1. Upgrade of the scintillator testing station in Prague
Testing station upgrade – vacuum, electronics, magnetic shielding
Magnetic aspects of the measurement
Electronics optimization
Observed spectra – 207Bi, 137Cs, spectrometer electron beam
V. Vorobel, SuperNEMO meeting, Aussois

2. V. Vorobel, SuperNEMO meeting, Aussois
Vacuum system upgrade
Vacuum probe installed.
Spectrometer sealed – vacuum improved from 300 Pa to 7 Pa.
We have to change a hoose for further improvement.
Efect of sealing on spectra is significant.
V. Vorobel, SuperNEMO meeting, Aussois

3. V. Vorobel, SuperNEMO meeting, Aussois
Electronics upgrade
PC controlled disriminator CAEN installed in VME – simplification of electronics, well defined and stable threshold, no possible interference between crates
Independent HV sources for different PMTs – to equilibrate differences in gains. We are waiting for delivery of VME PC controlled HV modules.
Cables fixation to prevent their braking on PCB.
Waiting for new PC controled HV modules and repaired VME doesn‘t prevent measurement.
V. Vorobel, SuperNEMO meeting, Aussois

4. Magnetic shielding upgrade
Four m-metal cylinders internal f133mm,length 305mm, thickness 1mm for PMT shielding instead of the steel cylinders which were used up to now.
Plan to make a m-metal box (thickness 1mm) to cover the spectrometer completly.
V. Vorobel, SuperNEMO meeting, Aussois

5. Magnetic shielding measurement
Magnetic sensor placed instead of PMT in measurement possition #1.
B-field measured in 3 directions in 3 shielding configurations (no shield, steel, m-metal) for currents in the coil corresponding to the electron beam energies keV, saturation.
V. Vorobel, SuperNEMO meeting, Aussois

6. Peak position and magnetic history
Our procedure to set a certain electron beam energy:
First increase the current in the coil to reach a magnetic saturation of the youk
Then decrease the current to the value corresponding to the desired energy.
Does the electron beam energy depend on the previously set energy due to the magnetic hysteresis?
1) If we keep the rule – first go up to magnetic saturation then go down to the desired energy
2) If we keep the rule – don‘t keep 1) if the desired energy < the original energy
We don‘t observe a systematic > 1%
Measured with steel shielding cylinder. 1%
down
0.6%
down
0.3%
down
0.3%
down
0.2%
down
Sat.
1600
1300
1000
700
300
V. Vorobel, SuperNEMO meeting, Aussois
Magnetic history notes

7. Peak position and width vs. measurement position number
Does the peak position depend on the location (measurement position) of the assembly in the Black-Box due to magnetic field variations?
Measured in the position #1, #2, #3, #4 and then again in #1.
1 again
1 again
1 again
V. Vorobel, SuperNEMO meeting, Aussois

8. Electronics settings optimization
The optimized parameters:
HV applied to the “main” PMT for the tested scintillator
HV for the DE detector PMTs – we are using 2 PMTs
Trigger signal length
DE PMTs threshold
V. Vorobel, SuperNEMO meeting, Aussois

9. Main PMT HV optimization
HV > 1400 V causes signal amplitude exceeding digitizer range.
We continue to use 1300 V.
Higher HV could be tried with use of an attenuator.
V. Vorobel, SuperNEMO meeting, Aussois

10. Trigger signal lenght scan
We continue to use 20 ns.
V. Vorobel, SuperNEMO meeting, Aussois

11. DE-detector HV and thresholds optimization
What is the best criterion?
Peak/pedestal ratio
Resolution
Resolution error
V. Vorobel, SuperNEMO meeting, Aussois

12. Measurement conditions
Threshold scans were performed for 3 different DE HV under such conditions:
DE HV 1050 V
E=1600 keV
Vacuum 44 Pa
DE HV 1100 V
E=1000 keV
Vacuum 6.5 Pa
DE HV 1200 V
E=1000 keV
Vacuum 7.0 Pa
Peak/pedestal ratio – DE threshold scan
V. Vorobel, SuperNEMO meeting, Aussois

13. Resolution – DE threshold scan
Resolution error – DE threshold scan
V. Vorobel, SuperNEMO meeting, Aussois

14. Resolution – DE threshold scan 1D
The higher is threshold the better is the ratio peak/pedestal
But the measurement accuracy is worse wit higher threshold because of the statistics decrease.
Peak width is not changing with the threshold.
V. Vorobel, SuperNEMO meeting, Aussois

15. Peak position – DE threshold scan
Possible explanation:
Higher threshold prefers the electrons which lose more energy in DE then less energy remains for the block.
V. Vorobel, SuperNEMO meeting, Aussois

16. Typical signal conditions
DE left
scint. block
DE right
Counts per 10 s
deltaE left
deltaE right
Scint block
coincidence
1439
2096 -
324
1401
405
311
2085
416
335
V. Vorobel, SuperNEMO meeting, Aussois

17. V. Vorobel, SuperNEMO meeting, Aussois
Observed spectra
137Cs
Pedestal = 50% of entries
PMT HV 1300 V
DE HV 1200 V
DE threshold 10 mV
Vacuum 7 Pa
207Bi
Pedestal = 20-30% of entries
Electron beam 1 MeV
Pedestal = 2% of entries
V. Vorobel, SuperNEMO meeting, Aussois

18. V. Vorobel, SuperNEMO meeting, Aussois
Summary
Better achieved vacuum 7 Pa gives cleaner electron spectrum.
We hope to improve the vacuum more.
New PC controlled discriminator – stable, repeatable measurements.
New HV modules and repaired VME crate will come soon.
Not confirmed influence of magnetic field to measurements.
In addition the steel mag shielding cylinders are changed to m-metal.
Plan to cover the spectrometer to m-metal box.
The expected upgrades don’t postpone possible measurements.
The station is ready to continue scintillators characterization.
V. Vorobel, SuperNEMO meeting, Aussois

19. V. Vorobel, SuperNEMO meeting, Aussois
Backup
V. Vorobel, SuperNEMO meeting, Aussois

20. V. Vorobel, SuperNEMO meeting, Aussois
Observed spectra
137Cs
Pedestal = 50% of entries
PMT HV 1300 V
DE HV 1200 V
DE threshold 10 mV
Vacuum 7 Pa
207Bi
Pedestal = 25% of entries
Spectrometer electron beam
Pedestal = 2% of entries
V. Vorobel, SuperNEMO meeting, Aussois

21. Magnetic shielding measurement
V. Vorobel, SuperNEMO meeting, Aussois

22. V. Vorobel, SuperNEMO meeting, Aussois
Electronics view
V. Vorobel, SuperNEMO meeting, Aussois

23. V. Vorobel, SuperNEMO meeting, Aussois
Testing station setup
V. Vorobel, SuperNEMO meeting, Aussois

24. V. Vorobel, SuperNEMO meeting, Aussois
Oscilloscope snap 1
DE left
scint. block
DE right
V. Vorobel, SuperNEMO meeting, Aussois

25. V. Vorobel, SuperNEMO meeting, Aussois
Oscilloscope snap 2
DE left
scint. block
DE right
V. Vorobel, SuperNEMO meeting, Aussois

26. V. Vorobel, SuperNEMO meeting, Aussois
Oscilloscope snap 3
DE left
scint. block
DE right
V. Vorobel, SuperNEMO meeting, Aussois

27. V. Vorobel, SuperNEMO meeting, Aussois
Oscilloscope snap 4
DE left
scint. block
DE right
V. Vorobel, SuperNEMO meeting, Aussois

28. V. Vorobel, SuperNEMO meeting, Aussois
Oscilloscope snap 5
DE left
scint. block
DE right
V. Vorobel, SuperNEMO meeting, Aussois

29. V. Vorobel, SuperNEMO meeting, Aussois
Oscilloscope snap 6
DE left
scint. block
DE right
V. Vorobel, SuperNEMO meeting, Aussois

30. V. Vorobel, SuperNEMO meeting, Aussois
Oscilloscope snap 7
DE left
scint. block
DE right
V. Vorobel, SuperNEMO meeting, Aussois

31. V. Vorobel, SuperNEMO meeting, Aussois
Oscilloscope snap 8
DE left
scint. block
DE right
V. Vorobel, SuperNEMO meeting, Aussois

32. V. Vorobel, SuperNEMO meeting, Aussois
Oscilloscope snap 9
DE left
scint. block
DE right
V. Vorobel, SuperNEMO meeting, Aussois

33. V. Vorobel, SuperNEMO meeting, Aussois
Oscilloscope snap 10
DE left
scint. block
DE right
V. Vorobel, SuperNEMO meeting, Aussois

34. V. Vorobel, SuperNEMO meeting, Aussois
Oscilloscope snap 11
DE left
scint. block
DE right
V. Vorobel, SuperNEMO meeting, Aussois

35. V. Vorobel, SuperNEMO meeting, Aussois
Oscilloscope snap 12
DE left
scint. block
DE right
V. Vorobel, SuperNEMO meeting, Aussois