I.N. Onishchenko

Vircator efficiency enhancement assisted by plasma

Experimental studies of microwave radiation generation in a system with a relativistic electron beam of over-limiting current and an external plasma source have been carried out. The results have shown that the presence of plasma essentially increases the power of microwave radiation in comparison to the vacuum case.

3D Analysis of Wake Field Excitation in a Dielectric Loaded Rectangular Resonator

The results of a three‐dimensional analysis of wake field excitation in a slab‐symmetric dielectric‐loaded resonator by rigid electron bunches are presented. The complete set of solutions, including the solenoidal and potential parts of the electromagnetic field, consists of LSM and LSE modes. Each of the LSM and LSE modes contains odd and even waves. A numerical analysis of wake field excitation by symmetric electron bunches is carried out. The three‐dimensional spatial structure of the longitudinal electric field is investigated. The influence of the drift vacuum channel on the wake field amplitude and on the coherent summation of wakefields for a regular sequence of bunches is studied.

Broadband emission from a relativistic electron bunch in a semi-infinite waveguide

A study is made of the excitation of a transition radiation pulse during the injection of a charged particle bunch through the end metal wall into a semi-infinite cylindrical waveguide. Exact analytic expressions for the fields of a thin ring-shaped bunch are obtained in terms of the Lommel functions of two variables. The energy efficiency, power, and spectrum of radiation emitted from a finite-size charged bunch in a vacuum waveguide are calculated numerically with allowance for the multimode nature of the excited field. It is shown that, under certain conditions, the bunch can generate a short, high-intensity electromagnetic pulse with a broad frequency spectrum. The effect of various parameters of the charged bunch-waveguide system (such as the bunch current, bunch duration, and waveguide radius) on the generation efficiency of a transition radiation pulse is investigated.

Charged particles accelerated by wake fields in a dielectric resonator with exciting electron bunch channel

We have studied the acceleration of electrons by wake fields excited in a resonator by a train of electron bunches. The resonator comprised a cylindrical metal waveguide section, containing a dielectric sleeve with a vacuum channel and ends closed by metal walls. Expressions describing the wake field excited by uniformly moving exciting electron bunches have been derived. The self-consistent process of resonator excitation by a train of charged bunches and the particle acceleration in the excited wake field has been numerically simulated.

Wakefield Excitation by a Sequence of Electron Bunches in a Rectangular Waveguide Lined with Dielectric Slabs

A rectangular dielectric‐lined metallic structure was studied that has an advantage over a cylindrical structure from the possibility of exciting by a sequence of bunches many equally‐spaced modes, thereby building up a larger mode‐locked wakefield. A rectangular vacuum copper waveguide was lined with two dielectric slabs, the size of which was calculated to provide resonant excitation of the fundamental LSM mode by a sequence of bunches with repetition frequency f0=2805 MHz, produced by linear resonant electron accelerator (4.5 MeV, number of bunches 6.103, diameter 1cm, duration 60 ps each, distance between bunches 300 ps, number of electrons in each bunch 109). The waveguide has cross section 85 mm × 180 mm, and Teflon (e = 2.1) plates were placed along the smaller sides of the waveguide, their thickness from the calculation being 22 mm. In experiments, the length of the resonator was 535mm. We found that the total wakefield is three times larger than the fundamental mode; thus a greater number of exci...

Excitation of a wake field by a relativistic electron bunch in a semi-infinite dielectric waveguide

A wake field excited by a relativistic electron bunch in a semi-infinite metal waveguide filled with a dielectric consists of the Vavilov-Cherenkov radiation, the “quenching”-wave field, and transient radiation, which interfere with each other. An exact analytic expression for the transient component of the field of a thin relativistic annular bunch is derived for the first time. The evolution of the space distribution of a field excited by a finite-size electron bunch is numerically calculated. The excitation of the wake field by a periodic train of electron bunches in a finite-length waveguide is studied.

The electron bunches dynamics at the Laser-Plasma interaction in the blowout regime

The accelerating gradients in conventional linear accelerators are currently limited for technical reasons to ∼100 MV/m [1], partly due to breakdown that occurs on the walls of the structure at the high accelerating field strength. To achieve the high energy of the accelerated particles, it is necessary to build more large-scale and expensive accelerators. Plasma-based accelerators have the ability to sustain accelerating gradients which is several orders of magnitude greater than that obtained in conventional linear accelerators [1, 2]. Due to the rapid development of laser technology [1 – 13] Laser-Plasma-based accelerators are of great interest now. At present, the intensity of the focused laser radiation exceeds the value of 1022 W/cm2. Over the past decade, successful experiments on Laser Wakefield Acceleration of charged particles in the plasma confirmed the relevance of this method of acceleration [2 – 7, 12]. Evidently, the extremely large accelerating gradients in the Laser Plasma Accelerators allow to reduce significantly the size and to cut the cost of accelerators, which are widely used in scientific research, material science, industry, medicine and biology. Another important advantage of the Laser-Plasma-based accelerators is that they have the potential to produce short electron bunches with high energy.

Low-frequency instability of an ion beam in the field of a high-current REB

A study is made of the linear and nonlinear stages of the low-frequency instability of an ensemble of ions that execute radial oscillations in the electric field of the space charge of an unneutralized high-current relativistic electron beam. Nonlinear mechanisms for stabilizing the low-frequency ion instability are considered. It is shown, in particular, that, under certain conditions, the development of the low-frequency instability can lead to the ejection of ions onto the walls of the drift chamber.

Cumulation of Ions by a Focused Ring Laser Pulse

The cumulation dynamics and acceleration of ions in deuterium plasma by a focused ring laser pulse of femtosecond duration are theoretically investigated. The laser pulse is focused by the lens. The spatial structure of the ring laser pulse field in the vicinity of the lens focus is determined. The values of the cumulation coefficient, ion energy, and cumulation region dimension are obtained.

Optimization of Wake Field Excitation in Cylindrical Resonator using the PIC Code Simulation

Resonant dependence of wakefield intensity versus bunches repetition rate in numerical simulation of cylindrical resonator partially filled with dielectric by relativistic train of electron bunches has been obtained.