1 / 17

Saturation Effects on the SVX Chip

Saturation Effects on the SVX Chip. Peter Hasiakos D0 test stand-May/Jun 2004. Purpose/motivation. Saturation  loss of signal on subsequent pulse Potential issue for high occupancy channels in accelerator Goals: to verify occurrence of this phenomenon, and to quantify it.

dawn
Download Presentation

Saturation Effects on the SVX Chip

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Saturation Effects on the SVX Chip Peter Hasiakos D0 test stand-May/Jun 2004

  2. Purpose/motivation • Saturation loss of signal on subsequent pulse • Potential issue for high occupancy channels in accelerator • Goals: to verify occurrence of this phenomenon, and to quantify it

  3. At the Test Stand… • 2 pulse generators trigger LED • Main pulse only sends 1 photon, so the early pulse makes the significant contribution to saturation • LED= light source (emulates photoelectric effect from collisions) • Photons VLPC SVX chip on AFE 1 board ADC counts • Sequencer, 1553 and VRB coordinate data • PC used to record, analyze (Poisson distributions)

  4. Details on SVX Saturation Event (Photon detected) Event clock 1 crossing=396 ns Eventually, the Amount of charge (signal) levels off Q1 Q0 SVX Saturation

  5. Timing issues * Data must be taken after this point (end of chip reset window)

  6. Task #1:Observe how signal decays as previous pulse increases Pedestal (@ RAMPTRIM=350), mean=Po=41.8 main generator activated (early pulse off): mean=56.4

  7. Task #1, Cont’d Main pulse held fixed, early pulse @ 8V, 20 nsec width: mean= 54.7 8V, 30 nsec width: mean=51.3

  8. Task #1, cont’d 8 V, 40 nsec width: mean=44.3… a drastic decrease  plots confirm hypothesis that signal decreases with increasing saturation

  9. Task #1: Primary results -this plot shows reduction in ADC mean (of the late pulse) as early pulse width increases Relative signal= s/s0-1, where s is the mean ADC signal of main pulse and s0 corresponds to no early pulse. We will call the quantity s/s0 the loss fraction, L. -Next step: determine how much light is in the early pulse

  10. Task #2: analyze amount of light in early pulse Pedestal (ramptrim @ 150--more light) Early pulse= 4 V, width=10 nsec

  11. Task #2, cont’d @ 8 V; width=10 ns @ 8 V; width=30 ns

  12. Determing number of pe’s for a given pulse of light We use the relationships N= /g N=(/)^2 * Calculated from Poisson distribution where =mean signal, N=number of pe’s, and g=gain, and =standard deviation

  13. Task #2: Raw results N=(/)^2 Dependence on mean ADC signal necessity to investigate if saturation is STILL occurring in single pulse run

  14. Problem: saturation also occurs with single, early pulse gain is calculated from  and  at varying amounts of light. Without saturation loss, gain=constant=g0 *We see that the gain drops ~10% at a width of 25 nsec (about 15 pe’s).

  15. Correcting the  problem -correct   valid calculations of N -because early pulse is the significant cause of saturation, we can use the same loss fraction, L, from Task 1 -Task 1 also indicated that before 10 pe’s, the gain stays at the value g0 and is unaffected by saturation ’= /L and N’= ’/ g0 Final result: corrected number of photons for each early pulse of light

  16. Final Results • In sum, we have used task 1 to find the magnitude of saturation effect, and task 2 to rescale in terms of #pe • After an arrival of ~10 pe’s, there is a 10% loss in signal • After an arrival of ~20 pe’s, there is a 30% loss in signal

  17. Conclusions • New test stand is working • SVX chip only gives correct results in proper time window • Results indicate that noticeable saturation effects begin occurring after a previous signal of ~10-15 pe’s

More Related