4,225 research outputs found
The Thin Gap Chambers database experience in test beam and preparations for ATLAS
Thin gap chambers (TGCs) are used for the muon trigger system in the forward
region of the LHC experiment ATLAS. The TGCs are expected to provide a trigger
signal within 25 ns of the bunch spacing. An extensive system test of the ATLAS
muon spectrometer has been performed in the H8 beam line at the CERN SPS during
the last few years. A relational database was used for storing the conditions
of the tests as well as the configuration of the system. This database has
provided the detector control system with the information needed for
configuration of the front end electronics. The database is used to assist the
online operation and maintenance. The same database is used to store the non
event condition and configuration parameters needed later for the offline
reconstruction software. A larger scale of the database has been produced to
support the whole TGC system. It integrates all the production, QA tests and
assembly information. A 1/12th model of the whole TGC system is currently in
use for testing the performance of this database in configuring and tracking
the condition of the system. A prototype of the database was first implemented
during the H8 test beams. This paper describes the database structure, its
interface to other systems and its operational performance.Comment: Proceedings IEEE, Nuclear Science Symposium 2005, Stockholm, Sweeden,
May 200
The cryogenic RWELL: a stable charge multiplier for dual-phase liquid-argon detectors
The operation of a cryogenic Resistive WELL (RWELL) in liquid argon vapor is
reported for the first time. It comprises a Thick Gas Electron Multiplier
(THGEM) structure coupled to a resistive Diamond-Like Carbon (DLC) anode
deposited on an insulating substrate. The multiplier was operated at cryogenic
temperature (90~K, 1.2~bar) in saturated argon vapor and characterized in terms
of charge gain and electrical stability. A comparative study with standard,
non-resistive THGEM (a.k.a LEM) and WELL multipliers, confirmed the RWELL
advantages in terms of discharge quenching - thus superior gain and stability
Multiple Core-Hole Coherence in X-Ray Four-Wave-Mixing Spectroscopies
Correlation-function expressions are derived for the coherent nonlinear
response of molecules to three resonant ultrafast pulses in the x-ray regime.
The ability to create two-core-hole states with controlled attosecond timing in
four-wave-mixing and pump probe techniques should open up new windows into the
response of valence electrons, which are not available from incoherent x-ray
Raman and fluorescence techniques. Closed expressions for the necessary
four-point correlation functions are derived for the electron-boson model by
using the second order cumulant expansion to describe the fluctuating
potentials. The information obtained from multidimensional nonlinear techniques
could be used to test and refine this model, and establish an anharmonic
oscillator picture for electronic excitations
Novel resistive charge-multipliers for dual-phase LAr-TPCs: towards stable operation at higher gains
Cryogenic versions of Resistive WELL (RWELL) and Resistive Plate WELL
(RPWELL) detectors have been developed, aimed at stable avalanche
multiplication of ionization electrons in dual-phase TPCs. In the RWELL, a thin
resistive layer deposited on top of an insulator is inserted in between the
electron multiplier (THGEM) and the readout anode; in the RPWELL, a resistive
plate is directly coupled to the THGEM. Radiation-induced ionization electrons
in the liquid are extracted into the gaseous phase. They drift into the THGEM's
holes where they undergo charge multiplication. Embedding resistive materials
into the multiplier proved to enhance operation stability due to the mitigation
of electrical discharges - thus allowing operation at higher charge gain
compared to standard THGEM (a.k.a. LEM) multipliers. We present the detector
concepts and report on the main preliminary results
Nitrogen storage and use of biochemical indices to assess nitrogen deficiency and growth rate in natural plankton populations
Various newly developed indicators of N deficiency, physiological state (approximate growth rate), and N source for growth were measured during five cruises to Dabob Bay, Washington from early spring to summer. Although nitrate and ammonium in the surface layer were depleted early in the spring, the plankton populations never became extremely N deficient, as indicated by high intracellular amino acid/protein ratios. However, growth rates, estimated from protein/DNA or RNA/DNA ratios, were usually low unless nitrate concentrations were high or had recently been high, as indicated by large intracellular nitrate pools or high nitrate reductase activities. High growth rates were observed during the spring bloom or as a result of the sporadic supply of nitrate to the euphotic zone, which was inferred from measurements of biochemical indicators on several cruises after the spring bloom. The sporadic supply of nitrate could account for the lack of N deficiency in these populations and mask diel periodicity in N utilization. These results demonstrate that biochemical indicators can be easily measured in the field and that variations in indicators such as intracellular amino acid/protein, protein/DNA, RNA/DNA ratios, NR activities and intracellular nitrate concentrations are an aid in understanding plankton dynamics
First in-beam studies of a Resistive-Plate WELL gaseous multiplier
We present the results of the first in-beam studies of a medium size
(1010 cm) Resistive-Plate WELL (RPWELL): a single-sided THGEM
coupled to a pad anode through a resistive layer of high bulk resistivity
(10cm). The 6.2~mm thick (excluding readout electronics)
single-stage detector was studied with 150~GeV muons and pions. Signals were
recorded from 11 cm square copper pads with APV25-SRS readout
electronics. The single-element detector was operated in Ne\(5%
) at a gas gain of a few times 10, reaching 99
detection efficiency at average pad multiplicity of 1.2. Operation at
particle fluxes up to 10 Hz/cm resulted in 23 gain drop
leading to 5 efficiency loss. The striking feature was the
discharge-free operation, also in intense pion beams. These results pave the
way towards robust, efficient large-scale detectors for applications requiring
economic solutions at moderate spatial and energy resolutions.Comment: Accepted by JINS
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