444 results found
Schulte M, Rochester GK, Shaul DNA, et al., 2006, The charge-management system on LISA-Pathfinder - Status & outlook for LISA, 6th International Laser Interferometer Space Antenna, Publisher: AMER INST PHYSICS, Pages: 165-+, ISSN: 0094-243X
Wass PJ, Araújo HA, Davidge D, et al., 2006, Charging of the LISA test masses: Sources, consequences and management, The Tenth Marcel Grossmann Meeting: On Recent Developments in Theoretical and Experimental General Relativity, Gravitation and Relativistic Field Theories, Pages: 2013-2018, ISBN: 9789812566676
© 2005 by World Scientific Publishing Co. Pte. Ltd. All rights reserved. Energetic particle radiation in the form of galactic cosmic rays and solar particles will cause the LISA test masses to become charged. This will give rise to disturbing forces on the test masses through both Lorentz and Couloumb interactions which can translate into acceleration noise, coupling of the spacecraft and test mass motion and coherent signals in the measurement bandwidth. To minimise these effects, the charge management system on LISA will control the amount of charge on the test masses through the photo-electric effect using a system of UV illumination. We present the estimates of the exposure of the spacecraft to energetic particles and the resultant test mass charging rates based on detailed charging simulations using GEANT4. We also describe the system used to measure and manage the charge on the test masses.
Wass PJ, Carbone L, Cavalleri A, et al., 2006, Testing of the UV discharge system for LISA pathfinder, 6th International Laser Interferometer Space Antenna, Publisher: AMER INST PHYSICS, Pages: 220-+, ISSN: 0094-243X
Alner GJ, Araujo H, Bewick A, et al., 2005, The DRIFT-II dark matter detector: Design and commissioning, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, Vol: 555, Pages: 173-183, ISSN: 0168-9002
Lockerbie NA, Sumner TJ, 2005, High precision tests of the Equivalence Principle, Pages: 19-25, ISSN: 0379-6566
This paper reviews experimental measurements of the Equivalence Principle, placing them in an historical context. Emphasis is given to prospective Space-based tests of the Equivalence Principle, where there is real potential for investigation into a region of the appropriate parameter space where the EP may well be violated. The STEP (Satellite Test of the Equivalence Principle) experiment, with a target sensitivity of 10-18 for the Eötvös ratio, η, is used as an exemplar for such experiments, arid is discussed in some detail.
Khan SA, Shafer RA, Benford DJ, et al., 2005, On the discovery of the first galaxy selected at 350 microns, ASTROPHYSICAL JOURNAL, Vol: 631, Pages: L9-L12, ISSN: 0004-637X
Carson M, Araujo HM, Davies JC, et al., 2005, Veto performance for large-scale xenon dark matter detectors, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, Vol: 548, Pages: 418-426, ISSN: 0168-9002
Dawson JV, Howard AS, Akimov D, et al., 2005, A study of the scintillation induced by alpha particles and gamma rays in liquid xenon in an electric field, Nuclear Instruments & Methods in Physics Research Section A - Accelerators Spectrometers Detectors and Associated Equipment, Vol: 545, Pages: 690-698, ISSN: 0168-9002
Scintillation produced in liquid xenon by alpha particles and gamma rays has been studied as a function of applied electric field. For back scattered gamma rays with energy of about 200 keV, the number of scintillation photons was found to decrease by 64±2% with increasing field strength. Consequently, the pulse shape discrimination power between alpha particles and gamma rays is found to reduce with increasing field, but remaining non-zero at higher fields.
Araujo HM, Kudryavtsev VA, Spooner NJC, et al., 2005, Muon-induced neutron production and detection with GEANT4 and FLUKA, Nuclear Instruments & Methods in Physics Research Section A - Accelerators Spectrometers Detectors and Associated Equipment, Vol: 545, Pages: 398-411, ISSN: 0168-9002
We report on a comparison study of the Monte Carlo packages GEANT4 and FLUKA for simulating neutron production by muons penetrating deep underground. GEANT4 is found to generate fewer neutrons at muon energies above View the MathML source, by at most a factor of 2 in some materials, which we attribute mainly to lower neutron production in hadronic cascades. As a practical case study, the muon-induced neutron background expected in a 250 kg liquid-xenon WIMP dark matter detector was calculated and good agreement was found for the recoil event rates. The detailed model of neutron elastic scattering in GEANT4 was also shown to influence the nuclear recoil spectrum observed in the target, which is presently a shortcoming of FLUKA. We conclude that both packages are suited for this type of simulation, although further improvements are desirable in both cases.
Alner GJ, Araujo HM, Arnison GJ, et al., 2005, Limits on WIMP cross-sections from the NAIAD experiment at the boulby underground laboratory, PHYS LETT B, Vol: 616, Pages: 17-24, ISSN: 0370-2693
The NAIAD experiment (NaI Advanced Detector) for WIMP dark matter searches at the Boulby Underground Laboratory (North Yorkshire, UK) ran from 2000 until 2003. A total of 44.9 kg x years of data collected with 2 encapsulated and 4 unencapsulated NaI(Tl) crystals with high light yield were included in the analysis. We present final results of this analysis carried out using pulse shape discrimination. No signal associated with nuclear recoils from WIMP interactions was observed in any run with any crystal. This allowed us to set upper limits on the WIMP-nucleon spin-independent and WIMP-proton spin-dependent cross-sections. The NAIAD experiment has so far imposed the most stringent constraints on the spin-dependent WIMP-proton cross-section. (c) 2005 Elsevier B.V. All rights reserved.
Alner GJ, Araujo H, Arnison GJ, et al., 2005, First limits on nuclear recoil events from the ZEPLIN I galactic dark matter detector, ASTROPARTICLE PHYSICS, Vol: 23, Pages: 444-462, ISSN: 0927-6505
Anza S, Armano M, Balaguer E, et al., 2005, The LTP experiment on the LISA Pathfinder mission, 5th International LISA Symposium/38th ESLAB Symposium, Publisher: IOP PUBLISHING LTD, Pages: S125-S138, ISSN: 0264-9381
Wass PJ, Araujo HM, Shaul DNA, et al., 2005, Test-mass charging simulations for the LISA Pathfinder mission, 5th International LISA Symposium/38th ESLAB Symposium, Publisher: IOP PUBLISHING LTD, Pages: S311-S317, ISSN: 0264-9381
Shaul DNA, Araujo HM, Rochester GK, et al., 2005, Evaluation of disturbances due to test mass charging for LISA, 5th International LISA Symposium/38th ESLAB Symposium, Publisher: IOP PUBLISHING LTD, Pages: S297-S309, ISSN: 0264-9381
Alner GJ, Araujo H, Arnison GJ, et al., 2005, Nuclear recoil limits from the ZEPLIN I liquid xenon WIMP dark matter detector, 6th UCLA Symposium on Sources and Detection of Dark Matter and Dark Energy in the Universe, Publisher: ELSEVIER SCI LTD, Pages: 245-249, ISSN: 1387-6473
Sumner TJ, 2005, The ZEPLIN III dark matter project, 6th UCLA Symposium on Sources and Detection of Dark Matter and Dark Energy in the Universe, Publisher: ELSEVIER SCI LTD, Pages: 277-281, ISSN: 1387-6473
Alner GJ, Atac M, Bewick A, et al., 2005, Status of the ZEPLIN II experiment, 6th UCLA Symposium on Sources and Detection of Dark Matter and Dark Energy in the Universe, Publisher: ELSEVIER SCI LTD, Pages: 259-263, ISSN: 1387-6473
Khan SA, Benford DJ, Clements DL, et al., 2005, Resolving IRAS 09111-1007 at 350 mu m: a different path to ULIRG formation?, MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Vol: 359, Pages: L10-L14, ISSN: 0035-8711
Shaul DNA, Sumner TJ, Rochester GK, 2005, Coherent Fourier components in the LISA measurement bandwidth from test mass charging: Estimates and suppression, INTERNATIONAL JOURNAL OF MODERN PHYSICS D, Vol: 14, Pages: 51-71, ISSN: 0218-2718
Araujo HM, Wass P, Shaul D, et al., 2005, Detailed calculation of test-mass charging in the LISA mission, Astroparticle Physics, Vol: 22, Pages: 451-469, ISSN: 1873-2852
The electrostatic charging of the LISA test masses due to exposure of the spacecraft to energetic particles in the space environment has implications in the design and operation of the gravitational inertial sensors and can affect the quality of the science data. Robust predictions of charging rates and associated stochastic fluctuations are therefore required for the exposure scenarios expected throughout the mission. We report on detailed charging simulations with the Geant4 toolkit, using comprehensive geometry and physics models, for Galactic cosmic-ray protons and helium nuclei. These predict positive charging rates of 50+e/s (elementary charges per second) for solar minimum conditions, decreasing by half at solar maximum, and current fluctuations of up to 30+e/s/Hz1/2. Charging from sporadic solar events involving energetic protons was also investigated. Using an event-size distribution model, we conclude that their impact on the LISA science data is manageable. Several physical processes hitherto unexplored as potential charging mechanisms have also been assessed. Significantly, the kinetic emission of very low-energy secondary electrons due to bombardment of the inertial sensors by primary cosmic rays and their secondaries can produce charging currents comparable with the Monte Carlo rates.
Turyshev SG, Dittus H, Lämmerzahl C, et al., 2005, Fundamental physics with the laser astrometric test of relativity, Pages: 11-18, ISSN: 0379-6566
The Laser Astrometric Test Of Relativity (LATOR) is a European-U.S. Michelson-Morley-type experiment designed to test the tensor metric nature of gravitation - the fundamental postulate of Einstein's theory of general relativity. By using a combination of independent timeseries of highly accurate gravitational deflection of light in the immediate proximity to the Sun along with measurements of the Shapiro time delay on the interplanetary scales (to a precision respectively better than 10-13 radians and 1 cm), LATOR will significantly improve our knowledge of relativistic gravity. The primary mission objective is to i) measure the key post-Newtonian Eddington parameter 7 with accuracy of a part in 109. (1 - γ) is a direct measure for presence of a new interaction in gravitational theory, and, in its search, LATOR goes a factor 30,000 beyond the present best result, Cassini's 2003 test. Other mission objectives include: ii) first measurement of gravity's non-linear effects on light to ∼0.01% accuracy; including both the traditional Eddington β parameter and also the spatial metric's 2nd order potential contribution(never been measured before); iii) direct measurement of the solar quadrupole moment J2 (currently unavailable) to accuracy of a part in 200 of its expected size; iv) direct measurement of the "frame-dragging" effect on light by the Sun's rotational gravitomagnetic field to one percent accuracy. LATOR's primary measurement pushes to unprecedented accuracy the search for cosmologically relevant scalar-tensor theories of gravity by looking for a remnant scalar field in today's solar system. The key element of LATOR is a geometric redundancy provided by the laser ranging and long-baseline optical interferometry. LATOR is envisaged as a partnership between European and US institutions and with clear areas of responsibility between the space agencies: NASA provides the deep space mission components, while optical infrastructure on the ISS
Sumner TJ, 2005, Advances in Space Research: Preface, ISSN: 0273-1177
Sumner T, 2005, Direct dark matter searches - DRIFT and ZEPLIN
© Copiright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. Three new direct dark matter detection experiments are nearing operations within our collaboration. DRIFT II is a next generation modular gas time projection chamber designed to demonstrate directionality with a scalable technology. The first module of this is operational in our underground laboratory at Boulby. ZEPLINs II and III are next generation liquid time projection chambers offering simultaneous measurement of scintillation and charge from liquid xenon. These two instruments will provide sensitivities into the 10−8 pb range. ZEPLIN II is just beginning science operations underground at Boulby. ZEPLIN III is in a final assembly in a surface laboratory. Our programme status will be presented.
Dittus H, Turyshev SG, Lämmerzahl C, et al., 2005, A mission to explore the Pioneer anomaly, Pages: 3-10, ISSN: 0379-6566
The Pioneer 10 and 11 spacecraft yielded the most precise navigation in deep space to date. These spacecraft had exceptional acceleration sensitivity. However, analysis of their radio-metric tracking data has consistently indicated that at heliocentric distances of ∼20-70 astronomical units, the orbit determinations indicated the presence of a small, anomalous, Doppler frequency drift. The drift is a blue-shift, uniformly changing with a rate of ∼ (5.99 ± 0.01) × 10-9 Hz s-1, which can be interpreted as a constant sunward acceleration of each particular spacecraft of aP = (8.74 ± 1.33) × 10-10 ms -2(Anderson et al. 1998; Turyshev et al. 1999; Anderson et al. 2002a). The nature of this anomaly remains unexplained. This signal has become known as the Pioneer anomaly. The inability to explain the anomalous behavior of the Pioneers with conventional physics has contributed to growing discussion about its origin. There is now an increasing number of proposals that attempt to explain the anomaly outside conventional physics. This progress emphasizes the need for a new experiment to explore the detected signal. Furthermore, the recent extensive efforts led to the conclusion that only a dedicated experiment could ultimately determine the nature of the found signal. We discuss the Pioneer anomaly and present the next steps towards an understanding of its origin. We specificallyfocus on the development of a mission to explore the Pioneer Anomaly in a dedicated experiment conducted in deep space. This joint European-US mission is motivated by the desire to better understand the laws of fundamental physics as they affect dynamics in the solar system. The mission could lead to a major discovery in the 21st century and, with readily available technologies, it could be flown well within the Cosmic Vision time frame.
Alner GJ, Araujo HM, Arnison GJ, et al., 2005, Zeplin I: first limits on nuclear recoil rate, Singapore, 5th international workshop on the identification of dark matter, 6 - 10 September 2004, Edinburgh, SCOTLAND, Publisher: World Scientific Publ Co Pte Ltd, Pages: 218-223
Alner GJ, Araujo HM, Arnison GJ, et al., 2005, Limits on wimp cross-sections from the NAIAD experiment at Boulby, Singapore, 5th international workshop on the identification of dark matter, 6 - 10 September 2004, Edinburgh, SCOTLAND, Publisher: World Scientific Publ Co Pte Ltd, Pages: 224-229
Wass PJ, Araujo HA, Davidge D, et al., 2005, Charging of the LISA test masses: sources, consequences and management, Proceedings of 10th Marcel Grossman meeting, Rio de Janeiro, 2003, Pages: 1-3
Alner GJ, Araujo H, Ayad R, et al., 2004, The DRIFT-I dark matter detector at Boulby: Design, installation and operation, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol: 535, Pages: 644-655, ISSN: 0168-9002
DRIFT-I, the first full-scale gaseous dark matter detector, has recently been installed at ∼1100 m depth at the Boulby Underground Laboratory, UK. The DRIFT concept offers high background discrimination and sensitivity to the direction of WIMP-induced nuclear recoils, the latter being of particular importance in the search for evidence of WIMPs in our galaxy, In this paper we discuss the design of the DRIFT-I detector and its installation and operation at Boulby. We also present results of early engineering runs and outline plans for the future. © 2004 Elsevier B.V. All rights reserved.
Alner GJ, Araujo H, Ayad R, et al., 2004, The DRIFT-I dark matter detector at Boulby: design, installation and operation, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, Vol: 535, Pages: 644-655, ISSN: 0168-9002
Ni WT, Ba G, Ba Y, et al., 2004, ASTROD I, test of relativity, solar-system measurement and G-wave detection, 6th International Conference on Gravitation and Astrophysics, Publisher: KOREAN PHYSICAL SOC, Pages: S118-S123, ISSN: 0374-4884
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