Searches for permanent electric dipole moments (EDMs) of fundamental particles, atoms and molecules are promising experiments to constrain and potentially reveal beyond Standard Model (SM) physics. A ...non-zero EDM is a direct manifestation of time-reversal (T) violation, and, equivalently, violation of the combined operation of charge-conjugation (C) and parity inversion (P). Identifying new sources of CP violation can help to solve fundamental puzzles of the SM, e.g., the observed baryon-asymmetry in the Universe. Theoretical predictions for magnitudes of EDMs in the SM are many orders of magnitude below current experimental limits. However, many theories beyond the SM require larger EDMs. Experimental results, especially when combined in a global analysis, impose strong constraints on CP violating model parameters. Including an overview of EDM searches, I will focus on the future neutron EDM experiment at TRIUMF (Vancouver). For this effort, the TUCAN (TRIUMF Ultra Cold Advanced Neutron source) collaboration is aiming to build a strong, world leading source of ultra cold neutrons (UCN) based on a unique combination of a spallation target and a superfluid helium UCN converter. Another focus will be the search for an EDM of the diamagnetic atom 129 Xe using a 3 He comagnetometer and SQUID detection. The HeXeEDM collaboration has taken EDM data in 2017 and 2018 in the magnetically shielded room (BMSR-2) at PTB Berlin.
Surface resistivity measurements are frequently used for material characterization. However, the influence of sample thickness is not covered sufficiently in ASTM D257 and IEC 62631-3-2 standards. In ...the present work, electric field simulations and polarization-depolarization current (PDC) measurements are used to study the thickness dependence of such measurements. It is found that measurements according to the standards are not reasonable for low thickness (< 1 mm) and high surface resistivity (> 10 13 ...10 14 Ω). The dependence on thickness is shown to be mainly due to the different tangential electric field stress along the measured surface. Furthermore, indications for charge injection at high electric field stress inside the sample volume are found by a positive polarity of the depolarization currents. A novel electrode configuration for more accurate (more than one order of magnitude) and much less thickness-dependent surface resistivity measurements is proposed in this work and its benefits are demonstrated. It is also shown how the parasitic influence of an electrode holder can be effectively reduced by more than one order of magnitude when measuring surface resistivities. In addition, it is found that polarization times for steady-state surface resistivity values should be at least several minutes instead of the suggested 60 s from standards.
The aim of the present manuscript is to contribute to the understanding of material performance of machine insulation film at high temperatures and changing relative humidity (RH). This represents a ...common stress under normal operation and may lower the material insulation performance. PET film is used as the example material and the complex dielectric permittivity is used as a marker to investigate changes in the dielectric properties. Measurements are carried out with a high precision dielectric spectrometer in a range of 10 −2 ..10 5 Hz at different temperatures (10..125 °C) and RH levels (0..80 %). In addition, evaluation of absorbed water at different RH levels (0..80 %) is done gravimetrically and exhibits a diffusion character according to Fick's law. Moreover, the proportionality of maximum absorption and RH level becomes apparent. Variation of temperature shows altered \alpha and \beta loss mechanisms as well as changed DC conductivity proportions. The continuous permittivity increase during water absorption indicates the higher (moisture-induced) polar content in the polymer. However, a small portion of water seems to be bound to terminal -OH groups of PET, thus leading to an altered \beta relaxation. The observed increase of DC conductivity, not only with higher temperature but also with higher water content, points out the humidity-driven charge transport through the dielectric. A further, frequency-dependent loss mechanism is only visible above a certain RH level that indicates pure water formation within the polymer. This study shows that even though the level of absorbed water for PET is below 0.4 %, the dielectric spectra reveal significant changes.
High voltage direct current (HVDC) power transmission is becoming increasingly competitive to high voltage alternating current (HVAC) power transmission, especially for bulk power transmission over ...long distances. For crossing wide metropolitan areas, long distances in the open sea, or latterly in Germany the planned underground North-South DC links, especially extruded HVDC cable lines are attractive because of significant advantages over other insulation types. Nevertheless, in HVDC insulation systems the electric field distribution is much more complex than in AC systems, because it strongly depends on the conductivities of the insulation. Especially the presence of space charges can lead to an increased electric field strength up to the failure of the device. Due to the mentioned challenges it is significant to develop new insulating materials suitable for HVDC applications. One promising approach is to introduce nanofillers in the insulating matrix for space charge suppression. The purpose of this paper is to present the results of the influence of nanoscale carbon black (CB) in liquid silicone rubber (LSR). Besides volume resistivity, dielectric breakdown strength is determined to check the influence of the CB concentration. In addition, TSC (Thermally Stimulated Current) measurements are performed on LSR samples with different CB concentrations to evaluate their properties.
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Polarized nuclei are a powerful tool in nuclear spin studies and in searches for beyond-the-standard model physics. Noble-gas comagnetometer systems, which compare two nuclear species, have thus far ...been limited by anomalous frequency variations of unknown origin. We studied the self-interactions in a \(^3\)He-\(^{129}\)Xe system by independently addressing, controlling and measuring the influence of each component of the nuclear spin polarization. Our results directly rule out prior explanations of the shifts, and demonstrate experimentally that they can be explained by species dependent self-interactions. We also report the first gas phase frequency shift induced by \(^{129}\)Xe on \(^3\)He.
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