“…The plasma flow was injected into the vacuum at the residual air pressure p 0 ∼ 3 -50 µ Torr and propagated in the ambient Bfield having strength from 45 to 450 G. The overall set-up, illustrated in Figure 2, is similar to that of the high-power laser experiment. The plasma was generated by a "cable gun" made of a 50 Ohm coaxial cable with a polyethylene insulator (Gushchin et al 2018;Korobkov et al 2019). The gun was installed at the centre of the area of the quasi-uniform magnetic field.…”
Section: Using a Plasma Gun At The Krot Facilitymentioning
Aims. EXor-type objects are protostars that display powerful UV-optical outbursts caused by intermittent and powerful events of magnetospheric accretion. These objects are not yet well investigated and are quite difficult to characterize. Several parameters, such as plasma stream velocities, characteristic densities, and temperatures, can be retrieved from present observations. As of yet, however, there is no information about the magnetic field values and the exact underlying accretion scenario is also under discussion. Methods. We use laboratory plasmas, created by a high power laser impacting a solid target or by a plasma gun injector, and make these plasmas propagate perpendicularly to a strong external magnetic field. The propagating plasmas are found to be well scaled to the presently inferred parameters of EXor-type accretion event, thus allowing us to study the behaviour of such episodic accretion processes in scaled conditions. Results. We propose a scenario of additional matter accretion in the equatorial plane, which claims to explain the increased accretion rates of the EXor objects, supported by the experimental demonstration of effective plasma propagation across the magnetic field. In particular, our laboratory investigation allows us to determine that the field strength in the accretion stream of EXor objects, in a position intermediate between the truncation radius and the stellar surface, should be of the order of 100 gauss. This, in turn, suggests a field strength of a few kilogausses on the stellar surface, which is similar to values inferred from observations of classical T Tauri stars.
“…The plasma flow was injected into the vacuum at the residual air pressure p 0 ∼ 3 -50 µ Torr and propagated in the ambient Bfield having strength from 45 to 450 G. The overall set-up, illustrated in Figure 2, is similar to that of the high-power laser experiment. The plasma was generated by a "cable gun" made of a 50 Ohm coaxial cable with a polyethylene insulator (Gushchin et al 2018;Korobkov et al 2019). The gun was installed at the centre of the area of the quasi-uniform magnetic field.…”
Section: Using a Plasma Gun At The Krot Facilitymentioning
Aims. EXor-type objects are protostars that display powerful UV-optical outbursts caused by intermittent and powerful events of magnetospheric accretion. These objects are not yet well investigated and are quite difficult to characterize. Several parameters, such as plasma stream velocities, characteristic densities, and temperatures, can be retrieved from present observations. As of yet, however, there is no information about the magnetic field values and the exact underlying accretion scenario is also under discussion. Methods. We use laboratory plasmas, created by a high power laser impacting a solid target or by a plasma gun injector, and make these plasmas propagate perpendicularly to a strong external magnetic field. The propagating plasmas are found to be well scaled to the presently inferred parameters of EXor-type accretion event, thus allowing us to study the behaviour of such episodic accretion processes in scaled conditions. Results. We propose a scenario of additional matter accretion in the equatorial plane, which claims to explain the increased accretion rates of the EXor objects, supported by the experimental demonstration of effective plasma propagation across the magnetic field. In particular, our laboratory investigation allows us to determine that the field strength in the accretion stream of EXor objects, in a position intermediate between the truncation radius and the stellar surface, should be of the order of 100 gauss. This, in turn, suggests a field strength of a few kilogausses on the stellar surface, which is similar to values inferred from observations of classical T Tauri stars.
“…2, is similar to that of the high-power laser experiment. The plasma was generated by a "cable gun" made of a 50 Ohm coaxial cable with a polyethylene insulator (Gushchin et al 2018;Korobkov et al 2019). The gun was installed at the centre of the area of the quasi-uniform magnetic field.…”
Section: Using a Plasma Gun At The Krot Facilitymentioning
Aims. EXor-type objects are protostars that display powerful UV-optical outbursts caused by intermittent and powerful events of magnetospheric accretion. These objects are not yet well investigated and are quite difficult to characterize. Several parameters, such as plasma stream velocities, characteristic densities, and temperatures, can be retrieved from present observations. As of yet, however, there is no information about the magnetic field values and the exact underlying accretion scenario is also under discussion.
Methods. We use laboratory plasmas, created by a high power laser impacting a solid target or by a plasma gun injector, and make these plasmas propagate perpendicularly to a strong external magnetic field. The propagating plasmas are found to be well scaled to the presently inferred parameters of EXor-type accretion event, thus allowing us to study the behaviour of such episodic accretion processes in scaled conditions.
Results. We propose a scenario of additional matter accretion in the equatorial plane, which claims to explain the increased accretion rates of the EXor objects, supported by the experimental demonstration of effective plasma propagation across the magnetic field. In particular, our laboratory investigation allows us to determine that the field strength in the accretion stream of EXor objects, in a position intermediate between the truncation radius and the stellar surface, should be of the order of 100 G. This, in turn, suggests a field strength of a few kilogausses on the stellar surface, which is similar to values inferred from observations of classical T Tauri stars.
“…Coaxial plasma guns (CPG) are the ion sources in the plasma opening switches that generate the plasma using the insulator's surface breakdown. These CPGs come under the erosional type of plasma generators in which material enters the regime of ionization and acceleration, resulting in the evaporation of insulators [1,2] or electrode material [3,4]. These CPGs have the advantage of obtaining high-energy plasmas eliminating the pulsed gas vents that require the accurate operation of electromagnetic valves involved in gas supply lines [5] and laser-produced plasma systems [6] without compromising the requirements of plasma source parameters.…”
Coaxial plasma guns are a type of plasma source that produces plasma which propagates radially and axially controlled by the shape of the ground electrode, which has attracted much interest in several applications. In this work, a 120° opening angle of CPG nozzle is used as a plasma gun configuration that operates at the energy of 150 J. The ionization of polyethylene insulator between the electrodes of the gun produces a cloud of hydrogen and carbon plasma. The triple Langmuir probe and Faraday cup are used to measure plasma density and plasma temperature. These methods are used to measure the on-axis and off-axis plasma divergence of the coaxial plasma gun. The peak values of ion densities measured at a distance of 25 mm on-axis from the plasma gun are (1.6±0.5) × 1019 m-3 and (2.8±0.6) × 1019 m-3 for hydrogen and carbon plasma respectively and the peak temperature is (3.02±0.5) eV. The mean propagation velocity of plasma is calculated using the transit times of plasma at different distances from the plasma gun and is found to be (4.54±0.25) cm/μs and (1.81±0.18) cm/μs for hydrogen and carbon plasma respectively. The Debye radius is obtained from the measured experimental data that satisfies the thin sheath approximation. The shot-to-shot stability of plasma parameters facilitates the use of plasma guns in laboratory experiments. These types of plasma sources can be used in many applications like plasma opening switches, plasma devices, and as plasma sources.
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