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It is well known that the use of electronics components in space exposes them to ionizing radiation, which can damage the devices. A careful characterization of the sensitivity to radiation-induced damages is thus of capital importance for the critical devices. VELA (VLSI Electronic for Astronomy) is an ASIC developed at the Politecnico of Milano in collaboration with Max-Planck-Institut Semiconductor Laboratory, in 0.35 µm AMS CMOS technology, which implements the readout front-end electronics for an innovative x-ray detector, the DEPMOS-based APS, Active Pixel Sensor. This sensor is capable of providing an excellent energy resolution even at very high speed readout. The absence of the charge transfer mechanism, makes APS sensors very attractive for harsh radiation space environments. The behavior of the front-end electronics under irradiation is then a critical issue. We present a study of the Single Event Effects induced by heavy ions in VELA, in view of a possible utilization in new generation satellites for X-ray astronomy. The tests have been carried out at the SIRAD facility of the Laboratori Nazionali INFN di Legnaro. In this paper we describe the measurements and the experimental setup, designed and realized ad hoc to monitor Single Event Latch-up (SEL) and Single Event Upset (SEU).

We propose a CMOS preamplifier-shaper circuit designed to be used with silicon drift detectors (SDDs) for X-ray spectroscopy and /spl gamma/-ray imaging applications. The circuit is composed by a low-noise preamplifier and by a 6th order semiGaussian shaping amplifier with four selectable peaking times from 1.7 /spl mu/s up to 6 /spl mu/s. The integrated time constant used for the shaping is implemented by means of a recently proposed 'RC' cell. This cell is based on the well known technique of demagnification of the current flowing in a resistor R by means of the use of current mirrors. The particular solution here adopted allows a precise and stable implementation of the desired time constant, for given values of R and C, and guarantees low-noise performances of the shaping amplifier when used with a cooled SDD or other solid-state detectors with low leakage current. In this work, the main features of the circuit are first presented. The experimental results obtained in the characterization of the first prototype realized in the 0.35 /spl mu/m AMS technology are then reported and discussed. The energy resolution measured using the chip with a SDD is 150 eV at 6 keV which corresponds to an electronics noise of 10.8 e/sup -/ rms.

A Monte Carlo optical code for the optimisation of scintillation gamma cameras based on a single scintillator coupled to arrays of Si photodiodes (PDs) or Si drift detectors (SDDs) have been developed. The simulator allows to calculate the expected gain (e-/keV), position resolution and energy resolution of the gamma detector for different geometries and boundary conditions at the crystal interfaces. A validation of the algorithm has been carried out by comparing the results of the simulations with the corresponding experimental results obtained on existing prototypes of detectors recently developed. An example of application of the proposed code in the study of a small scintillation camera is also reported.

We present an all-optical poling technique which permits the permanent polar ordering of organic chromophores embedded in polymer matrices. The microscopic processes involved, and their consequences on the dynamic and geometrical properties of this optical poling, are analyzed in the model. The authors use as an example azo-dye polymers.

Summary form only. Controlling the light emission properties of materials is a challenging issue. By analogy with semiconductor in which a potential periodicity allows modifications of electron propagation, periodic modulations of a material dielectric constant enables control of light propagation. We report here the development of a compact organic laser based on a distributed feedback scheme (DFB) achieved by permanent modulation of the polymer refractive index.