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To be position sensitive, silicon drift detectors (SDDs) require a trigger signal synchronous with the interaction time (i.e., the start of the electrons' motion) since the interaction position along the drift coordinate is obtained from the measurement of the electrons' drift time. In the case of a photon interaction, the trigger must be provided by the detector itself. One way to obtain a fast trigger signal exploits the induction signal given by the holes collected by the [p.sup.+] strips close to the interaction point. We have designed and instrumented a multilinear SDD especially intended to study the self-triggering technique and its application to two-dimensional (2-D) X-ray position sensing. The measured position resolution along the drift coordinate is of the order of 10 ns with 10 keV photons, leading to a position resolution of 30 [micro]m rms at typical drift velocities. A comparable position resolution can be obtained on the lateral coordinate. By engineering the electron trajectory in the collection region, the anode capacitance can be minimized ( Index Terms--High-rate spectroscopy, position-sensing detector, silicon drift detectors, X-ray imaging.

In this paper we present a new VLSI shaper amplifier suitable for multi-anode Silicon Drift Detectors, or other multi-element solid-state X-ray detection systems. The readout scheme has been conceived and developed for demanding applications with synchrotron light sources, such as X-ray holography or EXAFS experiments, where both high count-rates and high energy resolutions are required. The circuit is of time-variant nature, accepts randomly distributed events and features a finite-width (1.1 [[micro]second]) weight function, a low-level energy discrimination, a low power consumption (a few mW per channel) and a full compatibility with monolithic integration in CMOS technology. Its impulse response has a staircase-like shape, but the implemented weight function (which is in general different from the impulse response in time-variant systems) is quasi trapezoidal. A first prototype of the circuit is here described and the first experimental results are also reported.

In this paper the authors present a novel JFET/CMOS signal processor, ROtational TrapezOidal Readout (ROTOR), conceived for high-rate high-resolution X-ray spectroscopy with asynchronous event occurrence. The circuit is of time-variant nature, uses no fast channel as a trigger, and displays a quasitrapezoidal weight function with virtually no exponential tail. Such a finite-width weight function is typically nearly optimal for submicrosecond processing times and is adequate when intense radiation fluxes must be handled. The filter also permits us to suppress possible ballistic deficits. Index Terms - Semiconductor-drift-detector, spectroscopy amplifier, switched current amplifier, time-variant filter, VLSI circuits, X-ray spectroscopy.

In this paper we present the working principle and the design criteria of the Controlled-Drift Detector, a novel device suitable for the simultaneous measurement of energy and two-dimensional position of X rays. In the Controlled-Drift Detector the pixel structure typical of a charge-coupled device and the fast readout typical of a silicon drift detector are joined. When the radiation is to be detected, suitable potential barriers are generated to prevent the drift of the signal electrons that are confined within a matrix of integration wells. The potential barrier which prevents the drift is selectively removable to allow the fast transport of the confined signal electrons to the readout electrodes by means of a static drift field. In principle such a device can achieve excellent energy resolution and readout times of some tens of microseconds. Three different confining mechanisms that allow control of the drift of the stored electrons are studied, and their advantages and drawbacks are discussed. First prototypes of the Controlled-Drift Detector are currently in production. Index Terms - Fast read-out, high-energy resolution, silicon detector, X-ray imaging.

In this paper, a method for the identification of the poles' and zeros' position of an analog amplifier for nuclear spectroscopy used as a prefilter for a subsequent digital filter setup is presented. The proposed technique is based upon a subspace-based system state-space identification (4SID) method, which is well suited to a data set constituted by a noisy measurement of the sampled impulse response of the circuit. The algorithm runs unassisted and does not require skills by the operator. The experiments confirm that by using the so-obtained pole values, the shape of the impulse response of the amplifier can be fit with much better than 1% accuracy. Consequently, the overall filtering (analog + digital) can have finite duration and a top with a flatness much better than 1%. Index Terms - Hybrid filters, impulse response, nuclear spectroscopy, subspace-based identification.

In this paper we present a method to obtain the three-dimensional (3-D) solution of the Laplace equation in closed form suitable for semiconductor detector design. The method applies to planar geometry cases (microstrip detectors, pixel detectors, drift detectors, etc.) with possible mixed boundary conditions on the surfaces of the wafer. The solution inside the detector volume is expressed by a series of elementary functions. The method requires lower CPU time and memory than methods based on 3-D discretization, in particular for the study of 3-D carrier trajectories inside the volume of semiconductor detectors and for inter-electrode capacitance calculations.

A large area cylindrical drift detector with an active area of a three-inch diameter wafer was designed and tested. The fast charged articles which radially drifts towards an array of 360 anodes at the periphery measures radial and azimuthal coordinates. A noninteracting particle beam passes through a hole in the center of the detector. The longest drift distance is three centimeters and drift time reaches a maximum of four microseconds.

The theoretical basis of the non-destructive repetitive readout are reviewed. The shape of the induced charge and current signals is discussed. The optimum filter with assigned time domain constraints (e.g. arbitrary finite duration) and in presence of any kind of uncorrelated, stationary, additional noises has been calculated for boundary cases of the induced current signal shape. A test structure to perform non destructive repetitive readout of the signals from high resolution detectors built on a high purity silicon substrate such as Silicon Drift Detectors and fully depleted pn Charge-Coupled Devices has been designed and produced.

The Controlled-Drift Detector is a recently designed position-sensing X-ray detector. It operates by switching between integration and drift mode. The basic idea is to generate potential wells within the otherwise linear drift potential. During the integration mode signal electrons are being accumulated within these wells. The removal of the barriers in an externally controlled way restores a uniform drift field that sweeps the electrons towards the readout anodes. The height of the confining barrier depends on the drift field and on the amplitude of the potential perturbation at the surface. An experimental study of the charge handling capability has been carried out as a function of the amplitude of the surface perturbation (up to 2.1 V) and as a function of the drift field (250-400 V/cm). The study provides a sensitive measurement of the actual potential barrier of the integration well in different operating conditions. A detailed analysis and characterisation of the mechanisms to confine the signal electrons in the 3D well is presented. For a drift field of 300 V/cm, storage of more than 105 electrons in 180 x 180 [micro][m.sup.2] pixels has been achieved with 1.67 V surface perturbation.