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1.
Rev Sci Instrum ; 94(12)2023 Dec 01.
Article in English | MEDLINE | ID: mdl-38088779

ABSTRACT

The collective Thomson scattering of high-power millimeter-wave radiation on plasma density fluctuations (CTS) is widely used for diagnosing the velocity distribution function of energetic ions in fusion plasma. In this paper, we discuss a non-standard scheme of CTS measurements, which exploits strong refraction of probing and scattered microwave beams when reflecting from the cut-off layer in dense plasma. The scheme may be realized with the existing CTS diagnostic system at the Gas-Dynamic Trap (GDT) facility, a large open magnetic trap operating at Budker Institute (Novosibirsk, Russia). This requires a minor upgrade of the available hardware and essentially increases the range of plasma densities allowed for CTS measurements, as well as its sensitivity and spatial resolution. A detailed study of CTS efficiency for different geometries and plasma conditions at GDT is performed by means of an advanced numerical model that allows for an accurate description of non-Gaussian beam scattering in inhomogeneous plasma. To perform this task, we develop a quasi-optical theory of scattering, which itself may be of general interest.

2.
Phys Rev E ; 108(2-2): 025207, 2023 Aug.
Article in English | MEDLINE | ID: mdl-37723752

ABSTRACT

High-power electron cyclotron resonance discharge in a laboratory open trap is frequently accompanied by growth of electron cyclotron instabilities. We study a simple universal model that explains some of the stability conditions of such plasma observed experimentally, in particular, its crucial dependence on localization of the rf power deposition zone with respect to a minimum of B. An instability threshold seems to be sensitive to particular details of electron losses in a velocity space. Comparing theoretical predictions for the threshold condition with available measurements sheds light on a structure of fast-electron losses in ongoing experiments.

4.
Rev Sci Instrum ; 91(1): 013514, 2020 Jan 01.
Article in English | MEDLINE | ID: mdl-32012520

ABSTRACT

This paper presents a study of plasma flux characteristics flowing out from the gas-dynamic mirror trap along the magnetic field lines to a metal wall. The main feature of the current work is that the effect of ion acceleration by ambipolar potential is considered in the expander region. The developed model also takes into account a possibility of transition from the collisional expansion of electron flow in the vicinity of the magnetic plug to the collisionless regime. The developed model allows calculation of the ambipolar potential profile and plasma characteristics in the expander region.

5.
Phys Rev Lett ; 120(15): 155001, 2018 Apr 13.
Article in English | MEDLINE | ID: mdl-29756884

ABSTRACT

We report the first experimental evidence of a controlled transition from the generation of periodic bursts of electromagnetic radiation into the continuous-wave regime of a cyclotron maser formed in magnetically confined nonequilibrium plasma. The kinetic cyclotron instability of the extraordinary wave of weakly inhomogeneous magnetized plasma is driven by the anisotropic electron population resulting from electron cyclotron plasma heating in a MHD-stable minimum-B open magnetic trap.

6.
Angiol Sosud Khir ; 23(4): 159-163, 2017.
Article in Russian | MEDLINE | ID: mdl-29240070

ABSTRACT

Presented herein is a brief review of the world literature dedicated to methods of formation of composite arterial anastomoses in the femoropopliteal-tibial region The most justified is considered the use of a composite shunt formed proximally from a synthetic vascular graft made of polytetrafluoroethylene and distally with an extension from a portion of the suitable for reconstruction autovein (the so-called autovenous cuff of patch). The use of an autovenous cuff is more physiological since it provides closer correspondence of the diameters of the distal anastomosis being applied between the artery and autovenous extension, as well as contributes to creation of more adequate haemodynamic conditions in the shunt. Also analysed is the technique of performing the previously suggested anastomoses, demonstrating their main disadvantages. This is followed by describing a new original method of formation of a distal anastomosis using an autovenous insert, showing its advantages, with the main amongst them being the presence of only two vascular sutures and a decrease in the possibility of the onset and development of turbulence in the zone of the anastomosis. A conclusion is drawn that the suggested method contributes to decreasing the duration of the main stage of the operation, decreases the probability of technical defects and reduces the risk for the development of postoperative complications associated with impairments of the processes of haemodynamics in the zone of the anastomosis formed.


Subject(s)
Anastomosis, Surgical , Arterial Occlusive Diseases/surgery , Arteries/surgery , Blood Vessel Prosthesis/classification , Lower Extremity/blood supply , Vascular Grafting , Anastomosis, Surgical/instrumentation , Anastomosis, Surgical/methods , Humans , Polytetrafluoroethylene/therapeutic use , Vascular Grafting/instrumentation , Vascular Grafting/methods , Vascular Patency , Veins/transplantation
7.
Phys Rev Lett ; 114(20): 205001, 2015 May 22.
Article in English | MEDLINE | ID: mdl-26047233

ABSTRACT

This Letter describes plasma discharges with a high temperature of bulk electrons in the axially symmetric high-mirror-ratio (R=35) open magnetic system gas dynamic trap (GDT) in the Budker Institute (Novosibirsk). According to Thomson scattering measurements, the on-axis electron temperature averaged over a number of sequential shots is 660±50 eV with the plasma density being 0.7×10^{19} m^{-3}; in few shots, electron temperature exceeds 900 eV. This corresponds to at least a threefold increase with respect to previous experiments both at GDT and at other comparable machines, thus, demonstrating the highest quasistationary (about 1 ms) electron temperature achieved in open traps. The breakthrough is made possible by application of a new 0.7 MW/54.5 GHz electron cyclotron resonance heating system in addition to standard 5 MW heating by neutral beams, and application of a radial electric field to mitigate the flute instability.

8.
Phys Rev E Stat Nonlin Soft Matter Phys ; 78(6 Pt 2): 065602, 2008 Dec.
Article in English | MEDLINE | ID: mdl-19256897

ABSTRACT

The theory of linear mode conversion near evanescent layers is generalized for non-one-dimensionally inhomogeneous gyrotropic media. Effects are found that cannot be described within the standard one-dimensional paradigm of wave tunneling through the evanescent region when the mode coupling region assumes essentially two-dimensional topology.

9.
Phys Rev Lett ; 99(20): 205002, 2007 Nov 16.
Article in English | MEDLINE | ID: mdl-18233148

ABSTRACT

Conditions are found at which adiabatic magnetic compression of plasma confined in a mirror magnetic trap is accompanied by the accumulation of significant energy in a hot anisotropic electron tail with the subsequent release of this energy as a pulse of coherent electromagnetic radiation. The possibilities of creating THz radiation sources up to the GW power level are discussed.

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