136 research outputs found
Radiation Tolerance Tests of Ultrasonic Oxygen Deficiency Sensors
The Large Hadron Collider (LHC), presently under construction at CERN, will contain about 96 tons of high-density helium (liquid and supercritical), mostly located in the underground components of the LHC machine. To detect a dangerous decrease of oxygen concentration in the atmosphere caused by a potential release of helium, the Oxygen Deficiency Hazard Detection system will be applied for the LHC operation in the tunnel and other selected areas. The oxygen concentration is derived on the assumption that the gas added to the air is helium alone. A novel concept of oxygen deficiency detection system, built at the Wroclaw University of Technology (WUT) in Poland, allows verifying the oxygen concentration in the air by means of sound velocity measurements. The paper describes the design and functionality of two prototypes of ultrasonic ODH detection system tested by the WUT. In order to qualify the systems to be used in the LHC tunnel, the stability of ultrasonic transducers and electronics has been checked under radiation in an environment similar to that predicted for the LHC. At the beginning both systems have been tested in TCC2 test radiation zone at CERN. The complementary test, was performed in Institute of Atomic Energy (IEA) in Poland
Nuclear recoil measurements in Superheated Superconducting Granule detectors
The response of Superheated Superconducting Granule (SSG) devices to nuclear
recoils has been explored by irradiating SSG detectors with a 70MeV neutron
beam. In the past we have tested Al SSG and more recently, measurements have
been performed with Sn and Zn detectors. The aim of the experiments was to test
the sensitivity of SSG detectors to recoil energies down to a few keV. In
this paper, the preliminary results of the neutron irradiation of a SSG
detector made of Sn granules 15-20m in diameter will be discussed. For the
first time, recoil energy thresholds of 1keV have been measured.Comment: 7pages in Latex format, Preprint Bu-He 93/6 (University of Berne,
Switzerland), four figures available upon request via
[email protected] or [email protected]
Manufacturing and Installation of the Compound Cryogenic Distribution Line for the Large Hadron Collider
The Large Hadron Collider (LHC) [1] currently under construction at CERN will make use of superconducting magnets operating in superfluid helium below 2 K. A compound cryogenic distribution line (QRL) will feed with helium at different temperatures and pressures the local elementary cooling loops in the cryomagnet strings. Low heat inleak to all temperature levels is essential for the overall LHC cryogenic performance. Following a competitive tendering, CERN adjudicated in 2001 the contract for the series line to Air Liquide (France). This paper recalls the main features of the technical specification and shows the project status. The basic choices and achievements for the industrialization phase of the series production are also presented, as well as the installation issues and status
Recent results from the canfranc dark matter search with germanium detectors
Two germanium detectors are currently operating in the Canfranc Underground
Laboratory at 2450 m.w.e looking for WIMP dark matter. One is a 2 kg 76Ge IGEX
detector (RG-2) which has an energy threshold of 4 keV and a low-energy
background rate of about 0.3 c/keV/kg/day. The other is a small (234 g) natural
abundance Ge detector (COSME), of low energy threshold (2.5 keV) and an energy
resolution of 0.4 keV at 10 keV which is looking for WIMPs and for solar
axions. The analysis of 73 kg-days of data taken by COSME in a search for solar
axions via their photon Primakoff conversion and Bragg scattering in the Ge
crystal yields a 95% C.L. limit for the axion-photon coupling g < 2.8 10^-9
GeV^-1. These data, analyzed for WIMP searches provide an exclusion plot for
WIMP-nucleon spin-independent interaction which improves previous plots in the
low mass region. On the other hand, the exclusion plot derived from the 60
kg-days of data from the RG-2 IGEX detector improves the exclusion limits
derived from other ionization (non thermal) germanium detector experiments in
the region of WIMP masses from 30 to 100 GeV recently singled out by the
reported DAMA annual modulation effect.Comment: 6 pages, talk given at IDM2000, York, September 200
Reception Tests of the Cryogenic Distribution line for the Large Hadron Collider
The paper describes the thermo-mechanical validation of the first sector of cryogenic distribution line (QRL) [1]. The design of the line is recalled and the test methodology presented together with the main results of the reception test at cryogenic temperature
Crab Cavity and Cryomodule Development for HL-LHC
The HL-LHC project aims at increasing the LHC luminosity by a factor 10 beyond the design value. The installation of a set of RF Crab Cavities to increase bunch crossing angle is one of the key upgrades of the program. Two concepts, Double Quarter Wave (DQW) and RF Dipole (RFD) have been proposed and are being produced in parallel for test in the SPS beam before the next long shutdown of CERN acceleratorâs complex. In the retained concept, two cavities are hosted in one single cryomodule, providing thermal insulation and interfacing with RF coupling, tuning, cryogenics and beam vacuum. This paper overviews the main design choices for the cryomodule and its different components, which have the goal of optimizing the structural, thermal and electro-magnetic behavior of the system, while respecting the existing constraints in terms of integration in the accelerator environment. Prototyping and testing of the most critical components, manufacturing, preparation and installation strategies are also described
Comment on "Evidence for Neutrinoless Double Beta Decay"
We comment on the recent claim for the experimental observation of
neutrinoless double-beta decay. We discuss several limitations in the analysis
provided in that paper and conclude that there is no basis for the presented
claim.Comment: A comment written to Modern Physics Letters A. 4 pages, no figures.
Updated version, accepted for publicatio
The IGEX experiment revisited: a response to the critique of Klapdor-Kleingrothaus,Dietz, and Krivosheina
This paper is a response to the article "Critical View to" the IGEX
neutrinoless double-beta decay experiment..."published in Phys. Rev.D, Volume
65 (2002) 092007," by H.V.Klapdor-Kleingrothaus, A. Dietz, and I.V.Krivosheina,
published as preprint hep-ph/0403056. The criticisms are confronted, and the
questions raised are answered. We demonstrate that the lower limit quoted by
IGEX, for the half life of Ge-76 neutrinoless double beta decay, 1.57x10**25 y,
is correct and that there was no "arithmetical error"-as claimed in the "
Critical Review" article
A Decommissioned LHC Model Magnet as an Axion Telescope
The 8.4 Tesla, 10 m long transverse magnetic field of a twin aperture LHC
bending magnet can be utilized as a macroscopic coherent solar axion-to-photon
converter. Numerical calculations show that the integrated time of alignment
with the Sun would be 33 days per year with the magnet on a tracking table
capable of in the vertical direction and in the horizontal
direction. The existing lower bound on the axion-to-photon coupling constant
can be improved by a factor between 50 and 100 in 3 years, i.e.,
for axion masses
1 eV. This value falls within the existing open axion mass window.
The same set-up can simultaneously search for low- and high-energy celestial
axions, or axion-like particles, scanning the sky as the Earth rotates and
orbits the Sun.Comment: Final version, accepted for publication in Nucl. Instr. Meth. A. More
information can be found at http://wwwinfo.cern.ch/~collar/SATAN/alvaro.htm
Design, Production and First Commissioning Results of the Electrical Feedboxes of the LHC
A total of 44 CERN designed cryogenic electrical feedboxes are needed to power the LHC superconducting magnets. The feedboxes include more than 1000 superconducting circuits fed by high temperature superconductor and conventional current leads ranging from 120 A to 13 kA. In addition to providing the electrical current to the superconducting circuits, they also ensure specific mechanical and cryogenic functions for the LHC. The paper focuses on the main design aspects and related production operations and gives an overview of specific technologies employed. Results of the commissioning of the feedboxes of the first LHC sectors are presented
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