432 research outputs found
Position Sensing from Charge Dispersion in Micro-Pattern Gas Detectors with a Resistive Anode
Micro-pattern gas detectors, such as the Gas Electron Multiplier (GEM) and
the Micromegas need narrow high density anode readout elements to achieve good
spatial resolution. A high-density anode readout would require an unmanageable
number of electronics channels for certain potential micro-detector
applications such as the Time Projection Chamber. We describe below a new
technique to achieve good spatial resolution without increasing the electronics
channel count in a modified micro-detector outfitted with a high surface
resistivity anode readout structure. The concept and preliminary measurements
of spatial resolution from charge dispersion in a modified GEM detector with a
resistive anode are described below.Comment: 14 pages, 8 figures, submitted to Nucl. Inst. Meth; typo in eqn 4
corrected, fig 2 updated accordingl
Dynamical chiral symmetry breaking with Minkowski space integral representations
The fermion propagator is studied in the whole Minkowski space with the help
of the Schwinger-Dyson equations. Various integral representations are employed
to get solutions for the dynamical breaking of chiral symmetry in different
regimes of the coupling constant. In particular, in the case of massive boson,
we extend the singularity structure of the fermion propagator to the two real
pole Ansatz.Comment: 4 pages, 4 figures, published version in PR
A triple GEM detector with two dimensional readout
The triple GEM detector is a micropattern gas detector which consists of a
primary ionisation gap and three consecutive gas electron multiplier (GEM)
foils. A printed circuit board with readout strips detects the current induced
by the drifting electron cloud originating from the last GEM stage. Thus the
gas amplification and the signal readout are completely separated. Triple GEM
detectors are being developed as a possible technology for the inner tracking
in the LHCb experiment.
In an earlier note we have reported first experience with such a detector in
a test beam at PSI. Here we describe the construction of an improved version
(thinner transfer gaps, segmented GEM foils, two dimensional readout). Results
from performance measurements are presented using intense hadronic beams as
well as cosmic ray data.Comment: 20 pages, 24 figure
Capacity formulas in MWPC: some critical reflexions
An approximate analytical expression for "capacitance" of MWPC configurations
circulates in the literature since decades and is copied over and over again.
In this paper we will try to show that this formula corresponds to a physical
quantity that is different from what it is usually thought to stand for
Resolution studies of cosmic-ray tracks in a TPC with GEM readout
A large volume TPC is a leading candidate for the central tracking detector
at a future high energy linear collider. To improve the resolution a new
readout based on micro-pattern gas detectors is being developed. Measurements
of the spatial resolution of cosmic-ray tracks in a GEM TPC are presented. We
find that the resolution suffers if the readout pads are too wide with respect
to the charge distribution at the readout plane due to insufficient charge
sharing. For narrow pads of 2 x 6 mm**2 we measure a resolution of 100
micometer at short drift distances in the absence of an axial magnetic field.
The dependence of the spatial resolution as a function of drift distance allows
the determination of the underlying electron statistics. Our results show that
the present technique uses about half the statistical power available from the
number of primary electrons. The track angle effect is observed as expected.Comment: 18 pages, 8 figures, version as published in Nucl. Inst. Met
From Euclidean to Minkowski space with the Cauchy-Riemann equations
We present an elementary method to obtain Green's functions in
non-perturbative quantum field theory in Minkowski space from calculated
Green's functions in Euclidean space. Since in non-perturbative field theory
the analytical structure of amplitudes is many times unknown, especially in the
presence of confined fields, dispersive representations suffer from systematic
uncertainties. Therefore we suggest to use the Cauchy-Riemann equations, that
perform the analytical continuation without assuming global information on the
function in the entire complex plane, only in the region through which the
equations are solved. We use as example the quark propagator in Landau gauge
Quantum Chromodynamics, that is known from lattice and Dyson-Schwinger studies
in Euclidean space. The drawback of the method is the instability of the
Cauchy-Riemann equations to high-frequency noise, that makes difficult to
achieve good accuracy. We also point out a few curiosities related to the Wick
rotation.Comment: 12 pages in EPJ double-column format, 16 figures. This version: added
paragraph, two reference
Botanica applicata nei progetti di infrastrutture viarie
La progettazione di un’infrastruttura viaria è sottoposta come noto a procedura di Valutazione di Impatto Ambientale (VIA) nelle fasi di progetto preliminare e di progetto definitivo, in cui vengono principalmente: • messi a confronto i beni ambientali con le ipotesi di progetto dell’infrastruttura; • individuati i potenziali impatti e introdotte le opportune modifiche migliorative (tracciato, opere d’arte); • progettati gli interventi di mitigazione degli impatti residui. Di tutti i settori di analisi ambientale, risulta particolarmente importante quello botanico (flora e vegetazione) per le implicanze applicative negli interventi di mitigazione a verde e interventi di Ingegneria Naturalistica connesse con il progetto dell’infrastruttura
Persistence of planetary wave type oscillations in the mid-latitude ionosphere
Planetary wave type oscillations have been observed in the lower and middle atmosphere but also in the ionosphere,
including the ionospheric F2 layer. Here we deal with the oscillations in foF2 analysed for two Japanese
and two US stations over a solar cycle (1979-1989) with the use of the Morlet and Paul wavelet transforms.
Waves with periods near 5, 10 and 16 days are studied. Only events of duration of three wave-cycles and more
are considered. The results are compared with the results of a similar analysis made for foF2 and the lower ionosphere
over Europe (Lasˇtovicˇka et al., 2003a,b). The 5-day period wave events display a typical duration of 4
cycles, while the 10- and 16-day wave events are less persistent with typical duration of about 3.5 cycles and
rather 3 cycles, respectively, in all three geographic regions. The persistence pattern in terms of number of cycles
and in terms of number of days is different. In terms of number of cycles, the typical persistence of oscillations
decreases with increasing period. On the other hand, in terms of number of days the typical persistence evidently
increases with increasing period. The spectral distribution of event duration is too broad to allow for a
reasonable prediction of event duration. Thus the predictability of the planetary wave type oscillations in foF2
seems to be very questionable. The longitudinal size of the planetary wave type events increases with increasing
wave period. The persistence of the planetary wave type events in foF2 and the lower ionosphere is similar in
Europe, but the similarity in occurrence of individual events in foF2 and the lower ionosphere is rather poor
Spatial resolution of a GEM readout TPC using the charge dispersion signal
A large volume Time Projection Chamber (TPC) is being considered for the
central charged particle tracker for the detector for the proposed
International Linear Collider (ILC). To meet the ILC-TPC spatial resolution
challenge of ~100 microns with a manageable number of readout pads and channels
of electronics, Micro Pattern Gas Detectors (MPGD) are being developed which
could use pads comparable in width to the proportional-wire/cathode-pad TPC. We
have built a prototype GEM readout TPC with 2 mm x 6 mm pads using the new
concept of charge dispersion in MPGDs with a resistive anode. The dependence of
transverse resolution on the drift distance has been measured for small angle
tracks in cosmic ray tests without a magnetic field for Ar/CO2 (90:10). The
GEM-TPC resolution with charge dispersion readout is significantly better than
previous measurements carried out with conventional direct charge readout
techniques.Comment: 5 figures, 10 page
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