1. 1 Development of a new generation of micropattern gaseous detectors for high energy physics, astrophysics and medical applications A.Di Mauro, 1 P. Fonte 2, P. Martinengo 1, E.,Nappi 3, R. Oliveira 1, V. Peskov 1, P. Pietropaolo 4, P. Picchi 5 1 CERN, Geneva, Switzerland 2 LIP/ISEK Coimbra, Portugal 3 INFN Bari, Italy 4I NFN Padova, Italy 5 INFN Frascati, Italy

2. 2 In the last two decades very fast developments happened in the filed of gaseous detectors of photons and particles. Traditional gases detectors: wire–type and parallel plate-type (RPCs) -which are widely used in high energy and astrophysics experiments have now serious competitors: Micropattern Gaseous Detectors (MPGDs) Due to the importance of these developments an RD 51collaboration was formed a CERN The aim of this collaboration is to coordinate affords from various groups working on MPGDs

3. 3 1) Strip type Example: Microstrip gas counters (MSGCs) A. Oed, NIM A263, 1988, 351 Examples: CAT/WELL, Gas Electron multiplier (GEM) A.Del Guerra et al., NIM A257, 1987,609 M. Lemonnier et al., Patent FR 2727525, 1994 F. Sauli, NIM,A386,1997,531 3) Parallel-plate type Example: Micromesh gas chamber (MICROMEGAS) Y. Giomataris et al., NIM A376, 1996, 29 4) Hole type Glass substrate There are four main designs of micropattern gaseous detectors: CAT/WELL GEM Anodes ~100μm 2) Microdot S.Biagi et al., NIMA392, 1997, 131

4. 4 The main advantage of MPGDs is that they are manufactured by means of microelectronics technology, which offers high granularity and consequently an excellent position resolution. Due to their advantages the MPGDs cangue more and more applications. In high energy physics they were already successfully used in: Hera-B, COMPASS TOTEM, LHC B etc. Their use in CMS, ATLAS ALICE and in some other experiments under consideration

5. 5 However, the fine structure of their electrodes and the small gap between them make MPGDs electrically “weak.” In fact, their maximum achievable gain is usually not very high, compared to traditional detectors, and without special precautions they can be easily destroyed by sparks, which may occur during their operation (which is not the case of traditional detectors: wire and parallel-plate type)

6. 6 See, for example G. Charles et al., NIM A648, 2011, 174.. and sparks, unfortunately, in experiments are practically unavoidable

7. 7 There are several methods of protecting micropattern detectors and FEE from destruction: segmentation of electrodes on smaller parts, protective diodes… These methods were successfully implemented in the case of GEM and in some MICROMEGAS designs Alternative approach, which becomes more and more frequent inside the RD51collaboration, is the use resistive electrodes.

8. 8 The first micropattern detector with resistive electrodes was GEM, and later this approach was also applied to other detectors: MICROMEGAS and CAT (all had unsegmented electrodes) Res. GEM Oliveir at al., NIM A576, 2007, 362 Res. CAT A.Di Mauro et al., IEEE Nucl. Sci Conf Rec, 6, 2006,3852 Res. mesh R.Oliveira etal., IEEE Nucl. Sci 57,2010, 3744 Res. MICROMEGAS R.Oliveira etal., IEEE Nucl. Sci 57,2010, 3744

9. 9 They were hybrids layout between GEM and RPC The principle of operation of RPC: discharge energy is quenched because of the resistivity of electrodes -V Resistive electrodes

10. 10 This study triggered a sequence of similar developments, which are nowadays pursued not only by our group, but by several other groups in the frame work of CERN RD51 collaboration See recent reports at the 2 nd Intern. Conf. on Micro Pattern Gaseous Detectors, August 2011, Kobe, Japan (to be published in JINST) (http://ppwww.phys.sci.kobeu.ac.jp/%7Eupic/mpgd2011/abstracts.pdf) A couple of examples of main developments will be given below:

11. 11 See for example: a photo of RETGEM from: R. Akimoto et al, presentation at 1 st MPGDs conference in Crete,2009 or Several groups (mostly Japanese) are now successfully developing various designs of RETGEMs Spark protected RETGEMs and Res. CAT: Res. CAT developed by Breskin group L. Arazi et al., JINST 7 C05011, 2012

12. 12 Advantages: 1. More suitable for large-area detectors 2. Better fit requirements for position measurements 3.Flexible in design implementation 4. In some designs offer better rate characteristics Tested configurations: 1) Resistive strips without intermediate layer between the strips and the metal readout strip ( see for example V. Peskov et al., NIM, A610 2009 169) 2) Res. electrode strips with a thin FR-4 glue intermediate layer (R. Oliveura et al., NIM,A576,2007,362) 3) Resistive strips with a thick FR-intermediate layer ( T. Alexopoulos et al NIM A 640, 2011, 110) Today we would like to present a new approach: resistive electrodes segmented on strips with a network of metallic readout strips located under the resistive grid 1) 2) 3)

13. 13 As was shown in the previous slide, first we applied this new technology to resistive GEMs (~2009). In the last couple of years (2010-2012) we extended this approach to all other main micropattern designs. Below are examples of only three of such detectors. We choose them because they are oriented towards applications in which some members of our team are currently involved: 1.RICH, 2.Dual-phase noble liquid TPCs, 3. X/gamma ray imaging deices

14. 14 1. Resistive microstrip detector

15. 15 PCB with 5μm thick Cu layer on the top and two layers of readout strips (oriented perpendicularly) on the bottom Milled grooved 100 μm deep and 0.6 μm wide, pitch 1mm. The grooves were then filled with resistive paste (ELECTRA Polymers) By a photolithographic technology Cu 20 μm wide strips were created between the grooves 0.6mm 1mm 20μm a) b) c) d) 0.5mm e) Finally the entire detector was glued on a supporting FR-4 plate 0.2mm 0.1mm 0.5-1mm Cathode res. strips Anode strips

16. 16 Connections to X pick up strips Connections to Y pick up strips Anode strips Cathode resistive strips

17. 17 Gas gains Pos. resol. measurements Rate characteristics ~200μm

18. 18 2. Resistive microdot-microhole detector

19. 19 a) Multilayer PCB with Cu layers on the top and bottom and with the inner layer with readout strips Upper Cu layer etching The remaining grooves were then filled with resistive paste (ELECTRA Polymers) Removal of the Cu v v v v Filling with Coverlay with “dot” opening b) c) d) e) v v Resistive anode dots Resistive cathode strips Readout strips 1mm0.1mm Holes 0.1mm Manufacturing steps:

20. 20 Magnified photograph Schematic drawing and a principle of operation of res. microdot detector (resembling MHC, see: J. Maia et al., IEEE Trans. Nucl. Sci 49, 2002, 875 )

21. 21 Gas gain vs. the voltage of R- Microdot measured in Ne and Ne+1.5%CH 4 with alpha particles (filled triangles and squares) and with 55 Fe (empty triangles and squares). Gain (triangles) dependence on voltage applied to R-Microdotmeasured in Ar (blue symbols) and Ar+1.6%CH4 (red symbols)and in Ar+9%CO2. Filled triangles and squares –measurements performed with alpha particles, open symbols - 55Fe. Interesting feature: at high gains operates in self-quenched streamer mode In all gases tested the maximum gains achieved with the R-Microdot detectors were 3-10 time higher than with R-MSGCs

22. 22 3. Resistive microgap-microstrip detector

23. 23 a) Multilayer PCB with a Cu layer on the top and one layer of readout strips on the bottom, 0.5 pitch Upper Cu layer etching The grooves were then filled with resistive paste (ELECTRA Polymers) Removal of the Cu v If necessary, filling with Coverlay (an option) b) c) d) e) M-M- RPC manufacturing steps: Resistive strips Readout strips 0.5 mm0.2mm v 0.035mm 0.1mm

24. 24 A B C Contact pad Contact pad Resistive strips Total resistivity of the zone B 500MΩ (adjustable) Resistivity of zones A and C 500MΩ (adjustable) Surface resistivity 100kΩ/□ (can be adjusted to exper. needs) Top view:

25. 25 This plate is in fact a reproduction of the resistive MICROMEGAS anode board (see the following talks) The idea is to assemble from these plates a parallel- plate detector (M-M- RPC), so that the cathode metallic mesh is not used

26. 26 Orthogonal resistive strips Inner signal strips Artistic view of the M-M RPC PCB sheet From these plates RPC were assembled with gaps ether 0.5 or 0.18mm

27. 27 An option with pillars (similar to MICROMEGAS) Pillars Res. strips

28. 28 A fundamental difference between “classical “ RPC and M-M- RPC Film resistor M-M-RPC offers high2D position resolutions (with orthogonal strip or various stereo strip arrangements to avoid ambiguity) and have potential for good timing properties Usual RPC M-M-RPC “Signal” electrodes Current Orthogonal resistive strips Current 500MΩ Inner signal strips

29. 29 Gain estimation in an RPC geometry: CsI layer UV X-rays Fe anode 0.5mm 0.1-0.2mm Photoelectron tracks (Due to the time constrains the CsI coating was done by a spray technique) A=expαx x

30. 30 M-M-RPC with spacers in corners The highest gains were obtained with resistive micropattern detectors Typical rate response (combined current and pulsed measurements)

31. 31 Now shortly about the applications in which our team is involved

32. 32 1. RICH (recent results)

33. 33 The VHMPID should be able to identify, on a track-by- track basis, protons enabling to study the leading particles composition in jets (correlated with the π0 and /or γ energies deposited in the electromagnetic calorimeter). There is a proposal (LoI) to upgrade ALICE RICH detector in order to extend the particle identification for hadrons up to 30GeV/c. It is called VHMPID. (HMPID)

34. 34 The suggested detector will consist of a gaseous radiator (for example, CF 4 orC 4 F 10 ) and a planar gaseous photodetector The key element of the VHMPID is a planar photodetector C 4 F 10 For details see a talk at this conference: DI MAURO, Antonello (CERN) R&D for the high momentum particle identification upgrade detector for ALICE at LHC

35. 35 Our previous prototype (very successful!) Triple res. GEM with metallic strips P. Martinengo, V. Peskov, et al., NIM, 639,2011,126 V. Peskov et all., arXiv:1107.4314arXiv:1107.4314 (2011) 1-7 RE HMPID readout electronics Cherenkov light was detected (For more details see A.Di Mauro talk) MIP Cherenkov ring

36. 36 RETGEM coated with CsI R-MSGC or R-MICRODOT Main advantages: Two times less elements, Less voltages, Very high gain (an important safety factor) Concerns: Aging (to be studied) New prototype (recently tested) 1 10 100 FWHM (%) R-MSGC R-MSGC+Cs-IRETGEM Pilot studies: (while LoI was written and circulated)

37. 37 Inject EF and sealed when the signal was close to maximum Tests with EF vapors Ist day2d day QE enhancement (after correction) is about 50%; work is still going on) Preliminary

38. 38 2.A new double-phase detector (work in progress)

39. 39 The concept of usual double phase noble liquid dark matter detectors Two parallel meshes where the secondary scintillation light is produced Primary scintillation light From the ratio of primary/secondary lights one can conclude about the nature of the interaction

40. 40 Several groups are trying to develop designs with reduced number of PMs (there was work from Novosibirsk group, we made sealed gaseous PMs, Breskin group is working on sealed gaseous PMs..) In E. Aprile XENON: a 1-ton Liquid Xenon Experiment for Dark MatterXENON: a 1-ton Liquid Xenon Experiment for Dark Matter http://xenon.astro.columbia.edu/presentations.html It was suggested to use CsI photocathode immersed inside the noble liquid Large amount of PMs in the case of the large-volume detector significantly increase its cost (Another option for the LXe TPC, which is currently under the study in our group, is to use LXe doped with low ionization potential substances (TMPD and cetera). One large low cost “PM”

41. 41 This suggestion was based on our early studies which we made together with Aprile’s team

42. 42 However, this concept was never materialized in any detector… To verify feasibility of this approach we made some preliminary tests

43. 43 CsI photocathode grids PM 10 cm Alpha source Ar gas LAr Experimental setup (ICARUS cryostat combined with a purification system) Ar gas, room temper., 1 atm LAr+ gas phase V. Peskov, P. Pietropaolo, P. Pchhi, H. Schindler ICARUS group Performance of dual phase XeTPC with CsI photocathode and PMTs readout for the scintillation light PMTs readout for the scintillation light Aprile, E.; Giboni, K.L.; Kamat, S.; Majewski, P.; Ni, K.; Singh, B.Ketal Dielectric Liquids, 2005. ICDL 2005. 2005 IEEE International Conference Publication Year: 2005, 345 - 348 Dielectric Liquids, 2005. ICDL 2005. 2005 IEEE International Conference

44. 44 Event Charge hv R-Microdot CsI photocathode Shielding RETGEMs (with HV gating capability) LXe Photodetectors?? (if microdot gain is insufficient) AnodesResistive cathodes Multiplication region The possible way to suppress the feedback In hybrid R-MSGC, the amplification region will be geometrically shielded from the CsI photocathode (or from the doped LXe) and accordingly the feedback will be reduced

45. 45 Results obtained with alphas and 55 Fe Measurements in Ar at room and cryogenic temperatures (preliminary) “streamer” mode Stability with time No feedback pulses were observed 105-115K 300K

46. 46 3. Micrpstrip-microgap for imaging applications (Work just started)

47. 47 Scanners: 30% efficiency for 400 keV at shallow angle b) Gamma ray a)X-ray (edge on) T. Francke et al., NIM A508, 2003, 83 T. Francke et al., NIM A471, 2001, 85 I. Dorion et al., IEEE Nucl, Sci., 34. 1987,442 Contacts with industry are established; they already evaluate our prototypes Pos. resol. 50μm in digital form, rate 10 5 Hz/strip Tantalum convertor

48. 48 Another goal was/is to combine high pos. resolution with high time resolution. First step in this direction was already successfully done by Fonte et al (see Proc. of Science, RPC 2012, 081). Besides the particle detections another application is TOF- PET on which Fonte group is actively working Bidimentional position resolution 70μm in with combination 80 ps timing

49. 49 Above only three examples of applications in which members of our team are currently working were given In reality much more work is going on restive strip micropattern detectors. A few more examples:

50. 50 1) Res. TGEM with metallic strips for environmental and safety applications (CERN-KTT project) (this project is in a final stage, ready for commercialization) Prototype of a flame detector Sensitivity 100 higher any commercial detector Prototype of Rn detector Sensitivity is equal to commercial Rn detectors Operating in on line mode, but ~50 times cheaper

51. 51 2) A.Ochi et al., Resistive strips microdot detector Presented 10 th RD51 collaboration meeting, October 2012 3) D. Attie et al., A piggyback resistive Micromegas Presented at the RD51 meeting, December 2012

52. 52 Resistive MICROMEGAS is planned to be also used in some other applications, for example environmental (muon tomography of underground water reservoir), 4) However, the most remarkable example is MICROMEGAS for ATLAS upgrade P. Salin, Presenation at the RD51 meeting, december2012 …see also today presentations

53. 53 Conclusions: 1)A new generation of micropattern gaseous detectors with resistive-strip electrodes combined with metallic 2D readout strips was developed. They offer excellent position resolution and are spark protected 2) We try to implement these detectors in several applications: RICH, Noble liquid TPC, Scanner/medical, environmental/security 3) A similar approach was in parallel developed by MAMMA collaboration and resistive strip MICROMEGAS will be employed in the ATLAS small wheel. More developments are in progress 4) Of course, these detectors have limited rate capabilities and this can be an issue in high rate environment, however some improvements in their rate characteristics still are possible In progress In a final stage

54. 54 Back up slides

55. 55

56. 56 Optimization of the RPC electrodes resistivity for high rate applications P. Fonte et al., NIM A413,1999,154

57. 57 ATLAS R-MICROMEGAS characteristics T. Alexopoulos et al., NIM A640, 2011,110 10 3 Hz/mm 2 (2-3)10 4

58. 58 The concept of this detector is resembling the so called MHCP detector , however the important differences were that it was manufactured from a printed circuit plate 0.4 mm and had resistive cathode strips making it spark-protective.  J.M. Maia et al., NIM A504,2003, 364 Anode strips Cathode strips Holes

59. 59 Images with strip RETGEM

60. 60 Rate response (MSGC): The gas gain variations with counting rate. Measurements were performed in Ne+10%CO 2 at gas gain of 510 3 (signal drop at counting rate >10 3 Hz/mm 2 is due to the PCB board surface charging up, but not due to the voltage drop on resistive strips) 10 3

61. 61 Physics behind this phenomena

62. 62 Results of measurements induced signals profile from the readout strip oriented along (green curve with crosses) and perpendicular to the anode strips of R-MSGCs (rhombuses, triangles and squares). Rhombus- the collimator is aligned along the strip #0. Triangles -the collimator was moved on 200μm towards the strip#1. Squares- the collimator was aligned between the strip#0 and # 1. Measurements were performed in Ar+10%CO 2 at a gas gain of 5x10 3. Preliminary results of measuremenst the induced signals on the strips: More precisely the position resolution will be determined during the oncoming beam test Profiles of signals induced on pick up strips (0.3mm wide collimator) Correlation between the measured and actual position of the collimator Expected Measured

63. 63 Gas gains Pos. resol. measurements Rate characteristics

64. 64 The main detectors on which RD-51 is focused All of them can be done resistive, hence spark protected Micromegas GEMTGEM Micrpixel MHSC Ingrid