GEM_ICRR

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					 A novel imaging device based
on UV scintillators and a large
     area gas photomulitiplier
                         11th iWoRiD July 1 2009
                              Hiroyuki Sekiya
         Kamioka, ICRR/IPMU, University of Tokyo
           C.Ida, H.Kubo, S.Kurosawa, T.Tanimori
                    Dep. of Physics, Kyoto University
               A.Yoshikawa, T.Yanagida, Y.Yokota
                          IMRAM, Tohoku University
      K.Fukuda, S.Ishizu, N.Kawaguchi, T.Suyama
                               Tokuyama Coporation
                  Hiroyuki Sekiya 11th iWoRiD Jul 1 2009@Prague, Czech
Contents

 Motivation –Gas Photomultiplier
 VUV scintillator
 Setups of the detector
 Analog property
    ◦ 1p.e. level pulse mode operation
   Digital property
    ◦ Operation as a novel imaging detector
   Summary



                       Hiroyuki Sekiya 11th iWoRiD Jul 1 2009@Prague, Czech
 Gas Photomultipliers
  Photocathode
   + Micro Pattern Gaseous Detector




Possible features
 Large  Area
 Position resolution             Future Large Volume
 Low cost                        Detectors for
 Small Volume
                                  Dark Matter/neutrino
 Low background
                                 Inside of the 1 2009@Prague, Czech
                     Hiroyuki Sekiya 11th iWoRiD Jul Super-K detector
CsI photocathode for GPM
   Although only sensitive to <200nm, easy to handle
    (⇔ Bialkali PC)
    ◦ Strong for ion feedback flow: Low Ion induced electron
      emission probability
    ◦ Stable in dry air.
   Many possible applications
    ◦ Liq. Xe/Ar scintillators (λ<180nm)
       Single phase detector (DM search, XMASS)
        ◦ Tube type
       Double phase detector
        ◦ Both charge & photon detection
    ◦ VUV Crystal scintillators (our target)
       Like visible scintillators + PMT
        ◦ PET
        ◦ Color X-ray CT
        ◦ Gamma Camera

                                 Hiroyuki Sekiya 11th iWoRiD Jul 1 2009@Prague, Czech
UV scintillator
 We are developing Nd3+ doped fluoride crystals
  which emit VUV photons through 5d-4f transition.
 This time, we focused on LaF3(Nd) as a low
  intensity light source in order to test the detector
  for 1p.e. level.
 λ=172nm, τ= 6ns             X-ray induced luminescence spectrum
                                      1
                                      0.9
                                      0.8
                                      0.7
                                      0.6
                                      0.5
                                      0.4
                                      0.3
                                      0.2
                                      0.1
                                      0.0
                                            150 160 170 180 190 200 210 220 230 240 250 260


                                                           wavelength(nm)
                           Hiroyuki Sekiya 11th iWoRiD Jul 1 2009@Prague, Czech
LaF3(Nd) as a light source
    2cm size crystal covered with Teflon
                + 3kBq α from 241Am




    Light Yields were measured with VUV sensitive PMT R8778
                                               (HAMAMATSU)
                        Developed for XMASS
                        Quartz window
         • 30 p.e.
                        UV enhanced bialkali

                              Quantum efficiency 30%@172nm
                               → LY 100 photons/5.5MeV α

                            Hiroyuki Sekiya 11th iWoRiD Jul 1 2009@Prague, Czech
Semitransparent Photocathode
   5t MgF2 window
   Al vapor deposition on
    10mm edge.
   34mmΦ CsI vapor deposition
“The thickness is same as that of
   CsI PMTs(100M)” by Hamamatsu


                      QE curve




                              Hiroyuki Sekiya 11th iWoRiD Jul 1 2009@Prague, Czech
μPIC & GEMs:                                        electron multiplier
   Many R&D efforts on CsI+MPGDs.
     ◦ Cascade GEM/MHSP/THGEM and so on.
        ex) NIM A 595(2008) 116 and its refs
   Our strategy is GEMs+μPIC
     ◦ GEMs for ion feedback blocking
     ◦ μPIC for high gain / position resolution
    μPIC                            GEM/SMASH
    Cathode strips
                         Anode strips




       400μm                            Advanced                             Laser etched.
                                             MSGC                             100um LCP
                                        400μm pitch                             / 50um Capton
                 400μm
                                               strips                         140um pitch
                                        Kyoto/DNP                                     70umΦ
                                                                              RIKEN/SciEnergy



                                                 Hiroyuki Sekiya 11th iWoRiD Jul 1 2009@Prague, Czech
Large Area μPIC & GEM
    30cm size Area MPGDs are already used in
     many applications.

 30cm μ-PIC                 28cm GEM              28cm

                                                    23cm



    For the prototype detector, partly because the
     window size is limited for the moment, we
     adopted 10cm size MPGDs.
     10cm μ-PIC             10cm GEM


                        Hiroyuki Sekiya 11th iWoRiD Jul 1 2009@Prague, Czech
Set up for testing analog properties
  2 100μm-GEMs+μPIC with CsI photocathode
  Ar+C2H6(90:10)1atm
  Gas gain 2.6 x 105 μPIC 465V
                              GEMs 422V
             241Am

                     LaF3

                        CsI
                                Ed= 0.3kV/cm
 Electrode            13mm

                       2mm

                       4mm        EI= 1kV/cm



                              Hiroyuki Sekiya 11th iWoRiD Jul 1 2009@Prague, Czech
Photon Signal
    Readout: μPIC 64 strips summed
    Amplified with CP581 preamp (1V/pC)           Clearpluse co., ltd.




                120mV




     The gas gain 2.6×105
     Detected number of photoelectrons
               120mV/1V×1pC/(1.602×10-19)/ 2.6×105=2.9 p.e.


                             Hiroyuki Sekiya 11th iWoRiD Jul 1 2009@Prague, Czech
Spectrum


                                            Sensitive to 1p.e. !




   Source intensity 100 photon → QE ~ 1-2 %



       =    ∫            ×                      dλ
                  Agrees with QE curve and the luminescence spectrum

                          Hiroyuki Sekiya 11th iWoRiD Jul 1 2009@Prague, Czech
Set up for testing imaging properties
  2x50μm-GEMs+μPIC with CsI photocathode
  Ar+C2H6(90:10)1atm
  256ch x 256ch readouts
  2.6MBq 241Am for higher rate test

                  LaF3

                     CsI
           2.5mm           Ed= 0.5kV/cm

            2mm

            2mm            EI= 2.95kV/cm


        μPIC 490V
        GEMs 280V Gas gain 6.7 x 105

                            Hiroyuki Sekiya 11th iWoRiD Jul 1 2009@Prague, Czech
                                                 NIMA 513(2003) 94
Readout system
     ASD chip
     for ATLAS TGC
          0.8V/pC

                                                   Position Encoder
                                                      FPGA x 3
                                                    100MHz clock


                                                   Obtained image




                     Hiroyuki Sekiya 11th iWoRiD Jul 1 2009@Prague, Czech
Crystal Shape Reconstruction
   18x21x20mm3 LaF3(Nd) + 2.6MBq                      241Am



       Parallel composition                   Diagonal composition




                              Hiroyuki Sekiya 11th iWoRiD Jul 1 2009@Prague, Czech
Image Expansion by Electric Fields
    Lens Effect between the PC and the 1st GEM


         241Am

                 LaF3
                                                    X 1.6 expansion




    Large area MPGDs make the expansion possible
     and this effect may enhance the position
     resolution of Gas PMTs against the diffusion.
                        Hiroyuki Sekiya 11th iWoRiD Jul 1 2009@Prague, Czech
Evaluation of the magnification
   0.1t PVC sheets inserted                              LaF3

       10mm distance Slits
       2mm x 15mm

             Vertical composition                     horizontal composition



                    X projection                                 Y projection




              Uniformly x1.6 expanded
                              Hiroyuki Sekiya 11th iWoRiD Jul 1 2009@Prague, Czech
More Examples
5mm distance Slits
2mm x 15mm




   Star                           犬




                     Hiroyuki Sekiya 11th iWoRiD Jul 1 2009@Prague, Czech
Summary
   A new UV sensitive gas PMT with GEM/μPIC is
    being developed.
   Although the QE is still limited, 1 p.e. level
    signal is clearly detected.
   Combined with new VUV scintillators, new
    radiation imaging sensors are also being
    developed.
   With LaF3(Nd), the imaging capability of the
    detector was tested. It might have sub 1mm
    position resolution.
   Electric lens effect (expansion) was
    demonstrated thanks to the large area MPGDs.

                       Hiroyuki Sekiya 11th iWoRiD Jul 1 2009@Prague, Czech

				
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