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Highlights from the 2001 IEEE Nuclear Science Symposium

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Highlights from the 2001 IEEE Nuclear Science Symposium

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  1. Highlights from the 2001 IEEE Nuclear Science Symposium Detector Seminar Silvia Schuh CERN/EP

  2. Outline • Conference Overview • Gaseous Detectors • Aging in Gaseous Detectors • Micropattern gas detectors • GEMs • new applications • RPCs • Photon Detectors • HPD R&D • new developments • Semiconductor Detectors • diamond detectors Silvia Schuh, EP/CERN

  3. Conference Schedule • 3.5 days • 1 plenary session • otherwise 3 parallel sessions • full program @ http://www.nssmic.org/nsshome.html • Conference Record soon available online • VERY difficult to decide which session to choose! • DISCLAIMER: • Only selected topics discussed - many more interesting ones! Silvia Schuh, EP/CERN

  4. Conference Schedule Silvia Schuh, EP/CERN

  5. Gaseous Detectors • 4 dedicated sessions, 3 featured talks • many talks also in non-dedicated sessions • will discuss: • Aging in gaseous detectors • micropattern gas detectors • GEMs • new applications • RPCs Silvia Schuh, EP/CERN

  6. M. Titov www.desy.de/agingworkshop Scientific program: 10 invited talks , 31 contributed talk, 9 posters J.Va’vra, ``The basics on Aging and the Early Developments since the 1986 Workshop’’ H.Yasuda, ``New Insights into Aging Phenomena from Plasma Chemistry’’ M.Capeans, ``Aging & Materials: Lessons for Detectors and Gas Systems’’ C.Padilla, ``Aging Studies for the Outer Tracker of HERA-B’’ A.Romaniouk, ``Aging Studies for the Transition Radiation Tracker of ATLAS’’ T.Hott, ``Aging Problems of the Inner Tracker at HERA-B’’ V.Peskov, ``Aging in Gaseous Photodetectors’’ D.Marlow, `` Recent Experiences with Aging In Systems of Resistive Plate Chambers’’ F.Sauli, `` Review of Worskhop Results on the Fundamental Understanding of Aging Processes’’ B.Schmidt,``Recomendations for Building and Testing the Next Generation of Gaseous Detectors’’ Silvia Schuh, EP/CERN

  7. Gaseous discharges  molecules break up • collisions with electrons • de-excitation of atoms • UV-absoprtion processes • most ionization processes need Eelectron > 10eV • breaking of chemical bonds and free radicals • formation need ~ 3-4 eV M. Titov Wire Chamber Aging • Sustained irradiation permanent degradation of operating characteristicsremains main limitation to use in high-rate experiments • deposition of polymers on anode (and/or) cathode surfaces - manifest as: • Loss of gas gain and reduction of the plateau region • Loss of energy resolution • Excessive currents • Self-sustained current discharge • Sparking Free-radical polymerization seems dominating mechanism of wire chamber aging • Chemical reactions between polymer • atoms and atoms of electrode material • Electrostatic attraction to electrode (J. Va’vra) Modification of electric field Silvia Schuh, EP/CERN

  8. to understand polymerization  study plasma chemistry Silvia Schuh, EP/CERN

  9. Implicit assumption: Aging rate R  total accumulated charge (% per C/cm) not proven for high intensity environments! Aging phenomena depend on many highly correlated: M. Titov Wire Chamber Aging • Microscopic parameters: • particle type • energies • Electron, ion, radical densities • … • Macroscopic parameters: • Gas components • (nature of gas, trace contaminants) • Gas flow & Pressure • Geometry of electrodes • and configuration of electric field • Construction materials • Radiation intensity • Gas gain, current density • Size of irradiation area Too many variables in problem ! Difficult to truly understand any present aging measurement & extrapolate it to other operating conditions! Large progress since 1986 LBL workshop Silvia Schuh, EP/CERN

  10. Malter Effect M. Titov • Malter effect induced by insulating • deposits on cathode Ions which are not neutralized at the cathode L. Malter, Phys. Rev.50(1936)48-58 Large electric field across insulating layer Electrons ‘pulled out’ from the cathode • Factors which facilitate an ignition: • Poor cathode conductivity • (some oxides are highly resistive, carbon • composite materials may not be conducting • enough - Pokalon-C, HERA-B OTR) • Highly ionizing particles or sparks Once Malter current started it will lead to high local ionization densities and initiate production of new reactive species or produce them at much larger rates  promoting polymer formation !!! When Malter effect appears apply additives immediately or disconnect ‘damaged detectors’, otherwise it will spread out through your large system Silvia Schuh, EP/CERN

  11. M. Titov High radiation levels @ LHC, HERA-B from mC/cm  many C/cm enormeous R&D done: RD-10, RD-28, RD-6, ATLAS-TRT, ATLAS-MDT, CMS CSC, HERA-B OTR, HERA-B ITR, HERA-B Muon ... Silvia Schuh, EP/CERN

  12. Gold damage effects on wires M. Titov • Straws for ATLAS TRT: • Xe/CF4/CO2 (70:20:10) • Current density ~5mA/cm • Gold etching processes appear • for different accum.charges • (0.5 - 6 C/cm) • No F-based deposits observed Possible reasons for gold damage: • Main responsible components: • reactive species produced in • CF4 avalanches (prob.HF acid) • Presence of oxygen speeds • wire damage (WO deposit) • No gold damage effects • observed for H2O < 0.1% with • Xe/CF4/CO2 up to 20C/cm • Effect depends on type of wire • (producer and production • technology) (A. Romaniouk - Aging Workshop 2001, DESY) Silvia Schuh, EP/CERN

  13. Recommendationss: Materials and gases for 'standard' detectors Existing data,obtained either from systematic outgassing studies or experience gained with detector, has only a preselective character (a list of low outgassing assembly compounds exists, that includes epoxy compounds, rigid materials, sealants, elastomers,…) There are clearly many ‘bad’ and a lot of ‘usable’ materials A material is adequate or not for a very particular detector type and operating conditionstest to match your specific requirements Do not introduce bad components by unadequate assembly procedures (no quality checks, no personnel training, greasy fingers, polluted tools) No spontaneously chosen materials should be installed in the detector or in the gas system in the last moment, before the start of real operation Building of large detector needs a lot of communication and sharing of know how of all people in the business If you want to test the cleanliness of your gas system: install MSGC in your gas system, if it will survive  don’t worry M. Titov (B. Schmidt, M. Capeans, F. Sauli - Aging Workshop 2001, DESY) Silvia Schuh, EP/CERN

  14. Recommendations & Conclusions M. Titov New generation of high-rate experiments demand a higher radiation hardness than available from conventional mixtures (<< 1C/cm) Ar/CO2 -conventional backup mixture works up to ~C/cm (sensitive to impurities) Hydrocarbons are not trustable for long-term high-rate experiments Only limited choice of gases can be used: noble gases, CO2, CF4 and traces of H20, alcohols No CF4 free mixtures are able to tolerate doses up to ~10 C/cm Ar(Xe)/CF4/CO2 mixtures are the most attractive candidates for high-intensity environments !!! Very high aggressiveness of dissociative products from CF4 Gold damage effects were observed operating in Xe/CF4/CO2 !!! Presence of large amount of CF4in the mixture does not necessarily ensure good aging properties Fundamental problem: Cannot do realtime test  ? How to learn about long-term aging behaviour in reasonable time?  Build a full-size prototype detector  Expose full area of detector to real radiation profile (particle types!)  Choose your gases and materials very carefully  Vary all parameters systematically (gas gain, irradiation intensity, gas flow,…) and verify assumptions  If you observe unexpected results, understand reason Reproduce your results Need for a Global Universal Aging R&D Facility ??? Silvia Schuh, EP/CERN

  15. Micropattern Gas Detectors - GEMs B. Ketzer Silvia Schuh, EP/CERN

  16. Micropattern Gas Detectors - GEMs B. Ketzer Silvia Schuh, EP/CERN

  17. Micropattern Gas Detectors - GEMs B. Ketzer Silvia Schuh, EP/CERN

  18. Micropattern Gas Detectors - GEMs B. Ketzer Silvia Schuh, EP/CERN

  19. Micropattern Gas Detectors - GEMs B. Ketzer Silvia Schuh, EP/CERN

  20. Micropattern Gas Detectors - GEMs B. Ketzer Silvia Schuh, EP/CERN

  21. Micropattern Gas Detectors - GEMs B. Ketzer Silvia Schuh, EP/CERN

  22. Micropattern Gas Detectors - GEMs B. Ketzer Silvia Schuh, EP/CERN

  23. GEM - Aging M. Titov Silvia Schuh, EP/CERN

  24. GEM - Aging M. Titov Silvia Schuh, EP/CERN

  25. GEM - Aging M. Titov Silvia Schuh, EP/CERN

  26. X-ray Polarimetry with Micro Pattern Gas Detectors R. Bellazzini • definite test of strong field • gravity near very compact sources: • Black Hole binaries, Neutron Stars, • microquasars… • Unlike spectral data, polarization • data strongly affected by GR • effects According to Nature….. “ the work is highly significant for high energy astrophysics and astronomy in general. X-ray polarimetry is a unique probe of particle acceleration in the universe. It will provide a new tool for studying the fascinating and poorly understood jet sources. The instrumentation described here will very likely revolutionize this area of study …..” Silvia Schuh, EP/CERN

  27. 300 mm Micro Pattern Gas Detector S. Ahn GEM-type Detectors Using LIGA and Etchable Glass Technologies • new approach for fabrication of hole arrays with very steep wall • sides, based on “deep X-ray lithography”, or the “LIGA process” • [ H.K. Kim et al., IEEE Trans NS-47(3), 2000]. • present new results for various thicknesses of PMMA and the • LIGA process. • first measurements using the etchable glass, Foturan, patterned • by exposure to 300nm wavelength UV light. Cu Structure of LIGA Wafer 0.5-0.8 mm 150 mm 125-350 mm PMMA Silvia Schuh, EP/CERN

  28. 250 mm 130 mm 300 mm-thick Micro Pattern Gas Detector Foturan Glass S. Ahn • Photosensitive glass made by Schott Co. • Properties • - photostructurable : by 300nm UV light and proper etching • - temperature-resistant : safe up to 450 °C • - bulk resistivity : 8.1  1012  cm at 25 °C • - dielectric constant : 6.5 at 1MHz, 20 °C • - pore-free • - chemically stable Silvia Schuh, EP/CERN

  29. Micro Pattern Gas Detector S. Ahn Foturan Longer path through holes in thicker detectors increased surface charging & large gain drop? Silvia Schuh, EP/CERN

  30. RPC “standard designs single gap double gap P. Fonte [Santonico ‘81] [Santonico ‘88] multi gap hybrids [Williams ‘96] Silvia Schuh, EP/CERN

  31. RPC Rate Capability Standard RPCs Hybrid RPCs P. Fonte Silvia Schuh, EP/CERN

  32. RPC position resolution P. Fonte [Peskov ‘99] [Peskov & Francke ‘01] Silvia Schuh, EP/CERN

  33. RPC summary P. Fonte Silvia Schuh, EP/CERN

  34. RPC - BaBar Experience Barrel & endcap RPCs D. Strom Silvia Schuh, EP/CERN

  35. RPC - BaBar Experience Found: worst damage with HV & heating D. Strom Silvia Schuh, EP/CERN

  36. RPC - BaBar Experience D. Strom Silvia Schuh, EP/CERN

  37. RPC - BaBar Experience Efficiency decline started @ ~500C/m2 “Miracle Cures”: if linseed oil not fully cured  flow air/O2? Improvements temporary EC-Replacement: new QA/QC procedures - filter oil - no drilling for gasinlets - tests for “popped buttons” - cosmic test at factory D. Strom Barrel??? Silvia Schuh, EP/CERN

  38. RPC - BaBar Experience Back-up D. Strom Silvia Schuh, EP/CERN

  39. Photodetectors • 1 dedicated session, 1 featured talks • will discuss: • HPD R&D for CMS • other photodetectors • novel ideas Silvia Schuh, EP/CERN

  40. HPDs for CMS: Principle How they work • doesn’t break in 4T magnetic field • align tube axis parallel to field • Stringent Photodetector Requirements • B = 4T • Linear Response from • MIP to 3TeV Shower • DC Calibration to 2% • using radioactive Source • Integrated neutron dose • of up to 5  1010 n/cm2 • Integrated output charge • up to 3 Coulomb • Pixel position must be • measured (and aligned) • to 50 mm P. Cushman Silvia Schuh, EP/CERN

  41. HPDs for CMS: The phototube HV Discharge to HPD Mounting After silicon rubber potting, at 15 kV Current across mount at 12 kVwith normal RBX configuration Time (hrs) Time (hrs) nAmps nAmps P. Cushman Silvia Schuh, EP/CERN

  42. HPDs for CMS: The diode P. Cushman Silvia Schuh, EP/CERN

  43. HPDs for CMS: Pulse width R0003241 (200 micron, 73-channel new-style diode) Reminder: on the same scale Pulse Width in nsec • drift time of holes translates into pulse width D • Simple form for over-depletion matches data • pulse width can be shortened by reducing wafer • thickness d or by increasing bias voltage, Vb • for higher depletion (lower ohmic silicon) Vb-Vd~Vb • is not true  specify: diodes > 8kW-cm • flatter plateu and higher breakdown voltages for • new diodes  no breakdown even at Vb=500V P. Cushman Silvia Schuh, EP/CERN

  44. HPDs for CMS: AC Crosstalk Positive crosstalk now observed ! AC Crosstalk eliminated by surface Aluminization 33 34 35 36 37 Pixels in center row P. Cushman Silvia Schuh, EP/CERN

  45. HPDs for CMS: Backscatter Xtalk Ballistic model of backscattering, 10keV electrons B = 0.15 Tq = 45o Radial distance B = 0 Tq = 45o 0 1 2 3 4 mm Radial distance is a minimum here ! Positive Backscatter xtalk decreases for B > 0.3T! Do calibration in magnetic field! 0 1 2 3 4 5 6 7 mm B = 4 Tq = 75o P. Cushman 0 0.05 0.1 0.15 mm Silvia Schuh, EP/CERN

  46. HPDs for CMS: backscatter crosstalk solution P. Cushman Test confirms reflected light IMD - optical modeling package for multilayer structures; by David L. Windt, http://cletus.phys.columbia.edu/windt/idl Decrease reflectance: Silvia Schuh, EP/CERN

  47. HPDs for CMS: rad-hardness Radiation Damage:(10 CMS years = 5 x 1010 n/cm2 in worst region) Expose samples to Cf252 Oak Ridge: Early HPD version to 1013 n/cm2 in 1997 tests. Minnesota: Low flux drawer instrumented Aluminized new HPD to >1011 n/cm2 in 2001 Integrated Charge:(10 CMS years = 3 C over 25.6 mm2 pixel at high h) Expose to accelerated rate plus control pixel at CMS rate. P. Cushman 6 CMS months for high h towerat expected CMS rate Red = 73-ch aluminized HPD Blue = old tube w/ poor potting All curves normalized to reference diode & corr. For T-shifts 6 CMS years for high h towerat 13 x expected rate Silvia Schuh, EP/CERN

  48. HPDs for CMS: Conclusions • Conclusions: • 5 years ago, no existing technology could satisfy our specifications. • Development project was initiated with one Company - DEPwith backup plans which included Hamamatsu and Litton • Rigorous evaluation must include accelerated aging and test beamsand enough prototype detectors to understand the yield. • The anticipated problems are not the ones that really bite you. • The necessary R& D takes time! • HPD subsystem approached “critical path” in CMS Project last year. • Final Result: CMS HCAL gets what it needs (so we can find the Higgs) and a better product is offered to the general public. P. Cushman Silvia Schuh, EP/CERN

  49. Idea: detect visible light with stable operation in gas atmosphere Difficulties: cleanliness tiny impurities degrade photocathode Q.E. proper clean gas system (S. Majewski, Preprint CERN-IP/83-89, 1983)  photocathode protection by ~200Å CsI film or CsTe photocathode (T. Francke et al. IEEE 2001) photon feedback discharges due to photon & ion feedback: Ag=1 g … prob to create a secondary e- from cathode A… gas gain ordinary gaseous detectors g<10-6 high-eff photocathodes sensitive to visible light g<10-2  max achievable gain < 102 suppress photon & ion feedback! Gaseous Photomultipliers (GPM) V. Peskov Silvia Schuh, EP/CERN

  50. Photon feedback - solutions glass capillary plate GCP  PPMC  CsI photocathode  MWPC Gaseous Photomultipliers (GPM) V. Peskov • hybrid Gaseous PM (T. Francke et al., IEEE 2001) • Conclusions • seems possible to build gaseous detectors sensitive to visible light • simple, large area, no need for focussing, capable to operate in B Silvia Schuh, EP/CERN