Veto Wall Test

1. Veto Wall Test Hyupwoo Lee MINERvA/Jupiter Group Meeting Oct, 3, 2007

2. From the last presentation to now • The FEB which was a little modified by Paul was returned to me after collaboration meeting. • Have been struggled with huge signal and got some solutions. => It’s time to make a decision about it. I need your comments about it. • Have been looking for proper setup to fix the timing problem of trigger hit • Made an order for a pulse generator

3. Setup – 1 • Blue - Positive logic • Orange - NIM logic • Red - PMT signal Trigger hit Panel hit Trigger input

4. Setup – 2 (TriP-t register setting) • Basic TriP-t register setting • I followed Paul’s suggestions and Jesse’s note only but VTH and GAIN. • I set relatively very high threshold for big signal and big noise but it should be calibrated and cut more down in later time. • Recently, Paul suggest again to change IBPOPAMP(=60) and VREF(=200) but I couldn’t have tried with this value yet

5. Huge signal... • Using attenuator • Splitting signal • Attaching a AC coupling circuit on board? • Need a decision for following steps

6. Attenuator 1 • I tried to use an attenuator( ~6db : ~1/2 cut-down the signal size) again. • Seems that there still exist lost charge problem. • Impedance mismatching? ( Paul pointed out ) => I agree but I’m not sure about lost charge. • Paul says that data seems OK with attenuator and I can use attenuator.

7. Attenuator 2

8. Splitting signal • Using wire divider => split the signal and feed them into several channels • Paul agree with this method except but not using too many channels (OK with 2 or 3 channels) because of noise. => I tried with 3 channels • Still saturated with GAIN=11, so I tried to adjust gain. => The results will be shown in next 4 slides

9. Gain adjust 1

10. Gain adjust 2 • Relative ratio to GAIN=11 is 3/4

11. Gain adjust 3 • Relative ratio to GAIN=11 is 1/2

12. Gain adjust 4 • Relative ratio to GAIN=11 is 1/4 • Minimum board gain

13. Huge signal - conclusion • My preference is splitting method with GAIN=8 (lowest gain). • Is there any problem with this solution?

14. Trigger hit timing • I am using trigger hit signal as an indicator of reference position in time dimension. • Paul modified FEB a little but timing problem of trigger hit (delaying maybe caused by impedance mismatch) still remains. • I tried to fix it.

15. Using pulse generator 1 • Main idea : Make a pulse signal from 50 Ohm NIM logic signal => to confirm it can be fixable with another pulse generator • Use a function generator (from student lab) for Gate signal => I did not make veto signal for coincidence • Make trigger hit signal with the pulse generator which originally used for gate. • It might be fixable with new pulse generator.

16. Using pulse generator 2 • Using pulse generator : ch9 [trigger hit] I think it is caused by generator’s big internal delay => signal goes away from the time window for counting

17. Using 50-Ohm termination • I attached 50-Ohm resistor in parallel at the board side end of signal cable. • From this the impedance can be matched with. (The input resistor of FEB is 1M) • Almost all charges passing through the 50-Ohm resistor. So very small portion of charge comes into the board. => need to change cut condition for event selection. • Shows exact the same timing as scope.

18. Trigger hit -2 • Using 50 Ohms : ch6 [trigger hit w/ 50 Ohms], ch2 [trigger hit w/o 50 Ohms]

19. Plan for Future • Before getting new generator, I will do pedestal studies • There will be lots of things to do… Finding the proper threshold and the ratio of charge/ADC counts, taking real(?) data, and analysis the data.

20. Using trigger hit for timing test • Two kind of time information in output data file - Board clock counts for the fastest hit between the channels (It has random reference position in time dimension. One count matches with ~9.4ns) - Time difference from above time to the time of firing discriminator in ¼ clock count units for each channels (If there were no fire, it shows 0. The minimum quantized value is ~2.5ns) • There are no information about timing for trigger input in data output file! • Use trigger hit signal as an indicator of reference position in time dimension. (I have lots of unused channel!) • More over, it can give a good cut condition for event selection. (During a triggered gate, 4 events can be taken. If there were only one real event, the rooms for the others are filled with meaningless data. 3.9*9.4ns = ~40ns ~3.5ns

21. Problem with trigger hit -1 • Actual time difference( panel hit to trigger hit) is ~20ns but output data tells ~40ns (?) • I used NIM logic (need 50 ohm termination) for trigger hit signal but the input impedance of the FEB is not 50 ohm. ( So, impedance mismatching can make reflections, interferences, oscillations, and long discharging tail. ) • I need one more pulse generator in order to solve this problem. • However, I will assume that the signal patterns of trigger hit with the NIM logic are the same and I will do rough analysis for timing resolution.

22. Problem with trigger hit - 2 • During I tried to change VREF( Trip register ), I got a data set that the cross talk( of trigger hit ) fires discriminator. • The data show that cross talk seems to be an early walker than trigger hit. • The time difference from panel hit to cross talk is roughly matched with scope result => Something goes wrong with trigger hit and it shows more clear evident ~40ns ~20ns