1. Mariagrazia, Givi, Chiara, Alessia
Paddy tests May 2017
Mariagrazia, Givi, Chiara, Alessia

2. repeat measurements to….
understand if gain measured with Fe55 is different when using High/Low rate sources
understand if gain changes increasing Xrays rate
Our main doubts/corrections were relied to rate and amplitude measurements (perturbed by pile-up and baseline shift due to high rate signals 1ms wide)  preamplifier with short integration time: A-PIC
30 ns -> signal duration 300 ns -> 3 MHz

3. old fashioned … data taking scheme
resistors in series to HVmesh don’t change the HV (<< then previous tests , february 2017, when it was 100MOhm)
resistor in series with Keithley doesn’t affect the measurement

4. Pads connections
pads chained through the small panasonic-to-lemo boards
on those boards we had to remove any resistor and to add ground, when not present, to read properly the current
on pad-group 6 found one pad at ground (3.5 Ohm with multimeter) we cut the connection (Givi)
on pad-group 4 there was a similar problem but this time the problem was on the connector  solved (Givi)
pads connected to Keithley through a 100kOhm resistor (Eraldo)

5. A-PIC
fast preamplifier with shaping time switchable between 30 ns and 300 ns
input C switchable between 4nF and 0.4 nF (to be compared with detector C=…?, signal with 0.4nF was too small so we used 4nF…)
complementary outputs (+ and -, MCA and RATE)
could also be placed in series with the HV-Mesh
unfortunately, FAST (30ns)  more NOISE
noise was indipendent on input C and change of configuration (point 4)
reduced a lot connecting grounds of the A-PIC IN and OUT connectors (thanks to Eraldo!)
noise makes impossible the use on an amplifier after the A-PIC…..

6. Fe55 signal from A-PIC, HVmesh=550V,noise…, duration….

7. MCA peaks taken with Fe55 Low intensity source and with High intensity source MOVE (something like 25%..)
and this time we know that there are no pile-up nor baseline shift ……

9. with Fe55 High intensity source, you can observe a shift vs time of the spectra:

10. and a decrease vs time of the current indipendent from the preampl input C:
4nF
4nF
0.4nF

11. and a decrease vs time of the current:

12. Fe55 Low/High intensity source
so we took some new gain measurements (for HV_mesh between 500 and 550 V) with the following time sequence:
Low Fe55 - 3minutes without – High Fe minutes without
at the end of this scan, we went again from 550 to 500 only with High Fe55, without removing it (to check if we get the same..)
subtracting the rate without source……

13. Fe55 Low/High intensity source

14. Fe55 Low/High intensity source

15. Fe55 Low/High intensity source

16. Fe55 Low/High intensity source

17. 15 maggio

18. CONF, Preliminary
check errors

19. CONF, Preliminary

20. CONF, Preliminary

21. Fe55 Low/High intensity CONF, Preliminary
togliere i fit che sono ad una sola gaussiana….
gain reduction seen from the Fe55 spectra

22. Fe55 High intensity ? CONF, Preliminary
inserire plot degli spettri nel tempo e fare i fit ?
with Fe55 High intensity source, taking a sequence of Fe55 spectra every 2s, you can observe a shift vs time of the main peak (Auger):

23. Fe55 High intensity CONF, Preliminary
same behaviour for the detector current….. possible explanation: dielectric charge up, space charge effect ….
and a decrease vs time of the current:

24. check errors

25. Fe55 High intensity
correlation between detector current and Fe55 peak position during ‘charge up’
fare i fit per il centroide
punti più grandi

26. Fe55 vs time variazione picco nel tempo from 9pm to 9am
procurarsi il plot temperatura…

27. X Rays
3 mm
10 mm
1 mm

28. X_Rays Cdet estimate…. plate on Paddy with 10mm diameter hole
2 Cu foils
discriminator threshold = 125/60 mV
integration time = 30 ns
HVmesh= 530, 520, 510, 500 Hvdrift=Hvmesh+200V
Hvmesh = 530 repeated recentering the hole….
3mm diameter collimator
0 Cu foils
discriminator threshold = 60 mV
integration time = 30 ns
HV= 530, 510 V
1mm diameter collimator
0 Cu foils
discriminator threshold = 60 mV
integration time = 30 ns
HV= 530, 510 V
Cdet estimate….

29. 1 cm hole, HV=530/730
Rate without XRays
Rate with XRays
Rate difference

30. 1 cm hole, HV=530/730 V
ZOOM
Rate extrapolated from linear fit to first points
Rate with XRays – Rate without XRays

31. X Rays
ZOOM
I_Keithley vs I_Xray

32. X Rays
I_Keithley/I_XRay vs Ixray

33. X Rays Gain vs I_Xray, Rate with Xrays - Rate without
Gain vs I_Xray, extrapolated Rate

34. X Rays
gain drop = 27%
few % could be due to voltage drop on the pad resistors…
metterci i punti del Fe55 Low/High e ingrandimento parte iniziale

35. X Rays CONF, Preliminary gain drop = 27%
few % could be due to voltage drop on the pad resistors…
metterci i punti del Fe55 Low/High e ingrandimento parte iniziale

36. 3mm hole, HV=530/730
Rate with XRays
Rate difference
Rate without XRays

37. 3mm hole, HV=530/730 V
Rate extrapolated from linear fit to first points
ZOOM
Rate with XRays – Rate without XRays

38. X Rays
I_Keithley vs I_Xray

39. X Rays
I_Keithley/I_XRay vs Ixray

40. X Rays Gain vs I_Xray, Rate with Xrays - Rate without
Gain vs I_Xray, extrapolated Rate

41. X Rays blue Gain vs Rate, 10 mm, HV=530/730 V
red Gain vs Rate, 3 mm, HV=530/730 V

42. X Rays ? CONF, Preliminary stessa scala verticale plot precedente
inserire ingrandimento parte iniziale

46. 10mm, re-centered

48. 10mm, re-centered …… 11% more current, anche nel rate?