Runaway Electrons at the Formation of a Positive Ionization Wave in Nitrogen and Air

JETP Letters - The generation of runaway electrons (REs) at a subnanosecond breakdown of a “plane–needle” gap caused by the development of a positive ionization wave starting from...     

Scaling Properties of Runaway Electrons

Runaway electrons in tokamaks have been widely studied theoretically and experimentally. The runaway confinement time τ1 in ohmic and additionally heated tokamak plasmas presents an anomalous behavior when compared with theoretical predictions based on neoclassical models. Runaway electrons have received lately a great attention due to several reasons： （a） the possibility to study electromagnetic turbulence by measuring the runaway flux fluctuations and its energy spectra, and （ b ） the runaway electrons are powerful diagnostics capable of yielding valuable information on the actual distribution function of fusion experiments.     

Air Breakdown in the Field of Traveling Tem-Wave Assisted by Runaway Electrons

Russian Physics Journal - The method of dynamic time-domain reflectometry is used to investigate a pulsed breakdown of an air-filled coaxial line assisted by the traveling voltage wave with...     

Scaling Properties of Runaway Electrons in HL-1M Tokamak

1 Introduction Runaway electrons in tokamaks have been widely studied theoretically and experimentally. Runaway electrons have received lately a great attention due to several reasons： a） the possibility to study electromagnetic turbulence by measuring the runaway flux fluctuations and its energy spectra, and b） the runaway electrons are powerful diagnostics capable of yielding valuable information on the actual distribution function of fusion experiments.     

Scaling Law of Runaway Electrons in HL-1M Tokamak

Runaway electrons in tokamaks have been widely studied theoretically and experimentally. The runaway confinement time τr in ohmic and additionally heated tokamak plasmas presents an anomalous behavior compared with theoretical predictions based on neoclassical models. A one-dimensional numerical model including generation, acceleration and loss effect of runaway electrons is used to deduce the runaway energy εr dependence on the runaway confinement time.     

Anode and Cathode Spots in High-Voltage Nanosecond-Pulse Discharge Initiated by Runaway Electrons in Air

We report the experimental results with nanosecond-pulse discharges formed in the air gap between a fiat electrode and a sharp electrode. The appearance of anode and cathode spots on the electrodes is studied experimentally. It is considered that bright spots on the fiat cathode with positive polarity of the sharp electrode are formed due to the explosive electron emission on the cathode and the dynamic displacement current in the gap. It is also shown that with negative polarity of the sharp electrode, bright spots on the flat anode are formed after changing the polarity of the flat electrode due to the discharge oscillatory mode. Under these conditions, the explosive electron emission firstly forms on the sharp cathode. With negative polarity of the sharp electrode of the subnanosecond-pulse pulser, the runaway electron beam current is measured behind the anode foil with a time resolution of no more than 100ps.     

Observation of Runaway Electrons with Soft X-Ray Camera on HT-7 Tokamak

The runaway electron phenomenon caused by dis- ruptions is one of the challenging conditions on the ITER Tokamak, which may destroy the vacuum ves- sel. To avoid runaway electrons hitting the fist wall, there must be some monitor systems which can pro- vide position information of the runaway electron beam. Hard x-ray camera is the most conventional di- agnostic system to monitor the runaway electrons. While there is no hard x-ray camera working for the entire ITER operation phase even for D-D phase of ITER, there must be some systems playing the role of observation of the runaway electrons. In this case, with some international experiences from other Toka- mak devices, the soft x-ray camera can share the role of runaway electron observation. On JET and some other Tokamak devices, the runaway electron current generated by disruption has been observed by the soft x-ray camera system.     

Streamer Breakdown with Runaway Electrons Forming Diffuse Discharges in an Inhomogeneous Electric Field

Russian Physics Journal - The results of experimental investigations of formation of diffuse nanosecond discharges in a nonuniform electric field in air and other gases at the pressures within...     

On Thermal Runaway Electrons and the Polarization of X-ray Emission in Solar Flares

Journal of Experimental and Theoretical Physics - A model for the thermal runaway of electrons in solar flares based on an approximate analytical solution of the kinetic equation with a linearized...     

Electrons in a Nonideal Partially Degenerated Plasma with Multiple Ionization

We consider peculiarities in the behavior of free electrons in an extremely-dense hot plasma with multiple ionization and partial degeneration. In different ways, we exhibit the strong Coulomb coupling of electrons and ions in the behavior of low- and high-kinetic-energy electrons. As a result, a necessity arises to consider, along with classical fast Debye electrons, their complementary cellular group of electrons constantly interacting with central ions of cells. We discuss the distribution of free electrons between the two groups, along with the role of two-group effects, of a not point character of ions in electron-transfer processes, and the consequences of the X-ray emitting X-pinch hot spot for the plasma. The existence of the physical limits for X-pinch plasma compression is among those consequences.     

Luminescence From Minerals Excited by Subnanosecond Pulses of Runaway Electrons Generated in an Atmospheric-Pressure High-Voltage Discharge in Air

The duration of the luminescence from minerals excited by low-current subnanosecond pulses of runaway electrons generated in an atmospheric-pressure high-voltage discharge in air at high overvoltages was used to characterize specific minerals. Advantages of using an atmospheric-pressure air discharge as the electron source versus the use of evacuated acceleration tubes are discussed. The luminescence-duration measurement is a simpler approach as compared to other methods that are conventionally employed in the elemental analysis of minerals. PACS: 52.80.-s; 52.80.Tn; 52.80.Yr; 78.60.Hf; 91.60.Mk.      

On the Mechanism of the Generation of Runaway Electrons after a Breakdown of a Gap

JETP Letters - Data that explain the generation of runaway electrons after the breakdown of a gap with a sharply inhomogeneous distribution of the electric field strength are presented. Using a...