3,353 research outputs found
Development of a Detector Control System for the ATLAS Pixel Detector
The innermost part of the ATLAS experiment will be a pixel detector
containing around 1750 individual detector modules. A detector control system
(DCS) is required to handle thousands of I/O channels with varying
characteristics. The main building blocks of the pixel DCS are the cooling
system, the power supplies and the thermal interlock system, responsible for
the ultimate safety of the pixel sensors. The ATLAS Embedded Local Monitor
Board (ELMB), a multi purpose front end I/O system with a CAN interface, is
foreseen for several monitoring and control tasks. The Supervisory, Control And
Data Acquisition (SCADA) system will use PVSS, a commercial software product
chosen for the CERN LHC experiments. We report on the status of the different
building blocks of the ATLAS pixel DCS.Comment: 3 pages, 2 figures, ICALEPCS 200
Spectral UV measurements in Austria from 1994 to 2006: investigations of short- and long-term changes
The influence of variability of atmospheric parameters on short- and long-term changes of spectral UV irradiance measured at the Sonnblick observatory (47.03&deg; N, 12.57&deg; E, 3106 m) during the period from 1994 to 2006 is studied. Measurements were performed with the Brewer #093 single-monochromator spectrophotometer and with a Bentham DM 150 spectroradiometer (double-monochromator). <br> <br> The influence of ozone, albedo, snowline and clouds on UV variability is evaluated for each parameter separately using 10-year climatology. It is found that the effect of total ozone on short-term variability of UV irradiance at 305 nm can be more than 200% and on average more than 50%. Clouds can cause variability of 150% or more and on average 35%. Variability caused by albedo reaches a maximum of 32% in April (6% on average). In summer and autumn, total ozone and clouds strongly influence the variability of UV radiation, whereas in winter and spring ozone has the more pronounced effect. A decrease in snowline height from 3000 m to 800 m a.s.l. enhances the UV irradiance by a factor of 1.24 for clear sky conditions and by a factor of 1.7 for 8/8 cloud cover. <br> <br> Long-term trends are investigated for the time period from 1994 to 2006 based on clear-sky measurements, using the non-parametric Mann-Kendall trend test. Significant downward trends (99% confidence level) are found for solar zenith angle 55&deg; at wavelengths from 305 nm to 324 nm and erythemally weighted irradiance according to CIE, which are caused by an increase in sunshine duration during periods of high total column ozone. Significant trends (90% confidence level) were also found for other combinations of wavelength and SZA
A Combine On-Line Acoustic Flowmeter and Fluorocarbon Coolant Mixture Analyzer for The ATLAS Silicon Tracker
An upgrade to the ATLAS silicon tracker cooling control system may require a
change from C3F8 (octafluoro-propane) to a blend containing 10-30% of C2F6
(hexafluoro-ethane) to reduce the evaporation temperature and better protect
the silicon from cumulative radiation damage with increasing LHC luminosity.
Central to this upgrade is a new acoustic instrument for the real-time
measurement of the C3F8/C2F6 mixture ratio and flow. The instrument and its
Supervisory, Control and Data Acquisition (SCADA) software are described in
this paper. The instrument has demonstrated a resolution of 3.10-3 for
C3F8/C2F6 mixtures with ~20%C2F6, and flow resolution of 2% of full scale for
mass flows up to 30gs-1. In mixtures of widely-differing molecular weight (mw),
higher mixture precision is possible: a sensitivity of < 5.10-4 to leaks of
C3F8 into the ATLAS pixel detector nitrogen envelope (mw difference 160) has
been seen. The instrument has many potential applications, including the
analysis of mixtures of hydrocarbons, vapours for semi-conductor manufacture
and anaesthesia
A novel method for the absolute fluorescence yield measurement by AIRFLY
One of the goals of the AIRFLY (AIR FLuorescence Yield) experiment is to
measure the absolute fluorescence yield induced by electrons in air to better
than 10% precision. We introduce a new technique for measurement of the
absolute fluorescence yield of the 337 nm line that has the advantage of
reducing the systematic uncertainty due to the detector calibration. The
principle is to compare the measured fluorescence yield to a well known process
- the Cerenkov emission. Preliminary measurements taken in the BFT (Beam Test
Facility) in Frascati, Italy with 350 MeV electrons are presented. Beam tests
in the Argonne Wakefield Accelerator at the Argonne National Laboratory, USA
with 14 MeV electrons have also shown that this technique can be applied at
lower energies.Comment: presented at the 5th Fluorescence Workshop, El Escorial - Madrid,
Spain, 16 - 20 September 200
Temperature and Humidity Dependence of Air Fluorescence Yield measured by AIRFLY
The fluorescence detection of ultra high energy cosmic rays requires a
detailed knowledge of the fluorescence light emission from nitrogen molecules
over a wide range of atmospheric parameters, corresponding to altitudes typical
of the cosmic ray shower development in the atmosphere. We have studied the
temperature and humidity dependence of the fluorescence light spectrum excited
by MeV electrons in air. Results for the 313.6 nm, 337.1 nm, 353.7 nm and 391.4
nm bands are reported in this paper. We found that the temperature and humidity
dependence of the quenching process changes the fluorescence yield by a
sizeable amount (up to 20%) and its effect must be included for a precise
estimation of the energy of ultra high energy cosmic rays.Comment: presented at the 5th Fluorescence Workshop, El Escorial - Madrid,
Spain, 16 - 20 September 2007, to appear in Nuclear Instruments and Methods
Development of a custom on-line ultrasonic vapour analyzer/flowmeter for the ATLAS inner detector, with application to gaseous tracking and Cherenkov detectors
Precision sound velocity measurements can simultaneously determine binary gas
composition and flow. We have developed an analyzer with custom electronics,
currently in use in the ATLAS inner detector, with numerous potential
applications. The instrument has demonstrated ~0.3% mixture precision for
C3F8/C2F6 mixtures and < 10-4 resolution for N2/C3F8 mixtures. Moderate and
high flow versions of the instrument have demonstrated flow resolutions of +/-
2% F.S. for flows up to 250 l.min-1, and +/- 1.9% F.S. for linear flow
velocities up to 15 ms-1; the latter flow approaching that expected in the
vapour return of the thermosiphon fluorocarbon coolant recirculator being built
for the ATLAS silicon tracker.Comment: Paper submitted to TWEPP2012; Topical Workshop on Electronics for
Particle Physics, Oxford, UK, September 17-21, 2012. KEYWORDS: Sonar;
Saturated fluorocarbons; Flowmetry; Sound velocity, Gas mixture analysis. 8
pages, 7 figure
STRUCTURE OF METHYLPHEOPHORBIDE-RCI
he methanolic extract of the cyanobacterium (blue-green alga) Spirulina geitleri has been treated with methanolic acid to convert all chlorophyllous pigments to their methylpheophorbides. Fractionation of the latter from methylpheophorbide a by thin layer chromatography and high pressure liquid chromatography yielded methylpheophorbide-RCI. Its structure has been determined as 132S-hydroxy-20-chloro-methylpheophorbide a by 1H-nuclear magnetic resonance, absorption and circular dichroism spectroscopy, mass spectrometry and by partial synthesis from chlorophyll a. The pigment is isolated from Spirulina geitleri irrespective of the use or omission of chlorinated substances during the isolation procedure
Renormalized Harmonic-Oscillator Description of Confined Electron Systems with Inverse-Square Interaction
An integrable model for SU() electrons with inverse-square interaction
is studied for the system with confining harmonic potential. We develop a new
description of the spectrum based on the {\it renormalized
harmonic-oscillators} which incorporate interaction effects via the repulsion
of energy levels. This approach enables a systematic treatment of the
excitation spectrum as well as the ground-state quantities.Comment: RevTex, 7 page
Bosonic and fermionic single-particle states in the Haldane approach to statistics for identical particles
We give two formulations of exclusion statistics (ES) using a variable number
of bosonic or fermionic single-particle states which depend on the number of
particles in the system. Associated bosonic and fermionic ES parameters are
introduced and are discussed for FQHE quasiparticles, anyons in the lowest
Landau level and for the Calogero-Sutherland model. In the latter case, only
one family of solutions is emphasized to be sufficient to recover ES;
appropriate families are specified for a number of formulations of the
Calogero-Sutherland model. We extend the picture of variable number of
single-particle states to generalized ideal gases with statistical interaction
between particles of different momenta. Integral equations are derived which
determine the momentum distribution for single-particle states and distribution
of particles over the single-particle states in the thermal equilibrium.Comment: 6 pages, REVTE
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