1. Activity for GEM in KEK Detector Technology Project MPGD group M. Sekimoto, T. Murakami, M. Tanaka, S. Tanaka, N. Ujiie, and K. Nakayoshi (KEK) T. Uchida (University of Tokyo ) K. Kadomatsu and A. Sugiyama (Saga University ) E. Nakano and S. Nakagawa (Osaka City University) Shoji Uno (KEK) KEK Detector Technology Project March 23 rd, 2007

2. Contents Basic study of GEM –Effective gas gain –Charge distribution –Thicker GEM : 100  m t –Recovering for damaged GEM Applications –Neutron counter

3. Test Chamber ～ 2 mm 10 mm GEM1 GEM2 GEM3 ～ 2 mm 55 Fe (5.9 keV X-ray) 2200pF DRIFT TRANSFER 1 TRANSFER 2 INDUCTION PCB GAS Ar-CH 4 (90/10) (P-10) Ar-CO 2 (70/30) 1mm □15mm×15mm 36 ＝ 6×6 PCB

4. Pulse shape Signal from Readout pad Signal from GEM foil 80ns 150mV

5. Readout System Belle-CDC Pre-amp. Belle-CDC Pre-amp. ×7 RPN220×7 30 m 5 m RPN220Discr. T0 timing Fanin-Fanout Gate Gen. Coincidence 4ms delay Width 40ms CCNET GATE BUSY Gate Gen. GATE 120μs delay VETO Gate Gen. CAMAC ADC 2249A×9 GATE Scaler CAMAC Trg. Gate Gated trg. CLK Gen. （１ MH ｚ） 1s1s For beam test Timing Information Reset

6. Measurement of Effective Gas Gain

7. Effective gas gain vs ΔV GEM Ar-CO 2 P10

8. Gas gain vs various parameters P10 Ar-CO 2 P10 Ar-CO 2 EDED EIEI ETET EIEI

9. ΔV GEM =360V E T =1.6kV/cm E I =3.6kV/cm ΔV GEM =360V E T =1.6kV/cm E I =3.6kV/cm Electric Field Dependence in Drift Region 55 Fe (5.9 keV X-ray) EDED Ｄｒｉｆｔ region E D =3000V/cm E I =1000V/cm E D =500V/cm E I =1000V/cm Low Field in Drift Region High Field in Drift Region Δ Ｖ ＧＥＭ ＝３２０Ｖ Collection efficiency deceases in higher electric field, since some electric field lines reach on the surface of GEM. Normalized Effective Gain Electric Field in Drift Region (kV/cm)

10. ΔV GEM =350V E D =1.3kV/cm E T =2.1kV/cm ΔV GEM =350V E D =1.3kV/cm E T =2.1kV/cm Electric Field Dependence in Induction Region E D =3000V/cm E I =1000V/cm Low Field in Induction region Δ Ｖ ＧＥＭ ＝３２０Ｖ E D =3000V/cm E I =4000V/cm Δ Ｖ ＧＥＭ ＝３２０Ｖ High Field in Induction Region 55 Fe (5.9 keV X-ray) EIEI Induction Region Extraction efficiency increases in higher electric field, since most of field lines do not go back on the surface of GEM. Additional gas amplification starts for rather high electric field in the induction region. Electric Field in Induction Region (kV/cm) Normalized Effective Gain

11. ΔV GEM =350V E D =1.3kV/cm E I =5.95kV/cm ΔV GEM =350V E D =1.3kV/cm E I =5.95kV/cm Ar-CO 2 Electric Field Dependence in Transfer Region 55 Fe (5.9 keV X-ray) ETET ETET Transfer Region Eff(E T ) {Eff(E D )×Eff(E I )} ２ Transfer region plays as a extraction of upper GEM and also as a collection of lower GEM. Therefore, the electric field dependence can be represented based on the drift field dependence and the induction field dependence. Normalized Effective Gain Electric Field in Transfer Region (kV/cm)

12. Measurement of Charge Distribution on the readout board

13. Readout strip –Strip pitch ： 200  m –width ： 100  m –gap ： 100  m –length : 50mm –Number of strips = 64 Zoom up view 100  m 200  m

14. One Event Display Channel ADC 0 63 ADC 0 63 Channel

15. ΔV GEM ＝ 370V Ed= 0.5 kV/cm Et=2.59kV/cm Ei=5.18 kV/cm ΔV GEM ＝ 370V Ed= 0.5 kV/cm Et=2.59kV/cm Ei=5.18 kV/cm  = 181.2± 0.3  m Ar-CO 2 (70/30) Charge distribution -1 0 1 Triple GEM g D, g T1, g T2, g I =1.5, 1, 1, 1mm dX （ each strip － COG) ｍｍ  = 359.7±0.4  m P10 ΔV GEM ＝ 330V Ed= 0.5 kV/cm Et=1.65 kV/cm Ei= 3.3 kV/cm ΔV GEM ＝ 330V Ed= 0.5 kV/cm Et=1.65 kV/cm Ei= 3.3 kV/cm ADC SUMADC -1 0 1

16. Measurement results  for a gauss fit in a charge distribution Unit : mm GEM structureTotal gapP10Ar-CO 2 Tripleg D,g T1,g T2,g I = 4, 2, 2, 170.465 g D,g T1,g T2,g I = 1.5, 2, 2, 15.750.4170.207 g D,g T1,g T2,g I = 1.5, 1, 1, 24.750.3900.203 g D,g T1,g T2,g I = 1.5, 1, 1, 13.750.3430.181 Doubleg D,g T1,g I = 1.5, 2, 13.750.3400.173 g D,g T1,g I = 1.5, 1, 12.750.157 Total gap : g D /2 + (g T1 + g T2 ) + g I

17. P10 Ar-CO 2 Data MagBoltz  2 (mm 2 )

18. MagBoltz vs. Measurement Data P10 Ar-CO 2 Data MagBoltz Electric field in transfer region (kV/cm)

19. 100  m GEM

20. 100  m-GEM1 Drift Plate 2 ｍｍ E D =0.75kv/cm E I =7kv/cm Single GEM-100  m Test Chamber 2 ｍｍ Drift Aria→E D Induction Aria →E I GAS Ar-CO 2 (70/30) 2200pF Read out 55 Fe (5.9 keV X-ray) PCB 1mm □15mm×15mm 36 ＝ 6×6 PCB

21. Single GEM Δ Ｖ ＧＥＭ Ed=1.5kv/cm Ei=6.0kv/cm

22. ΔVgem=660V Ei=6.0kv/cm E D dependence 90  V.S. 70 

23. Recovering for damaged GEM

24. Recovering We try to recover the damaged GEM. –Soft etching Chemical etching –Plasma etching Dead GEM Normal Damaged There are damaged spots. Zoom

25. As a result of recovering Soft etching –Etching time is shorter than usual chemical etching. Plasma etching –An etching effect is stronger than chemical etching. –Damaged GEMs, which can not be recovered by soft etching, are reprocessed by Plasma etching. Recovery of GEM is basically possible. About 90% of Damaged GEMs can be recovered by Soft or Plasma etching.

26. Applications -Neutron Counter-

27. Detection of Thermal Neutron GEM1-B GEM2-B GEM3-Cu Ar-CO 2 gas 2 mm 1 mm No need of expensive ３ He Gas –No need of pressure vessel Free readout pattern High resolution –Position and Time Insensitive against  ray Capability against high counting rate Readout board ｎ  8 foils for real test chamber

28. Signal Shape and Pulse Height Distribution Threshold for Neutron measurement Threshold for  -ray measurement Neutron (2.2 Å ) 200mV/div １ 00nsec ADC counts

29. Imaging Data using Radioactive Source 83×83mm 2 1.6mm pitch XY strip

30. Detection Efficiency 1mm φ Pin Hole 3 He Counter –72413counts/100sec Boron-GEM Foil –17355counts/100sec Detection Efficiency –24.0% with 8 GEM foils Boron-10 : 0.6  m t  1.2  m t per one GEM foil

31. Position Resolution 1D Liner scale Strip pitch : 1.6mm 2D Log scale with 0.5mm  pin hole

32. Diffraction Pattern for Single Crystal K 2 SeO 4 22 ~40° ~90° λ ＝ 2.2 Å Neutron Beam Sample

33. Single Crystal NaCl 2  = 38°(1,1,1) 2  = 50°(0,0,2) 2  = 76°(0,2,2)2  = 90°(1,1,3) λ ＝ 2.2 Å

34. Small Angle Scattering at NOP Sample Silica Particle (SiO 2 )Hypresica Background Direct Beam HPS 500nm HPS 200nm

35. Summary In order to understand features of GEM chamber, we have measured effective gas gain and charge distribution for various parameters. We started to produce new type of GEM to get higher effective gas gain with a single GEM configuration. Recovering for damaged GEM succeed with large probability. Neutron counter with Boron coated on the GEM was constructed and tested. Results show it is promising as neutron detectors at neutron facility in J-PARC.

36. Backup

37. GEM foils made by Japanese company New method (plasma etching) was tried in a few years ago. –Not chemical etching (CERN) –M. Inuzuka, et al., NIM A 525(2004) 529-534 Plasma + Laser –To reduce sparks It is convenient for us to make new types of GEM foils. –Fine pitch/small hole : 50  m/30  m –Thicker/thinner : 100(150)  m/ 25  m –Other activities in Japan Tokyo Univ. RIKEN etc Today, I will report on results with standard GEM foils. –50  m thick –140  m pitch 70  m diameter 10cm Scienergy Co., Ltd. (Japanese company) http://www.scienergy.jp/

38. Signal Shape and Timing Signal Shape T0 Signal within gate Gate 4msec-44msec 200nsec

39. Time dependent Diffraction Pattern for Diamond Powder at KENS 3 He Counter Chamber Sample Diamond Powder Cd slit Beam 22 Time slice without Cd slit

40. Mono-crystal K 2 SeO 4 Cd Plates （ 5mm x 5mm ） Drift plane 1mm Al plate Cd plate Neutron Beam Sample 14mm GEM1 Same high voltage was supplied on Al plate as that on plate of drift plane. Sample

41. Simlation L=26m 2  =65deg. Mono-crystal K 2 SeO 4 Laue spots Flight time (Wave length) msec Counts/0.1msec 83mm by Kamiyama

42. 最後に 高エネルギー加速器研究機構素粒子原子核研究所 測定器開発室 MPGD グループ –KEK IPNS 宇野彰二 (shoji.uno@kek.jp) 、 関本美智子、 村上武、 田中真伸、 氏家宣彦、 仲吉一男 – 佐賀大理工 門松宏治、 杉山晃 – 大阪市大理 中川真介、 中野英一 – 東京理科大理工 杉山史憲 – 東京大理 内田智久 GEM –CERN 製 http://ts-dep-dem.web.cern.ch/ts-dep-dem/products/gem/ – 日本製 サイエナジー株式会社 http://www.scienergy.jp/ 海外での GEM 型中性子検出器 –http://www.physi.uni-heidelberg.de/physi/cascade/index.html

43. Naive estimation using MagBoltz without GEM structure 55 Fe (5.9 keV X-ray) ｇIｇI ｇDｇD ｇ T2 ｇ T1 E T1 ： σ d (E=E T1 ) E I ： σ d (E=E I ) E D ： σ ｄ (E=E D ) E T2 ： σ d (E=E T2 ) σ ｄ 2 ＝ σ ｄ （ E=E D ) 2 × ｇ D /2 + σ ｄ （ E=E T1 ) 2 × ｇ T1 + σ ｄ （ E=E T2 ) 2 × ｇ T2 + σ ｄ （ E=E I ) 2 × ｇ I σ ｄ （ E=E T2 ) 2 × ｇ T2 + σ ｄ （ E=E I ) 2 × ｇ I σ ｄ 2 ＝ σ ｄ （ E=E D ) 2 × ｇ D /2 + σ ｄ （ E=E T1 ) 2 × ｇ T1 + σ ｄ （ E=E T2 ) 2 × ｇ T2 + σ ｄ （ E=E I ) 2 × ｇ I σ ｄ （ E=E T2 ) 2 × ｇ T2 + σ ｄ （ E=E I ) 2 × ｇ I Electric field : MagBoltz

44. MagBoltz data P10 Ar-CO 2

45. Ed=1.5kv/cm ΔVgem=660V E I dependence 90Φ,V,S 70Φ

46. Source Test Test chamber Water Moderator 1MeV 10meV Energy (eV) 252 Cf ( =2.14MeV)

47. Thickness of Boron-10 Thickness of B-10 per GEM foil (  m) Number of counts

48. Detection efficiency ｖｓ Number of Foils Thickness of B-10 : 1.2  m/foil(single side:0.6  m) Number of B-10 GEM foils Number of counts

49. 2D Readout Board X,Y Strip Strip pitch 1.6mm Number of strips 52×52 Active area 83mm×83mm X Y （ Rear ）

50. Image data with Neutron Beam 27 mm Ｓｌｉｔ Cd slit with ”K” 27 mm =17 x 1.6mm Slit 83mm Beam Profile

51. PNSE ： 0.670±0.014 Frequency ： 17.060±0.006μsec PNSE ： 0.650±0.007 Frequency ： 16.700±0.004μsec Ｂ－ＧＥＭチェンバー Li - Sincilator ＋ ＰＭＴ (R3292) Black Points Read points Time resolution at MINE Time (20nsec/bin) Normalized Hit Counts

52. Distortion of detection position No distortion Moving the chamber by 16mm steps in X-Y both directions

53. Uniformity for detection efficiency 1.000.981.031.020.99 0.970.990.981.020.98 0.991.00 0.98 0.971.011.001.010.98 1.001.051.031.020.98 Normalized in center