Towards a Compton Telescope for Gamma-Ray Astronomy in the MeV range CSNSM-Orsay, AIM/CEA-Saclay, APC-Paris, MPE-Garching, NSI-Copenhagen AHEAD meeting, 9-10 February 2009, Roma The 0.1  10 MeV photon energy range is the domain of nuclear line spectroscopy  Interaction of low-energy CRs with the ISM  Gamma-ray emissions of SN Ia and classical novae  Radioactive line emission from the solar atmosphere  …  We seek a gain in sensitivity of 2 orders of magnitude as compared to INTEGRAL

Compton telescope constitution Compton telescope constitution To optimize background rejection (=sensitivity), Compton imaging and polarization studies:  Fine 3-D position resolution (~1 mm 3 )  Good energy resolution (better than 1  2 %)  Tracking of the initial recoil electron  Very fast timing of interactions ( < 1 ns) to allow ToF selection with a compact instrument Refs: ACT Study Report (Boggs et al. 2006); GRIPS proposal (Greiner et al. 2007) Tracker. Low-Z material for optimizing Compton scattering and minimizing Doppler broadening  Si Calorimeter. High-Z material for an efficient absorption of the scattered photon Anticoincidence detector to veto charged-particle induced background e-e-

R&D of pixelated CdTe detector technology Thanks to INTEGRAL and SWIFT, CdTe and CZT semiconductors are already qualified for space applications New development: Caliste 64 for the HED (8-100 keV) of SIMBOL-X 10 mm 18 mm CdTe detector (64 pixels, 1mm pitch, 1mm thick, guard ring) Front-end electronics (4 IDeF-X 1.1 ASIC of 16 analogue channels) Rear interface (7x7 pin grid array, 1.27 mm pitch) X radiography

Promising technology for the calorimeter: high efficiency, excellent position and energy resolutions (alternative to Ge for hard X-ray spectroscopy) R&D challenge: extension of the bandpass beyond 1 MeV Caliste 64 Sum of 64 spectra -10°C, -400 V, 241 Am: 805 eV 60 keV (1.35%) R&D of pixelated CdTe detector technology  Multi-layers of pixelated detectors  Extension of the dynamics of the IDeF-X ASIC up to 1 MeV/layer  Detector substrate with high transparency  Bigger CdTe crystals: 256 pixel detectors, 1 mm pitch,  6 mm thick

Relevant X- and Gamma ray detector Activities for AHEAD at NSI CZT test crystals: 10 mm x 10 mm Pixel pitch: 2.5 mm Thickness: 5 – 10 mm (μτ) e >10 -2 cm 2 /V, (μτ) h <10 -4 cm 2 /V 1) CZT pixel detectors for the ESA ASIM mission 3D position information, high energy resolution, high efficiency Normalized depth 3D CZT-pixel detector configuration for the calorimeter DTU Space, Technical University of Denmark 0.66% 662 keV

E. Caroli et al. (2008), Proc. SPIE, Vol. 7011, 70113G 2) 3D CZT drift strip detectors PTF = Photon Transverse Field: the field is perpendicular to ‘optical’ axis CZT crystal units 10×10×2.5 mm 3 Relevant X- and Gamma ray detector Activities for AHEAD at NSI DTU Space, Technical University of Denmark 0.70% 356 keV

“A good choice for a  -ray spectrometer for future space applications” (Drozdowski et al. 2007, program “Gamma Ray Scintillator Development” of ESA, Cosine Research BV, St Gobain and Delft University of Technology) The new LaBr 3 :Ce scintillator could be an alternative for the calorimeter  High stopping power (comparable to CZT) and can be fabricated in large volumes  Good energy resolution above a few hundreds of keV  Very fast response (CRT ~ 0.2 ns  light transit distance of 6 cm in vacuum) R&D of LaBr 3 :Ce technology R&D of LaBr 3 :Ce technology Saint Gobain Technical Note on BrilLanCe TM Scintillators

LaBr 3 :Ce  3D position resolution Coupling of a LaBr 3 crystal (5  5 cm 2, 2 cm thick) to a 16  16 multianode PMT (Hamamatsu H9500) to form an Anger camera In addition to the X-Y position of the  -ray interaction, depth Z from the signal distribution within the sensor plane New ASICs (coll. LAL/CSNSM). Duplication of each output signal with 2 different integration times to optimize the energy and position resolutions Specific data acquisition system for a real-time  -ray tracking (multi-hit events ?) from a library of scintillation signal distributions Note: the effect of the intrinsic background of LaBr 3 (EC and  - decay of 138 La, 0.09% nat. ab.) should be suppressed  X= keV (Pani et al. 2007)

Case et al., NIM A 563 (2006) 355 LaBr3:Ce + fibres design o The position X, Y could be measured by using orthogonal optical fibre grids on each side of a LaBr3 scintillator to convey the light to a MAPMT. Z-coordinate from the distribution of scintillation signals o The measure of the deposit energy E could be done by looking through the system with larger PMT  Less electronics channels  Reduction in the power requirements Coupling of the scintillation crystal to waveshifting optical fibres Ex: design proposed for the CASTER mission (McConnell et al. 2006)

LaBr 3 :Ce  Neutron irradiation LaBr 3 has a satisfactory radiation tolerance to irradiation by MeV protons (Owens et al. 2007; Drozdowski et al. 2007a) and MeV  -rays (Normand et al. 2007; Drozdowski et al. 2007b) Neutron irradiation using the 7 Li(p,n) 7 Be reaction at the - CENBG/Van de E beam =3 MeV - E beam =5  7 MeV  quasi-monoenergetic neutron beams between 0.5 and 5 MeV Online measurements of the prompt  -ray emission + offline analyses of the activation  radioisotope production yields  Calculations with the nuclear reaction code TALYS shield Ge p beam 7 Li  n LaBr 3 n neutron detector

Simulation of the full chain from the spatial environment to the data treatment using :  Cosmic environment simulators, for given period and orbits.  Detector simulators (Geant 4).  On-board data treatment simulators (C++).  On-ground data reduction simulators (C++). Monte-Carlo simulations and accelerator tests Test of mock-ups in “ real ” conditions in particle accelerators in order to check the estimates we derived from simulations  Optimization of the anticoincidence detector  Full performances of the Compton telescope