1 / 24

High-Pressure Gaseous Xenon TPC for 0- v  Search in 136 Xe

High-Pressure Gaseous Xenon TPC for 0- v  Search in 136 Xe. Azriel Goldschmidt, Tom Miller, David Nygren, Josh Renner, Derek Shuman, Helmuth Spieler, Jim Siegrist LBNL. Motivations. Xenon gas at high pressure offers excellent energy resolution - in principle

wilda
Télécharger la présentation

High-Pressure Gaseous Xenon TPC for 0- v  Search in 136 Xe

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. High-Pressure Gaseous Xenon TPCfor 0-v Search in 136Xe Azriel Goldschmidt, Tom Miller, David Nygren, Josh Renner, Derek Shuman, Helmuth Spieler, Jim Siegrist LBNL TIPP 2011

  2. Motivations • Xenon gas at high pressure offers excellent energy resolution - in principle (within a factor 3 of best Ge diodes! ) • Electroluminescence provides linear gain with extremely low fluctuations - helps to preserve this high intrinsic energy resolution. • HP Xe TPC can provide total energyand image of the particle tracks for topological discrimination of event type (Gotthard TPC: x30  rejection) TIPP 2011

  3. Context R&D is focused on the NEXTCollaboration, now preparing for a 100 kg 136Xe TPC detector for Canfranc Underground Laboratory, Spain. NEXT is funded by Spain at ~5M € for construction Spain-Portugal-Colombia-France-Russia-US collaboration Applications may include -ray imaging for Homeland security/non-proliferation, medical physics/imaging TIPP 2011

  4. Xenon: Strong dependence of energy resolution on density! Large fluctuations between light/charge WIMPs: S2/S1 suffers! Ionization signal only Here, the fluctuations are normal For  <0.55 g/cm3, ionization energy resolution is “intrinsic” TIPP 2011

  5. Intrinsic energy resolution E/E = 2.35  (FW/Q)1/2 • F  Fano factor: F = 0.15 (HPXe) (LXe: F ~20) • W  Average energy per ion pair: W ~ 25 eV • Q  Energy deposited, e.g. 662 keV from Cs137 -rays: E/E = 0.56% FWHM (HPXe) N = Q/W ~26,500 primary electrons N =(FN)1/2~63 electrons rms! TIPP 2011

  6. Intrinsic energy resolution E/E = 2.35  (FW/Q)1/2 F  Fano factor: F = 0.15 (HPXe) (LXe: F ~20) W  Average energy per ion pair: W ~ 25 eV Q  Energy deposited, e.g. 2457 keV from 136Xe --> 136Ba: E/E = 0.28% FWHM (HPXe) N = Q/W ~100,000 primary electrons N =(FN)1/2~124 electrons rms! TIPP 2011

  7. Gain and noise Impose a requirement: (noise + fluctuations)  N (noise + fluctuations)  124 e— Simple charge detection can’t meet this goal  Need gain with very low noise/fluctuations!  Electroluminescence (EL) is the key TIPP 2011

  8. Electro-Luminescence (EL) (aka: GasProportional Scintillation) • Physics process generates ionization signal • Electrons drift in low electric field region • Electrons enter a high electric field region • Electrons gain energy, excite xenon: 8.32 eV • Xenon radiates VUV (175 nm, 7.5 eV) • Electron starts over, gaining energy again • Linear growth of signal with voltage • Photon generation up to ~1000/e, but no ionization • Sequential gain; no exponential growth  fluctuations are very small • NUV = JCP  N1/2 • Optimal EL conditions: JCP = 0.01 (Poisson: JCP = 1) TIPP 2011

  9. Gain and noise F  constraint due to fixed energy deposit = 0.15 Let “G” represent noise/fluctuations in EL gain Uncorrelated fluctuations can add in quadrature: n = ((F + G)N)1/2 EL: G = JCP/NUV + (1 + 2PMT)2/Npe Npe = number of photo-electrons per electron G  1.5/Npe Npe > 10 per electron for G ≤ F E/E = 0.9% FWHM 137Cs 662 keV TIPP 2011 9

  10. Virtues of Electro-Luminescence in HPXe • Linearity of gain versus pressure, HV • Immunity to microphonics • Tolerant of losses due to impurities • Absence of positive ion space charge • Absence of ageing, quenching of signal • Isotropic signal dispersion in space • Trigger, energy, and tracking functions are accomplished with optical detectors TIPP 2011

  11. TPC with Electroluminescence: Total Energy and Track Imaging Readout Plane A - position Readout Plane B - energy Electroluminescent Layer TIPP 2011

  12. Pressure vessel design study at 15 bars for 100 kg NEXT ~120 cm TIPP 2011

  13. Laboratorio Subterraneo de Canfranc Waiting for NEXT... TIPP 2011

  14. LBNL-TAMU TPC Prototype TIPP 2011

  15. Field cages/Light cagePTFE with copper stripes 19 PMTs and PMT bases Electroluminescence region10 kV across a 3 mm gap TIPP 2011

  16. PMT Array: inside the pressure vesselQuartz window 2.54 cm diameter PMTs TIPP 2011

  17. Inserting the TPC... carefully! TIPP 2011

  18. TIPP 2011

  19. A Diagonal Muon Track - “reconstructed” ~ 14 cm TIPP 2011

  20. A typical 137Cs  waveform (sum of 19 PMTs)~300,000 detected photoelectrons Primary Scintillation (S1) T0 of event Electroluminescence (S2) Structure indicates topology due to Compton scatters Drift Time:z-position (~0.01mm/sample) TIPP 2011 10ns/sample

  21. Charge vs Drift Timeelectron lifetime of 900 ms ~5% charge loss forlongest drift of 60 ms (8 cm) TIPP 2011

  22. HPXe @ 10 Atm, 137Cs 662 keVDrift time correction applied Counts keV TIPP 2011

  23. HPXe @ 10 Atm, 137Cs 662 keV Drift Time and Position corrections applied 1.8% FWHM Counts 29-36 keV Xe x-rays escape keV TIPP 2011

  24. Conclusions and Outlook • Successful operation of xenon EL TPC in 10-15 Bar range • We have achievedE/E = 1.8% FWHM @ 662 keV (10 Atm) • If F = G, and if no other effects, we expect: E/E = 0.9% FWHM • We do not yet claim to understand this factor of 2, but... • We do expect that this gap will be substantially reduced • Likely contributing factors: • localization - dependence of signal on radius • calibration of gain and QE of each PMT • dissociative attachment of electrons in EL region to water/oxygen • mesh flatness • PMT after-pulsing • NEXT is starting to happen! 100 kg 136Xe awaits us! TIPP 2011

More Related