In this paper we propose a representative simulation test-case of E × B discharges accounting for plasma wall interactions with the presence of both the electron cyclotron drift instability and the ...modified-two-stream-instability. Seven independently developed particle-in-cell (PIC) codes have simulated this benchmark case, with the same specified conditions. The characteristics of the different codes and computing times are given. Here, results show that both instabilities were captured in a similar fashion and good agreement between the different PIC codes is reported as main plasma parameters were closely related within a 5% interval. The number of macroparticles per cell was also varied and statistical convergence was reached. Detailed outputs are given in the supplementary data, to be used by other similar groups in the perspective of code verification.
In partially magnetized plasmas, in which the electrons are magnetized and the ions are unmagnetized, it is known that the cross-field electron transport does not follow the classical transport ...theory, assuming collisional transport. Recent studies suggest that plasma waves driven by kinetic instabilities lead to the enhanced transport and diffusion of electrons across the magnetic fields. One example of such instabilities is the electron cyclotron drift instability (ECDI) due to the \mathrm{E}\times \mathrm{B} drift. For partially magnetized plasmas with multiple ion species, ion-ion two stream instability (IITSI) may also be present. Previous work 1 has demonstrated that, in the presence of cold ions, three-dimensional (3D) ECDI and IITSI couple such that the resulting mode is no longer a superposition of the two instabilities. In this talk, we extended the capabilities of the 3D generalized dispersion solver to include the effects of the ion temperature. The impact of ion Landau damping 2 on the development of coupled ECDI-IITSI is investigated, including the effects of anisotropic ion temperature. The resulting growth rates and phase velocities will be calculated as a function of wavenumber for various plasma conditions and compared with experimental observations.
A massive, but light, Abelian U(1) gauge boson is a well-motivated possible signature of physics beyond the standard model of particle physics. In this Letter, the search for the signal of such a ...U(1) gauge boson in electron-positron pair production at the spectrometer setup of the A1 Collaboration at the Mainz Microtron is described. Exclusion limits in the mass range of 40 MeV/c^{2} to 300 MeV/c^{2}, with a sensitivity in the squared mixing parameter of as little as ε^{2}=8×10^{-7} are presented. A large fraction of the parameter space has been excluded where the discrepancy of the measured anomalous magnetic moment of the muon with theory might be explained by an additional U(1) gauge boson.
A new exclusion limit for the electromagnetic production of a light U(1) gauge boson γ' decaying to e + e- was determined by the A1 Collaboration at the Mainz Microtron. Such light gauge bosons ...appear in several extensions of the standard model and are also discussed as candidates for the interaction of dark matter with standard model matter. In electron scattering from a heavy nucleus, the existing limits for a narrow state coupling to e + e- were reduced by nearly an order of magnitude in the range of the lepton pair mass of 210 MeV/c2}<me +}e-<300 MeV/c2. This experiment demonstrates the potential of high current and high resolution fixed target experiments for the search for physics beyond the standard model.
We report on a comprehensive reinterpretation of the existing cross-section data for elastic electron-proton scattering obtained by the initial-state radiation technique, resulting in a significantly ...improved accuracy of the extracted proton charge radius. By refining the external energy corrections we have achieved an outstanding description of the radiative tail, essential for a detailed investigation of the proton finite-size effects on the measured cross sections. This development, together with a novel framework for determining the radius, based on a regression analysis of the cross sections employing a polynomial model for the form factor, led us to a new value for the charge radius, which is
(
0.878
±
0
.
011
stat
.
±
0
.
031
sys
.
±
0
.
002
mod
.
)
fm
•Nuclear thermal propulsion (NTP) is efficient for Mars missions and beyond.•NTP can produce high thrust and high specific impulse.•Previous historical programs focused on highly enriched uranium ...(HEU).•LEU tungsten cermet fuel engine is proposed here.•Neutronic and T/H studies are conducted to identify the trade-offs.•The result is an engine design capable of meeting NASA’s requirements.
Nuclear thermal propulsion is the high thrust, high specific impulse rocket engine technology of choice for future missions to Mars and beyond. Previous engines designed and built under NASA’s Rover program made use of highly enriched uranium, a significant barrier to development today due to the political climate. This paper focuses on developing a nuclear thermal rocket engine based on a low enriched uranium (LEU) tungsten cermet fuel. Generally, this design is based on the Pewee reactor built by NASA under the Rover program. However, multiple modifications are introduced to optimize the proposed LEU engine to produce the maximum efficiency while meeting NASA’s ground rules as defined in the latest Mars reference missions. This paper presents numerous neutronic and thermal-hydraulic tradeoff studies to approach a near-optimum design. The result is an engine design capable of meeting, and in many cases surpassing, NASA’s requirements of a 25 klbf thrust engine with a thrust-to-weight ratio greater than 3.5 and a specific impulse greater than 900 s.
Radiative corrections to elastic scattering represent an important part of the interpretation of electron-induced nuclear reactions at small energy transfers, where they represent a dominant part of ...the background. Here we present and validate a new event generator for simulating QED radiative processes in electron-carbon scattering that exactly calculates the coherent sum of the Bethe-Heitler amplitudes for the leading diagrams. We demonstrate that the generator describes the shape of the radiative tail of an elastic peak with a precision better than
10
%
over the whole energy range of the scattered electrons and can thus be reliably employed in the analyses of electron scattering experiments for more precise extraction of inelastic cross-sections.
The helicity-dependent recoil proton polarizations P_{x}^{'} and P_{z}^{'} as well as the helicity-independent component P_{y} have been measured in the p(eover →,e^{'}pover →)π^{0} reaction at ...four-momentum transfer Q^{2}≃0.1 GeV^{2}, center-of-mass proton emission angle θ_{p}^{*}≃90°, and invariant mass W≃1440 MeV. This first precise measurement of double-polarization observables in the energy domain of the Roper resonance P_{11}(1440) by exploiting recoil polarimetry has allowed for the extraction of its scalar electroexcitation amplitude at an unprecedentedly low value of Q^{2}, establishing a powerful instrument for probing the interplay of quark and meson degrees of freedom in the nucleon.
The MAGIX focal plane time projection chamber Caiazza, S S; Achenbach, P; Aulenbacher, S ...
Journal of physics. Conference series,
04/2020, Letnik:
1498, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The MAGIX experiment is a versatile system optimized for low-energy nuclear and particle physics measurements. The setup is currently under development and will be installed at the MESA electron ...accelerator, at the Institute for Nuclear Physics of the University of Mainz. The main detectors of that experiment are a couple of high-precision magnetic spectrometers, each of them equipped with a GEM-based TPC at the focal plane to achieve a momentum resolution and angular resolution at the scattering vertex respectively of ≈δPP<10−4and≈1 1 mrad on scattered electron momenta between 1 MeV/c and 105 MeV/c. The limiting factor to achieve those results is the amount and uniformity of the material before the focal plane and even the presence of the TPC field cage can be relevant. Therefore we developed, and hereby introduce, an open field-cage TPC to fulfil those challenging requirements.
PDF
