22 research outputs found
Thick GEM-like hole multipliers: properties and possible applications
The properties of thick GEM-like (TGEM) gaseous electron multipliers,
operated at 1-740 Torr are presented. They are made of a G-10 plate, perforated
with millimeter-scale diameter holes. In single-multiplier elements, effective
gains of about 104, 106, and 105 were reached at respective pressures of 1, 10
Torr isobutane and 740 Torr Ar/5%CH4, with pulse rise-times in the few
nanosecond scale. The high effective gain at atmospheric pressure was measured
with a TGEM coated with a CsI photocathode. The detector was operated in single
and cascaded modes. Potential applications in ion and photon detection are
discussed.Comment: Contribution to the 2004 Vienna Conference on Instrumentatio
CsI-THGEM gaseous photomultipliers for RICH and noble-liquid detectors
The properties of UV-photon imaging detectors consisting of CsI-coated THGEM
electron multipliers are summarized. New results related to detection of
Cherenkov light (RICH) and scintillation photons in noble liquid are presented.Comment: 5 Pages, 10 Figures; Presented at the 7th International Workshop on
Ring Imaging Cherenkov Detectors (RICH 2010) RICH2010 - Cassis, Provence,
France, 3-7 May 201
Performance test of a micro-pattern stereo detector with two gas electron multipliers [online]
We report on the performance of a large micro-pattern detector
with two gas electron multiplier foils (GEM) and a two-layer
readout structure at ground potential. The two readout layers
each have a 406 micro-m pitch and cross at an effective angle of
6.7 degrees. This structure allows for two orthogonal
coordinates to be determined. Using a muon beam at CERN together
with a silicon tracking system, the position resolutions of the
two coordinates are measured to be 50 micro-m and 1 mm
respectively (1 stand.dev.). The muon detection efficiency for
the two-dimensional space points reaches 96%. The detector was
found to be well operational over a wide range in the settings
of the different electrical fields
Construction and performance of a micro-pattern stereo detector with two gas electron multipliers [online]
The construction of a micro-pattern gas detector of dimensions
40 x 10 cm² is described. Two gas electron multiplier foils
(GEM) provide the internal amplification stages. A two-layer
readout structure was used, manufactured in the same technology
as the GEM foils. The strips of each layer cross at an effective
crossing angle of 6.7 degrees and have a 406 micro-m pitch. The
performance of the detector has been evaluated in a muon beam at
CERN using a silicon telescope as reference system. The position
resolutions of two orthogonal coordinates are measured to be
50 micro-m and 1 mm, respectively. The muon detection efficiency
for two-dimensional space points reaches 96%.
Key words:
detector, position sensitive, GEM, two-layer readou
Influence of Surface Treatments on DC-Performance of GaN-Based HFETs
This work reports on the influence of the surface and the gate length on the performance of AlGaN/GaN based Hetero Field Effect Transistors (HFETs). Differently NH4Sx treated surfaces result in variation of the drain current IDmax of more then 100%. Gate recessing by photoelectrochemical treatment changes the threshold voltage Vth but affects the drain current little. Next, the reduction of the gate length increases the IDmax further by more than 60%. The IDmax values for the transistors are 350 mA mm––1 for the NH4Sx-treated, 850 mA for the untreated, and 1.43 A mm––1 for the one with a 0.2 mm gate length. The corresponding transconductances gm are 66, 150, and 280 mS mm––1, respectively. Surface analysis with Auger Electron Spectroscopy (AES) and contact characterization (TLM) reveals, that the NH4Sx treatment removes the native oxide and increases the contact resistance as well. Therefore we attribute the increase of IDmax and gm mainly to a beneficial behavior of gallium-oxide at the surface on the sheet carrier density nS of the 2DEG at the heterointerface
High rate behavior and discharge limits in micro-pattern detectors
We present and discuss a set of systematic measurements, carried out with gaseous proportional micro-pattern detectors, in order to assess their maximum gain when irradiated with high-rate soft X-rays and heavily ionizing alpha particles. The inventory of detectors tested includes: micro-strips, micromegas, micro-dot, gas electron multiplier, CAT (compteur a trous), trench (or groove), micro-CAT (or WELL) detectors, as well as systems with two elements of gaseous amplification in cascade. We confirm the general trend of all single-stage detectors to follow Raether's criterion, i.e. a spontaneous transition from avalanche to streamer, followed by a discharge, when the avalanche size reaches a value of a few 107; a noticeable exception is the micro-clot counter holding more than 108. In multiple structures, where the gain is shared between two devices in cascade, the maximum overall gain under irradiation is increased by at least one order of magnitude; we speculate this to be a consequence of a voltage dependence of Raether's limit, larger for low operating potentials. Our conclusion is that only multiple devices can guarantee a sufficient margin of reliability for operation in harsh LHC running conditions.F.I. 1,0910Elsevier, Amsterdaminfo:eu-repo/semantics/publishe