Single-shot measurement of longitudinal phase space beam profile in an electron storage ring

A novel scheme to measure the longitudinal emittance and phase space profile in an electron storage ring by using correlations between time and the vertical coordinate, and between energy and the horizontal coordinate, is proposed. This longitudinal profile measurement scheme will help to demonstrate recent results of advanced studies for manipulating the longitudinal beam profile and for investigating beam instability in an electron storage ring.

Two-dimensional internal gravity wave beam instability

<p>The instability of propagating internal gravity waves is of long-standing interest in geophysical fluid dynamics since breaking gravity waves exchange energy and momentum with the large-scale flow and hence support the large-scale circulation. In this study a low-order gravity wave beam model is used to delineate the linear stability of wave beams and also to study subcritical non-modal transient instability. Assuming that the dissipation of the linearly unstable beam equilibrates with the small-scale turbulence, the model explains the constancy with the height of the amplitude of the wave beam, so that oblique wave beams can reach significant altitudes without disintegrating due to the instability that arises [1]. We further study the robustness of the transient growth when the initial condition for optimal growth is randomly perturbed [2]. It is concluded that for full randomization, in particular, shallow wave beams can show subcritical growth when entering a turbulent background field. Such growing and eventually breaking wave beams might add turbulence to existing background turbulence that originates from other sources of instability.</p><p>[1] Kurgansky and Harlander (2021) Two-dimensional internal gravity wave beam instability. Part I: Linear theory, submitted.</p><p>[2] Harlander and Kurgansky (2021) Two-dimensional internal gravity wave beam instability. Part II: Subcritical instability, submitted.</p>

Electromagnetic Proton Beam Instabilities in the Inner Heliosphere: Energy Transfer Rate, Radial Distribution and Effective Excitation

<p>Differential flow among different ion species are always observed in the solar wind, and such ion differential flow can provide a free energy to drive the Alfven/ion-cyclotron and fast-magnetosonic/whistler instabilities. Previous works on the ion beam instability are mainly focused on the solar wind parameters at 1 au. We extend this study using the radial model of the magnetic field and plasma parameters in the inner heliosphere. We present the distributions of the energy transfer rate among the unstable waves and the particles, which would be useful to predict the change of parallel and perpendicular temperatures during the instability evolution. Moreover, we propose an effective growth length to estimate the effective growth in each instability, and we explore that the oblique Alfven/ion-cyclotron instability, the oblique fast-magnetosonic/whistler instability and the oblique Alfven/ion-beam instability can be effectively driven by proton beams having speed of 500-2000 km/s in the solar atmosphere. We also show that the unstable waves driven by the proton beam instability would be responsible for the solar corona heating. These predictions can be checked by in situ satellite measurements in the inner heliosphere.</p>

Computer model of a plasma layer formed by an electron beam

The problem of this work is development of scientific foundations of technological plasma processes for defect-free synthesis and processing of nanoscale structures for use in nanoelectronics. The goal of this work is development of a method for numerical calculation of the parameters of the ion flow to the sample for the real geometry of the beam-plasma installation. Results. We have created a numerical model for the development of a beam-plasma discharge by an electron beam in the absence of a buffer plasma and a longitudinal magnetic field. It is shown that the KARAT code allows us to solve the problem of developing beam instability in the absence of a buffer plasma. It was also shown that beam instability develops without a longitudinal magnetic field. The electric field created by the instability does not affect the peripheral plasma. The experimental verification of the numerical modeling results is carried out. The plasma concentration and electron temperature distributions obtained in the model are in qualitative agreement with the experimental ones. Practical significance. The model allows us to select the optimal modes of a plasma-chemical reactor based on a beamplasma discharge for the implementation of processes of defect-free ion-plasma treatment and synthesis of nanoscale structures.