1,069 research outputs found
Advances in Thick GEM-like gaseous electron multipliers. Part I: atmospheric pressure operation
Thick GEM-like (THGEM) gaseous electron multipliers are made of standard
printed-circuit board perforated with sub-millimeter diameter holes, etched at
their rims. Effective gas multiplication factors of 100000 and 10000000 and
fast pulses in the few nanosecond rise-time scale were reached in single- and
cascaded double-THGEM elements, in atmospheric-pressure standard gas mixtures
with single photoelectrons. High single-electron detection efficiency is
obtained in photon detectors combining THGEMs and semitransparent UV-sensitive
CsI photocathodes or reflective ones deposited on the top THGEM face; the
latter benefits of a reduced sensitivity to ionizing background radiation.
Stable operation was recorded with photoelectron fluxes exceeding MHz/mm2. The
properties and some potential applications of these simple and robust
multipliers are discussed.Comment: 41 pages, 27 figures. Submitted to Nucl. Instr. and Meth. A, Dec 21,
200
DBSolve Optimum: a software package for kinetic modeling which allows dynamic visualization of simulation results
<p>Abstract</p> <p>Background</p> <p>Systems biology research and applications require creation, validation, extensive usage of mathematical models and visualization of simulation results by end-users. Our goal is to develop novel method for visualization of simulation results and implement it in simulation software package equipped with the sophisticated mathematical and computational techniques for model development, verification and parameter fitting.</p> <p>Results</p> <p>We present mathematical simulation workbench DBSolve Optimum which is significantly improved and extended successor of well known simulation software DBSolve5. Concept of "dynamic visualization" of simulation results has been developed and implemented in DBSolve Optimum. In framework of the concept graphical objects representing metabolite concentrations and reactions change their volume and shape in accordance to simulation results. This technique is applied to visualize both kinetic response of the model and dependence of its steady state on parameter. The use of the dynamic visualization is illustrated with kinetic model of the Krebs cycle.</p> <p>Conclusion</p> <p>DBSolve Optimum is a user friendly simulation software package that enables to simplify the construction, verification, analysis and visualization of kinetic models. Dynamic visualization tool implemented in the software allows user to animate simulation results and, thereby, present them in more comprehensible mode. DBSolve Optimum and built-in dynamic visualization module is free for both academic and commercial use. It can be downloaded directly from <url>http://www.insysbio.ru</url>.</p
THGEM-based detectors for sampling elements in DHCAL: laboratory and beam evaluation
We report on the results of an extensive R&D program aimed at the evaluation
of Thick-Gas Electron Multipliers (THGEM) as potential active elements for
Digital Hadron Calorimetry (DHCAL). Results are presented on efficiency, pad
multiplicity and discharge probability of a 10x10 cm2 prototype detector with 1
cm2 readout pads. The detector is comprised of single- or double-THGEM
multipliers coupled to the pad electrode either directly or via a resistive
anode. Investigations employing standard discrete electronics and the KPiX
readout system have been carried out both under laboratory conditions and with
muons and pions at the CERN RD51 test beam. For detectors having a
charge-induction gap, it has been shown that even a ~6 mm thick single-THGEM
detector reached detection efficiencies above 95%, with pad-hit multiplicity of
1.1-1.2 per event; discharge probabilities were of the order of 1e-6 - 1e-5
sparks/trigger, depending on the detector structure and gain. Preliminary beam
tests with a WELL hole-structure, closed by a resistive anode, yielded
discharge probabilities of <2e-6 for an efficiency of ~95%. Methods are
presented to reduce charge-spread and pad multiplicity with resistive anodes.
The new method showed good prospects for further evaluation of very thin
THGEM-based detectors as potential active elements for DHCAL, with competitive
performances, simplicity and robustness. Further developments are in course.Comment: 15 pages, 11 figures, MPGD2011 conference proceedin
VHMPID: a new detector for the ALICE experiment at LHC
This article presents the basic idea of VHMPID, an upgrade detector for the
ALICE experiment at LHC, CERN. The main goal of this detector is to extend the
particle identification capabilities of ALICE to give more insight into the
evolution of the hot and dense matter created in Pb-Pb collisions. Starting
from the physics motivations and working principles the challenges and current
status of development is detailed.Comment: 4 pages, 6 figures. To be published in EPJ Web of Conference
R&D Proposal Development of Micro-Pattern Gas Detector Technologies
Development of advanced gas-avalanche detector technologies and associated electronic-readout systems for applications in basic and applied researc
On the operation of a Micropattern Gaseous UV-Photomultiplier in Liquid-Xenon
Operation results are presented of a UV-sensitive gaseous photomultiplier
(GPM) coupled through a MgF2 window to a liquid-xenon scintillator. It
consisted of a reflective CsI photocathode deposited on top of a THick Gaseous
Electron Multiplier (THGEM); further multiplication stages were either a second
THGEM or a Parallel Ionization Multiplier (PIM) followed by a MICROMEsh GAseous
Structure (MICROMEGAS). The GPM operated in gas-flow mode with non-condensable
gas mixtures. Gains of 10^4 were measured with a CsI-coated double-THGEM
detector in Ne/CH4 (95:5), Ne/CF4 (95:5) and Ne/CH4/CF4 (90:5:5), with soft
X-rays at 173 K. Scintillation signals induced by alpha particles in liquid
xenon were measured here for the first time with a double-THGEM GPM in He/CH4
(92.5:7.5) and a triple-structure THGEM/PIM/MICROMEGAS GPM in Ne/CH4 (90:10)
with a fast-current preamplifier.Comment: 12 pages, 9 figures, submitted to JINS
Transverse sphericity of primary charged particles in minimum bias proton-proton collisions at , 2.76 and 7 TeV
Measurements of the sphericity of primary charged particles in minimum bias
proton--proton collisions at , 2.76 and 7 TeV with the ALICE
detector at the LHC are presented. The observable is linearized to be collinear
safe and is measured in the plane perpendicular to the beam direction using
primary charged tracks with GeV/c in . The
mean sphericity as a function of the charged particle multiplicity at
mid-rapidity () is reported for events with different
scales ("soft" and "hard") defined by the transverse momentum of the leading
particle. In addition, the mean charged particle transverse momentum versus
multiplicity is presented for the different event classes, and the sphericity
distributions in bins of multiplicity are presented. The data are compared with
calculations of standard Monte Carlo event generators. The transverse
sphericity is found to grow with multiplicity at all collision energies, with a
steeper rise at low , whereas the event generators show the
opposite tendency. The combined study of the sphericity and the mean with multiplicity indicates that most of the tested event generators
produce events with higher multiplicity by generating more back-to-back jets
resulting in decreased sphericity (and isotropy). The PYTHIA6 generator with
tune PERUGIA-2011 exhibits a noticeable improvement in describing the data,
compared to the other tested generators.Comment: 21 pages, 9 captioned figures, 3 tables, authors from page 16,
published version, figures from
http://aliceinfo.cern.ch/ArtSubmission/node/308
Charge separation relative to the reaction plane in Pb-Pb collisions at TeV
Measurements of charge dependent azimuthal correlations with the ALICE
detector at the LHC are reported for Pb-Pb collisions at TeV. Two- and three-particle charge-dependent azimuthal correlations in
the pseudo-rapidity range are presented as a function of the
collision centrality, particle separation in pseudo-rapidity, and transverse
momentum. A clear signal compatible with a charge-dependent separation relative
to the reaction plane is observed, which shows little or no collision energy
dependence when compared to measurements at RHIC energies. This provides a new
insight for understanding the nature of the charge dependent azimuthal
correlations observed at RHIC and LHC energies.Comment: 12 pages, 3 captioned figures, authors from page 2 to 6, published
version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/286
A note on comonotonicity and positivity of the control components of decoupled quadratic FBSDE
In this small note we are concerned with the solution of Forward-Backward
Stochastic Differential Equations (FBSDE) with drivers that grow quadratically
in the control component (quadratic growth FBSDE or qgFBSDE). The main theorem
is a comparison result that allows comparing componentwise the signs of the
control processes of two different qgFBSDE. As a byproduct one obtains
conditions that allow establishing the positivity of the control process.Comment: accepted for publicatio
Multiplicity dependence of jet-like two-particle correlations in p-Pb collisions at = 5.02 TeV
Two-particle angular correlations between unidentified charged trigger and
associated particles are measured by the ALICE detector in p-Pb collisions at a
nucleon-nucleon centre-of-mass energy of 5.02 TeV. The transverse-momentum
range 0.7 5.0 GeV/ is examined,
to include correlations induced by jets originating from low
momen\-tum-transfer scatterings (minijets). The correlations expressed as
associated yield per trigger particle are obtained in the pseudorapidity range
. The near-side long-range pseudorapidity correlations observed in
high-multiplicity p-Pb collisions are subtracted from both near-side
short-range and away-side correlations in order to remove the non-jet-like
components. The yields in the jet-like peaks are found to be invariant with
event multiplicity with the exception of events with low multiplicity. This
invariance is consistent with the particles being produced via the incoherent
fragmentation of multiple parton--parton scatterings, while the yield related
to the previously observed ridge structures is not jet-related. The number of
uncorrelated sources of particle production is found to increase linearly with
multiplicity, suggesting no saturation of the number of multi-parton
interactions even in the highest multiplicity p-Pb collisions. Further, the
number scales in the intermediate multiplicity region with the number of binary
nucleon-nucleon collisions estimated with a Glauber Monte-Carlo simulation.Comment: 23 pages, 6 captioned figures, 1 table, authors from page 17,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/161
- …