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Hadron Blind Detector

This article discusses the development and implementation of the Hadron Blind Detector (HBD) at the PHENIX experiment, outlining its features, R&D process, and future outlook. It also highlights a realized example by R.P. Pisani et al. and references relevant studies.

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Hadron Blind Detector

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  1. Hadron Blind Detector 東京大学　小沢恭一郎

  2. Outline • Hadron Blind Detector (HBD)at PHENIX exp. • R&D at RIKEN (advertisement) • Outlook PHENIX ws@RIKEN 小沢恭一郎(東大)

  3. Hadron Blind Detector PHENIX ws@RIKEN 小沢恭一郎(東大)

  4. Realized example R.P. Pisani et. al, NIM A400(1997) 243 PHENIX ws@RIKEN 小沢恭一郎(東大)

  5. Realized example R.P. Pisani et. al, NIM A400(1997) 243 PHENIX ws@RIKEN 小沢恭一郎(東大)

  6. Realized example R.P. Pisani et. al, NIM A400(1997) 243 Total Charge [A.U.] 8 12 16 0 4 Number of Pad PHENIX ws@RIKEN 小沢恭一郎(東大)

  7. PHENIX HBD • 紫外域に感度を持つ光検出器 • 読み出しにPadを用いることで位置情報も得られる • PHENIX実験では、Window lessのCherenkov検出器として用いられる。 • 具体的には、 • GEM３層を増幅部に使用 • １層あたりの増幅率は低く安定な動作 • GEM上面にCsIを蒸着 • Radiator ガスと増幅用のガスにCF4を用いた場合、５０ｃｍのRadiatorの長さで約40個のp.e. • References • 1. NIM A523, 345, 2004 • 2. NIM A546, 466, 2005 PHENIX ws@RIKEN 小沢恭一郎(東大)

  8. CSIを用いた光電面 • 3種類の光電子収集の方法 Transmissive By Weitzman • Transmissiveを選択 • 比較的高い量子効率 • 少ないphoton feedback 一番上のGEMにCSIを蒸着して実現 ５ １０ １５ [eV] CSIの量子効率 PHENIX ws@RIKEN 小沢恭一郎(東大)

  9. CsI Au Ni Cu Kapton Cu CsIの蒸着 • CSIのGEMへの蒸着 • GEMにニッケルと金をメッキし、CsIを蒸着 • 基本的な手順： • 真空度: a few x 10-7 Torr • GEMをマスクしCsIを事前に少し飛ばす • ボートやCsI表面の不純物の除去のため • （高純度のCsIを使用しているが） • GEMを少しあたためる • 不純物や水分の除去のため • Quartz で厚さをモニター • ５％程度 • ２０００A　ないし　５０００A程度の蒸着 • ベッセル内で、密封 PHENIX ws@RIKEN 小沢恭一郎(東大)

  10. Photocathode Test Independent Lamp Monitor MgF2 Windows Photocathode or Triple GEM VUV beam Absorption Length ~ 30cm Vacuum Vessel (“cross”) Beam splitter/Collimator Testing Apparatus • Absolute QE of produced Photocathodes Vs Wavelength • Photoelectron signal in CF4 (CF4 transmittance) • GEM systematics (gain, stability, etc.) • Systematic Measurements of CsI Coated Triple GEM • (pe collection efficiency Vs ED, etc) PHENIX ws@RIKEN 小沢恭一郎(東大)

  11. @BNL QE in CF4 at High and Low Collection Fields PHENIX ws@RIKEN 小沢恭一郎(東大)

  12. @Weizmann Fe55 x-ray UV lamp 光検出器としてのテスト Gas gain Stainless steel box Pumped to 10-6 before gas filling • Gains in excess of 104 are easily attainable • Voltage for CF4 is ~140 V higher than for Ar/CO2 but slopes are similar for both gases • Gain increases by factor ~3 for ΔV = 20V • Pretty good agreement between gain measured with Fe55 and UV lamp Measurements: * Fe55 x-rays * Am241  source * UV lamp GEM foils of 3x3, 10x10 and 25x25 cm2 produced at CERN PHENIX ws@RIKEN 小沢恭一郎(東大)

  13. Cherenkov response to S1.S2.S4 Cosmic trigger S1.S2.S4 • pth 3.8 GeV • 1.30 m long • rate  1/min C: CO2 radiator • 50 cm long • directly coupled to detector S1.S2.S4.C  mip S1.S2.S4.C  “electron” CF4 Radiator • triple GEM + CsI • test with Fe55, UV lamp,  Detector Box Cosmic ray tests: Experimental Set-up C S4 S1,S2 PHENIX ws@RIKEN 小沢恭一郎(東大)

  14. ED = -0.5 KV/cm (“repulsion”) ED = 1 KV/cm (“collection”) Signal = Cherenkov photons Signal = mip + Cherenkov photons response to “electrons” All spectra calibrated into pe using the response to Fe55 x-rays. PHENIX ws@RIKEN 小沢恭一郎(東大) @Weizmann

  15. Small GEMs: 3x3 cm2 ΔVGEM HV segmented GEMs 10x10 cm2 ΔVGEM Discharge Probability • Stability of operation and absence of • discharges in the presence of heavily ionizing particles is crucial for the operation of the HBD • Use Am241 to simulate heavily ionizing particles • In Ar-CO2, discharges increase sharply when total charge is close to the Raether limit of 108 • In CF4 discharges do not depend on • the presence of  particles. It seems that • local defects are responsible for the • discharges • CF4 more robust against discharges • than Ar/CO2 • HBD expected to operate at gains < 104 • i.e. with comfortable margin below • the discharge threshold PHENIX ws@RIKEN 小沢恭一郎(東大) @Weizmann

  16. Hg lamp Independent of gas Absorber Mesh E=0 CsI GEM1 Independent of Et 1.5mm GEM2 1.5mm GEM3 2mm PCB Depends only on EI (at low EI some charge is collected at the bottom face of GEM3) pA Ion back-flow Fraction of ion back-flow defined here as: Iphc / IPCB Ions seem to follow the electric field lines. In all cases, ion back-flow is of order 1!!! PHENIX ws@RIKEN 小沢恭一郎(東大) @Weizmann

  17. Aging CsI photocathode: * In spite of the large ion back-flow there is no dramatic deterioration of the CsI QE. * For a total irradiation of ~10mC/cm2 , the QE drops by only 20%. (The total charge in 10 years of PHENIX operation is conservatively estimated to 1mC/cm2.) Stability measurements performed during day 3 (4 mC/cm2 ), day 4 (3 mC/cm2 ), day 5 (2 mC/cm2 ). GEM foils: * During the whole R&D period we never observed aging effects (e.g. loss of gain) on the GEM foils. Total irradiation was well in excess of 10mC/cm2 . PHENIX ws@RIKEN 小沢恭一郎(東大) @Weizmann

  18. Hadron Blind Suppress electrons from ionization Apply Reverse field PHENIX ws@RIKEN 小沢恭一郎(東大)

  19. Hadron Blindness (I): UV photons vs.  particles @Weizmann At slightly negative ED, photoelectron detection efficiency is preserved whereas charge collection is largely suppressed. PHENIX ws@RIKEN 小沢恭一郎(東大)

  20. Suppressed ionization ED = 0 Full charge collection GEM1 GEM2 GEM3 PCB Suppression limited by ionization between GEM1 and GEM2.  Asymmetric operation Hadron Blindness (II) :response to mip @KEK ED = 1 KV/cm (“collection”) ED = -0.5 KV/cm (“repulsion”) Average amplitude dropped by a factor of ~2.5 and rate dropped by a factor of 12 Strong Hadron Suppression PHENIX ws@RIKEN 小沢恭一郎(東大)

  21. 実機製作 • 筐体・GEM供給 • Ｗｅｉｚｍａｎｎによる • CsI蒸着 • ＣｓＩには、潮解性　（取り扱い注意） • 蒸着後、空気に触れずに組立、搬入が必要 • BNL近く、Stony Brook校で、作業 • 組立 • CsI潮解を考え、巨大グローブボックス内を数ppmレベルに • 埃は、放電を呼ぶ。クリーン環境での作業 PHENIX ws@RIKEN 小沢恭一郎(東大)

  22. Clearance +/- 3 mm Z= 656.4 mm HBD final design 2x21 HV connectors serving 2x3 detector modules Gas out Removable window FR4 frame all around the cover PHENIX ws@RIKEN 小沢恭一郎(東大)

  23. HBD exploded view PHENIX ws@RIKEN 小沢恭一郎(東大)

  24. Full Scale Prototype at Weizmann PHENIX ws@RIKEN 小沢恭一郎(東大)

  25. Full Scale Prototype Gas Tightness Test • We started Nitrogen flow (200 l/h) with a single 50 um mylar window • With single mylar we reached 15-20 ppm water level • With double mylar window we reached 5-6 ppm • Bypassing the HBD showed 2 ppm in the gas system • On 19.04.05 we replaced 50 um window by 127 um mylar window coated with Al • With this single window we reached the same 5-6 ppm • On 06.05.05 we opened box and put into it several GEMs and resumed the Nitrogen flow I.Ravinovich PHENIX ws@RIKEN 小沢恭一郎(東大)

  26. 蒸着・組立 PHENIX ws@RIKEN 小沢恭一郎(東大)

  27. PHENIX ws@RIKEN 小沢恭一郎(東大)

  28. PHENIX ws@RIKEN 小沢恭一郎(東大)

  29. PHENIX ws@RIKEN 小沢恭一郎(東大)

  30. PHENIX ws@RIKEN 小沢恭一郎(東大)

  31. PHENIX ws@RIKEN 小沢恭一郎(東大)

  32. signal electron e- partner positron needed for rejection Cherenkov blobs e+ qpair opening angle ~ 1 m @ PHENIX PHENIX ws@RIKEN 小沢恭一郎(東大)

  33. PHENIX ws@RIKEN 小沢恭一郎(東大)

  34. Performance in Run9 Rejection factor Hadron Projected Performance @ Run10 few pe Np.e. of single electron Single electron Signal significance 1.4 /nb recorded improves effective statistics by ≥ 35 ~20 pe Luminosity [unit of Run4 ] PHENIX ws@RIKEN 小沢恭一郎(東大)

  35. R&D @ RIKEN PHENIX ws@RIKEN 小沢恭一郎(東大)

  36. Summary • PHENIX実験では、GEMとCSIカソードを用いた光検出器を読み出し部に用いるガスチェレンコフ検出器を開発している • R&Dは、Weizmannで行われ、Cosmic rayでのテストなどに成功した。その後、実機製作が行われ、実際に電子を捉えることに成功した。 • 理研・放射線研においても、CSIを用いた光検出器の開発を行っている。 PHENIX ws@RIKEN 小沢恭一郎(東大)

  37. Back ups

  38. Scintillation of CF4 • CF4 scintillates at 160nm. • Two measurements in the literature: • * NIM A371, 300 (1996):  110 ph/MeV • * NIM A354, 262 (1995):  200 ph/MeV • Planned to be measured at BNL 2/2003 • Results of simple simulations: (using 200 ph/MeV, QE=0.3, Nch = 250) * signal/noise  10 * shades can reduce the noise by at least a factor of 3. PHENIX ws@RIKEN 小沢恭一郎(東大)

  39. メモ Pion: 198.9 17.3electronに当る Electronは、1.38倍 198.9*1.38 = 274.5 (23.9) Electron(measured): 284.1 (24.7) 差は、チェレンコフ分で、1 p.e.くらい 光量　∝ N0 / γｔｈ^2 * L WeitzmanHBD40 p.e. L = 50 cm CNS 14 p.e. PHENIX ws@RIKEN 小沢恭一郎(東大)

  40. ガスチェレンコフ型電子検出器 • 荷電粒子がガス中を通過する事により発生するチェレンコフ光により、電子を同定する検出器 • 従来の検出器は、鏡とPMTを持つ • 大立体角を覆うのが難しい。 崩壊比の小ささからくる大きな立体角への要求 光電面の付いた電子増幅部を光検出部として一面に貼り付けることで、解決か？！ • 本講演では、 • あたらしい検出器のコンセプト • プロトタイプの製作、動作確認 • KEKでのテスト実験の結果、問題点 • 今後の取り組み PHENIXの次期検出器 PS-E325のガスチェレンコフ PHENIX ws@RIKEN 小沢恭一郎(東大)

  41. チェレンコフ光 CSI GEM3層 パッド 検出器のアイデア • 鏡なしのチェレンコフ検出器 • 全体で一つのガスベッセル • Radiatorと光検出が同じガス • Ar-C2H6 (γｔｈ~　２５) 電子 Radiator ガス ハドロン • CSI光電面 • UV sensitive (6 eV, 200nm) • １４ p.e. for 75cm radiator 光電子増幅部でのハドロンのEnergy lossによりハドロンに対しても信号を出す可能性 光検出部 ガス 光電子 • 3層のGEMを使用 • 1層の増幅率は低くハドロンからの2次電子は、十分に増幅されない。 増幅 2次電子 開発要素：　GEM、CSIカソード、ガス PHENIX ws@RIKEN 小沢恭一郎(東大)

  42. GEM チェレンコフ光 CSI GEM3層 パッド 主な開発要素の現状 電子 Radiator ガス 国内での製作に成功 長期的安定性を測定中 • CSIカソード 浜松PMTに依頼して蒸着 ビームで動作確認をトライした。 検出効率測定用の装置を準備 光検出部 ガス 光電子 • ガス 最適なガス、混合比を決定し、 水、酸素の影響を測定予定 PHENIX ws@RIKEN 小沢恭一郎(東大)

  43. Weitzman Institute CF4を使った同タイプの検出器の開発 KEKで共同でテスト 7 p.e. 程度のチェレンコフ光の信号を確認 BNL GEM TPCのR&D CERN, 渕上, ３Mの3種類のGEMを比較 ゲインの上昇を確認 関連のR&D electron p Gain stability by B. Azmoun Response of Weitzman detector PHENIX ws@RIKEN 小沢恭一郎(東大)

  44. Overall Set-up 50 cm long CF4 Radiator D2 UV Lamp Detector box Weizmannでのテスト Detector Box GEM foils of 3x3 and 10x10 cm2 produced at CERN PHENIX ws@RIKEN 小沢恭一郎(東大)

  45. Fe55 x-ray UV lamp Gain Curve: Triple GEM with CsI in CF4:measured with Fe55 and with UV lamp • Pretty good agreement • between gain measured • with Fe55 and UV lamp. • Gains in excess of 104 are • easily attainable. • Voltage for CF4 is ~140 V • higher than for Ar/CO2 but • slopes are similar for both • gases. • Gain increases by factor ~3 • for ΔV = 20V PHENIX ws@RIKEN 小沢恭一郎(東大)

  46. Total Charge in Avalanche in Ar-CO2 and CF4 measured with Am241 Charge saturation in CF4 !!! When the total charge in CF4 exceeds 4 x 106 a deviation from exponential growth is observed leading to gain saturation when the total charge is ~2 x 107. PHENIX ws@RIKEN 小沢恭一郎(東大)

  47. Calibrated PMT Bandwidth: 6.2 – 10.3 eV PMT and CsI have same solid angle C1 optical transparency of mesh (81%) C2 opacity of GEM foil (83.3%) All currents are normalized to I(PMT-0) CsI on GEM QE(CsI) = QE(PMT) x I(CsI) / [ I(PMT) x C1 x C2 ] CsI absolute QE • Many measurements of CsI QE in 6-8 eV range • No data beyond 8.3 eV • Measurements extended to 10.3 eV confirm ~linear behavior of QE Extrapolation to 11.5 eV: N0 ≈ 820 cm-1 PHENIX ws@RIKEN 小沢恭一郎(東大)

  48. In Ar-CO2, the discharge threshold is close to the Raether limit (at 108), whereas in CF4 the discharge threshold seems to depend on GEM quality and occurs at voltages VGEM 560-600V vs. ΔVGEM CF4 more robust against discharges than Ar/CO2 . HBD expected to operate at gains < 104 i.e. with very comfortable margin below the discharge threshold vs. Gain Discharge Probability • Stability of operation and absence of • discharges in the presence of heavily ionizing • particles is crucial for the operation of the HBD. • Use Am241 to simulate heavily ionizing particles. PHENIX ws@RIKEN 小沢恭一郎(東大)

  49. At ED = 0: - signal drops dramatically as anticipated. - rate also drops dramatically large hadron suppression Charge Collection in Drift Gap : Mean Amplitude Rate PHENIX ws@RIKEN 小沢恭一郎(東大)

  50. Radiation Length Budget CDR Preamps: 0.95 % Sockets: 0.60% Total = 0.92 + 0.54 + 0.95 +0.60 = 3.01 % PHENIX ws@RIKEN 小沢恭一郎(東大)

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