Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userThe role of rf-scattering in high-energy electron losses from minimum-B ECR ion source
81
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The measurement of the axially lost electron energy distribution escaping from a minimum-B electron cyclotron resonance ion source in the range of 4-800 keV is reported. The experiments have revealed the existence of a hump at 150-300 keV energy, containing up to 15% of the lost electrons and carrying up to 30% of the measured energy losses. The mean energy of the hump is independent of the microwave power, frequency and neutral gas pressure but increases with the magnetic field strength, most importantly with the value of the minimum-B field. Experiments in pulsed operation mode have indicated the presence of the hump only when microwave power is applied, confirming that the origin of the hump is rf-induced momentum space diffusion. Possible mechanism of the hump formation is considered basing on the quasi-linear model of plasma-wave interaction.
rate research
Read More
The three-dimensional particle-in-cell model NAM-ECRIS is used for investigation of how the DECRIS-PM Electron Cyclotron Resonance Ion Source is reacting to changes in the source magnetic configuration. The accent is made on changes in the magnetic field at the magnetic trap center, the minimum-B value. It is calculated that the optimal normalized value of the field is ~0.8, close to the experimental observations. The reasons for existence of the optimum are discussed. It is observed that the electron energies are increasing with the increased minimum-B values due to enhanced confinement of the energetic electrons in the plasma. Bumps in energy spectra of the radially lost electrons are observed and explained to be due to nonadiabatic losses of electrons.
A new method for determining plasma parameters from beam current transients resulting from short pulse 1+ injection into a Charge Breeder Electron Cyclotron Resonance Ion Source (CB-ECRIS) has been developed. The proposed method relies on few assumptions, and yields the ionisation times $1/n_eleftlanglesigma vrightrangle^{text{inz}}_{qto q+1}$, charge exchange times $1/n_0leftlanglesigma vrightrangle^{text{cx}}_{qto q-1}$, the ion confinement times $tau^q$, as well as the plasma energy contents $n_eleftlangle E_erightrangle$ and the plasma triple products $n_e leftlangle E_erightrangle tau^q$. The method is based on fitting the current balance equation on the extracted beam currents of high charge state ions, and using the fitting coefficients to determine the postdictions for the plasma parameters via an optimisation routine. The method has been applied for the charge breeding of injected K$^+$ ions in helium plasma. It is shown that the confinement times of K$^{q+}$ charge states range from 2.6$^{+0.8}_{-0.4}$ ms to 16.4$^{+18.3}_{-6.8}$ ms increasing with the charge state. The ionisation and charge exchange times for the high charge state ions are 2.6$^{+0.5}_{-0.5}$ ms--12.6$^{+2.6}_{-3.2}$ ms and 3.7$^{+5.0}_{-1.6}$ ms--357.7$^{+406.7}_{-242.4}$ ms, respectively. The plasma energy content is found to be $2.5^{+4.3}_{-1.8}times 10^{15}$ eV/cm$^3$.
Mutual collisions between ion-acoustic (IA) solitary waves are studied based on a fully kinetic simulation approach. Two cases, small and large relative velocity, are studied and the effect of trapped electron population on the collision process are focused upon. It is shown that, for the case of small relative velocity, the repelling force between the trapped populations of electrons results in scattering of electron holes. However, this phenomenon can not be witnessed if the relative velocity is considerably high, since the impact of trapped population stays very weak.
The local magnetic field in a Penning-Malmberg trap is found by measuring the temperatures that result when electron plasmas are illuminated by microwaves pulses. Multiple heating resonances are observed as the pulse frequencies are swept. The many resonances are due to electron bounce and plasma rotation sidebands. The heating peak corresponding to the cyclotron frequency resonance is identified to determine the magnetic field. A new method for quickly preparing low density electron plasmas for destructive temperature measurements enables a rapid and automated scan of microwave frequencies. This technique can determine the magnetic field to high precision, obtaining an absolute accuracy better than $1,mathrm{ppm}$, and a relative precision of $26,mathrm{ppb}$. One important application is in situ magnetometry for antihydrogen-based tests of charge-parity-time symmetry and of the weak equivalence principle
We compute electrical and thermal conductivities of hydrogen plasmas in the non-degenerate regime using Kohn-Sham Density Functional Theory (DFT) and an application of the Kubo-Greenwood response formula, and demonstrate that for thermal conductivity, the mean-field treatment of the electron-electron (e-e) interaction therein is insufficient to reproduce the weak-coupling limit obtained by plasma kinetic theories. An explicit e-e scattering correction to the DFT is posited by appealing to Matthiessens Rule and the results of our computations of conductivities with the quantum Lenard-Balescu (QLB) equation. Further motivation of our correction is provided by an argument arising from the Zubarev quantum kinetic theory approach. Significant emphasis is placed on our efforts to produce properly converged results for plasma transport using Kohn-Sham DFT, so that an accurate assessment of the importance and efficacy of our e-e scattering corrections to the thermal conductivity can be made.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
