"FAZIA: a new detector for nuclear physics"
Stefano Carboni, INFN Firenze
(id #113)
Seminar: NoPoster: Yes
Invited talk: No
For the next generation of nuclear physics experiments it is important to optimize the isotopic resolution of reaction fragments with the lowest possible thresholds. Pulse Shape Analysis techniques coupled to digital signal processing are very useful to this aim.
In the last years the FAZIA collaboration and other groups have investigated the behaviour of silicon detectors for pulse shape applications. It was found that, for stopped ions, the discrimination capability with PSA strongly depends on the homogeneity of the detector resistivity and on a careful control of channeling-related effects.
Previous studies of the FAZIA collaboration demonstrated the importance of using silicon detectors from wafers cut along the so called “random” directions, namely those which make the crystal appear like an amorphous material to impinging particles.
The silicons of the FAZIA telescopes were built adopting such type of cut. Moreover only detectors with doping inhomogeneities of about 1% or better were used. This last selection was done with a laser-based non-destructive method developed by the collaboration, that allows building a map of the resistivity as a function of the position on the silicon.
In the present work the response of eight silicon-silicon-CsI(Tl) and silicon-silicon telescopes with purposely developed high quality silicon detectors has been tested. In particular the silicon detectors were manufactured with stringent requirements for what concerns doping homogeneity, thickness uniformity and crystal orientation, to avoid channeling effects. All these features are obtained by proper choice of the silicon material and cutting geometry, without significantly affecting the cost of the detectors. Custom-developed digital electronics and original digital signal processing techniques have been extensively used.
Beams of 84Kr and 129Xe at 35A MeV, accelerated by the CS in Laboratori Nazionali del Sud (Catania), impinging on targets of natNi, 93Nb, 120Sn and Au, produced fragments over a large range of charge, mass and energy. The aim was to explore the capabilities of various solutions exploiting the digital techniques of Pulse Shape Analisys (PSA) for the Z and A identification of stopped ions.
The results of the digital PSA technique for identifying stopped ions are very satisfactory: full charge separation is obtained up to the maximum observed Z=54. Partial mass identification until Z=12 has been observed with a higher energy gain in other beam-tests done in Laboratori Nazionali di Legnaro and GANIL.
The ΔE-E (Si-Si) correlations allow isotopic separation up to Z=23-24, not far from the physical limit imposed by the energy straggling, as suggested by simulations.
In the last years the FAZIA collaboration and other groups have investigated the behaviour of silicon detectors for pulse shape applications. It was found that, for stopped ions, the discrimination capability with PSA strongly depends on the homogeneity of the detector resistivity and on a careful control of channeling-related effects.
Previous studies of the FAZIA collaboration demonstrated the importance of using silicon detectors from wafers cut along the so called “random” directions, namely those which make the crystal appear like an amorphous material to impinging particles.
The silicons of the FAZIA telescopes were built adopting such type of cut. Moreover only detectors with doping inhomogeneities of about 1% or better were used. This last selection was done with a laser-based non-destructive method developed by the collaboration, that allows building a map of the resistivity as a function of the position on the silicon.
In the present work the response of eight silicon-silicon-CsI(Tl) and silicon-silicon telescopes with purposely developed high quality silicon detectors has been tested. In particular the silicon detectors were manufactured with stringent requirements for what concerns doping homogeneity, thickness uniformity and crystal orientation, to avoid channeling effects. All these features are obtained by proper choice of the silicon material and cutting geometry, without significantly affecting the cost of the detectors. Custom-developed digital electronics and original digital signal processing techniques have been extensively used.
Beams of 84Kr and 129Xe at 35A MeV, accelerated by the CS in Laboratori Nazionali del Sud (Catania), impinging on targets of natNi, 93Nb, 120Sn and Au, produced fragments over a large range of charge, mass and energy. The aim was to explore the capabilities of various solutions exploiting the digital techniques of Pulse Shape Analisys (PSA) for the Z and A identification of stopped ions.
The results of the digital PSA technique for identifying stopped ions are very satisfactory: full charge separation is obtained up to the maximum observed Z=54. Partial mass identification until Z=12 has been observed with a higher energy gain in other beam-tests done in Laboratori Nazionali di Legnaro and GANIL.
The ΔE-E (Si-Si) correlations allow isotopic separation up to Z=23-24, not far from the physical limit imposed by the energy straggling, as suggested by simulations.
