Search

The processes of plasma wave transformation into electromagnetic radiation during strong interaction of a relativistic electron beam with magnetized plasma are studied in BINP in collaboration with NSU. Since 2010, experimental studies on such transformation processes were carried out on the GOL-3 facility by measuring the radiation emitted from beam-plasma system. Then after 2014 the GOL-PET device is used for these studies. Results of these experiments on emission in the frequency interval 0.1-0.5 THz from a long plasma column due to E-beam injection are described in the presented paper. The experimental results have been compared with theoretical ones obtained for EM-wave generation by the beam-plasma system.

Results from different facilities for plasma-surface interaction (PSI) studies are compared and their relevance to each other and conditions of ITER transient events are discussed. For PSI studies different types of devices were used including open traps, tokamaks, linear plasma machines including quasi-stationary plasma accelerators, electron beams and lasers. The same damage thresholds were demonstrated with different techniques. At energy loads corresponding to ITER transient events (edge localized modes (ELMs), disruptions, etc.) only macroscopic erosion mechanisms are important. They are cracking, droplet formation and macroscopic mass losses of the target. Cracking occurs during cooling stage after irradiations. Details of plasma stream parameters are of secondary importance for cracks formation; only target temperature plays a role. Macroscopic mass losses strongly correspond with melting of a thin surface layer and heat loads play a key role for melting. Heat flux defines the targets surface erosion.

Technical solutions of the concept exploration device SMOLA for longitudinal plasma flow suppression in linear plasma trap by active plasma pumping in helicoidal magnetic field are described in the article. Vacuum system, magnetic system, plasma source and the source of the radial electric field are discussed.

This article describes the diagnostic complex for investigation of plasma electromagnetic emission during beam-plasma interaction. Multichannel polychromator is used for measurements of spectral power density in frequency band of 100 ÷ 500 GHz. Two-channel polarimeter is used for obtaining information about emission polarization. The new cryogenic detector will be used for measurements of electromagnetic radiation over 600 GHz. Calorimetric detectors can also be used to increase the number of possible spatial registration points. Because experiments data interpretation depend on local plasma parameters such as plasma density or temperature diagnostic, complex include system of registration of density based on CO2-interferometry and Nd-laser scattering. The information about plasma temperature is obtained from diamagnetic loops.

In the paper, last experiment’s results on sub-THz wave emission from the area of relativistic electron beam-plasma interaction in the GOL-PET device are described. A plasma column with the diameter of 6 cm, length of 2.5 m and electron density (0.2-2)×1015 cm−3 is confined by multiple-mirror magnetic field with mean value of 4 T. The relativistic electron beam injected into the column, has the following parameters: energy Eb ∼ 0.8 MeV, current Ib ∼ 30 kA, current density Jb ∼ 2 kA/cm2 in the mean magnetic field. Previous studies have shown that the beam pumps the plasma electron oscillations in a vicinity of the upper hybrid wave branch. These plasma oscillations can be converted in electromagnetic waves on regular or artificial plasma density gradients in a vicinity of upper hybrid frequency. The electromagnetic waves with the double upper hybrid frequency are also generated in the beam-plasma system due to coalescence of the plasma oscillations in case of high level of the oscillation energy density. T...

New experimental results on magnetic compression and transport of low-temperature arc plasma at ∼3 m distance are presented. The magnetic compression ratio of the plasma stream varied from 5 to 60 at the initial plasma diameter about 5 cm. Theory predicts that the multiple-mirror magnetic field should not significantly decelerate and weaken the collisional low-temperature arc plasma. In the experiments, the transport efficiency of the plasma stream in the multiple-mirror configuration of the solenoid was compared with the same in a uniform solenoidal field. As the result, the plasma with (1–4)×1020 m−3 density at the axis was obtained at ∼3 m distance from the arc plasma source. The experiments simulated the baseline scenario of GOL-NB filling by the start plasma. Finally, the experiments described in the paper validated the decisions made for the GOL-NB start plasma source.

Helicons (circularly-polarized electromagnetic waves) propagate in a plasma with density exceeded cut-off for its frequency, and provide effective energy delivery to plasma. Accordingly, helicon discharge is one of the most suitable way for production of high-density low-temperature plasma. Helicon plasma sources, operating in the MHz frequency range and respectively low magnetic fields (0.01-0.1 T), capable to create plasma with density up to 1013 cm−3. At the same time, next generation of linear plasma facilities for both for PMI studies and fusion applications requires production of plasma with density above this limit. Theoretical studies predict that such increasing of density can be achieved by application of powerful microwave sources of GHz range frequency. The aim of the presented experiments is experimental verification of theoretical predictions and search of conditions for effective delivery of electromagnetic power to plasma towards development of stationary source of dense plasma for linear ...

A fusion reactor concept on the basis of a linear trap is developing in BINP. These studies incorporate multiple-mirror sections which should reduce significantly longitudinal plasma losses from a confinement zone. In the paper, physics on the multiple-mirror confinement relevant to plasma behavior at reactor conditions will be discussed. Basic results were received in the GOL-3 multiple-mirror trap in which plasma of 1021 m−3 density was heated by a high-power electron beam up to 2 – 4 keV temperature. The key milestones were: the demonstration of effective plasma heating by the electron beam due to collective effects, the achievement of theoretically predicted level of energy confinement time under optimal conditions, and finally, the discovery of a bounce instability that improves longitudinal confinement. Direct demonstration of a confinement improvement by multi-mirror sections in the magnetic configuration relevant to the reactor one will be done in the GOL-NB facility that will be created in BINP. ...