Gamma Spectrometry beyond Chateau Crystal J. Gerl, GSI SPIRAL 2 workshop October 5, 2005 Ideas and suggestions for a calorimeter with spectroscopy capability

High-resolution momentum measurement Fragments Neutrons Protons Neutrons Exotic beam from Super-FRS  rays B  = m  v / Z Reactions with Relativistic Radioactive Beams R3B at NUSTA/FAIR A versatile setup for kinematical complete measurements Large-acceptance measurements

Goals and Requirements  -sum energy  sum > 80%;  (E sum )/ < 10%  multiplicity  (N  )/ < 10%  energies  E  /E  < 2%  times  t  < 3 (1) ns Total excitation energy; angular momentum; decay path; discrete line spectroscopy; neutron/charged particle discrimination; background discrimination

144 Elements / 2  CsI(Na)  detector ( LAND )

LAND Target Detector Intrinsic energy resolution ( 60 Co): 7 (1) % Sum energy resolution ( 60 Co) : 6.7 %  fe at 1.8 MeV: - single mode: 9.3 % - addback mode: 16.3 % - summing mode: 37.0 % GEANT simulation for moving source: 250 MeV/u600 MeV/u  fe :~ 45 %~ 55 % Doppler broadening:~ 3 %~ 5 % Intrinsic energy resolution ( 60 Co): 7 (1) % Sum energy resolution ( 60 Co) : 6.7 %  fe at 1.8 MeV: - single mode: 9.3 % - addback mode: 16.3 % - summing mode: 37.0 % GEANT simulation for moving source: 250 MeV/u600 MeV/u  fe :~ 45 %~ 55 % Doppler broadening:~ 3 %~ 5 % No spectroscopy capability

Crystal Ball at LAND

Crystal Ball 162 NaI(Tl) crystals spherical shell, 22 cm thick, diam. 50 cm  int = 93 %,  fe = keV  sum = 85 %,  (E sum )/ = 5 MeV = 1.2,  (N  )/ = M=10  E  = keV,  t  = 3.5 ns Doppler broadening:  MeV/u

Spectroscopy set-up at LAND RIBs: E ≈ 200 MeV/u; I = pps ! n-rich Mg to Ca nuclei

Multiplicity gated  spectra from Crystal Ball 28 Mg + C → 28 Mg 27 Mg 26 Mg M  increases with number of knocked out nucleons ΔE  ≈ 10 % dominated by Doppler broadening

Sum energy – Multiplicity correlation 27 Mg + C → 26 Mg

(8 + ) Cr 140 MeV/u 55 Ni on 9 Be Mirror symmetry 2+2 2+2+2   MeV/u 136 Nd on Au Triaxiality Reaction types at relativistic energies

Applications of a calorimeter Spectroscopy - Weak channel detection - Selectivity by higher folds - Sum/multiplicity filter Reaction mechanism - Excitation energy - Angular momentum - Isomerism Independent of beam energy

New Opportunities Solid state Ge detectors efficiency, timing resolution, prohibitive cost Liquid Xenon scintillators experience?, purity maintenance, high pressure container New inorganic scintillator materials LaBr 3,.... Cooled standard inorganic scintillators CsI(pure), NaI(pure),...

Properties of pure, cooled CsI Light yield: 1∙10 4 Photons/MeV Light emission: 320 nm Decay time: 16 ns Density: 4.5 g/cm 3 Energy resolution: 1.6 % at 662 keV (LN2 temp.) Time resolution: 380 ps (against plastic)

Properties of scintillators

Energy resolution of LaBr 3 :Ce E = 60 keVE = 668 keV Crystal at room temperature, Read-out: APD at -23 °C K.S. Shah et al., IEEE NS/MIC/RTSD 2003  FWHM < 1.3 MeV

Energy resolution limitations (  E/E) 2 = 5.6·(1/N·  ) + R sci 2 + R noise 2 Photon statistics and quantum efficieny: N·  Crystal inhomogeinity, non-proportionality, light losses: R sci Electronic noise: R noise  Cooling to improve R noise ?

K.S. Shah et al., IEEE NS Vol. 50 (2003) 2410 Time resolution of LaBr 3 :Ce Time resolution depends on Ce dopant concentration 5% Ce

Manufacturer's view  limited crystal size (LaBr 3 : 1" x 2", LaCl 3 3" x 3")  very hygroscopic → sealed housing, glass window?  hard and brittle → cutting and polishing problematic  Best suited for medical imaging → Attractive market Crystal treatment is expensive Lot of development is going on Costs: Raw LaBr 3 crystal: ~ 30€ Scint. detector: ~ 1500€ + 300€/cm 3

What to build.... Pencil detector: ≈ 0.5x0.5 cm 2, cm long, ≈ (1...3)x10 4 elements

Large position sensitive LaBr 3 :Ce detector AB ab A C B D E =  (E a...E D ) pos(x,y,z) = centroid of light distribution 5 cm 6 cm A few 100 elements...

Requires cooling to reduce noise

Features Gain above 1,000 at operating condition of best signal-to-noise ratio. (Maximum gain of 10,000.) Large active area High quantum efficiency (QE) extends beyond visible spectrum High speed at 1064 nanometer wavelength of YAG lasers Pulse counting mode is the most-frequent style of use. Optical Photon Counting (2-3 photons) when cooled 14x14 pixel APD APDs from Radiation Monitoring Devices Inc.

Conclusion A 4  scintillator shell is highly beneficial for most spectroscopy experiments with RIBs! Cooled inorganic scintillators (CsI, NaI) or La halides seem appropriate A lot of R&D is needed including crystals, light readout, electronics Can we find a common solution....