Scintillators for photon detection at at medium energies

Transcription

1 Scintillators for photon detection at at medium energies R.Novotny II.Physics II.Physics Institute, Institute, University University Giessen, Giessen, Germany Germany and and for for the the TAPS TAPS and and CRYSTAL CRYSTAL CLEAR CLEAR collaborations collaborations experimental requirements at medium energies comparison BaF 2, CeF 3 and PbWO 4 photon response particle identification/discrimination time-of-flight pulse-shape analysis phoswich technique particle response conclusions and outlook CeF 3 BaF 2 PWO

2 experimental requirements at at medium energies < 1-2 GeV low cross sections compact set-up dense material detection of low and high energy photons good energy resolution sufficient luminescence low cross sections high count rates fast scintillator high multiplicity of neutral/charged particles fast scintillator pulse-shape sensitivity time-of-flight PSA

3 relevant properties of of the investigated crystal scintillators crystal BaF 2 CeF 3 PWO density (g/cm 3 ) radiation length (cm) Moliere radius (cm) luminescence (nm) , decay time (ns) relative light output comp. to NaI(Tl)

4 counts experimental technique: energy marked photons R T M 2 full spectrum of the MAMI, Mainz counts counts R T M 1 R T M 3 linear accelerator 3 accelerator stages 1 counts MeV 1 MeV 14 MeV 18 MeV 298 MeV due to coincidence with tagger scintillators energy photons photons 45 MeV 599 MeV 1 79 MeV energy /a.u. energy bins: DE ~ 1-2 MeV electron beam 855 MeV radiator

5 photon response: BaF 22 σ E 137 [ 662keV, Cs] = 4.9% (15.1%) fast: 195, 21 nm slow: ~ 31 nm s / E TAPS detector: 12X 59mm Ø fast slow σ E [ 1 GeV] = 5.1% photon energy / GeV shower leakage! lineshapes measured with tagged photons

6 photon response: CeF 33 P1 P2 P3 P4 P5 P6 each tower consists of 2-4 elements total length ~ 4mm ~ 25 X o individually wrapped read-out with PM-tubes 3x3mm 2 1 transmission [%] CeF 3 # E g =54.6 MeV s/e=11.5% wavelength [nm] counts / a.u E γ = 55 MeV 227 MeV 48 MeV experiment 769 MeV 2x2mm 2 GEANT energy / MeV

7 photon response: CeF 33 E.Auffray et al. NIM A378(1996)171 e, µ, p: 1 15 GeV/c s/e 5 GeV with Si PD read-out 12 CeF 3 - Array s/e [%] 1 8 σ E = 2.17% E[GeV] + 2.7% 6 4,,1,2,3,4,5,6,7,8 photon energy [GeV] in collaboration with: P.Lecomte et al., CC-Collaboration

8 photon response: PbWO 44 lineshape 1 ns digital scope: Tektronix TDS 744A E g ~ 4 MeV recorded after 5 m RG58 cable K 1ns 1µs = yield yield > 96.5% no significant slow decay components

9 photon response: PbWO 44 response to low energy g - sources pwo 158 tapered 98/1/ pwo 158 tapered 98/1/ Cs 662 kev Co ~1.25 MeV 6 4 s/e ~ 3% s/e ~ 25% Narrow light output [a.u.] Narrow PM: R259-1

10 photon response: PWO:Tb, PWO:Mo enhanced luminescence by selected doping optical transmission 8 7 Tb-PWO Nb/La-PWO Cs (662keV) 12 Tb-PWO Nb/La-PWO Mo-PWO counts [a.u.] Mo-PWO photopeak position [a.u.] wavelength [nm] Cs (662 kev) Mo-PWO Tb-PWO Nb/La-PWO,,5 1, 1,5 2, 2,5 3, 3,5 4, 4,5 5, integration gate [ms] energy [a.u.] increased light-yield but: longer integration time

11 photon response: PbWO 44 determination of the luminescence yield using hybrid photodiodes # 158 Nb/La-PWO #315 Sb-PWO plastic scintillator 6 Co g -source counts 1 3 ID Entries Mean RMS test crystal 1 < p.e.>=5. < p.e.>=5.3 HPD 1 delivered by: Bogoroditsk TCP delivered by: Shanghai SICCAS test set-up light-output [a.u.]

12 photon response: PbWO 44 determination of the luminescence yield using hybrid photodiodes samples light output /p.e. first matrix Nb doped Nb/La square Nb/La tapered Shanghai BGRI 32x32 RINC 32x32 prototypes for Proton

13 photon response: PbWO 44 experimental set-up cooled T ~ 6 o C 5x5 matrix electrons photons 5-85 MeV plastic veto photomultiplier read-out Philips XP1911 or Hamamatsu R4125 (19 mm ) DAQ : individual processing of energy and time information using commercial CAMAC electronics.

14 2.5 x 2.5 mm photon response: PbWO x 22.7 mm 2 E g = a ~.4 o 15 mm delivered by: Bogoroditsk TCP counts E g =45.4 MeV s/e=7.4% 1 E g =15.6 MeV s/e=5.3% energy / a.u. improved resolution below 15 MeV in spite of reduced PM-coverage of the crystal endface no correction for finite energy bin ( MeV) s 141. % = + E E[GeV] 9. %

15 particle response: BaF 22 fast timing signal time resolution: s t > t ps ps optimum time resolution in spite of large crystal size! time-of-flight / ns 2 AGeV Ca+Ca particle identification energy / MeV

16 particle response: BaF 22 proton time plastic VETO BaF 2 -detector photon E-fast photons all events fast component protons total light output E-total signal integration width pulse-shape sensitivity reaction products: 2 AGeV Ar + Ca charged events protons neutral events photons n

17 particle response: BaF 22 charged particle time E-fast p d t photons fast component total light output signal integration width E-total phoswich: plastic/baf 2 BaF 2 -detector plastic scintillator common PM-read-out

18 neutron response: BaF BaF 2 2 identification: time-of-flight, plastic VETO, PSA neutron efficiency depends strongly on energy and detector threshold E n < 3 MeV: neutron identification via exclusively measured reaction g + p p + p + + n efficiency: E n > 75 MeV 17%

19 experimental tests of of charged particle response FZ Jülich target 5x5 matrix protons p = 2. GeV/c secondary target charged reaction products µ plastic scintillator 5x5 matrix TOF start detector plastic scintillator cooled T ~ 11 o C TOF start detector TOF distance: 2.9 m 1.2 GeV p + Al Al measurement: measurement: energy, energy, TOF TOF of of charged reaction products particle ID ID (p (p +/- +/-,, p, p, d, d, t, t, e +/- +/- )) energy response

20 charged particle response: GeV p + Al time-of-flight relative to photons / ns p proton calibration t d p MIP counts p E p = 5 MeV 16 d t π energy / MeV E p = 2 MeV p d counts hadrons deposited energy / MeV MIP E.M.shower MIP proton calibration s/e % protons deuterons pions multiplicity E.M.shower due to e +/- total energy / MeV photon response energy / MeV

21 PWO matrix response: 1.2 GeV p + Al counts <M> ~1.5 high multiplicity events M > 3 multiplicity Multiplicity below the values obtained for EM-showers: <M> = 45 MeV <M> = E threshold = 5 kev all kinematical correlations disappeare!

22 pion response of of PWO: 1.2 GeV p + Al Al g proton γ = ( 1 β 2 ) 1 = E m kin + 1 p proton-calibration fails! K MIP p d deposited energy / MeV quenching effects? p / p ~ 3 / 1 energy determined from TOF / MeV 6 E tof = E dep E(tof)= *E(dep) deposited energy (proton calibration) / MeV

23 pion response of of PWO: 1.2 GeV p + Al indication of pulse-shape sensitivity excitation density dependence of the emission spectrum (excitation with 1eV photons) exp. sensitivity: integration gate QE of PM time-resolved emission spectra at different excitation energies I.A.Kamenskikh et al., Proc. SCINT97, p.195

24 experimental tests of of charged particle response Groningen target foil (C, CH 2 ) active collimator protons E = 85 MeV charged reaction products vacuum chamber MeV p + C, C, CH 22 measurement: measurement: energy energy of of scattered protons protons energy response of of BaF BaF 2, 2, CeF CeF 3 and 3 and PWO

25 experimental tests of of charged particle response individual detector: particle impact selected by active collimator (plastic scintillator BC 48) Groningen p+c plastic collimator PM collimator PM p+ch 2 light-tight housing collimated events

26 proton response: MeV p + CH comparison: CeF 3 BaF 2 PWO PWO:Mo 2 12 counts 15 1 CeF 3 2 x 2 x 14 cm 3 8 BaF 2 TAPS geometry 25 cm counts counts 15 1 CeF 3 2 x 2 x 14 cm BaF 2 TAPS geometry 25 cm PbWO 4 2 x 2 x 15 cm PbWO 4 :Mo 1.5 x 1.5 x 1.5 cm 3 1 PbWO 4 2 x 2 x 15 cm PbWO 4 :Mo 1.5 x 1.5 x 1.5 cm proton energy / MeV proton energy / MeV proton energy / MeV MeV p + C 85 MeV p + CH 2

27 proton response: MeV p + CH s / E % PWO 2 x 2 x 15 cm 3 PWO 3 x 3 x 12 cm 3 PWO 3 x 3 x 12 cm 3 PWO:Mo 1.5 x 1.5 x 1.5 cm 3 CeF 3 2 x 2 x 14 cm 3 CeF 3 3 x 3 x 13.2 cm 3 BaF 2 TAPS 25 cm energy / MeV PWO PWO:Mo CeF 3 BaF 2

28 proton response: comparison BaF 22 CeF 33 PWO s / E / % BaF 2 #1 BaF 2 #2 photon response s / E / % CeF 3 #1 CeF 3 #2 photon response,2,4,6,8,1 energy / GeV,2,4,6,8,1 energy / GeV s / E / % photon response matrix response PWO 2x2 cm 2 PWO 3x3 cm 2 PWO 3x3 cm 2 PWO:Mo 1.5x1.5 cm 2,2,4,6,8,1 energy / GeV

29 s/e / % s / E % comparison of of photon and particle response CeF 3 PbWO 4 BaF 2 fast / total ,,1,2,3,4,5,6,7,8,9 1, 1, photon energy / GeV PWO CeF 3 BaF energy / MeV PWO:Mo CeF 3 PWO BaF 2 photon response σ E = A E / GeV BaF 2 CeF 3 PWO photons A / % B / % s/e / % 662keV 4.9 <3 5 MeV GeV protons A / %.97 B / % 3.33 s/e / % 8 MeV time-of-flight s / ps 85 <17 <13 + B

30 Apparatus for studies of Nucleon and Kaon Ejectiles outlook outlook one of the internal beam facilities of COSY up-grade up-gradeby byaanew newphoton photonball ball to todetect detect neutral neutralmesons mesons in incoincidence: coincidence: complete completemeasurements measurements magnetic spectrometer 3 C-shaped dipoles D2: spectrometer magnet ramped synchronously with COSY during accelerating phase the theparticle particlespectrometer spectrometer ANKE@COSY ANKE@COSY

31 technical constraints limited space in the target region compact design dense detector material operation in the magnetic strayfield of D2 field strength.2 Tesla field vectors point in various directions detector requirements good energy resolution up to E g = 2 GeV crystal length 12 X position resolution high granularity large solid angle 3p background suppression fast response fast read-out with PM on-line charged particle discrimination future option: stand alone 4p-device 12cm PbWO 4 R 555 soft iron cylinder thickness 3mm signal amplitude [a.u.] beam 7 U b = -195V orientation R = 6 1mm shielding 2mm shielding magnetic field [Gauss] PM signal [a.u.] ramping of D2: up to 1.6 Tesla operation time [Dt=1s]

32 presented for the TAPS and Crystal Clear collaborations W.Döring, M.Hoek, V.Metag, K.Römer II. Physikalisches Institut, Universität Giessen A.Hofstaetter I. Physikalisches Institut, Universität Giessen R.Beck Institut für Kernphysik, Universität Mainz V.Hejny, H.Ströher Institut für Kernphysik, FZ Jülich M.Korzhik RINC, Minsk, Belarus research has been supported by BMBF, DFG, FZ-Jülich