摘要:

TheK‐shell x ray yields from argon gas puff Z pinches are observed to increase from 3.5±1.0 kJ to 13±1.0 kJ when inwardly tilted nozzles are used on a 6 TW, 4 MA generator. This increase is associated with the elimination of the zipper effect and the achievement of higher density plasmas, as confirmed by x‐ray diagnostics. Two‐dimensional (2‐D) magnetohydrodynamic modeling of the gas puff implosions indicates that the collapsing shell reaches a higher density and smaller diameter when the axial zipper is eliminated. The calculations show that axial mass flow in the zippering cases result in nonhollow collapses which limit the final pinch radii and densities. The calculations also indicate that narrower nozzle exits contribute to increasing the assembled plasma density.

ISSN:0899-8221    

DOI:10.1063/1.860949

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A two‐dimensional magnetohydrodynamic code is developed to study the dynamic performance of a magnetically induced compression (MIC) gas puff. It is shown that the plasma temperature in the gas puff plenum can rise up to 10–12 eV. The maximum calculated sheath velocity is in the 107cm/sec range. Calculations also show that the pressure in the gas puff plenum can rise by a factor of 570–1360, depending on the initial pressure. The mass flow rate and the injected gas density fall in the proper range for the operation of a Z pinch only when a relatively high initial pressure is used. The simulated ion‐induced and light‐induced voltages in the ion and light detectors provide means of comparing the numerical results with measurements. The calculated results are found to match reasonably well with the measured values.

ISSN:0899-8221    

DOI:10.1063/1.860502

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Spectroscopic and calorimetric measurements have been made using a 50 kW radio frequency inductively coupled plasma torch operated at atmospheric pressure with maximum temperatures and electron densities near 8500 K and 3×1021m−3, respectively. The plasma flowed through a water‐cooled quartz test section which enabled the study of nonequilibrium effects on both a recombining pure argon plasma and a recombining argon plasma with hydrogen, nitrogen, or neon. The pure argon plasma is found to be well described by a partial equilibrium model in which the free and bound‐excited electrons are in mutual equilibrium irrespective of possible departures from equilibrium with the ground state. The addition of just tenths of a percent of either atomic hydrogen or nitrogen (but not neon, in contrast) is found to significantly affect the plasma’s state of equilibrium for electron densities roughly less than 1021m−3because of a nearly gas‐kinetic reaction between argon’s first excited state and the diluent’s ground state. This ‘‘quenching’’ reaction provides a depopulating mechanism for argon’s first excited state and thereby inhibits the establishment of partial equilibrium which then invalidates several common diagnostic methods. The extent of quenching depends on the particular diluent, the amount of diluent relative to the electron number density, and on the temperature. These experimental observations are supported by an appropriately modified argon collisional–radiative model.

ISSN:0899-8221    

DOI:10.1063/1.860503

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Slow‐time‐scale magnetic fields driven by fast‐time‐scale electric fields are discussed from Vlasov–Maxwell equations in unmagnetized plasma. An equation for slow‐time‐scale magnetic fields is obtained for nonstationary plasma.

ISSN:0899-8221    

DOI:10.1063/1.860504

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The growth rate of the resistive tearing mode is investigated in the presence of a sub‐Alfve´nic equilibrium plasma shear flow along the confining magnetic field and fluid viscosity. The flow exerts a destabilizing influence and the well‐known instability condition, &Dgr;’≳0, is modified to yield the possibility of instability with &Dgr;’≤0. The effects of viscosity on the marginal stability condition and the transition between the inviscid and viscous‐dominated limits are considered in detail.

ISSN:0899-8221    

DOI:10.1063/1.860505

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Three‐dimensional magnetohydrodynamics equilibria with surface currents on a toroidal ‘‘canal’’ surface are constructed. Inside the surface the pressure is constant and the magnetic field vanishes. The vacuum magnetic field lines on the surface are closed in the poloidal section which corresponds to infinite rotational transform.

ISSN:0899-8221    

DOI:10.1063/1.860506

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Several points concerning the section ‘‘Comparison with the Swedish stability and transport analysis’’ in the paper by Hortonetal. are discussed and clarified. In particular it is pointed out that the Swedish model gives about the right ratio of &khgr;e/&khgr;ifor the Tokamak Fusion Test Reactor (TFTR) [Phys. Rev. Lett.63, 520 (1989)] density modification experiment.

ISSN:0899-8221    

DOI:10.1063/1.860507

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The instability growth rates on the tokamak fusion test reactors are commented upon. Comments by Nordman and Weiland 1,3,4on mode stability and transport are discussed. (AIP)

ISSN:0899-8221    

DOI:10.1063/1.860508

出版商:AIP    

年代:1993

数据来源: AIP

ISSN:0899-8221    

DOI:10.1063/1.860509

出版商:AIP    

年代:1993

数据来源: AIP