1980, a revolution in silicon detectors, from energy spectrometer to radiation imager: Some technical and historical details

Silicon nuclear particle detectors were introduced just 50 years ago, after single crystal manufacturing was mastered. A major change took place around 1980 when the 'planar' MOS (Metal Oxide Semiconductor) technology developed in microelectronics was systematically applied also in detector construction. With the simultaneous introduction of matched readout chips this eventually would lead to pixelized matrix detectors that function as radiation imaging devices. The critical contributions to this revolution by Josef Kemmer and Paul Burger are described. Performance of the segmented planar technology detectors improved significantly in comparison with the earlier spectrometric diodes. With efficient industrial support the use of silicon detectors in many new applications has become possible and detector systems with a sensitive area of several tens to >100 m^2 have been constructed recently

Microscopic imaging of muons and 120 GeV/c pion interactions in a single, low-noise 256x256 Si pixel detector

With a 256x256 pixel matrix on a 300\mum thick silicon sensor, placed parallel to the particles in the CERN H6 beam, it proves possible to record electronically in real time the microscopic details of particle trajectories and interactions. The Medipix2 readout chip, matched to this matrix of 55\mum square pixels, contains a tuneable discriminator and a pulse counter in each pixel. The noise of the signal processing chain in each pixel is on average 135e^- (equivalent electrons) r.m.s. A threshold not much higher than 800e^- allows discrimination of full signals ~3800e^- as well as partial signals from a minimum ionizing particle in adjacent 55\mum thick pixels. With binary pixel information, exploiting charge diffusion and redundancy in the large matrix, the vectors of trajectories can be reconstructed with angular accuracy <1mradian and positions with respect to the detector coordinates often with sub-\mum precison. Close tracks can be resolved down to 100\mum distance. The width of the trail in the matrix sometimes can provide information on the energy deposition as well. A variety of applications can be imagined, the more so if several such detectors could be stacked to create a true 3-dimensional position-sensitive volume

X-ray imaging using single photon processing with semiconductor pixel detectors

More than 10 years experience with semiconductor pixel detectors for vertex detection in high energy physics experiments together with the steady progress in CMOS technology opened the way for the development of single photon processing pixel detectors for various applications including medical X-ray imaging. The state of the art of such pixel devices consists of pixel dimensions as small as 55x55 um2, electronic noise per pixel <100 e- rms, signal-to-noise discrimination levels around 1000 e- with a spread <50 e- and a dynamic range up to 32 bits per pixel. Moreover, the high granularity of hybrid pixel detectors makes it possible to probe inhomogeneities of the attached semiconductor sensor

Radiation tolerant VLSI circuits in standard deep submicron CMOS technologies for the LHC experiments: practical design aspects

We discuss design issues related to the extensive use of Enclosed Layout Transistors (ELT's) and guard rings in deep submicron CMOS technologies in order to improve radiation tolerance of ASIC's designed for the LHC experiments (the Large Hadron Collider at present under construction at CERN). We present novel aspects related to the use of ELT's: noise measured before and after irradiation up to 100 Mrad (SiO/sub 2/), a model to calculate the W/L ratio and matching properties of these devices. Some conclusions concerning the density and the speed of IC's conceived with this design approach are finally drawn. (16 refs)

Performance of 4096 pixel photon counting chip

A 4096 pixel Photon Counting Chip (PCC) has been developed and tested. It is aimed primarily at medical imaging although it can be used for other applications involving particle counting. The readout chip consists of a matrix of 64 x 64 identical square pixels, whose side measures 170 mm and is bump-bonded to a similar matrix of GaAs or Si pixel diodes covering a sensitive area of 1.18 cm . The electronics in each cell comprises a preamplifier, a discriminator with variable threshold and a 3-bit threshold tune as well as 15-bit counter. Each pixel can be individually addressed for electrical test or masked during acquisition. A shutter allows for switching between the counting and the readout modes and the use of a static logic in the counter enables long data taking periods. Electrical tests of the chip have shown a maximum counting rate of up to 2 MHz in each pixel. The minimum reachable threshold is 1400 e with a variation of 350 e rms that can be reduced to 80 e rms after tuning with the 3-bit adjustment. Electical noise at the input is 170 e rms. Several read-out chips have been bump-bonded to 200 mm thick GaAs detectors. Tests with g-rays and b sources have been carried out. A number of objects have been imaged and 260 mm thick aluminium foil which represents a contrast to the surrounding aire of only 1.9% has been correctly imaged