channel –Xtalk vs chip –Conclusions

3. 3 0 1 2 3 4 5 6 78 9 10 11 12 13 14 15 1.5 1.4 B1.4(0-7) and B1.5(8-15) on Pile-Up hybrid at NIKHEF read out in one-port mode. 4 chips of each flavour included –The first two (0, 1 / 8, 9 ), one in the “middle” (3 / 11) and the “last one” (7 / 15) 4 even and 4 odd channels evenly distributed among the 128 Beetle channels were pulsed. Xtalk defined as fraction of pulse channels adjacent to the pulsed channel, measured at the same point in time. See setup details on last slide

4. 4 From ADC  xtalk measurement Raw ADC, header bits +128 channels Gaussian fit to projection of signal in pulsed channel Gaussian fit to baseline projection Mean value from fits is used to get a baseline corrected ADC value per channel Xtalk is expressed as a fraction of the signal in the pulsed channel.

5. 5 Odd/even dependency Odd and even channels have been observed before to show different xtalk behaviour. Also in this data, that effect can be seen. –Virtually no xtalk(~1-3‰) from Odd  next Even  previous So, the 128 Beetle channels can be thought of as 64 channel pairs that xtalk within the pair but aren’t affected by signals in neighbouring pairs.

6. 6 Xtalk vs channel number? Channels 11,15,41,56,71,86,101,116 were pulsed, 4 even and 4 odd. CERN data showed a difference in xtalk between different Beetle links (and hence different channels). So, is there a difference in xtalk between different channels when reading out in one-port mode? Xtalk from odd to previous ch and even to next channel are plotted here. Xtalk from even to previous and odd to next channel are so small that they are not plotted. (See pair behaviour, previous slide)

7. 7 Xtalk vs channel number, B1.4, Even to next channel

8. 8 Xtalk vs channel number, B1.5, even to next channel

9. 9 Xtalk vs channel number, B1.4, odd to previous channel

10. 10 Xtalk vs channel number, B1.5, odd to previous channel

11. 11 Xtalk vs channel, conclusion Xtalk difference between different channels of the same chip is ~ 1-3‰. True for both odd and even channels True for both B1.4 and B1.5

12. 12 Xtalk vs chip Is there a difference in xtalk between chips? If there is a difference, is the difference correlated to the position of the chip on the hybrid? (this was proposed as an explanation to why xtalk for B1.5 was so much higher than other flavours in CERN testbeam-like setup measurements. Since xtalk is more or less independent of channel number (see previous part) the mean xtalk per chip is compared.

13. 13 Xtalk vs chip number Beetle 1.4 Beetle 1.5

14. 14 Xtalk vs chip results Some differences, max ~1% of pulse height, between chips of same beetle flavour. No clear trends can be seen between chips, i.e. increasing/decreasing xtalk with increasing chip number.

15. 15 Comparison with old results CERN data NIKHEF Big forward xtalk in B1.5 compared with B1.4 seen in CERN data cannot be seen in NIKHEF and Heidelberg data. NIKHEF and Heidelberg agree on all except xtalk from odd to forward channel where there is a big discrepancy. Hmm.. Xtalk levels between Heidelberg and NIKHEF agree (~2%) Absolute xtalk values from CERN data cannot be compared with NIKHEF/Heidelberg due to different experimental setup and different method of measuring xtalk. Heidelberg

16. 16 Summary No big channel number difference observed No big difference between chips. Xtalk seems independent of chip position on hybrid. Odd channel xtalks with previous channel. Even channel xtalks with next channel. Almost completely “symmetric” xtalk (odd  even ~= even  odd) About 2 % xtalk for both B1.4 and B1.5 Odd channel xtalk to next channel ~ O(‰) Even channel to previous channel ~ O(‰) –Very close to “normal” noise level in the rest of the chip!

17. 17 Conclusions Good news: –We can safely choose the B1.5 from a xtalk point of view! –Xtalk in the Beetle is neither channel dependent, nor dependent on the location of the chip on the hybrid. –Comparing different chips of same flavour all give xtalk around 2%, no big differences observed. The biggest source of xtalk at LHCb will probably NOT come from the Beetle but rather from the analogue link.

18. 18 Reference: Measurement details Pile-up hybrid, fully populated with 8 1.4 and 8 1.5 Beetle chips. Default Beetle Settings (latency set to 11) 400MHz differential probe (Tektronix P6246) Tektronix TDS3034B scope 8bit scope ADC  LabView VI Sampling frequency to disk ~ 2 Hz. 2000 pulses per channel recorded.