Search results for "techniques"
showing 10 items of 4426 documents
KRYLOV-BOGOLIUBOV APPROACH TO NON-LINEAR HYSTERETIC INSTABILITY IN ROTORDYNAMICS
2012
The internal friction due to the shaft hysteresis or the shrink fitting release exerts a destabilizing effect on the overcritical rotor whirl, but may be counteracted by other external dissipative sources and/or by proper anisotropy of the support stiffness. The internal friction effect may be treated by either dry or viscous models, obtaining similar results in the hypothesis of small dissipation levels, provided that proper equivalence criteria are defined between the two approaches. The equivalence is here stated by imposing the same energy dissipation over a large number of shaft revolutions. Approximate closed-form autonomous solutions for a symmetric rotor arrangement subject to Coulo…
The translationally-invariant coupled cluster method in coordinate space
2000
We study a formulation of the translationally-invariant coupled cluster method in coordinate space. Previous calculations in configuration space showed poor convergence, a problem that the new formulation is expected to remedy. This question is investigated for a system of bosons interacting through the Wigner part of the Afnan-Tang S3 interaction, where previous results exist.
The polarized double cell target of the SMC
1999
The polarized target of the Spin Muon Collaboration at CERN was used for deep inelastic muon scattering experiments during 1993-1996 with a polarized muon beam to investigate the spin structure of the nucleon. Most of the experiments were carried out with longitudinal target polarization and 190 GeV muons, and some were done with transverse polarization and 100 GeV muons. Protons as well as deuterons were polarized by dynamic nuclear polarization (DNP) in three kinds of solid materials - butanol, ammonia, and deuterated butanol - with maximum degrees of polarization of 94%, 91% and 60%, respectively. Considerable attention was paid to the accuracies of the NMR polarization measurements and …
Aging measurements with the gas electron multiplier (GEM)
2001
Abstract Continuing previous aging measurements with detectors based on the Gas Electron Multiplier (GEM), we investigated a 31×31 cm 2 triple-GEM detector, as used in the small area tracking of the COMPASS experiment at CERN. With a detector identical to those installed in the experiment, long-term high-rate exposures to 8.9 keV X-ray radiation were performed to study its aging properties. In standard operation conditions, with Ar/CO2 (70:30) gas filling and operated at an effective gain of 8.5×103, no change in gain and energy resolution is observed after collecting a total charge of 7 mC / mm 2 , corresponding to seven years of normal operation. This observation confirms previous results…
Nonperturbative effective model for the Higgs sector of the standard model
2010
A nonperturbative effective model is derived for the Higgs sector of the Standard Model which is described by a simple scalar theory. The renormalized couplings are determined by the derivatives of the Gaussian effective potential that are known to be the sum of infinite bubble graphs contributing to the vertex functions. A good agreement has been found with strong coupling lattice simulations when a comparison can be made.
Calibration of the ISOLDE acceleration voltage using a high-precision voltage divider and applying collinear fast beam laser spectroscopy
2011
A high-voltage divider with accuracy at the ppm level and collinear laser spectroscopy were used to calibrate the highvoltage installation at the radioactive ion beam facility ISOLDE at CERN. The accurate knowledge of this voltage is particularly important for collinear laser spectroscopy measurements. Beam velocity measurements using frequencycomb based collinear laser spectroscopy agree with the new calibration. Applying this, one obtains consistent results for isotope shifts of stable magnesium isotopes measured using collinear spectroscopy and laser spectroscopy on laser-cooled ions in a trap. The long-term stability and the transient behavior during recovery from a voltage dropout were…
Atomic beam magnetic resonance apparatus for systematic measurement of hyperfine structure anomalies (Bohr-Weisskopf effect)
1993
Abstract An atomic beam magnetic resonance (ABMR) apparatus has been constructed at Orsay, and has been installed at the CERN PS Booster ISOLDE mass separator facility for “on-line” work with radioactive isotopes in a program to measure hyperfine structure anomalies (the Bohr-Weisskopf effect) over long isotopic chains. The hfs anomalies result from the effect of the spatial distribution of the nuclear magnetization on the atomic hfs interaction. Constructional details of the system are described: emphasis is placed on the measurement of nuclear g-factors by a triple resonance, laser state selected, ABMR method. A precision better than 10−4 for gI values has been obtained in stable atomic b…
The ASTERIX spectrometer at LEAR
1989
The ASTERIX spectrometer has been used to study the formation and the ground state of the pp atom and exclusive final states of pp annihilation at rest in a H2 gas target at NTP, using antiprotons from the Low Energy Antiproton Ring (LEAR) at CERN. The article describes the mechanical construction of the apparatus, the trigger logic, the chamber readout, and the data acquisition system. The detector calibration and the offline processing of the 55 million reconstructed events are illustrated. An overview is given about the new physics results obtained by the experiment.
Pre-production validation of the ATLAS level-1 calorimeter trigger system
2006
The Level-1 Calorimeter Trigger is a major part of the first stage of event selection for the ATLAS experiment at the LHC. It is a digital, pipelined system with several stages of processing, largely based on FPGAs, which perform programmable algorithms in parallel with a fixed latency to process about 300 Gbyte/s of input data. The real-time output consists of counts of different types of trigger objects and energy sums. Prototypes of all module types have been undergoing intensive testing before final production during 2005. Verification of their correct operation has been performed stand-alone and in the ATLAS test-beam at CERN. Results from these investigations will be presented, along …
Upgrade Analog Readout and Digitizing System for ATLAS TileCal Demonstrator
2013
A potential upgrade for the front-end electronics and signal digitization and data acquisition system of the ATLAS hadron calorimeter for the high luminosity Large Hadron Collider (HL-LHC) is described. A Demonstrator is being built to readout a slice of the TileCal detector. The on-detector electronics includes up to 48 Analog Front-end Boards for PMT analog signal processing, 4 Main Boards for data digitization and slow controls, 4 Daughter Boards with high speed optical links to interface the on-detector and off-detector electronics. Two super readout driver boards are used for off-detector data acquisition and fulfilling digital trigger.\n The ATLAS Tile Calorimeter on-detector electron…