The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
Victor V. Flambaum - One of the best experts on this subject based on the ideXlab platform.
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Weak quadrupole moments
Journal of Physics G: Nuclear and Particle Physics, 2018Co-Authors: B. G. C. Lackenby, Victor V. FlambaumAbstract:Collective effects in deformed atomic nuclei present possible avenues of study on the non-spherical distribution of neutrons and the violation of the local Lorentz invariance. We introduce the weak quadrupole moment of nuclei, related to the quadrupole distribution of the weak charge in the nucleus. The weak quadrupole moment produces tensor weak interaction between the nucleus and electrons and can be observed in atomic and molecular experiments measuring parity nonconservation. The dominating contribution to the weak quadrupole is given by the quadrupole moment of the neutron distribution, therefore, corresponding experiments should allow one to measure the neutron Quadrupoles. Using the deformed oscillator model and the Schmidt model we calculate the quadrupole distributions of neutrons, $Q_{n}$, the weak quadrupole moments ,$Q_{W}^{(2)}$, and the Lorentz Innvariance violating energy shifts in $^{9}$Be, $^{21}$Ne , $^{27}$Al, $^{131}$Xe, $^{133}$Cs, $^{151}$Eu, $^{153}$Eu, $^{163}$Dy, $^{167}$Er, $^{173}$Yb, $^{177}$Hf, $^{179}$Hf, $^{181}$Ta, $^{201}$Hg and $^{229}$Th.
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Weak quadrupole moment, quadrupole distribution of neutrons and Lorentz invariance violation in deformed nuclei
2017Co-Authors: B. G. C. Lackenby, Victor V. FlambaumAbstract:Collective effects in deformed atomic nuclei present possible avenues of study on the non-spherical distribution of neutrons and the violation of the local Lorentz invariance. We introduce the weak quadrupole moment of nuclei, related to the quadrupole distribution of the weak charge in the nucleus. The weak quadrupole moment produces tensor weak interaction between the nucleus and electrons and can be observed in atomic and molecular experiments measuring parity nonconservation. The dominating contribution to the weak quadrupole is given by the quadrupole moment of the neutron distribution, therefore, corresponding experiments should allow one to measure the neutron Quadrupoles. Using the deformed oscillator model and the Schmidt model we calculate the quadrupole distributions of neutrons, $Q_{n}$, the weak quadrupole moments ,$Q_{W}^{(2)}$, and the Lorentz Innvariance violating energy shifts in $^{9}$Be, $^{21}$Ne , $^{27}$Al, $^{131}$Xe, $^{133}$Cs, $^{151}$Eu, $^{153}$Eu, $^{163}$Dy, $^{167}$Er, $^{173}$Yb, $^{177}$Hf, $^{179}$Hf, $^{181}$Ta, $^{201}$Hg and $^{229}$Th.
D. J. Douglas - One of the best experts on this subject based on the ideXlab platform.
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mass selective axial ion ejection from linear Quadrupoles with added octopole fields
Journal of the American Society for Mass Spectrometry, 2008Co-Authors: Annie Moradian, D. J. DouglasAbstract:Mass selective axial ejection of ions from linear Quadrupoles with added octopole fields is described. Quadrupoles with 2.0% and 2.6% added octopole fields have been tested and compared with a conventional quadrupole. The effects of trapping ions at different q values, excitation voltage, scan direction, balanced and unbalanced rf voltages on the rods, and dc applied between the rods have been investigated. The highest scan speeds and best resolution are obtained with resonant excitation and ejection at high q (q=0.8). With axial ejection, the quadrupole with a 2.0% added octopole field provides mass resolution and ejection efficiencies similar to a conventional rod set. Quadrupole, dipole, and simultaneous dipole—dipole excitation between the x and y rod pairs were compared, and no advantage was found with quadrupole or dipole—dipole excitation. The effects of scan speed were investigated and a resolution at half height of about 1600 is possible at scans speed up to 5000 Th/s.
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linear Quadrupoles with added hexapole fields
Journal of the American Society for Mass Spectrometry, 2006Co-Authors: N V Konenkov, Frank A Londry, Chuanfan Ding, D. J. DouglasAbstract:Linear Quadrupoles with added hexapole fields are described. The shifts in ion oscillation frequency caused by the addition of a hexapole field are calculated within the effective potential model. Methods to construct linear Quadrupoles with added hexapole fields with exact electrode geometries and with round rods are discussed. A quadrupole with added hexapole field can be constructed with round rods by rotating two rods (say the y rods) towards an x rod. Computer simulations are used to investigate the possibility of mass analysis with Quadrupoles with added hexapole fields. We find that a quadrupole with an added hexapole field in the range 2–12% can provide mass analysis provided the dc is applied with the correct polarity and value. When a rod set is constructed with round rods, other multipoles in the potential degrade the peak shape, resolution and transmission. The largest of these after the quadrupole and hexapole are a dipole and octopole term. With round rod sets, the peak shape can be improved by using different diameters for the x and y rod pairs to minimize the octopole term in the potential and by injecting ions at the field center where the dipole term is zero. Calculations of the boundaries of the stability diagram for this case show the boundaries move out, relative to those of a pure quadrupole field, but remain sharp.
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linear Quadrupoles with added octopole fields
Rapid Communications in Mass Spectrometry, 2003Co-Authors: Michael Sudakov, D. J. DouglasAbstract:Two methods of adding relatively small octopole fields to the main quadrupole field of Quadrupoles and linear ion traps with cylindrical rods are investigated. The first, ‘stretching’ the quadrupole by moving two rods out from the axis, produces a combination of higher order fields with similar magnitudes in which the octopole field is not necessarily the greatest. The quadrupole field strength is changed significantly and a large potential appears on the axis. The second method uses rod pairs of different diameters. It adds octopole components of up to several percent while all other higher order fields remain small. An axis potential is also added, but it is only a few percent of the radio-frequency (RF) voltage and approximately equal to the strength of the octopole field. The axis potential can be removed by moving the larger rod pair out from the axis or applying unbalanced RF to the electrodes. Copyright © 2003 John Wiley & Sons, Ltd.
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an interface with a linear quadrupole ion guide for an electrospray ion trap mass spectrometer system
Analytical Chemistry, 2000Co-Authors: Michael W Blades, D. J. DouglasAbstract:A new ion sampling interface for an electrospray ionization 3D ion trap mass spectrometer system is described. The interface uses linear rf Quadrupoles as ion guides and ion traps to enhance the performance of the 3D trap. Trapping ions in the linear Quadrupoles is demonstrated to improve the duty cycle of the system. Dipolar excitation of ions trapped in a linear quadrupole is used to eject unwanted ions. A resolution of ejection of up to 254 is demonstrated for protonated reserpine ions (m/z 609.3). A composite waveform with a notch in frequency space is used to eject a wide range of matrix ions and to isolate trace analyte ions in a linear quadrupole before ions are injected into the 3D trap. This is useful to overcome space charge problems in the 3D trap caused by excess matrix ions. For trace reserpine in a 500-fold molar excess of poly(propylene glycol) (PPG), it is demonstrated that the resolution and sensitivity of the 3D trap can be increased dramatically with ejection of the excess PPG matrix io...
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A novel tandem quadrupole mass analyzer
Journal of the American Society for Mass Spectrometry, 1999Co-Authors: D. J. DouglasAbstract:A new “tandem mass analyzer” is described. Two quadrupole mass filters are operated in series. Each is operated at low resolution and a small mass offset is introduced between the two Quadrupoles so that the pair operate together to give higher resolution. The resolution of the tandem analyzer can be changed by changing the mass offset. The transmission is highest when the Quadrupoles are operated as close together as possible with the poles aligned, with no intervening ion lens, and with the radio frequency (rf) voltages phase locked. A phase shift between the rf voltages applied to the Quadrupoles also improves the ion transmission. For a given resolution the tandem analyzer has transmission comparable to that of a single quadrupole. Results obtained with operation of the Quadrupoles in the first, second, and third stability regions are described. Operation in the third stability region is particularly advantageous because the tandem analyzer exhibits good abundance sensitivity on the low and high mass sides under conditions where a single quadrupole produces a long peak tail on at least one side. It is also shown that scattering losses in the tandem analyzer are about half of those of a conventional quadrupole. The results suggest that it may be possible to build a low cost tandem analyzer that has relatively poor mechanical precision and yet that produces satisfactory peak shape and resolution.
B. G. C. Lackenby - One of the best experts on this subject based on the ideXlab platform.
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Weak quadrupole moments
Journal of Physics G: Nuclear and Particle Physics, 2018Co-Authors: B. G. C. Lackenby, Victor V. FlambaumAbstract:Collective effects in deformed atomic nuclei present possible avenues of study on the non-spherical distribution of neutrons and the violation of the local Lorentz invariance. We introduce the weak quadrupole moment of nuclei, related to the quadrupole distribution of the weak charge in the nucleus. The weak quadrupole moment produces tensor weak interaction between the nucleus and electrons and can be observed in atomic and molecular experiments measuring parity nonconservation. The dominating contribution to the weak quadrupole is given by the quadrupole moment of the neutron distribution, therefore, corresponding experiments should allow one to measure the neutron Quadrupoles. Using the deformed oscillator model and the Schmidt model we calculate the quadrupole distributions of neutrons, $Q_{n}$, the weak quadrupole moments ,$Q_{W}^{(2)}$, and the Lorentz Innvariance violating energy shifts in $^{9}$Be, $^{21}$Ne , $^{27}$Al, $^{131}$Xe, $^{133}$Cs, $^{151}$Eu, $^{153}$Eu, $^{163}$Dy, $^{167}$Er, $^{173}$Yb, $^{177}$Hf, $^{179}$Hf, $^{181}$Ta, $^{201}$Hg and $^{229}$Th.
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Weak quadrupole moment, quadrupole distribution of neutrons and Lorentz invariance violation in deformed nuclei
2017Co-Authors: B. G. C. Lackenby, Victor V. FlambaumAbstract:Collective effects in deformed atomic nuclei present possible avenues of study on the non-spherical distribution of neutrons and the violation of the local Lorentz invariance. We introduce the weak quadrupole moment of nuclei, related to the quadrupole distribution of the weak charge in the nucleus. The weak quadrupole moment produces tensor weak interaction between the nucleus and electrons and can be observed in atomic and molecular experiments measuring parity nonconservation. The dominating contribution to the weak quadrupole is given by the quadrupole moment of the neutron distribution, therefore, corresponding experiments should allow one to measure the neutron Quadrupoles. Using the deformed oscillator model and the Schmidt model we calculate the quadrupole distributions of neutrons, $Q_{n}$, the weak quadrupole moments ,$Q_{W}^{(2)}$, and the Lorentz Innvariance violating energy shifts in $^{9}$Be, $^{21}$Ne , $^{27}$Al, $^{131}$Xe, $^{133}$Cs, $^{151}$Eu, $^{153}$Eu, $^{163}$Dy, $^{167}$Er, $^{173}$Yb, $^{177}$Hf, $^{179}$Hf, $^{181}$Ta, $^{201}$Hg and $^{229}$Th.
A.j Parker - One of the best experts on this subject based on the ideXlab platform.
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Computer simulations using a longitudinal quadrupolar Gay–Berne model: effect of the quadrupole magnitude on the formation of the smectic phase
Chemical Physics Letters, 1998Co-Authors: Maureen P. Neal, A.j ParkerAbstract:Abstract Systems of Gay–Berne particles with longitudinal linear Quadrupoles are studied by molecular dynamics simulations. The effect of the magnitude of the quadrupole on the smectic phase is investigated. It is found that the quadrupole destabilises the formation of the smectic phase which disappears altogether with high-magnitude Quadrupoles. As the magnitude of the quadrupole is reduced a variety of smectic phases are formed, including smectic A, smectic C and smectic B, with the eventual formation of a crystal. The maximum magnitude of the tilt observed is 17.2°, comparable with experimentally observed magnitudes.
Paolo Ferracin - One of the best experts on this subject based on the ideXlab platform.
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Summary of Test Results of MQXFS1—The First Short Model 150 mm Aperture Nb$_3$Sn Quadrupole for the High-Luminosity LHC Upgrade
2017Co-Authors: Stoyan Stoynev, Giorgio Ambrosio, Michael Anerella, Rodger Bossert, Eugenio Cavanna, Daniel R. Dietderich, Joseph Dimarco, Helene Felice, Daniel Cheng, Paolo FerracinAbstract:The development of $Nb_3Sn$ quadrupole magnets for the High-Luminosity LHC upgrade is a joint venture between the US LHC Accelerator Research Program (LARP)* and CERN with the goal of fabricating large aperture Quadrupoles for the LHC in-teraction regions (IR). The inner triplet (low-β) NbTi Quadrupoles in the IR will be replaced by the stronger Nb3Sn magnets boosting the LHC program of having 10-fold increase in integrated luminos-ity after the foreseen upgrades. Previously LARP conducted suc-cessful tests of short and long models with up to 120 mm aperture. The first short 150 mm aperture quadrupole model MQXFS1 was assembled with coils fabricated by both CERN and LARP. The magnet demonstrated strong performance at the Fermilab’s verti-cal magnet test facility reaching the LHC operating limits. This paper reports the latest results from MQXFS1 tests with changed pre-stress levels. The overall magnet performance, including quench training and memory, ramp rate and temperature depend-ence, is also summarized.
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Performance of the First Short Model 150-mm-Aperture Nb$_3$Sn Quadrupole MQXFS for the High-Luminosity LHC Upgrade
2016Co-Authors: Gguram Chlachidze, Giorgio Ambrosio, Michael Anerella, Rodger Bossert, Eugenio Cavanna, Daniel W. Cheng, Daniel R. Dietderich, Joseph Dimarco, Helene Felice, Paolo FerracinAbstract:The US LHC Accelerator Research Program (LARP) and CERN combined their efforts in developing Nb3Sn magnets for the High-Luminosity LHC upgrade. The ultimate goal of this collaboration is to fabricate large aperture Nb3Sn Quadrupoles for the LHC interaction regions (IR). These magnets will replace the present 70 mm aperture NbTi quadrupole triplets for expected increase of the LHC peak luminosity by a factor of 5. Over the past decade LARP successfully fabricated and tested short and long models of 90 mm and 120 mm aperture Nb3Sn Quadrupoles. Recently the first short model of 150 mm diameter quadrupole MQXFS was built with coils fabricated both by the LARP and CERN. The magnet performance was tested at Fermilab’s vertical magnet test facility. This paper reports the test results, including the quench training at 1.9 K, ramp rate and temperature dependence studies.
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design studies for the low beta Quadrupoles for the lhc luminosity upgrade
IEEE Transactions on Applied Superconductivity, 2013Co-Authors: E Todesco, Paolo Ferracin, F Borgnolutti, Herve Allain, G Ambrosio, F Cerutti, D R Dietderich, L S Esposito, H Felice, G SabbiAbstract:In this paper, we outline the present status of the design studies for the high-luminosity Large Hadron Collider, focusing on the choice of the aperture of the inner triplet Quadrupoles. After reviewing some critical aspects of the design such as energy deposition, shielding, heat load, and protection, we present the main tentative parameters for building a 150-mm-aperture Nb3Sn quadrupole, based on the experience gathered by the LARP program in the past several years.
