Showing papers on "Plasma channel published in 1982"

Plasma channel formation with ultraviolet lasers

Abstract: The beam from a low‐divergence KrF laser (λ=248 nm) has been used to generate long plasma channels in low pressure gases. Current‐carrying channels 60 cm in length were produced with 5 mJ of laser energy. Channels exceeding 1 m in length were also initiated. The ionization source producing the plasma is laser‐induced resonant two‐step photoionization of organic molecules which are seeded in a buffer gas.

Plasma studies on a hollow cathode, magnetic multipole ion source for neutral beam injection

Abstract: A series of Langmuir probe studies has been undertaken on the hydrogen plasma of an 8×8‐cm extraction area hollow cathode, magnetic multipole ion source intended for use in neutral beam injection systems. Five movable probes were utilized to measure plasma density, electron temperature, plasma potential, and primary electron density as a function of position in the plasma generator and performance of the ion source. The measurements indicate that at discharge current below 150 A, a fairly uniform plasma over the source volume, with a potential positive with respect to the anode, is generated. The performance of the plasma generator at low currents resembles the filament discharge, magnetic multipole confinement ion source. The ion source in this case has good efficiency and plasma uniformity, but atomic species fractions of less than 70%. As the discharge current is increased, the plasma separates into a high‐density, high‐ionization, positive potential region near the cathode, and a lower‐density, negati...

Proton-Beam Transport through Wall-Confined Plasma Channel in the Nagaoka ETIGO-I

Abstract: Transport of an intense pulsed proton beam has been studied experimentally through a wall-confined plasma channel (1-m long) in the Nagaoka ETIGO-I. A proton beam with an energy of 800-keV is injected into the channel. The transport efficiency increases with increasing channel current or decreasing channel pressure, being in good agreement with the existing theories. Changing the timing between channel current and beam injection, we have found that there exists a good timing for the beam injection. In some cases, the beam ceases to be transported probably due to some plasma instabilities.

The influence of molecular nitrogen upon plasma channel formation by laser resonance saturation

Abstract: Laser resonance saturation of alkali vapors represents a very attractive method of creating the extended plasma channels of interest in light ion beam fusion. We have undertaken a preliminary study of the influence of molecular nitrogen upon this laser ionization technique. Our results indicate that the electron cooling, resonance quenching, and the increase in the laser energy requirement are acceptable, providing that the alkali seeding exceeds 0.5%.

Characteristics of Transported Ion Beam in Laser-Initiated Plasma Channels

Abstract: The propagation of intense ion beams through a laser-initiated plasma channel is reported. The ion beams were generated using a pinch-reflex ion diode on a Reiden IV generator and were transported over 40 cm in the plasma channel. The beam orbits, estimated from the pattern on the detector-film with energy resolution, were in good agreement with theory.

Behavior of a plasma in a high-density gas-embedded Z-pinch configuration

Abstract: The theoretical analysis of a high density Z-pinch (HDZP) begins with an examination of the steady state energy balance between ohmic heating and bremsstrahlung radiation losses for a plasma column in pressure equilibrium. The model is then expanded to include the time-varying internal energy and results in a quasi-equilibrium prescription for the load current through a constant radius plasma channel. This set of current waveforms is useful in the design of experimental systems. The behavior of a plasma for physically realizable conditions is first examined by allowing adiabatic changes in the column radius. A more complete model is then developed by incorporating inertial effects into the momentum equation, and the resultant global MHD computational model is compared with more sophisticated, and costly, one- and two-dimensional computer simulations. These comparisons demonstrate the advantages of the global MHD description over previously developed zero-dimensional models.

Ion temperature and the density distribution in the corona of a dense z pinch

Abstract: Magnetic field measurements, which are performed at a dynamic z‐pinch experiment, yield the ion temperature of the dense plasma column. The value of the ion temperature is consistent with results obtained from the speed of signal propagation, from the equilibrium of the pressure of the plasma boundary and from a consideration of the balance of energy. From an analysis of the speed of compressional Alfven waves in the region between the wall and the compressed plasma channel, the density outside the dense column is derived. The electron density in the corona is about three orders of magnitude smaller than in the core.

Plasma sweeper to control the coupling of RF power to a magnetically confined plasma

Abstract: A device for coupling RF power (a plasma sweeper) from a phased waveguide array for introducing RF power to a plasma having a magnetic field associated therewith comprises at least one electrode positioned near the plasma and near the phased waveguide array; and a potential source coupled to the electrode for generating a static electric field at the electrode directed into the plasma and having a component substantially perpendicular to the plasma magnetic field such that a non-zero vector cross-product of the electric and magnetic fields exerts a force on the plasma causing the plasma to drift.

Production of a hot dense plasma in the pinching of a laser burst at the diode of a high-current accelerator

Abstract: A pinch effect has been observed in a laser burst (a low-entropy burst in the initial stage of compression of the object) in the diode of the comparatively small DON accelerator/sup 3/ (20 GW, 200 kV, 100 kA. The beam from a neodymium laser (5 J, 30 ns) was focused through an orifice in the anode onto the plane surface of an aluminum cathode target. The torch-shaped expansion of the plasma from the focal point produces a plasma channel in the diode. The laser plasma expands at approx.10/sup 7/ cm/s, and teh diode is filled with a plasma of density n/sub e/ = 10/sup 15/-10/sup 16/ cm/sup -3/ by the time at which the current pulse begins. (AIP)

Relativistic electron‐beam transport in curved channels

Abstract: Collisionless single particle trajectories are modeled for a single plasma channel having one section curved in a circular arc. The magnetic field is developed by superposition of straight and curved channel segments. The plasma density gives charge and beam‐current neutralization. High transport efficiencies are found for turning a relativistic electron beam 90° under reasonable conditions of plasma current, beam energy, arc radius, channel radius, and injection distributions in velocity and in position at the channel entrance. Channel exit distributions in velocity and position are found consistent with those for a straight plasma channel of equivalent length. Such transport problems are important in any charged particle‐beam application constrained by large diode‐to‐target distance or by requirements of maximum power deposition in a confined area.