Difference between revisions of "04-20-2015"

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=Fake stop time=
 
=Fake stop time=
 +
Discriminator width was decreased from 40 ns (255 on discriminator display)  to 6.3 ns (10 on discriminator display)
  
−
Found some double pulsing out of the discriminator that was 100 ns later in time causing a second peak other than the expected one at 400 ns.
+
Discriminator threshold is set to 100 mv
 +
 
 +
The delay for the fake stop is set to 800 ns
  
−
Below is a picture of a double pulse
 
  
 
[[File:FakeStop_4-20-2015_A.png| 200 px]]
 
[[File:FakeStop_4-20-2015_A.png| 200 px]]
  
−
Below is a picture of the typical 400 ns fake stop pulse that should appear as a second hit in the Multihit TDC.
+
 
 +
CODA/CODAreader/ROOT_V5.30/R1DC/evio2nt -fr4516.dat > /dev/null
 +
 
 +
 
 +
R1DC->Draw("(evt.TDC1190[1][6]-evt.TDC1190[2][6])/10>>(4096,-4096,4096)");
 +
 
 +
Run 4536
 +
 
 +
 
 +
Below is a picture of the typical 800 ns fake stop pulse that should appear as a second hit in the Multihit TDC.
 +
 
 +
 
 +
[[File:r4536FakeStop_C.png| 200 px]]
 +
 
 +
 
 +
 
 +
 
 +
Now decrease delay of fake stop to 400 ns
 +
 
  
  
 
[[File:FakeStop_4-20-2015_B.png| 200 px]]
 
[[File:FakeStop_4-20-2015_B.png| 200 px]]
 +
 +
[[File:r4537FakeStop_C.png| 200 px]]
 +
 +
=Terminator test=
 +
 +
==Change discriminator threshold with terminators in==
 +
 +
PMT detector #4 HV at -1000 Volts
 +
 +
 +
 +
Run 4537 had a discriminator threshold set to 100 mv and the terminators were in.  I see very few multiple hits in Detector 4
 +
 +
[[File:r4537_PMT4_TDCmultihits.png | 200 px]]
 +
 +
 +
Now change threshold to 30 mv
 +
 +
Run 4538
 +
 +
I see two pulses from the discriminator but only one from the delayed fake stop (perhaps our delay module Ortec 416A is ignoring the second pulse)
 +
 +
[[File:r4538_Scope.png | 200 px]]
 +
 +
[[File:r4538_PMT4_TDCmultihits.png | 200 px]]
 +
 +
 +
Now change threshold to 16 mv
 +
 +
Run 4539
 +
 +
[[File:r4539_PMT4_TDCmultihits.png | 200 px]]
 +
 +
 +
 +
==Change discriminator threshold with terminators out==
 +
 +
PMT detector #4 HV at -1000 Volts
 +
 +
Run 4540 had a discriminator threshold set to 16 mv and the terminators were out. 
 +
 +
[[File:r4540_PMT4_TDCmultihits.png | 200 px]]
 +
 +
Run 4541 had a discriminator threshold set to 30 mv and the terminators were out. 
 +
 +
[[File:r4541_PMT4_TDCmultihits.png | 200 px]]
 +
 +
 +
Run 4541 had a discriminator threshold set to 60 mv and the terminators were out. 
 +
 +
[[File:r4543_PMT4_TDCmultihits.png | 200 px]]
 +
 +
Run 4542 had a discriminator threshold set to 100 mv and the terminators were out. 
 +
 +
[[File:r4542_PMT4_TDCmultihits.png | 200 px]]
 +
 +
 +
clearly one can turn up the threshold high enough to get rid of the ring with the terminators out.
 +
 +
But are the terminators reducing the ring effect by attenuating or by reducing reflections (the ring) in the output pulse.
 +
 +
Using the scope I did not observe an attenuation of the PMT output by more than a factor of two when inserting 50 ohm terminators on both ends of the cable.
 +
 +
 +
I still see the ring when the discriminator is set to 60 mV and the terminators are out.  If I insert the terminators I do not see the ring at a discriminator threshold of 16 mV.
 +
 +
Unless the 50 Ohm terminators are attenuating the signal by more than a factor of 2, the attenuators appear to also be removing some of the "ring" output of the PMT base.
 +
 +
  
  
 
[[2nCor_44#Run_Plan]]
 
[[2nCor_44#Run_Plan]]

Latest revision as of 18:43, 20 April 2015

Started testing detector 4 again.

Fake stop time

Discriminator width was decreased from 40 ns (255 on discriminator display) to 6.3 ns (10 on discriminator display)

Discriminator threshold is set to 100 mv

The delay for the fake stop is set to 800 ns


FakeStop 4-20-2015 A.png


CODA/CODAreader/ROOT_V5.30/R1DC/evio2nt -fr4516.dat > /dev/null


R1DC->Draw("(evt.TDC1190[1][6]-evt.TDC1190[2][6])/10>>(4096,-4096,4096)");

Run 4536


Below is a picture of the typical 800 ns fake stop pulse that should appear as a second hit in the Multihit TDC.


R4536FakeStop C.png



Now decrease delay of fake stop to 400 ns


FakeStop 4-20-2015 B.png

R4537FakeStop C.png

Terminator test

Change discriminator threshold with terminators in

PMT detector #4 HV at -1000 Volts


Run 4537 had a discriminator threshold set to 100 mv and the terminators were in. I see very few multiple hits in Detector 4

R4537 PMT4 TDCmultihits.png


Now change threshold to 30 mv

Run 4538

I see two pulses from the discriminator but only one from the delayed fake stop (perhaps our delay module Ortec 416A is ignoring the second pulse)

R4538 Scope.png

R4538 PMT4 TDCmultihits.png


Now change threshold to 16 mv

Run 4539

R4539 PMT4 TDCmultihits.png


Change discriminator threshold with terminators out

PMT detector #4 HV at -1000 Volts

Run 4540 had a discriminator threshold set to 16 mv and the terminators were out.

R4540 PMT4 TDCmultihits.png

Run 4541 had a discriminator threshold set to 30 mv and the terminators were out.

R4541 PMT4 TDCmultihits.png


Run 4541 had a discriminator threshold set to 60 mv and the terminators were out.

R4543 PMT4 TDCmultihits.png

Run 4542 had a discriminator threshold set to 100 mv and the terminators were out.

R4542 PMT4 TDCmultihits.png


clearly one can turn up the threshold high enough to get rid of the ring with the terminators out.

But are the terminators reducing the ring effect by attenuating or by reducing reflections (the ring) in the output pulse.

Using the scope I did not observe an attenuation of the PMT output by more than a factor of two when inserting 50 ohm terminators on both ends of the cable.


I still see the ring when the discriminator is set to 60 mV and the terminators are out. If I insert the terminators I do not see the ring at a discriminator threshold of 16 mV.

Unless the 50 Ohm terminators are attenuating the signal by more than a factor of 2, the attenuators appear to also be removing some of the "ring" output of the PMT base.



2nCor_44#Run_Plan

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