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 Trigger hit Trigger input Blue - Positive logic Orange - NIM logic Red - PMT signal Panel hit

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 ~20ns ~40ns