Showing papers by "Wladyslaw Dabrowski published in 2004"

Fast CMOS binary front-end for silicon strip detectors at LHC experiments

Abstract: We present the design and the test results of a front-end circuit developed in a 0.25 /spl mu/m CMOS technology. The aim of this work is to study the performance of a deep submicron process in applications for fast binary front-end for silicon strip detectors. The channel comprises a fast transimpedance preamplifier working with an active feedback loop, two stages of the amplifier-integrator circuits providing 22 ns peaking time and two-stage differential discriminator. Particular effort has been made to minimize the current and the power consumption of the preamplifier, while keeping the required noise and timing performance. For a detector capacitance of 20 pF noise below 1500 e/sup -/ ENC has been achieved for 300 /spl mu/A bias current in the input transistor, which is comparable with levels achieved in the past for a front-end using bipolar input transistor. The total supply current of the front-end is 600 /spl mu/A and the power dissipation is 1.5 mW per channel. The offset spread of the comparator is below 3 mV rms.

RX64DTH - a fully integrated 64-channel ASIC for digital X-ray imaging system with energy window selection

Abstract: We report on the multichannel IC (RX64DTH) designed for position sensitive X-ray measurements with silicon strip detectors and dedicated to medical imaging applications. This integrated circuit has a binary readout architecture and possibility of selecting energy window for measured signals. The design has been realized in 0.8 /spl mu/m CMOS process. The core of the RX64DTH chip consists of 64 readout channels. The single channel is built of four basic blocks: charge sensitive preamplifier, shaper, two independent discriminators and two independent 20-bit counters. Each readout channel counts pulses, which are above low discriminator threshold and independently pulses above high discriminator threshold. The energy resolution in such architecture is limited by noise of a single channel and by channel to channel threshold spread. We present noise and matching performance of a single chip and the performance of 384-channel system built of silicon strip detector and six RX64DTH chips. In the 384-channel system an equivalent noise charge of about 200 el. rms has been achieved for shaper peaking time of 0.8 /spl mu/s and the strip capacitance of 3 pF. The deviation of discriminator thresholds for the whole system is only 87 el. rms. The obtained results show clearly that the energy resolution and uniformity of analog parameters (noise, gain, offsets) are sufficient for medical diagnostic applications such as dual energy mammography and angiography.

New developments in CVD diamond for detector applications

Abstract: Chemical Vapor Deposition (CVD) diamond has been discussed extensively as an alternative sensor material for use very close to the interaction region of the LHC and other machines where extreme radiation conditions exist. During the last seven years the RD42 collaboration has developed diamond detectors and tested them with LHC electronics towards the end of creating a device usable by experiments. The most recent results of this work are presented. Recently, a new form of CVD diamond has been developed: single crystal CVD diamond which resolves many of the issues associated with poly-crystalline CVD material. The first tests of this material are also presented.

A silicon microstrip system equipped with the RX64DTH ASIC for dual energy mammography

Abstract: We present results obtained with a single photon counting system of 384 silicon microstrips (100 micron pitch) equipped with six RX64DTH ASICs including charge preamplifier, shaper, two discriminators and two 20-bit counters for each channel. The energy resolution of the system was determined to be of 0.72 keV (rms) with a spread of threshold setting of 0.32 keV for the whole 384-channel module (at energies of 29-33 keV), indicating its excellent potential for dual-energy imaging. Images of a mammographic test object made of PMMA, polyethylene and water were taken in scanning mode (strips parallel to incoming X-rays) under the dual energy X-ray beams. Images were subsequently processed with the dual energy subtraction technique (Alvarez and Macovski, 1976). Experimental results agree well with MCNP simulations of the mammographic phantom and demonstrate the capability of our system to obtain contrast cancellation between two kinds of materials, thereby enhancing the visibility of small features in the third material.

Comparison Between Two Monte Carlo Simulations of Angiographic Phantom Coupled to Silicon Strip Detector

Abstract: Preliminary results of a dual energy angiography simulation using the Monte Carlo package GEANT 3.2113 are presented and compared to Monte Carlo MCNP‐4C results reported before. The simulation is based on an experimental set up consisting of a Plexiglas‐aluminium step wedge phantom with 4 cylindrical cavities filled with iodated contrast medium. The silicon 384 microstrip detector was set into edge‐on configuration (incoming X‐rays parallel to longitudinal axis of the strips) and the properties of the simulated detector just resemble the ones of the real detector. Monochromatic photon beams of 31.5keV and 35.5keV are used to take advantage of the discontinuous variation of the iodine photon absorption at the energy of the K‐shell, the key to dual energy subtraction imaging.