1. Large THGEM sampling elements for DHCAL status report
S. Bressler, L. Arazi, A. Broisman, A. Breskin, L. Moleri, M. Pitt, C. D. R. Azevedo, J. F. C. A. Veloso, F. D. Amaro, J. M. F. dos Santos
Weizmann Institute of Science, Israel
Aveiro University, Portugal
Coimbra University, Portugal
Calice Week September 2014, CIEMAT-Madrid

2. Thick Gas Electron Multiplier (THGEM)
The THGEM is an expanded version of the GEM, made from a G10/FR4 substrate:
G10 board is covered with copper on both sides
Small holes are mechanically drilled.
Cheap and easy to produce over large areas (standard PCB technology)
Self sustainable (no need to be attached/glued to a frame)
Very Robust, resistant to damage (discharges, mechanical stress)
High gains can be achieved in several gas mixtures
Typical values:
thickness= 0.4/0.8 mm
a= 1 mm
d= 0.5 mm
h= 0.1/ no rim
Calice Week September 2014, CIEMAT-Madrid

3. THGEM Structures: Double and Single sided
300×300 mm2 individual elements
Two type of structures were made:
Double and Single sided with and without rim
Segmented (6 strips 300 x ~48 mm2)
Gap ~ 2 mm
300×300 mm2 individual elements
Small defects may occur
A single defect in one of the holes can ruin an entire board
Calice Week September 2014, CIEMAT-Madrid

4. Calice Week 15-17 September 2014, CIEMAT-Madrid
300300 mm2 elements
2 Chambers were constructed and are operating at the Weizmann Institute (Israel) and Aveiro University (Portugal)
Working in parallel at both labs.
Test several configurations and find the most stable for test beam
Calice Week September 2014, CIEMAT-Madrid

5. THGEM Structures: Double and Single sided
Standard (Double Sided)
Copper clad on both sides of the THGEM
Usual configuration with a few mm drift and Induction gap
charge multiplication in the induction gap is possible.
Single Sided – WELL type
Copper covered only in one of the sides
No Induction gap: electrode is attached to readout
Multiplication at the bottom of the well.
Large gains achieved due to electric field confinement
No induction gap; thinner detector.
Calice Week September 2014, CIEMAT-Madrid

6. Single Sided – WELL type configurations
Resistive layer quenches the energy of occasional discharges
Resistive layer + Cu electrodes
Cu electrodes (thin wires) allow the rapid clearance of the charge, preventing its spreading across the resistive layer
Less inductive signals in the neighboring pads
Lower multiplicity
300×300 mm2
elements
Resistive Plate
Small prototypes
Calice Week September 2014, CIEMAT-Madrid

7. Single Sided – WELL type Resistive Plate
Plastic Material with high bulk resistivity
mm thick
Connected to readout using conductive ink / glue
Small prototypes have been tested: detector becomes more stable; with less discharges at higher gains.
A. Rubin “First studies with the Resistive-Plate WELL gaseous multiplier” 2013 JINST 8 P11004
Calice Week September 2014, CIEMAT-Madrid

8. Single Sided – WELL type Resistive Plate
Recent tests with thinner plates have been very successful in reproducing the results obtained with thicker plates.
Larger area resistive plates are now being produced (10x10 and 30x30 cm2)
New gluing/painting techniques are required and are being tested.
Calice Week September 2014, CIEMAT-Madrid

9. Calice Week 15-17 September 2014, CIEMAT-Madrid
300300 mm2 elements
SRS/APV READOUT
Fe55 Spectra
Calice Week September 2014, CIEMAT-Madrid

10. Detection of low rate MIP with cosmic rays
300300 mm2 elements
Detection of low rate MIP with cosmic rays
Calice Week September 2014, CIEMAT-Madrid

11. Trigger from top THGEM electrode
MICROROC
Trigger from top THGEM electrode
Efficiency 97%
Multiplicity 1.16
Study the detector response to MIPs (not x-rays) using cosmic muons
Study discharge probability
With an injector
Assemble large prototype
Design is in progress
Test beam
Fe55
Calice Week September 2014, CIEMAT-Madrid

12. 300300 mm2 elements Long term measurement – WELL configuration
Single WELL THGEM setup. Several days monitoring and recording:
gain
atmospheric pressure
room temperature
HV trips
Ne/CH4 (95/5)
Calice Week September 2014, CIEMAT-Madrid

13. Calice Week 15-17 September 2014, CIEMAT-Madrid
300300 mm2 elements Long term measurement – WELL configuration
Calice Week September 2014, CIEMAT-Madrid

14. Calice Week 15-17 September 2014, CIEMAT-Madrid
300300 mm2 elements Long term measurement – WELL configuration
After a few days of stable operation gas flow was increased (10 mL/h to 20 mL/h). Gain increased but a power failure in the building prevented further measurements.
After Power was restored, power up the detector at same voltage but higher gas flow 50 mL/h.
Initial gain decrease is not explained by P&T variations. Compatible with charging up.
Calice Week September 2014, CIEMAT-Madrid

15. Calice Week 15-17 September 2014, CIEMAT-Madrid
300300 mm2 elements Long term measurement – WELL configuration
After several days at 50 mL/h the gas flow was decreased to 20 mL/h. Immediate decrease in charge gain (gas purity?).
After stabilization the source was removed for several hours. Discharge rate is independent on the source. Once irradiated again the charge gain dropped due to charging up. Discharge probability continuously dropping.
Calice Week September 2014, CIEMAT-Madrid

16. Calice Week 15-17 September 2014, CIEMAT-Madrid
300300 mm2 elements Long term measurement – WELL configuration
Voltage at the WELL was increased. As expected gain increased and so did the discharge probability
Calice Week September 2014, CIEMAT-Madrid

17. Calice Week 15-17 September 2014, CIEMAT-Madrid
300300 mm2 elements Long term measurement – WELL configuration
Gain change upon controlled change of operation conditions
The gain is constant for constant conditions
Discharge rate proportional to the gain.
Overall the 300x300 mm2 THGEM is now stable for more than one month (since 25/07 and still running ), even surviving a major power failure.
Calice Week September 2014, CIEMAT-Madrid

18. Improvements: Uniform Gas Flow inside the chamber
Snake like structure inside the chamber:
gas flows uniformly trough the chamber
provides support for THGEM
Calice Week September 2014, CIEMAT-Madrid

19. Calice Week 15-17 September 2014, CIEMAT-Madrid
Future developments
Smaller is better?
Combining several small high quality elements makes it easier to produce a larger picture.
Calice Week September 2014, CIEMAT-Madrid

20. Calice Week 15-17 September 2014, CIEMAT-Madrid
Future developments
Same principle can be applied to THGEM: large area coverage can be achieved by stacking smaller elements/tiles.
Mechanical support will be given by the snake like structure inside the chamber.
Assembly Stage:
quality control on smaller elements
Choose only good quality elements
Defective elements can be easily discarded
Production is easier (post treatment is currently done to the larger electrodes)
Trieste Group developed brushing technique to improve the quality
Very easy to assemble
Final result will be cheaper/better quality
It will be developed with Industry (Weizmann is advising)
Calice Week September 2014, CIEMAT-Madrid

21. Calice Week 15-17 September 2014, CIEMAT-Madrid
Future developments
Technology transfer to industry ……
Calice Week September 2014, CIEMAT-Madrid

22. Calice Week 15-17 September 2014, CIEMAT-Madrid
Future developments
Technology transfer to industry ……
…… and back (?)
Calice Week September 2014, CIEMAT-Madrid

23. Future developments Technology transfer to industry …… …… and back (?)
Israeli company (Lingacom Ltd‏) is commissioning a large ( 20/30 m2 ) THGEM detector for cargo screening applications.
Electrodes are already produced, prototype phase will take place during the next couple of months.
strip readout
high efficiency
large area coverage
First time a MPGD detector is developed in the industry
The Weizman Institute and Lingacom Ltd‏ have applied for a common grant:
possible synergies: production and testing facilities from Lingacom Ltd will be available to the scientific community.
Calice Week September 2014, CIEMAT-Madrid

24. Large THGEM sampling elements for DHCAL
Two prototypes operating at Weizmann and Aveiro
Cosmic rays detection
Microroc and SRS readout
300x300 mm2 THGEM continuously operating for almost 2 months
Gain is stable for controlled conditions
Next Test beam (Dec. 2014)
We plan to test two 300x300 mm2 chambers and 100x100 mm2 RPWELL
Connection with industry:
tile detector, with several elements stacked side by side.
Snake like structure inside the detector will ensure a proper gas flow in the chamber
Sharing the production and testing facilities developed in Industry will make the THGEM more affordable and available to the scientific community.
The progress made so far show that we are on the good track.
THGEM potential is huge and exciting times lay ahead of us.
Calice Week September 2014, CIEMAT-Madrid