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At least 55 records · Page 3Linked to original sources
arXiv2008

Fast beam stacking using RF barriers

Two barrier RF systems were fabricated, tested and installed in the Fermilab Main Injector. Each can provide 8 kV rectangular pulses (the RF barriers) at 90 kHz. When a stationary barrier is combined with a moving barrier, injected beams from the Booster can be continuously deflected, folded and stacked in the Main Injector, which leads to doubling of the beam intensity. This paper gives a report on the beam experiment using this novel technology.

physics.acc-ph↗
arXiv2008

Contrast Enhancement of Binary Star System Using an Optical Vortex Coronagraph

Using an optical vortex coronagraph and simple adaptive optics techniques we have made the first convincing demonstration of an optical vortex coronagraph that is coupled to a star gazing telescope. In particular we suppressed by 97% the primary star of a barely resolvable binary system, Cor Caroli, having an effective angular separation of only 1.4 lambda/D. The secondary star suffered no suppression.

physics.optics↗
arXiv2008

Additional Comments on "New Limits on Spin-Independent Couplings of Low-Mass WIMP Dark Matter with a Germanium Detector at a Threshold of 200 eV"

In a previous comment (arXiv:0806.1341v1) we criticized purely technical aspects of arXiv:0712.1645 but pointed out that many other inconsistencies were readily apparent. In view of the imminent posting of another version of arXiv:0712.1645, still containing these issues, we would like to offer with this additional note a critical guide to the methodology followed by the TEXONO collaboration, in their effort to extract dark matter limits from a spectral region completely dominated by electronic noise. We find that systematics have been neglected through a combination of erroneous assumptions and failure to explore all of their possible sources.

hep-ex↗
arXiv2008

The EDELWEISS-II experiment

EDELWEISS is a direct dark matter search situated in the low radioactivity environment of the Modane Underground Laboratory. The experiment uses Ge detectors at very low temperature in order to identify eventual rare nuclear recoils induced by elastic scattering of WIMPs from our Galactic halo. The commissioning of the second phase of the experiment, involving more than 7 kg of Ge, has been completed in 2007. Two new type of detectors with active rejection of events due to surface contamination have demonstrated the performances required to achieve the physics goal of the present phase.

astro-ph↗
arXiv2008

Three-Tone Intermodulation Distortion Generated by Superconducting Bandpass Filters

Microwave bandpass filters constructed from materials exhibiting some nonlinearity, such as superconductors, will generate intermodulation distortion (IMD) when subjected to signals at more than one frequency. In commercial applications of superconductive receive filters, it is possible for IMD to be generated when a weak receive signal mixes with very strong out-of-band signals, such as those coming from the transmitter. A measurement procedure was developed and data were taken on several different types of superconducting bandpass filters, all developed for commercial application. It was found that in certain interference situations, the 3-tone mixing can produce a spur that is noticeable by the receiver, but that there are simple preventative design solutions.

cond-mat.supr-con↗
arXiv2008

Beam Coupling Impedance Measurement and Mitigation for a TOTEM Roman Pot

The longitudinal and transverse beam coupling impedance of the first final TOTEM Roman Pot unit has been measured in the laboratory with the wire method. For the evaluation of transverse impedance the wire position has been kept constant, and the insertions of the RP were moved asymmetrically. With the original configuration of the RP, resonances with fairly high Q values were observed. In order to mitigate this problem, RF-absorbing ferrite plates were mounted in appropriate locations. As a result, all resonances were sufficiently damped to meet the stringent LHC beam coupling impedance requirements.

physics.ins-det↗
arXiv2008

Monolithic Active Pixel Sensors (MAPS) in a quadruple well technology for nearly 100% fill factor and full CMOS pixels

In this paper we present a novel, quadruple well process developed in a modern 0.18mu CMOS technology called INMAPS. On top of the standard process, we have added a deep P implant that can be used to form a deep P-well and provide screening of N-wells from the P-doped epitaxial layer. This prevents the collection of radiation-induced charge by unrelated N-wells, typically ones where PMOS transistors are integrated. The design of a sensor specifically tailored to a particle physics experiment is presented, where each 50mu pixel has over 150 PMOS and NMOS transistors. The sensor has been fabricated in the INMAPS process and first experimental evidence of the effectiveness of this process on charge collection is presented, showing a significant improvement in efficiency.

physics.ins-det↗
arXiv2008

Geant4 validation with CMS calorimeters test-beam data

CMS experiment is using Geant4 for Monte-Carlo simulation of the detector setup. Validation of physics processes describing hadronic showers is a major concern in view of getting a proper description of jets and missing energy for signal and background events. This is done by carrying out an extensive studies with test beam using the prototypes or real detector modules of the CMS calorimeter. These data are matched with Geant4 predictions. Tuning of the Geant4 models is carried out and steps to be used in reproducing detector signals are defined in view of measurements of energy response, energy resolution, transverse and longitudinal shower profiles for a variety of hadron beams over a broad energy spectrum between 2 to 300 GeV/c.

physics.ins-det↗
arXiv2008

Method of accelerator search for dark matter

A method to search for dark matter by studying the interaction of accelerator beam particles with residual gas in dependence on gas pressure is proposed. The sensitivity of the method is estimated.

hep-ex↗
arXiv2008

The construction and commissioning of the CMS Silicon Strip Tracker

As the start up date for LHC approaches, the detectors are readying for data taking. Here a review will be given on the construction phase with insights into the various difficulties encountered during the process. An overview will also be given of the commissioning strategy and results obtained so far. The CMS tracker is the largest silicon microstrip detector ever built. Consisting of three main subsystems, Inner Barrel and Disks, Outer Barrel and End Caps, it is 5.4m long and is 2.4m in diameter. Total detector surface is an unprecedented 200m^2 with more than 15000 detector modules. The various integration procedures and quality checks implemented are briefly reviewed. Finally an overview is given of checkout procedures performed at CERN, after the final underground installation of the detector.

physics.ins-det↗
arXiv2008

Precision Polarimetry at the International Linear Collider

The International Linear Collider (ILC) will collide polarised electrons and positrons at beam energies of 45.6 GeV to 250 GeV and optionally up to 500 GeV. To fully exploit the physics potential of this machine, not only the luminosity and beam energy have to be known precisely, but also the polarisation of the particles has to be measured with an unprecedented precision of dP/P ~ 0.25% for both beams. An overall concept of high precision polarisation measurements at high beam energies will be presented. The focus will be on the polarimeters (up- and downstream of the e+e- interaction point) embedded in the ILC beam delivery system. Some challenges concerning the design of the Compton spectrometers and the appropriate Cherenkov detectors for each polarimeter are discussed. Detailed studies of photodetectors and their readout electronics are presented focusing specifically on the linearity of the device, since this is expected to be the limiting factor on the precision of the polarisation measurement at the ILC.

physics.ins-det↗
arXiv2008

Application of a miniaturized photoacoustic cell for high-sensitivity laser detection of ammonia in gas media

We present a photoacoustic resonant cell, the internal volume of which is ~ 0.5 cm^3. The cavity shape of the cell is so adapted in order to minimize the background signal arising due to absorption of laser beam in the cell windows. An experimental setup, measurement procedure and design of the cell are described. Results of detection of ammonia in nitrogen flow with the help of a CO2-laser are represented. The minimal detectable absorption for the cell is estimated in the experiment to be ~ 5.1 10^(-8) cm^(-1) W Hz^(-1/2)

physics.optics↗
arXiv2008

Alignment of the ATLAS barrel muon spectrometer

The muon spectrometer of the ATLAS experiment is one of the largest detectors ever built. At the LHC, new physics signs could appear through high momentun muons (1 TeV). Identification and precise momentum measurement of such muons are two of the main challenges of the ATLAS muon spectrometer. In order to get a good resolution for high energy muons (i.e. 10% at 1 TeV), the accuracy on the alignment of precision chambers must be of the order of 50 microns. Several procedures have been developed to reach such a precision. This document describes complementary techniques used to align the muon sub-detectors, and their results : the optical system, the muon cosmic rays and the straight tracks coming from collisions.

physics.ins-det↗
arXiv2008

Alignment of the ATLAS Inner Detector Tracking System

The ATLAS detector at CERN's Large Hadron Collider (LHC) is equipped with a tracking system at its core (the Inner Detector, ID) consisting of silicon and gaseous straw tube detectors. The physics performance of the ID requires a precision alignment; a challenge involving complex algorithms and significant computing power. The alignment algorithms were already validated on: Combined Test Beam data, Cosmic Ray runs and simulated physics events. The alignment chain was tested on a daily basis in exercises that mimicked ATLAS data taking operations. ID commissioning after final installation into the ATLAS detector has yielded thousands of reconstructed cosmic ray tracks, which have been used for an initial alignment of the ID before the LHC start-up. A hardware system using Frequency Scanning Interferometry will be used to monitor structural deformations. Given the programme outlined here, the ATLAS Inner Detector has had a solid preparation for LHC collisions.

physics.ins-det↗
arXiv2008

A Contribution for the Construction of Parabolic Mirrors

We present a new procedure for the construction of parabolic mirrors using low cost materials. We build a spinning system composed of nylon threads, fish hooks and a plastic bucket. We pour liquid plaster into the bucket and set it in constant rotational motion relative to the earth. A liquid substance assumes a parabolic profile when spinning at constant angular velocity relative to an inertial frame under the influence of an uniform vertical gravitational field. By keeping the bucket under rotation for a long time, the plaster solidifies into a parabolic format. We utilize this solidified plaster paraboloid as a model to construct a counter-mould of glass fibre and resin. Over this counter-mould it is placed stretched laminated foil and then it is poured thick plaster over it. In this way it is obtained a parabolic mirror made of laminated foil and plaster. Our only objective here is to present a new method for the construction of parabolic mirror using low cost materials. This allows further exploration of this procedure by teachers and students either in high-schools or in universities.

physics.pop-ph↗
arXiv2009

ATLAS RPC offline monitoring and data quality assessment

In this work several aspects of ATLAS RPC offline monitoring and data quality assessment are illustrated with cosmics data selected by RPC trigger. These correspond to trigger selection, front-end mapping, detection efficiency and occupancy, which are studied in terms of low level quantities such as: RPC off-line hits and standalone tracks. The tools and techniques presented are also extended to the forthcoming LHC p-p beam collisions.

physics.ins-det↗