41 research outputs found
The detection of single electrons by means of a Micromegas-covered MediPix2 pixel CMOS readout circuit
A small drift chamber was read out by means of a MediPix2 readout chip as
direct anode. A Micromegas foil was placed 50 m above the chip, and
electron multiplication occurred in the gap. With a He/Isobutane 80/20 mixture,
gas multiplication factors up to tens of thousands were achieved, resulting in
an efficiency for detecting single electrons of better than 90% . We recorded
many frames containing 2D images with tracks from cosmic muons. Along these
tracks, electron clusters were observed, as well as delta-rays.Comment: 15 pages, 9 included postscript figures, 5 separate jpeg figures,
submitted to Nucl. Instr. and Meth. A. A complete postscript version with
high resolution figures 1, 3, 11, 12 and 14 can be found at
http://www.nikhef.nl/~i06/RandD/final/letter4.p
3rd European Symposium on Semiconductor Detectors : New Developments in Silicon Detectors
Reminscenses of Rolf Hagedorn
This is a personal recollection of the influence that Rolf Hagedorn had on the launch of the CERN heavy-ion program and on the physics choices made by my colleagues and myself in that context
An integrated readout system for drift chambers: the application of monolithic CMOS pixel sensors as segmented direct anode
X-ray imaging using a hybrid photon counting GaAs pixel detector
The performance of hybrid GaAs pixel detectors as X-ray imaging sensors were investigated at room temperature. These hybrids consist of 300 μm thick GaAs pixel detectors, flip-chip bonded to a CMOS Single Photon Counting Chip (PCC). This chip consists of a matrix of 64 × 64 identical square pixels (170 μm × 170 μm) and covers a total area of 1.2 cm2. The electronics in each cell comprises a preamplifier, a discriminator with a 3-bit threshold adjust and a 15-bit counter. The detector is realized by an array of Schottky diodes processed on semi-insulating LEC-GaAs bulk material. An IV-characteristic and a detector bias voltage scan showed that the detector can be operated with voltages around 200 V. Images of various objects were taken by using a standard X-ray tube for dental diagnostics. The signal to noise ratio (SNR) was also determined.The applications of these imaging systems range from medical applications like digital mammography or dental X-ray diagnostics to non destructive material testing (NDT). Because of the separation of detector and readout chip, different materials can be investigated and compared