345 research outputs found
Advances in imaging THGEM-based detectors
The thick GEM (THGEM) [1] is an "expanded" GEM, economically produced in the
PCB industry by simple drilling and etching in G-10 or other insulating
materials (fig. 1). Similar to GEM, its operation is based on electron gas
avalanche multiplication in sub-mm holes, resulting in very high gain and fast
signals. Due to its large hole size, the THGEM is particularly efficient in
transporting the electrons into and from the holes, leading to efficient
single-electron detection and effective cascaded operation. The THGEM provides
true pixilated radiation localization, ns signals, high gain and high rate
capability. For a comprehensive summary of the THGEM properties, the reader is
referred to [2, 3]. In this article we present a summary of our recent study on
THGEM-based imaging, carried out with a 10x10 cm^2 double-THGEM detector.Comment: 3 pages, 3 figures. Presented at the 10th Pisa Meeting on Advanced
Detectors; ELBA-Italy; May 21-27 200
A concise review on THGEM detectors
We briefly review the concept and properties of the Thick GEM (THGEM); it is
a robust, high-gain gaseous electron multiplier, manufactured economically by
standard printed-circuit drilling and etching technology. Its operation and
structure resemble that of GEMs but with 5 to 20-fold expanded dimensions. The
millimeter-scale hole-size results in good electron transport and in large
avalanche-multiplication factors, e.g. reaching 10^7 in double-THGEM cascaded
single-photoelectron detectors. The multiplier's material, parameters and shape
can be application-tailored; it can operate practically in any counting gas,
including noble gases, over a pressure range spanning from 1 mbar to several
bars; its operation at cryogenic (LAr) conditions was recently demonstrated.
The high gain, sub-millimeter spatial resolution, high counting-rate
capability, good timing properties and the possibility of industrial production
capability of large-area robust detectors, pave ways towards a broad spectrum
of potential applications; some are discussed here in brief.Comment: 8 pages, 11 figures; Invited Review at INSTR08, Novosibirsk, Feb
28-March 5 200
A Novel UV Photon Detector with Resistive Electrodes
In this study we present first results from a new detector of UV photons: a
thick gaseous electron multiplier (GEM) with resistive electrodes, combined
with CsI or CsTe/CsI photocathodes. The hole type structure considerably
suppresses the photon and ion feedback, whereas the resistive electrodes
protect the detector and the readout electronics from damage by any eventual
discharges. This device reaches higher gains than a previously developed
photosensitive RPC and could be used not only for the imaging of UV sources,
flames or Cherenkov light, for example, but also for the detection of X-rays
and charged particles.Comment: Presented at the International Workshop on Resistive Plate Chambers,
Korea, October 200
THGEM operation in Ne and Ne/CH4
The operation of Thick Gaseous Electron Multipliers (THGEM) in Ne and Ne/CH4
mixtures, features high multiplication factors at relatively low operation
potentials, in both single- and double-THGEM configurations. We present some
systematic data measured with UV-photons and soft x-rays, in various Ne
mixtures. It includes gain dependence on hole diameter and gas purity,
photoelectron extraction efficiency from CsI photocathodes into the gas,
long-term gain stability and pulse rise-time. Position resolution of a 100x100
mm^2 X-rays imaging detector is presented. Possible applications are discussed.Comment: Submitted to JINST, 25 pages, 33 figure
Further progress in ion back-flow reduction with patterned gaseous hole-multipliers
A new idea on electrostatic deviation and capture of back-drifting
avalanche-ions in cascaded gaseous hole-multipliers is presented. It involves a
flipped reversed-bias Micro-Hole & Strip Plate (F-R-MHSP) element, the strips
of which are facing the drift region of the multiplier. The ions, originating
from successive multiplication stages, are efficiently deviated and captured by
such electrode. Experimental results are provided comparing the ion-blocking
capability of the F-R-MHSP to that of the reversed-bias Micro-Hole & Strip
Plate (R-MHSP) and the Gas Electron Multiplier (GEM). Best ion-blocking results
in cascaded hole-multipliers were reached with a detector having the F-R-MHSP
as the first multiplication element. A three-element F-R-MHSP/GEM/MHSP cascaded
multiplier operated in atmospheric-pressure Ar/CH4 (95/5), at total gain of
~10^{5}, yielded ion back-flow fractions of 3*10^{-4} and 1.5*10^{-4}, at drift
fields of 0.5 and 0.2 kV/cm, respectively. We describe the F-R-MHSP concept and
the relevance of the obtained ion back-flow fractions to various applications;
further ideas are also discussed.Comment: 17 pages, 11 figures, published in JINS
Mapping the Sensitive Volume of an Ion-Counting Nanodosimeter
We present two methods of independently mapping the dimensions of the
sensitive volume in an ion-counting nanodosimeter. The first method is based on
a calculational approach simulating the extraction of ions from the sensitive
volume, and the second method on probing the sensitive volume with 250 MeV
protons. Sensitive-volume maps obtained with both methods are compared and
systematic errors inherent in both methods are quantified.Comment: 27 pages, 8 figures. Submitted to JINST, Jan. 16 200
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