39 research outputs found
Simulation of ion behavior in an open three-dimensional Paul trap using a power series method
Simulations of the dynamics of ions trapped in a Paul trap with terms in the
potential up to the order 10 have been carried out. The power series method is
used to solve numerically the equations of motion of the ions. The stability
diagram has been studied and the buffer gas cooling has been implemented by a
Monte Carlo method. The dipole excitation was also included. The method has
been applied to an existing trap and it has shown good agreement with the
experimental results and previous simulations using other methods
E1 transitions between states with n = 1 to 6 in helium-like carbon, nitrogen, oxygen, neon, silicon, and argon
Wavelengths and transition rates are given for E1 transitions between singlet
S, P, D, and F states, between triplet S, P, and D states, and between triplet
P and singlet S states in ions of astrophysical interest: helium-like carbon,
nitrogen, oxygen, neon, silicon, and argon. All possible E1 transitions between
states with J < 4 and n < 7 are considered. Energy levels and wave functions
used in calculations of the transition rates are obtained from relativistic
configuration-interaction calculations that include both Coulomb and Breit
interactions.Comment: submitted to Astrophysical Journa
Interatomic Coulombic Decay as a New Source of Low Energy Electrons in slow Ion-Dimer Collisions
We provide the experimental evidence that the single electron capture process
in slow collisions between O ions and neon dimer targets leads to an
unexpected production of low-energy electrons. This production results from the
interatomic Coulombic decay process, subsequent to inner shell single electron
capture from one site of the neon dimer. Although pure one-electron capture
from inner shell is expected to be negligible in the low collision energy
regime investigated here, the electron production due to this process overtakes
by one order of magnitude the emission of Auger electrons by the scattered
projectiles after double-electron capture. This feature is specific to low
charge states of the projectile: similar studies with Xe and Ar
projectiles show no evidence of inner shell single-electron capture. The
dependence of the process on the projectile charge state is interpreted using
simple calculations based on the classical over the barrier model
Weak Interaction Studies with 6He
The 6He nucleus is an ideal candidate to study the weak interaction. To this
end we have built a high-intensity source of 6He delivering ~10^10 atoms/s to
experiments. Taking full advantage of that available intensity we have
performed a high-precision measurement of the 6He half-life that directly
probes the axial part of the nuclear Hamiltonian. Currently, we are preparing a
measurement of the beta-neutrino angular correlation in 6He beta decay that
will allow to search for new physics beyond the Standard Model in the form of
tensor currents.Comment: 5 pages, 4 figures, proceedings for the Eleventh Conference on the
Intersections of Particle and Nuclear Physics (CIPANP 2012
Paul trapping of radioactive 6He+ions and direct observation of their beta-decay
We demonstrate that abundant quantities of short-lived beta unstable ions can
be trapped in a novel transparent Paul trap and that their decay products can
directly be detected in coincidence. Low energy 6He+ (807 ms half-life) ions
were extracted from the SPIRAL source at GANIL, then decelerated, cooled and
bunched by means of the buffer gas cooling technique. More than 10^8 ions have
been stored over a measuring period of six days and about 10^5 decay
coincidences between the beta particles and the 6Li^{++} recoiling ions have
been recorded. The technique can be extended to other short-lived species,
opening new possibilities for trap assisted decay experiments.Comment: 4 pages, 4 figures, submitted to Phys.Rev.Let
Measured and Simulated Nitrous Oxide Emissions from Ryegrass- and Ryegrass/White Clover-Based Grasslands in a Moist Temperate Climate
There is uncertainty about the potential reduction of soil nitrous oxide (N2O) emission when fertilizer nitrogen (FN) is partially or completely replaced by biological N fixation (BNF) in temperate grassland. The objectives of this study were to 1) investigate the changes in N2O emissions when BNF is used to replace FN in permanent grassland, and 2) evaluate the applicability of the process-based model DNDC to simulate N2O emissions from Irish grasslands. Three grazing treatments were: (i) ryegrass (Lolium perenne) grasslands receiving 226 kg FN ha−1 yr−1 (GG+FN), (ii) ryegrass/white clover (Trifolium repens) grasslands receiving 58 kg FN ha−1 yr−1 (GWC+FN) applied in spring, and (iii) ryegrass/white clover grasslands receiving no FN (GWC-FN). Two background treatments, un-grazed swards with ryegrass only (G–B) or ryegrass/white clover (WC–B), did not receive slurry or FN and the herbage was harvested by mowing. There was no significant difference in annual N2O emissions between G–B (2.38±0.12 kg N ha−1 yr−1 (mean±SE)) and WC-B (2.45±0.85 kg N ha−1 yr−1), indicating that N2O emission due to BNF itself and clover residual decomposition from permanent ryegrass/clover grassland was negligible. N2O emissions were 7.82±1.67, 6.35±1.14 and 6.54±1.70 kg N ha−1 yr−1, respectively, from GG+FN, GWC+FN and GWC-FN. N2O fluxes simulated by DNDC agreed well with the measured values with significant correlation between simulated and measured daily fluxes for the three grazing treatments, but the simulation did not agree very well for the background treatments. DNDC overestimated annual emission by 61% for GG+FN, and underestimated by 45% for GWC-FN, but simulated very well for GWC+FN. Both the measured and simulated results supported that there was a clear reduction of N2O emissions when FN was replaced by BNF
Characteristics of ammonia, acid gases, and PM<sub>2.5</sub> for three typical land-use types in the North China Plain
Air pollution is one of the most serious environmental problems in China due to its rapid economic development alongside a very large consumption of fossil fuel, particularly in the North China Plain (NCP). During the period 2011–2014, we integrated active and passive sampling methods to perform continuous measurements of NH3, HNO3, NO2, and PM2.5 at two urban, one suburban, and two rural sites in the NCP. The annual average concentrations of NH3, NO2, and HNO3 across the five sites were in the ranges 8.5–23.0, 22.2–50.5, and 5.5–9.7 μg m−3, respectively, showing no significant spatial differences for NH3 and HNO3 but significantly higher NO2 concentration at the urban sites. At each site, annual average concentrations of NH3 and NO2 showed increasing and decreasing trends, respectively, while there was no obvious trend in annual HNO3 concentrations. Daily PM2.5 concentrations ranged from 11.8 to 621.0 μg m−3 at the urban site, from 19.8 to 692.9 μg m−3 at the suburban site, and from 23.9 to 754.5 μg m−3 at the two rural sites, with more than 70 % of sampling days exceeding 75 μg m−3. Concentrations of water-soluble ions in PM2.5 ranked differently between the non-rural and rural sites. The three dominant ions were NH4 +, NO3 −, and SO4 2− and mainly existed as (NH4)2SO4, NH4HSO4, and NH4NO3, and their concentrations averaged 48.6 ± 44.9, 41.2 ± 40.8, and 49.6 ± 35.9 μg m−3 at the urban, suburban, and rural sites, respectively. Ion balance calculations indicated that PM2.5 was neutral at the non-rural sites but acidic at the rural sites. Seasonal variations of the gases and aerosols exhibited different patterns, depending on source emission strength and meteorological conditions. Our results suggest that a feasible pathway to control PM2.5 pollution in the NCP should target ammonia and acid gases together
Kinematically Complete Charge Exchange Experiment in the Cs+ + Rb Collision System Using a MOT Target
International audienc
Space-charge effects in Penning ion traps
The influence of space-charge on ion cyclotron resonances and magnetron eigen frequency in a gas-filled
Penning ion trap has been investigated. Off-line measurements with 39K using the cooling trap of the
WITCH retardation spectrometer-based setup at ISOLDE/CERN were performed. Experimental ion cyclotron resonances were compared with ab initio Coulomb simulations and found to be in agreement.
As an important systematic effect of the WITCH experiment,the magnetron eigen frequency of the ion
cloud was studied under increasing space-charge conditions. Finally, the helium buffer gas pressure in
the Penning trap was determined by comparing experimental cooling rates with simulations.publisher: Elsevier
articletitle: Space-charge effects in Penning ion traps
journaltitle: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
articlelink: http://dx.doi.org/10.1016/j.nima.2015.02.057
content_type: article
copyright: Copyright © 2015 CERN for the benefit of the Authors. Published by Elsevier B.V.status: publishe
Using GPU parallelization to perform realistic simulations of the LPCTrap experiments
The LPCTrap setup is a sensitive tool to measure the β − ν angular correlation
coefficient, aβν, which can yield the mixing ratio ρ of a β decay transition. The latter
enables the extraction of the Cabibbo-Kobayashi-Maskawa (CKM) matrix element Vud. In
such a measurement, the most relevant observable is the energy distribution of the recoiling
daughter nuclei following the nuclear β decay, which is obtained using a time-of-flight
technique. In order to maximize the precision, one can reduce the systematic errors through
a thorough simulation of the whole set-up, especially with a correct model of the trapped ion
cloud. This paper presents such a simulation package and focuses on the ion cloud features;
particular attention is therefore paid to realistic descriptions of trapping field dynamics,
buffer gas cooling and the N-body space charge effects.status: publishe