R&D on CsI(Tl) + APD Optimisation of the energy resolution M. Gascón I.Durán

R3B calorimeter Total absorption efficiency 80 % (E  =15 MeV lab) Very large crystals E  sum  (E sum )/ <10%(same as  E/E)  Multiplicity  (N  )/ < 10% Moliere Radius  E/E for  2-3 %Scintillation properties Detector granularity  E/E for p (up to 300 MeV) Calorimeter for p 3 %Large crystals Dynamic range Large dynamic range for detecting p,  Inner radius 35 cm ( house Si trackers) Main characteristics (from R3B Tech Proposal) : R&D on crystals + readout systems Design based on CAD + GEANT4 full simulations see -> calorimeter -> reports and talks

Calorimeter sectors Demonstrator meeting, Madrid May-09 Due to the Lorentz boost we identify three sectors: E CM = 10 MeV β =

Crystals !? R3B/EXL meeting Milan Oct-06

Crystals M. Mozynski et al., NIM A 485(2002)504 (API LAAPD)

CsI (Tl) 10x10x10, 10x10x50,10x10x100, 10x20x170 mm CsI (pure) 10x10x10, 10x10x50,10x10x100 mm LaCl3(Ce) 10x10x10, 10x10x50,10x10x100, 10x20x170 mm Standard 10-stage, 19 mm tube, lima glass, Green bi-alkaliXP1901 Standard 10-stage, 19 mm tube, fused silica, UV bi-alkaliXP1918 Standard 10-stage, 25 mm tube, borosilicate glass, bi-alkaliXP mm 2 UV extended ( nm)S5345+ API 10x10 mmS (PANDA) 5x5 mmS (CMS) St Gobain Photonis Hamamatsu R3B/EXL meeting Milan Oct-06 Material we used for test

R&d on crystals and APDs Crystals from StGobain (France) tested coupled to LAAPD from Hamamatsu (Japan) and API (USA)

R3B/EXL meeting Milan Oct-06 Data-taking setups Standard pulse-height analysis : - preamplifiers: Canberra 2001A, Ortec R142 - Shapping amplifier: Canberra Multichannel analyzer: Ortec Maestro or Amptek MCA-8000 Pulse-shape analysis : - Oscilloscope Tektronix TDS3054B - Off-line Digital filtering: Trapezoidal finite-impulse algorithm Not used for APDs but providing the best results for PMT!

Experimental setup

Test at Genp-Lab (USC)

APD gain vs. Bias Voltage 5 cm length The energy resoltution depends on the APD gain and the Bias Voltage ~380V Dgain/DV= 2.84 % The energy resoltution shows a minimum when The APD Bias Voltage=380

Dependence on shapping time For small crystals 4ms is a good compromise between energy-resolution and pile-up

Dependence on the acquisition time Best results achieved for acquisition times between s These curves conatin two effects: statistics and bias voltage drift. Could be solved by controling Temperature and Bias Voltage

Dependence on Amplifier Gain Energy resolution improves by increasing the amplifier gain

Best results

Study of the non-uniformity Energy resolution dependence on the first interaction point Non-uniformity ~ 8.4 %, to compare with < 3% measured by St. Gobain Light collection uniformity CMS CAL P. Sempere PhD Thesis

CsI(Tl) Resolution R3B/EXL meeting Milan Oct-06 Energy resolution improves for increasing energy CsI(Tl) with a 60 Co source (1171 keV) and (1332 keV)

Some conclusions Several test (wrapping, optical coupling,amplifier gain, shapping time) have been performed to optimise the energy resolution of CsI(Tl) APDs from API showed the best energy resolution for CsI(Tl) crystals APDs S from Hamamatsu showed a very good energy resolution almost independent on the crysal size The main drawback of APDs vs PMT is the strong dependence of the gain with Temperature and Bias Voltage How to improve the resolution: -Better stabilisation of both temperature and bias-voltage. - Better optical coupling --> Scionix - Surface coating --> Ukranian Institute for Crystals - New generation of scintillating crystals

T and V dependence Both Crystals and APDs response depends on Tº  T must be kept very stable ! ~0.1 o otherwise, T should be accurately measured in order to keep gain constant by controlling the bias voltage

Characterization of S APD T. Ikagawa et al., NIM A 538(2995) 640 T stabilisation ~0.1ºC keep the gain variarion ~ 0.3%

Temperature stabilisation Refrigerator 4-5 º C Humidity control box < 30% (1%) radiator Resistor warm focus T probe T stable within 0.1ºC Ceramics Cold focus ~ 10ºC T controller 22ºC Allow pulse shape analysis with Tektronix TDS3054B

Crystal type-2 Bi-frustrum shaped Waiting for an agreement with StGobain and IMP- Lanzhou(China) --> Price drop! Exit face fits to LAAPD S under negotiation First prototypes done at Lanzhou (China Further tests through prototype Good results are only achieved when there is a perfect matching between the crystal exit surface and the APD entrance area Type 2 View of the Barrel average dimensions 3x1x13 cm

Study of St. Gobain vs IMP Lanzhou crystals Tests performed with API APD Crystal dimensions 1x1x1 cm Very similar behaviour

Resolution achieved IMP Lanzhou St. Gobain

R3B Type Crystal

Uniformity of the crystal Wrapped with ESR (from 3M), tested with 60Co