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The effect of paper thermal destruction on its luminescence spectra and luminescence excitation spectra in the spectral ranges of 400-550 nm and 250-450 nm, respectively, was studied. It is proposed to use the characteristic changes in the intensity and shape of the luminescence spectra as a criterion for the state of paper insulation of power transformers. On the basis of the analysis performed, it was concluded that when luminescence is excited at a wavelength of 360 nm, none of the main components of the paper can contribute to the recorded luminescence spectra. It is assumed that the resulting luminescence spectra are due to the emission of various impurities that enter the paper during its production.

The low‐frequency polarisation information of oil‐paper insulation could be easily obscured by the conductance effect, and the contained polarisation information thus can not be readily extracted from the frequency domain spectroscopy (FDS). Given this issue, an alternative idea is reported to extract the low‐frequency polarisation information by using logarithmic‐derivative spectroscopy (LDS). The present findings proved that the parameters extracted by using the LDS can be applied for studying the low‐frequency polarisation behaviour under the moisture effect. In that respect, the novelty of this work is in the exploration of the LDS as a potential tool to extract feature parameters for analyzing the low‐frequency polarisation information of transformer oil‐paper insulation.

This paper proposes a method of distinguishing the contributions of ionized and injected charges to the charge transport in oil immersed paper in triple-layer and double-layer samples. With the double-layer sample, the apparent mobility including the ions contribution is obtained by the calculation according to the speed of accumulated charge density at the interface. The contribution of ions is excluded by subtracting the accumulated charge density in the triple-layer sample from that in the double-layer sample. It is found that the interface charge mainly comes from the ionization charges under a low field, and the contribution of injected charge takes a more important part at higher electric field.

The analytical performance and a suggested mechanism for zero volt paper spray using chromatography paper are presented. A spray is generated by the action of the pneumatic force of the mass spectrometer (MS) vacuum at the inlet. Positive and negative ion signals are observed, and comparisons are made with standard kV paper spray (PS) ionization and nanoelectrospray ionization (nESI). While the range of analytes to which zero volt PS is applicable is very similar to kV PS and nESI, differences in the mass spectra of mixtures are interpreted in terms of the more significant effects of analyte surface activity in the gentler zero volt experiment than in the other methods due to the significantly lower charge. The signal intensity of zero volt PS is also lower than in the other methods. A Monte Carlo simulation based on statistical fluctuation of positive and negative ions in solution has been implemented to explain the production of ions from initially uncharged droplets. Uncharged droplets first break up due to aerodynamics forces until they are in the 2-4 ?m size range and then undergo Coulombic fission. A model involving statistical charge fluctuations in both phases predicts detection limits similar to those observed experimentally and explains the effects of binary mixture components on relative ionization efficiencies. The proposed mechanism may also play a role in ionization by other voltage-free methods. (Figure Presented). � 2015 American Chemical Society.

We demonstrate edge electron emission from flexible free-standing graphene paper (GP). The turn-on field is measured at 2.2 V/ $\mu{\rm m}$ , and the maximum emission current density at 3 ${\rm A}/{\rm cm}^{2}$ . The field emission properties of GP can be optimized by adjusting the thickness and annealing temperature. Because it is flexible, it can be shaped into different forms to meet the requirements of specific applications. The electron beam shape can range from a sheet electron beam to a cylindrical (hollow) electron beam.

An oil-paper insulation system which will withstand DC voltage under normal conditions is a key component of converter transformers as well as high voltage direct current (HVDC) bushings. When the system changes its state, operating overvoltage appears. This kind of overvoltage will consequently affect the application of oilimmersed facilities and the safety of entire grid. Therefore, this paper studies the charge coupling behavior of double-layer oil-paper insulation under DC and pulse voltages. From the research of different pulse voltage amplitudes, pulse numbers and polarity, conclusions can be drawn that, with the increase of the pulse voltage amplitudes, DC and pulse voltages in the same polarity cause the absolute value of the initial surface potential to decrease and then rise; while in different polarities, the charge with the same polarity as the pulse voltage increases. Furthermore, for the same pulse voltage, the absolute initial value of the DC voltage applied in the same polarity is higher than that in different polarities. Considering the pulse number effect, it is obvious that the initial value increases with the increase in the pulse number, and then reaches saturation. Also, with the increase in pulse number, the decay rate decreases and thus the charge is slowly dissipated. From the tdV/dt and the decay time curves, the peak value increases with the increase in the pulse number, while the characteristic time varies by the polarity of the DC and pulse voltages.

The determination of the neutrino mass is still an open issue in particle physics. The calorimetric measurement of the energy released in a nuclear beta decay allows measuring the whole energy, except the fraction carried away by the neutrino: due to the energy conservation, a finite neutrino mass m ν causes the energy spectrum to be truncated at Q-m ν , where Q is the transition energy of the decay. The electron capture of 163 Ho (Q ~ 2.5 keV) is an ideal decay, due to the high fraction of events close to the endpoint (i.e., the maximum energy of the relaxation energy spectrum). In order to achieve enough statistics, a large number of detectors (~10 4 ) are required. Superconducting microwave microresonators are detectors suitable for large-scale multiplexed frequency-domain readout, with theoretical energy and time resolution on the order of electronvolts and microseconds, respectively. Our aim is to develop arrays of microresonator detectors applicable to the calorimetric measurement of the energy spectrum of 163 Ho. Currently, a study aimed at the selection of the best design and material for the detectors is in progress. In order to obtain low-Tc detectors, with Tc ranging between ~0.5 and 2 K, different Ti/TiN (titanium nitride) multilayer films were produced. The reduced Tc was obtained by superposing thin layers of stoichiometric TiN to pure Ti layers, and the Tc was tuned by varying the ratio between the thickness of the layers. In this contribution, a comparison between the measurements (critical temperature, gap parameter, and X-ray energy spectra) made with stoichiometric and substoichiometric TiN and Ti/TiN multilayer film microresonators is presented.

Recent upgrades to the FIDA (fast-ion D-alpha) diagnostic at ASDEX Upgrade allow to reconstruct the fast-ion phase space at several radial positions with decent energy and pitch resolution. These new diagnostic capabilities are applied to study the physics of 2nd harmonic ion cyclotron heating, which is a foreseen heating scenario for ITER. In particular, the acceleration of deuterium beam ions above the injection energy by absorption of ion cyclotron waves at the 2nd harmonic is investigated and compared to theoretical predictions by the TORIC-SSFPQL and TORIC-NUBEAM code packages. Furthermore, comparisons to other fast-ion diagnostics (neutron yield and neutral particle analyzers) are discussed. EUROfusion Consortium 633053

Accurate theoretical knowledge of the (1s2p)3P1–(1s2s)1S0 splitting in He-like ions is demanded for future experimental studies of the nuclear spin-dependent part of the weak interaction. In this paper we perform a calculation of the hyperfine structure of (1s2p)3P1–(1s2s)1S0 within 3 ≤ Z ≤ 35, Z being the atomic number. In this Z range parity nonconservation (PNC) effects are amplified by the close energy proximity of the opposite parity levels (1s2p)3P1 and (1s2s)1S0. We find that the hyperfine structure is relevant for Z > 12, and produces splitting among the hyperfine sublevels as large as 150 meV for medium Z He-like ions (Z ∼ 35).

The pure vibrational transition frequencies of magnetically trapped cold XH molecules are useful to detect the variance in the proton-to-electron mass ratio β (X: alkali-earth atom). This paper compares the accuracies of the vibrational transition frequencies for different XH molecules.

The long quest for a measurement of the Lamb shift in muonic hydrogen is over. Last year we measured the 2S 1/2F=1 –2P 3/2F=2 energy splitting (Pohl et al., Nature, 466, 213 (2010)) in μp with an experimental accuracy of 15 ppm, twice better than our proposed goal. Using current QED calculations of the fine, hyperfine, QED, and finite size contributions, we obtain a root-mean-square proton charge radius of rp = 0.841 84 (67) fm. This value is 10 times more precise, but 5 standard deviations smaller, than the 2006 CODATA value of rp. The origin of this discrepancy is not known. Our measurement, together with precise measurements of the 1S–2S transition in regular hydrogen and deuterium, gives improved values of the Rydberg constant, R∞ = 10 973 731.568 160 (16) m–1 and the rms charge radius of the deuteron rd = 2.128 09 (31) fm.

We plan to measure several 2S–2P transition frequencies in μ4He+ and μ3He+ by means of laser spectroscopy with an accuracy of 50 ppm. This will lead to a determination of the corresponding nuclear rms charge radii with a relative accuracy of 3 × 10−4, limited by the uncertainty of the nuclear polarization contribution. First, these measurements will help to solve the proton radius puzzle. Second, these very precise nuclear radii are benchmarks for ab initio few-nucleon theories and potentials. Finally when combined with an ongoing measurement of the 1S–2S transition in He+, these measurements will lead to an enhanced bound-state QED test of the 1S Lamb shift in He+.

The method of two-photon approximation for multiphoton decay is applied to the decay of the 4d state in the hydrogen atom. In the process of four-photon decay the two-photon contribution that leads to radiation escape, from the interaction with matter, is considered. This may be helpful for a strict description of the recombination process in the hydrogen atom and, in principle, for the history of hydrogen recombination in the early universe.

Atomic parity violation (APV) experiments are sensitive probes of the electroweak interaction at low energy. These experiments are competitive with and complementary to high-energy collider experiments. The APV signal is strongly enhanced in heavy atoms, and it is measurable by exciting suppressed (M1, E2) transitions. The predicted enhancement factor of the APV effect in the S-D transition in Ra+ is about 50 times larger than the S-S transition in neutral Cs. However, certain spectroscopic information on Ra+, needed to constrain the required atomic many-body theory, was lacking. Using the AGOR cyclotron and the TRIμP facility at KVI in Groningen, short-lived 212–214Ra+ ions were produced and trapped. First ever excited-state laser spectroscopy was performed on the trapped ions. These measurements provide a benchmark for the atomic theory required to extract the electroweak mixing angle to sub 1% accuracy and are an important step towards an APV experiment in a single trapped Ra+ ion. A lower bound on the radiative lifetime of the 62D5/2 state was found of 232(4) ms. This experimental confirmation of the long coherence time of the meta-stable 62D5/2 state is important in light of the possibility of using a single trapped radium ion as an optical frequency standard.

Precise determination of bound-electron g-factors in highly charged ions provides stringent tests for state of the art theoretical calculations. The scope reaches from relativistic electron-correlation effects on the one hand to bound-state QED terms on the other. Besides, the investigation can contribute to the determination of the fine-structure constant α. In a first approach with boron-like ions of spinless nuclei (e.g., 40Ar13+ and 40Ca15+), we will excite the 22P1/2 – 22P3/2 fine-structure transition with laser radiation and probe microwave transitions between Zeeman sublevels. From this laser-microwave double-resonance technique the g-factor can be determined on a ppb level of accuracy. We have prepared a cryogenic trap assembly with a creation trap and a spectroscopy trap — a half-open compensated cylindrical Penning trap. Argon gas will be injected through a remotely controlled valve, working at cryogenic temperature and in the field of a superconducting magnet. Ions are produced by electron impact ionization and transferred to the spectroscopy trap. In the future, the trap will be connected to the HITRAP facility at GSI, and the method will be applied to hyperfine-structure transitions of hydrogen-like heavy ions to measure electronic and nuclear magnetic moments. We present important techniques employed in the experiment.

Calculational results are presented for the fine structure splitting of the 23P state of helium and helium-like ions with nuclear charge Z up to 10. Theoretical predictions are in agreement with the latest experimental results for the helium fine structure intervals as well as with the most of the experimental data available for light helium-like ions. Comparing the theoretical value of the 23P0-23P1 interval in helium with experimental results (Zelevinsky et al. Phys. Rev. Lett. 95, 203001 (2005)), we determine the value of the fine structure constant α with an accuracy of 31 ppb.

High resolution ro-vibrational spectroscopy of H 2+ or HD+ can lead to a significantly improved determination of the electron to proton mass ratio me/mp if the theoretical determination of transition frequencies becomes sufficiently accurate. We report on recent theoretical progress in the description of the hyperfine structure of H 2+ , as well as first steps in the evaluation of radiative corrections at order mα7. Completion of the latter calculation should allow us to reach the projected 10−10 accuracy level and open the road to mass ratio determination.

The purpose of this article is twofold. First, we attempt to give a brief overview of the different application areas of quantum electrodynamics (QED). These include fundamental physics (prediction of atomic energy levels), where the atom may be exposed to additional external fields (hyperfine splitting and g factor). We also mention QED processes in highly intense laser fields and more applied areas like Casimir and Casimir–Polder interactions. Both the unifying aspects as well as the differences in the the theoretical treatment required by these application areas (such as the treatment of infinities) are highlighted. Second, we discuss an application of the formalism in the fundamentally interesting area of the prediction of energy levels, namely, the hyperfine structure of P states of muonic hydrogen.

Cooling antihydrogen atoms is important for future experiments both to test the fundamental CPT symmetry by high resolution laser spectroscopy and also to measure the gravitational acceleration of antimatter. Laser cooling of antihydrogen can be done on the strong 1S–2P transition at the wavelength of Lyman-alpha (121.6 nm). A continuous wave laser at the Lyman-alpha wavelength based on solid-state fundamental lasers is described. By using a two-photon and a near one-photon resonance a scan across the whole phase matching curve of the four-wave mixing process is possible. Furthermore the influence of the beam profile of one fundamental beam on the four-wave mixing process is studied.

We present preparatory measurements for an improved test of time dilation at the experimental storage ring (ESR) at GSI in Darmstadt. A unique combination of particle accelerator experiments and laser spectroscopy is used to perform this test with the highest precision. 7Li+ ions are accelerated to 34% of the speed of light at the GSI Helmholtzzentrum für Schwerionenforschung and stored in the experimental storage ring. The forward and backward Doppler shifts of an electric dipole transition of these ions are measured with laser spectroscopy techniques. From these Doppler shifts, both the ion velocity β = ν/c and the time dilation factor [Formula: see text] can be derived for testing Special Relativity. Two laser systems have been developed to drive the 3S1→3P2 transition in 7Li+. Moreover, a detector system composed of photomultipliers, both to monitor the exact laser ion beam overlap as well as to optimize fluorescence detection, has been set up and tested. We investigate optical-optical double-resonance spectroscopy on a closed Λ-type three-level system to overcome Doppler broadening. A residual, broadened fluorescence background caused by velocity-changing processes in the ion beam is identified, and a background subtraction scheme implemented. At the present stage the experimental sensitivity, although already comparable with previous measurements on slower ion beams at the TSR storage ring that led to [Formula: see text] –8, suffer from a poor signal-to-noise ratio. Modifications of the ion source as well as the detection system are discussed that promise to improve the sensitivity by one order of magnitude.

Atomic parity violation (APV) can be measured in a single Ra+ ion, enabling a precise measurement of the electroweak mixing angle in the Standard Model of particle physics at low momentum transfer. This provides sensitivity to new particles such as extra Z0 bosons or leptoquarks. The Weinberg angle can be measured via a determination of the light shift in the forbidden 72S1/2–62D3/2 transition in a single trapped Ra+. Ultra-narrow transitions in such an ideal system can also be exploited to realize a high stability frequency standard. At the TRIμP facility of KVI, we have succeeded in the production of a series of radioactive short-lived radium isotopes. The radium isotopes produced were stopped and thermalized to Ra+ in a thermal ionizer, mass separated in a Wien filter, cooled in a gas filled radio frequency quadrupole and subsequently trapped as a cloud in a linear Paul trap. Laser spectroscopy in the trapped radium ions has been performed. The results of hyperfine structure, isotope shift, and lifetime measurements are important experimental inputs to test the accuracy of atomic theory, the precision of which is indispensable for extracting the Weinberg angle. These results are also of relevance for a possible atomic clock, based on trapped Ra+.

Recent progress on the precision laser spectroscopy of antiprotonic helium atoms, as well as on the X-ray spectroscopy of kaonic helium atoms, are presented. These two may appear to be unrelated topics (except that both involve exotic helium atoms), but in fact a past study of kaonic helium system led to the serendipitous discovery of antiprotonic helium. Some historical background connecting these two exotic helium atoms, as well as future prospects, are discussed.

Absolute electron impact ionization cross sections for CH3X, where X = H, F, Cl, Br, and I Claire Vallance et al 1997 J. Phys. B: At. Mol. Opt. Phys. 30 2465–2475 Absolute electron-impact ionization cross sections for a range of C1 to C5 chlorocarbons James E Hudson et al 2001 J. Phys. B: At. Mol. Opt. Phys. 34 3025–3039 Absolute electron impact ionization cross-sections for CO, CO2, OCS and CS2 James E Hudson et al 2004 J. Phys. B: At. Mol. Opt. Phys. 37 445–455 We have recently re-examined some published binary-encounter–Bethe (BEB) calculations on the electron impact ionization cross sections for halogenated hydrocarbons and sulfur-containing molecules, and found a discrepancy with our earlier results. Please see the PDF file for full details.

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Conduction currents and thermally stimulated discharge (TSD) currents were studied in aramid paper at various field strengths and temperatures. At low field strengths the conductivity is ohmic, and at higher field strengths (up to 30 MV/m), ionic conduction is a possible mechanism. The activation energy of low field conduction is determined and at high electric fields the hopping distance for ions is in the range of 4.4 to 8.0 nm. TSD currents are also measured at various poling fields, formation and storage times, and rates of heating. The TSD current shows a peak at 135 degrees C for a rate of heating of 1 K/min and shifts to a higher value when the rate of heating is increased. The peak current and the charge released to the external circuit is proportional to the poling field. The observed peak is attributed to the depolarization of permanent dipoles with a room temperature relaxation time of 5.3*10/sup 5/ s. >

Journal URL: http://www.sciencedirect.com/science/journal/03796779

Journal URL: http://www.sciencedirect.com/science/journal/03796779

To date, most resources for ion beam fusion have been devoted to development of accelerators and target physics; relatively few resources have gone into ion beam transport development. Because of theoretical studies and substantial experience with electron beam transport, the ion beam transport community is now poised to develop and optimize ion beam transport for ICF. Because of this Tri-Lab effort, a path for coordinated development of ion beam transport has been established. The rate of progress along this path will now be determined largely by the availability of resources.

We show that the numerical code used in the above mentioned paper does not take into account the multiple scattering effects of electromagnetic fields properly and is, therefore, incorrect.

Theoretical models have been developed, and are currently being refined, to explain the edge plasma-antenna interaction that occurs during ICRF heating. The periodic structure of a Faraday shielded antenna is found to result in strong ponderomotive force in the vicinity of the antenna. A fluid model, which incorporates the ponderomotive force, shows an increase in transport to the Faraday shield. A kinetic model shows that the strong antenna near fields act to increase the energy of deuterons which strike the shield, thereby increasing the sputtering of shield material. Estimates of edge impurity harmonic heating show no significant heating for either in or out-of-phase antenna operation. Additionally, a particle model for electrons near the shield shows that heating results from the parallel electric field associated with the fast wave. A quasilinear model for edge electron heating is presented and compared to the particle calculations. The models' predictions are shown to be consistent with measurements of enhanced transport.

The waves that can propagate in the edge plasma during fast wave ion cyclotron resonance heating (ICRH) for densities sufficiently high that ω

Parametric instabilities in the scrape-off layer (SOL) of tokamak plasmas are studied in the presence of ICRF and/or IBW RF fields. Growth rates and typical threshold RF fields are deduced for multi-ion species plasmas for pump frequencies in the vicinity of the first few ion cyclotron harmonics. Decay instabilities into ion Bernstein waves and quasi-modes are predicted to occur. Such decay waves may lead to edge heating and impurity generation.

Heating experiments in the second harmonic ion cyclotron range of frequencies (ICRF) have been performed with a phased array of 2×2 loop antennas in JT-60. Properties of antenna-plasma coupling are examined by phasing antenna currents in the toroidal direction. In particular, it is first found that the antenna-plasma coupling resistance increases after the H-mode transition in out-of-phase excitation of antenna currents. This result is well explained with the cold plasma coupling theory which takes into account a change in the edge density profile at the transition. Two types of parametric decay instabilities near the plasma edge are observed. One type is decay into an ion Bernstein wave (IBW) and an ion cyclotron quasimode (IQM) and the other into an ion Bernstein wave and a cold electrostatic ion cyclotron wave (CESICW) or an electron quasimode (EQM). Intensity of IBW detected by a probe near the antenna in the decay into IBW and IQM increases with reduction of B T and I p . The decay instabilities are observed only in the case of in-phase excitation. The edge plasma is heated by the decay instability and the radiation loss during ICRF heating increases with the decay activity.

The release of Faraday screen material into the plasma by a powered ICRF antenna is investigated in this report. JET spectroscopic data has been analyzed to give scalings of the metal impurity influx from a chromium-plated screen with antenna voltage and edge density. Modeling of the metal influx data by an RF sheath mechanism and scrape off layer model has been carried out including the sputtering contributions of deuterium and carbon ions and the self-sputtering of the Faraday screen material. The predictions of the model for JET parameters are compared with the Cr data and are also employed to investigate the sputtering influx of Be from Be-coated Faraday screens.

The work of the late Theo Thole is introduced in five sections, discussing (1) multiplet theory, (2) the branching ratio, (3) dichroism and sum rules, (4) X-ray photoemission and (5) resonant X-ray scattering. At the end of the paper a complete list of all papers published by Theo Thole is included.

From magnetic systems to the crust of the earth, many physical systems that exibit a multiplicty of metastable states emit pulses with a broad power law distribution in energy. Digital audio recordings reveal that paper being crumpled, a system that can be easily held in hand, is such a system. Crumpling paper both using the traditional hand method and a novel cylindrical geometry uncovered a power law distribution of pulse energies spanning at least two decades: (exponent 1.3 - 1.6) Crumpling initally flat sheets into a compact ball (strong crumpling), we found little or no evidence that the energy distribution varied systematically over time or the size of the sheet. When we applied repetitive small deformations (weak crumpling) to sheets which had been previously folded along a regular grid, we found no systematic dependence on the grid spacing. Our results suggest that the pulse energy depends only weakly on the size of the paper regions responsible for sound production., 12 pages of text, 9 figures, submitted to Phys. Rev. E, additional information availible at http://www.msc.cornell.edu/~houle/crumpling/

An overview is given of the interactions that determine the XANES spectral shapes of transition metal compounds. The interactions are divided into ground state effects, final state effects and transition effects. The metal L edges, metal K edges and ligand K edges are analysed with respect to these interactions. The importance of XANES is partly due to its wide versatility in measurement conditions. XANES spectra can be measured using a number of sample environments, ranging from vacuum to ambient pressures for soft x-rays and up to extreme conditions with hard X-rays. These in-situ XANES spectra can be measured with a spatial resolution of 10 to 30 nm. XANES spectral shapes can be used as resonant channels in resonant photoemission, resonant x-ray emission or resonant diffraction experiments. This gives rise to a large number of resonant techniques that also allow the detection of site, valence, spin and symmetry selective XANES spectra and/or XANES spectra revealing information with a resolution better than its lifetime broadening.