1. High Pressure Electroluminescent TPC studies @ CIEMAT/IFAE
Roberto Santorelli
On behalf of
I. Gil-Botella, E. Calvo, S. Jimenez Cabre, C. Palomares, A. Verdugo (CIEMAT-MADRID)
O. Ballester, A. Garica-Soto, J. Illa, A. Lostao-Viñolas, T.Lux, F. Sanchez (IFAE-Barcelona)
Advances in Neutrino Technology 2013, May 9-12 Lake Tahoe

2. R.Santorelli - ANT 2013, May 12 Lake Tahoe
General concept
Electroluminescence (EL) detectors have a wide range of applications
Several gas TPCs (both Ar and Xe researches) have been developed in a joint R&D activity by CIEMAT (Madrid) and IFAE (Barcelona)
(Ar and Xe scintillation studies…)
Main research line: medium size (110x200 mm) High-Pressure Gas Xe TPC with 25 APDs
Combined energy resolution and tracking studies
R.Santorelli - ANT 2013, May 12 Lake Tahoe

3. R.Santorelli - ANT 2013, May 12 Lake Tahoe
Example I: simple setup for QE studies (GXe)
241Am
R.Santorelli - ANT 2013, May 12 Lake Tahoe

4. R.Santorelli - ANT 2013, May 12 Lake Tahoe
EL signal
R.Santorelli - ANT 2013, May 12 Lake Tahoe

5. Example II: small EL-TPC for spectroscopy studies (GAr)
UV1
VIS1
VIS2
VUV1
UV2 UV IR
VIS
VUV
R.Santorelli - ANT 2013, May 12 Lake Tahoe

6. R.Santorelli - ANT 2013, May 12 Lake Tahoe
EPL, 91 (2010) 62002
GAr
LAr
R.Santorelli - ANT 2013, May 12 Lake Tahoe

7. R.Santorelli - ANT 2013, May 12 Lake Tahoe
EL signals
Va=1.5 kV , Vk=0
Va=2.5 kV , Vk=0
Va=3.0 kV , Vk=0
Va=3.0 kV , Vk=3.0 kV
R.Santorelli - ANT 2013, May 12 Lake Tahoe

8. R.Santorelli - ANT 2013, May 12 Lake Tahoe
Main R&D activity
Excellent performances of the gas TPCs in respect of energy resolution have been proved
Limited knowledge about their tracking capabilities on larger scale
Study of an APD readout for EL detectors
Goal: Good energy resolution and investigation of possible tracking capabilities at the same time
R.Santorelli - ANT 2013, May 12 Lake Tahoe

9. R.Santorelli - ANT 2013, May 12 Lake Tahoe
Experimental Setup
HP TPC (30 cm long, 30 diameter)
HV power supplies (20 and 35 kV)
Preamp, ADC, APD power supply
Cosmic ray trigger
Xenon recovery system
Getter
PMT power supply
Vacuum pump system
R.Santorelli - ANT 2013, May 12 Lake Tahoe

10. R.Santorelli - ANT 2013, May 12 Lake Tahoe
“CIFA” chamber
7 mm
110 mm
200 mm
R.Santorelli - ANT 2013, May 12 Lake Tahoe

11. R.Santorelli - ANT 2013, May 12 Lake Tahoe

12. R.Santorelli - ANT 2013, May 12 Lake Tahoe
Readout array
Array of 5x5 S8664-SPL APDs from Hamamatsu (5x5 mm2) powered independently
Pitch 15 mm
2 PMTs for t0 measurements
3 custom made preamp/shaper boards
V1740 CAEN ADC for digitization
DAQ based on Midas
R.Santorelli - ANT 2013, May 12 Lake Tahoe

13. R.Santorelli - ANT 2013, May 12 Lake Tahoe
Previous Studies
Small HP chamber with 5 APDs
All APDs at the same voltage
Allowed to develop readout electronics
Excellent energy resolution achieved
xenon
(8.2 ± 0.1)% FWHM
J.Phys.Conf.Ser.309, pp
R.Santorelli - ANT 2013, May 12 Lake Tahoe

14. R.Santorelli - ANT 2013, May 12 Lake Tahoe
Vertex Distribution
Am-241 X-ray source (installed at the center of the cathode)
Pressure: 2 bar
Drift field: 200 V/cm/bar
EL field: 4.5 kV/cm/bar
Likelihood fit using light profile model for energy and position reconstruction
R.Santorelli - ANT 2013, May 12 Lake Tahoe

15. First Results: Energy Resolution
keV
keV
keV
59.5 keV
A.U.
Maximum signal in one of the 9 APDs in the center
Signal summed over 24 APDs
No correction yet for drift/diffusion, attachment…etc
 Room for improvement
R.Santorelli - ANT 2013, May 12 Lake Tahoe

16. First Results: Energy Resolution
keV
A.U.
Maximum signal in the central APD
R.Santorelli - ANT 2013, May 12 Lake Tahoe

17. R.Santorelli - ANT 2013, May 12 Lake Tahoe
INTERCALIBRATION
Problems:
APDs gain very sensitive to the temperature and the voltage.
The set up makes challenging to calibrate the APDs one by one.
Solution:
Intercalibration based on the position simmetry
Key point  Use symmetry in light deposition around the maximum:
It quantify the difference of energy between APDi and APDj when the maximum signal is in the one between them.
59.5 keV X-ray peak of 241Am used.
R.Santorelli - ANT 2013, May 12 Lake Tahoe

18. R.Santorelli - ANT 2013, May 12 Lake Tahoe
For events where the energy deposition in the middle APD is maximum, Aij should be 0 (assuming a symmetric EL shower).
Due to different APD gains this Aij≠0.
Correct these Ei and Ej using a calibration factor to avoid this problem.
where
After calibration:
This αij should tend to one and A’ij to zero after calibration is done.
R.Santorelli - ANT 2013, May 12 Lake Tahoe

19. R.Santorelli - ANT 2013, May 12 Lake Tahoe
Assymetry before calibration:
Assymetry after calibration:
A’ij tends to zero.
Behavior of some of the alpha coeficients during calibration steps:
Clear tendency
of α to 1
R.Santorelli - ANT 2013, May 12 Lake Tahoe

20. INTERCALIBRATION: Preliminary results
242Am spectrum (when the energy deposition is maximum in one of the 9 central APDs):
No calibration:
Calibration (1st iteration):
Calibration (2nd iteration):
RE=13.12%
RE=9.35%
RE=9.04%
The intercalibration process improves the resolution as we expected.
R.Santorelli - ANT 2013, May 12 Lake Tahoe

21. First Results: Parameter Scan
R.Santorelli - ANT 2013, May 12 Lake Tahoe

22. First Results: Tracking
Cosmic rays trigger
Very primitive cluster finder
R.Santorelli - ANT 2013, May 12 Lake Tahoe

23. R.Santorelli - ANT 2013, May 12 Lake Tahoe
First Results: T0
Sum of all waveforms over all events
Possible to vary drift distance
t between external trigger and signal arrival allows to estimate drift velocity
vd= ~0.17 cm/us (theory: 0.1 cm/us)
Probably N2 impurity
Clear peak in both PMTs at t≈0
PMT UP
PMT DOWN
Peak in the sum of all APDs
 Can we see this on event by event basis???
Sum APDs
t [s]
R.Santorelli - ANT 2013, May 12 Lake Tahoe

24. R.Santorelli - ANT 2013, May 12 Lake Tahoe
Summary and Outlook
Different EL-TPCs built in collaboration between CIEMAT and IFAE
EL-TPC with 25 APDs for high pressure XE-gas studies in operation
Energy resolution 60 keV (room for improvements)
Preliminary track reconstruction proved
Study for t0 detection on going
R.Santorelli - ANT 2013, May 12 Lake Tahoe

25. CIEMAT LAr lab 450 liters liquid nitrogen dewar.
2 cryostats of 70 liters each, high vacuum graded, for liquid argon.
Turbomolecular pump for high vacuum.

26. R.Santorelli - ANT 2013, May 12 Lake Tahoe
Vis2
Vis1
UV2
UV1
Pe/25
R.Santorelli - ANT 2013, May 12 Lake Tahoe