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Short overview of LIP-Coimbra activity in view of 1 - RPCs for time-tagged tracking and

Short overview of LIP-Coimbra activity in view of 1 - RPCs for time-tagged tracking and 2 - GEMs for high sensitivity L-Xe experiments. 1 – RPCs: Commitments within RD51. WG2 - COMMON CHARACTERIZATION AND PHYSICS ISSUES Generic aging and material radiation-hardness studies

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Short overview of LIP-Coimbra activity in view of 1 - RPCs for time-tagged tracking and

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  1. Short overview of LIP-Coimbra activity in view of 1 - RPCs for time-tagged tracking and 2 - GEMs for high sensitivity L-Xeexperiments

  2. 1 – RPCs: Commitments within RD51 WG2- COMMON CHARACTERIZATION AND PHYSICS ISSUES • Generic aging and material radiation-hardness studies WG3 - APPLICATIONS+ WG4 – SIMULATIONS S/W TOOLS • MPGD based RPCs for tracking and ToF • Medical applications  

  3. 1 - RPCs for time-tagged tracking ... Long list of authors (see next slide) Early work (ALICE TOF, 1999) 1.1 –Timing RPC (tRPC) Developments 1.2 –Larger and still fast 1.3 –High count-rate (CBM) 1.4 –HADES ToF wall 1.5 –Localization capability 1.6 –Small animal PET Goal within RD51 1.7–Pixelized RPC TOF tracker (the concept)

  4. RPC work teams HADES-RPC group D.Gonzalez W.Koenig A.Blanco N.Carolino O.Cunha P.Fonte L.Lopes A.Pereira C.Silva C.C.Sousa D.Belver P.Cabanelas E.Castro J.A.Garzón M.Zapata J.Diaz A.Gil RPC-PET team A. Blanco1, N. Carolino1, C.M.B.A. Correia2, M.Couceiro1,5, L. Fazendeiro1, Nuno C. Ferreira3, M.F. Ferreira Marques4,5, R. Ferreira Marques1,6, C. Gil4, M. P. Macedo2,5 1 LIP, Laboratório de Instrumentação e Física Experimental de Partículas, 3004-516 Coimbra, Portugal. 2 CEI, Centro de Electrónica e Instrumentação, Univ. Coimbra, 3004-516 Coimbra, Portugal. 3 IBILI, Instituto Biomédico de Investigação de Luz e Imagem, Faculty of Medicine, 3000, Coimbra Portugal. 4 ICEMS, Departamento de Física, Universidade de Coimbra, 3004-516 Coimbra, Portugal. 5 ISEC, Instituto Superior de Engenharia de Coimbra, 3031-199 Coimbra, Portugal 6 Departamento de Física, Universidade de Coimbra, 3004-516 Coimbra, Portugal.

  5. 1.1 Timing RPC (tRPC) – the 1st prototype -HV Particle 3x3 cm2 E Resistive material, black glass  ~2-3 1012 cm Conductive material, Al Sensitive Region Precise gas gap with few 100 m Main features • Timing resolution ~ 50 ps σ. • Efficiency 75% for a 300 μm gap • No energy resolution. • Possibility to measure the position. Gas gap MIPS ~1 pC ~3 ns

  6. -HV 3 1.1 Timing RPC (tRPC) – the 1st prototype 4 x 0.3 mm gaps 3x3 cm2 [ Fonte 2000] Aluminum Glass Sharp timing but small Resolution of thereference counter • = 99.5 % for MIPs (75%/gap)‏ (optimum operating point  1% of discharges)‏

  7. 1,6 m HV 4 timing channels 5 cm 1.2 - 2nd prototype: a large counter Active area = 10 cm160 cm = 0.16 m2(400 cm2/electronic channel)‏ Top view Cross section Ordinary 3 mm “window glass”  ~81012 cm Copper strips [Blanco 2001]

  8. 100%  = 95 to 98 % 99% 98% 97% Time efficiency 96% Strip A 95% Strip B 94% Strips A+B 93% -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 Center of the trigger region along the strips (cm)‏ 100  = 50 to 75 ps 90 80 Time resolution (ps )‏ 70 60 50 40 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 Center of the trigger region along the strips (cm)‏ 1.2 - 2nd prototype: a large counter Efficiency and time resolution [Blanco 2001] Large and yet sharp timing ! No degradation when the area/channel was doubled (800 cm2/channel)‏

  9. Time resolution  (ps)‏ Measured with 511keV photons 1.3 Another step: “high-rate” ceramic timing RPCs for CBM@GSI 75kHz/cm2 Previously2kHz/cm2  ~1109 cm ... + rate capability  9% drop/(100kHz/cm2)in 1 gap [Lopes 2006]

  10. 1.4 - 1st application: shielded tRPCs for HADES@GSI Shielded - No cross-talk (>GHz b.w.) - Robust multihit performanceRedundant - Pure gaussian response

  11. K- 1.4 - 1st application: shielded tRPCs for HADES@GSI Tail cancellation using redundant information Tails: 0.55% above 700 ps • 6 m2 installed by next spring • PID capability to separate K/ ~ 1 / 104

  12. Time signal HV X right X left 4 cm XY readout plane out left RC passive network 10 strips for each coordinate at 4 mm pitch Y-strips (on PCB) out right RC passive network X-strips (deposited on glass) 1.5 - 2D position sensitive readout Precise construction 2 mm thick black glass lapped to ~1m flatness metal box (no crosstalk)‏ 300 m thick high  glass disk (corners)‏ Well carved into the glass (avoid dark currents from the spacer)‏ [Blanco 2002] Resistive division (for small and accurate TOF systems)

  13. 1500 Trigger edge (3 mm)‏ Chamberedge 1000 Events/0.5mm 500 0 Y(mm)‏ -25 -20 -15 -10 -5 0 5 10 15 20 25 Events/mm2 Position along X (mm)‏ 1500 4 mm strip pitch 1000 Events/0.5mm 500 X (mm)‏ 0 10 15 20 -25 -20 -15 -10 -5 0 5 25 Position along Y (mm)‏ 2 2 10 10 Events/4ps Events/4ps 1 1 10 10 0 0 10 10 -1000 -500 0 500 1000 -1000 -500 0 500 1000 Time difference (ps)‏ Time difference (ps)‏ 1.5 - 2D position sensitive readout Position resolution ... + localization capability  (=75%)‏ No edge effects edges  3 mm resolution  3 mm FWHM (strips=4mm)‏ Edge & Corner Sigma=76.9 ps (66 ps)‏ Center Sigma=74.0 ps (62 ps)‏ [Blanco 2002]

  14. 1.6 Small animal PET - a first prototype Charge-sensitive electronics allowing interstrip position interpolation Aimed at verifying the concept and show the viability of a sub-millimetric spatial resolution. 32 strips 16 plates ....... ....... 16 stacked RPCs Depth of interaction Z 2D measurement of the photon interaction point (X,Z) X Transaxial

  15. Copper (on a PCB) and glass electrodes. • 32 1-mm wide X pickup strips. • 0.3 mm gas gap. • Not optimized for high efficiency (2 mm glass)‏ ANODE: glass electrode glued on PCB CATHODE: PCB copper layer X Transaxial coordinate Depth of interaction 1.6 Small animal PET - a first prototype Active area 32 x 10 mm2 0.3 mm spacers

  16. 1.6 Small animal PET - a first prototype The system at work LOR = Line of Response, connects the two photon interaction points. Intrinsic spatial resolution Custom-made 22Na source 0.22 Ø x 0.5 mm Red lines correspond to real data (LORs) acquired with the 22Na source D = Distance between each LOR and the center of the system

  17. 9mm 1 1 Proceeding IEEE MIC (2004) M2-177 1.6 Small animal PET - a first prototype Image spatial resolution (gaussian fitting) Maximum likelihood-expectation maximization with resolution modeling (ML-EM)‏ ~310 m FWHM 810 m FWTM Filtered Back Projection FBP 510 m FWHM 1050 m FWTM • Twice as good as any other PET system • Approaching the physical limit (~350 m) 0.31 0.30 0.32 [Blanco, IEEE MIC 2004] 0.29

  18. 1.7 Near future (RD51) The pixelized RPC TOF tracker • High granularity: just depending on the pads size • Sub-millimetric position resolution: 0.5 mm or better • State-of-the art time resolution: 50 ps Position-measurement electronics Time-measurement electronics Position measured with patterned electrode Time measured on opposing pads Resistive plates General look of a demonstration module

  19. 2 – GEMs: Commitments within RD51 WG3 Cryogenic detectors + WG4 Simulatios & s/w tools MPGDs in double phase xenon detectors for rare low energy events LIP-Coimbra + U.Coimbra/U.Aveiro1) GEM tests at reduced vapour pressure 2) MHSP tests in 2-phase xenon  WG3 Medical applications+ WG7 Common Test Facilities Study of MPGDs for gamma-ray imagingLIP-Coimbra 1) GEM/mini-strip readout in double phase xenon 2) Small prototype of liquid xenon gamma-ray imager 

  20. 2 -GEMs for high sensitivity experiments Filipa Balau, Isabel Lopes, Vitaly Chepel*RD51 and Vladimir Solovov, within the ZEPLIN Dark Matter programme 2.1 –High sensitivity experiments 2.2 –Double phase Xe detectors 2.3 –Our measurements with a GEM 2.4 –Results

  21. 2.1 High sensitivity experiments GOAL: Detection of a few electrons signal (ideally a single e–) in gaseous phase of a LXe double phase detector Ex.1: Direct search for Dark Matter in the form of WIMPs through elastic scattering on Xe nuclei Ex.2: Coherent neutrino scattering on a nucleus WIMP n mW ~ 100 GeV EW ~ 50 keV En ~ 50 MeV nuclear recoil nuclear recoil Energy of nuclear recoil:0 to ~50 keV

  22. E1 e- E2 Xe+ 2.2 Double phase Xe detectors Measuringt ionisation from recoil tracks • Total gain of ~104 required • Stability of GEM operation in saturated gas • (high density, low T, dependence on T fluctuations) ? • Condensation of the liquid on the GEM ? • Operation in ultrapure environment ?

  23. Qext Q0 – 4 kV 2.2 Double phase Xe detectors Our measurements with a single GEM Qext – charge reaching collector grid Gain = Qext / Q0 Q0 – charge collected at lower GEM face (same potential applied to both sides) • Mind ... • Ultrapure xenon • Only clean materials used • Good temperature stabilization

  24. T Gmax 2.2 Results Gain as a function of VGEM 241Am spectra 60 keV g 5.5 MeV a • Continuous stable operation repeatedly observed over hours • Gmax=150 ( ~ 2 atm) dependent on T 19% [Balau et al.,NIM; in press] X-rays 60 keV g Max gain Near future plans: - Lower T (... approaching tripple point, -111 C) - MHSP

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