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Application of new photo-detectors to calorimetry and medical physics

Application of new photo-detectors to calorimetry and medical physics. Nicola D’Ascenzo, Erika Garutti University of Hamburg – DESY Alexander Tadday University of Heidelberg. The Geiger Mode Avalanche Photodiode. Why is this detector so interesting ?.

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Application of new photo-detectors to calorimetry and medical physics

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  1. Application of new photo-detectors to calorimetry and medical physics Nicola D’Ascenzo, Erika Garutti University of Hamburg – DESY Alexander Tadday University of Heidelberg

  2. The Geiger Mode Avalanche Photodiode Why is this detector so interesting ? • High gain (Typically 105 - 106) • Low bias voltage (30 V -70 V) • Small area (1 mm2) • Up to 1600 pixels per mm2 • Not sensitive to magnetic field Devices from MEPHI, Hamamatsu and SensL currently avalaible in DESY: Good possibility of comparison and testing PD07 Kobe

  3. ILC Physics: challenges in calorimetry • Electron-positron accelerator • Energy: 500 GeV up to 1 TeV • ILC physics places premium on jet measurements and flavoure tagging, in an environment where event reconstruction is possible • tth  8 jets • hZ  2l + 2 jets, 4 jets • hhZ  2l + 4 jets, 6jets Aim to fully reconstruct final state • + SUSY, quark, τ tagging, lepton/hadron id • Missing energy signatures of SUSY and extra-dimensions This requires a calorimeter which is: COMPACT – Inside the magnetic coil HIGH GRANULAR – Imaging calorimeter HERMETIC PD07 Kobe

  4. HCAL ECAL TPC The scintillator tile hadron calorimeter • Sampling calorimeter : absorber stainless steel, active medium plastic organic scintillator. • High granular, compact, hermetic. • Along the magnetic field direction it extends in -220 cm < z <220 cm • It covers the detector along the radius in the region 180 cm< r < 290 cm • The test beam prototype: 1 m3 . • Test beam prototype : 38 layers, 216 channel per layer. • Fully equipped with MEPHI/PULSAR SiPM PD07 Kobe

  5. SiPM: a good photodetector for hadron calorimetry Test Beam CERN. 10 GeV Pion in the HCAL The minimum signal in 1 cell is a m.i.p. • The good SiPM for this application: • Low noise above the suggested cut on the mip spectrum (Controlled dark rate and cross talk) • Light Yield not exceeding the saturation behaviour of the device, but high enough to detect a m.i.p. with at least 95% efficiency. (good PDE in the light peak spectrum) • Stable and controlled production • Compactness, unsensitivity to magnetic field up to 5 T, radiation hardness ... The test beam prototype, fully equipped woth MEPHI SiPMs, is showing good performances for a long time operation of the device: the high granular calorimeter operated with SiPMs is starting to be a suitable option. Test Beam data are under analysis PD07 Kobe

  6. New approach to the calorimeter design:the direct readout of the scintillator R&D Present status • Scintillator tile (Uniplast, Vladimir (RU)) • Green wavelength shifter fiber (Kurakay) • Mirror • In order to: • Assure Light yield (MEPHI SiPM is green sensitive) • Assure Light collection uniformity • The direct readout is easier to extend to • a large scale production. • What is the solution which respects the required bounds • on the parameters: • Blue Sensitive? • Green sensitive and large? PD07 Kobe

  7. The MPPC produced by Hamamatsu Blue sensitive Multi Pixel Photon Counter PD07 Kobe

  8. Direct readout with MPPC • Readout of a plastic scintillator tile directly and comparison with mediated green fiber • Tile wrapped with a 3M reflector. In case of the direct readout, only a window of 1mm x 1mm is open in front of the MPPC • Source: Ru106 • Integration gate 80 ns • External trigger (Photomultiplier tube) • Reproducibility of the measurement +- 3% • systematic (coupling, positioning etc ...) PD07 Kobe

  9. 1600 px 400 px Direct readout with MPPC : Most Probable Value of the mip response spectrum Direct (Blue dots) and Wavelength shifter mediated readout (Green dots) . Light Yield in the calorimeterprototype PD07 Kobe

  10. Direct readout with MPPC: mip collection efficiency 1600 px Cut at3KHz 400 px The cut at 3 KHz (as in the actual prototype) corresponds to a low number of pixels (low dark rate and cross talk). The efficiency is, then, always more than 97 %. PD07 Kobe

  11. 3x3 MPPC: direct readout Ru106 response • About 50 p.e. Per MPV • Good single photoelectron resolution! LED Light PD07 Kobe

  12. The direct readout of MPPC: discussion • MPPCs are a good starting point for the discussion of the direct readout in the hadron calorimetry: • High PDE in the blue emission of the scintillator: good m.i.p. signal determination. • Low dark rate and cross talk: cut for noise even for the stricter requirement of ILC (300 Hz), without loosing m.i.p efficiency (>95%) • High dinamic range (up to 1600 pixels) • Some points under investigation: • Uniformity of the light collection • Done in laboratory setup in ITEP and LNF-FRASCATI • Real prototype (ECAL): Japan • Radiation hardness • Under investigation in ITEP • For a thinner scintillator solution, the tested samples seem to have a too low Light Yield in this readout configuration. PD07 Kobe

  13. Application of Geiger Mode Avalanche Photodiodes to PET: motivations and goals • Why applying these photodetectors to PET? • Compact • Not sensitive to magnetic field (Combination with MRI) • Coupling with cristal (1x1 mm2): high space resolution. • The calorimeter is just a big PET machine: • A calorimeter measures the energy deposited. • The hadron calorimeter has a very high granularity: imaging detector! • It is only needed to: • Change scintillator (from organic to inorganic) • Change granularity (from 3x3 cm2 to ~1x1 mm2) PD07 Kobe

  14. Energy and time resolution in PET The scattered coincidences can be cut with a good energy resolution: only the photoelectric peak is allowed. Good PDE in the blue region. The timing resolution of the module restricts the analysis area. 500 ps (FWHM) -> 7.5 cm (FWHM) PD07 Kobe

  15. Application of MPPC in PET: setup 2 LSO Crystals (Hilger Crystals, emission peak at 420 nm, 40 ns decay time) of 1mm x 1mm x 15mm (3mm x3mmx15mm) 2 LFS crystals (Lebedev institute, Moscow, new crystal, with few specifications) of 3mm x3mmx15mm Read out by 1x1 mm (3x3 mm) Hamamatu MPPC, coupled 1:1 with the photodetector. No amplification needed !!! Timing with 4 GHz Oscilloscope (50 ps resolution) Reproducibility of the measurement : 5% (Coupling is the main systematic problem) & QDC PD07 Kobe

  16. Application of MPPC in PET: energy resolution (LSO) 3mmx3mm LSO crystal Coupled with a 3mmx3mm MPPC 1mmx1mm LSO crystal Coupled with a 1mmx1mm MPPC Resolution (FWHM) ~10 % ~500 p.e. Resolution (FWHM) ~14 % ~300 p.e. The typical value of the single LSO crystal energy resolution (at 511 KeV) measured with the traditional photomultiplier tube is 10 %. PD07 Kobe

  17. Energy resolution: LSO and LFS 3mmx3mm LFS crystal Coupled with a 3mmx3mm MPPC 3mmx3mm LSO crystal Coupled with a 3mmx3mm MPPC Resolution (FWHM) ~11 % Resolution (FWHM) ~10 % Spectra acquired at the same voltage. The difference of the resolution is inside the reproducibility of the measurement. The crystals look equivalent. PD07 Kobe

  18. Timing resolution in PET 2 1 3mmx3mm LSO crystal Coupled with a 3mmx3mm MPPC 1 : Define a coincidence threshold 2 : Define a timing threshold N_cut Dt = t(s1>N_cut) – t(s2>N_cut) sigma150 ps expected from the formula. 150-200 ps typical with PM tube (Bill Moses, LBL) A background is superimposed and ruins the time resolution... Mean1: 4.42 ± 0.02 Sigma1: 0.171 ± 0.020 Mean2: 4.39 ± 0.01 Sigma2: 0.639± 0.015 PD07 Kobe

  19. Application of MPPC in PET:timing resolution (1x1) Mean1: 5.36 ± 0.01 Sigma1: 0.276 ± 0.005 Mean2: 4.9 ± 10.3 Sigma2: 0.570± 0.050 Mean1: 4.42 ± 0.02 Sigma1: 0.295 ± 0.020 Mean2: 4.39 ± 0.01 Sigma2: 0.570± 0.050 Coincidence At ~30 p.e. Coincidence At ~10 p.e. 1mmx1mm LSO crystal Coupled with a 1mmx1mm MPPC 1mmx1mm LSO crystal Coupled with a 1mmx1mm MPPC Mean1: 5.39 ± 0.02 Sigma1: 0.286 ± 0.020 Coincidence At ~50 p.e. Background Signal 1mmx1mm LSO crystal Coupled with a 1mmx1mm MPPC Compton Photoelectric PD07 Kobe

  20. MPPC in PET : discussion • MPPC show for the first time a very promising possibility of application of Geiger Mode avalnche photodiodes to Positron Emission Tomography: • Energy resolution 10% with LSO DONE!!!! • Time resolution (500 ps FWHM) ALMOST THERE!!!! • More studies needed: • Study in magnetic field, combined with Magnetic Resonance. • What crystal ? WORK IN PROGRESS (LSO, LSF, YAP...) • Study spatial resolution of a matrix • Buid a prototype and verify the concept PD07 Kobe

  21. Outlook ... A big effort is running , all over the world, in order to steer the production of the Geiger Mode avalanche photodiodes: • Blue sensitivity • Good dynamic range • Low noise This is not more a dream... The Particle Physics and the Medical Physics communities are profiting of a continous interchange... PD07 Kobe

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