摘要:

Some methods of the plasma liner stabilization in addition to entraining of an initial axial magnetic field were used in the experiments on the SNOP‐3 generator (Im ≃ 1.1 MA,&Tgr; ≃ 100 ns). Helical current return rods were used to stabilize the liner (annular gas puff) at the beginning of the implosion. A 50‐fold stable radial compression of the krypton liner was observed using a time‐integrated pinhole camera.Double shell liners with an initial magnetic field are attractive from the viewpoint of stable high‐radius‐ratio liner implosions and efficient energy transfer from the generator to the plasma pinch of massm < m1(m1is the liner mass required to implode the liner at the peak of the current pulse).Model 0‐dimensional calculations of the motion dynamics of the shells and experiments on double shell liner implosions were perfomed. The radius of a stable compressed argon inner shell was measured to be 50–60 &mgr;m (at an initial radius of 5 mm).The maximum magnetic fieldBm ≃ 6000 Twas estimated using the measured radius of the compressed nitrogen inner shell.The effect of liner stabilization on the X‐ray yield and the possible future experiments using the stable liner implosions are discussed.

ISSN:0094-243X    

DOI:10.1063/1.2949228

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

In this paper, we will describe the time evolution of am=0instability which was recorded on AGLAE, a 1 TW generator, during the collapse of a neon gas puff. We observe a correlation between images produced by a visible streak camera with slit parallel to the axis of the pinch and that of a temporally resolved pinhole array. The pinhole images are recorded by a four strip X‐Ray MCP camera (Slix) which uses three different filters showing the temporal evolution of a simple spectrum. We also use a two channel time integrated pinhole camera. The behavior of the instability will be correlated with a simple theoretical analysis of the phenomenon. A brief description of the experiment and the diagnostic arrangement will be given. Then detailed analysis of experimental data and their correlation with a snowplow MHD model will be given.

ISSN:0094-243X    

DOI:10.1063/1.2949229

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Experimentally the radial extent of fibre Z‐pinch plasmas is typically found to be much greater than predicted by simple MHD theory. Usually these differences are attributed to the presence of large scale MHD instabilities. Here an alternative explanation is offered in terms of micro‐instability behaviour. Since fibre Z‐pinehes are surrounded by vacuum, the plasma density is zero at the pinch surface. If the current density remains finite near the pinch surface, the electron drift speed will exceed the local ion sound speed and micro‐instabilities will result. These micro‐instabilities are self‐limiting in that they give rise to anomalous resistivity which heats the ions and reduces the local current density thereby reducing the ratio of the electron drift velocity to the ion sound speed. The lower hybrid drift instability is found to be particularly important in the pinch formation phase where the line density of charged particles is very small. Inclusion of micro‐turbulent resistivity in 1‐D simulations of the ionisation stage of fibre Z‐pinch experiments shows the formation of a high temperature, low density, low current density coronal plasma which expands out to large radius. This corona persists throughout the duration of the experiment and has consequences for the overall degree of plasma confinement attainable in fibre Z‐pinches.

ISSN:0094-243X    

DOI:10.1063/1.2949136

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Non‐LTE radiation hydrodynamic numerical simulations in 1‐D and 2‐D are performed for multi‐terawatt driven argon and krypton gas puff loads. The influence of enhanced transport coefficients on the plasmas' implosion dynamics and the effects it has on the radiation yield and spectral distribution are discussed. Also presented are simulations for the performance of a krypton gas puff driven by a class of future generators.

ISSN:0094-243X    

DOI:10.1063/1.2949138

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

This paper is devoted to the describing of numeric method for solving 2.5D MHD equations. The method is based on splitting the original system onto two systems : hyperbolic and diffusive. Explicit difference scheme for the first system is of TVD type, and implicit scheme for the second one has been got through the approximation of energy function. The results of some illustrative calculations are shown.

ISSN:0094-243X    

DOI:10.1063/1.2949139

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

One dimensional magnetohydrodynamic code that takes into account a resonance line reabsorbtion and time‐dependence of average ionization level is presented. It is based on Braginakii type MHD equations. Reabsorbtion of resonance lines is described by Biberman‐Holstein method. Distribution on ionization stages is calculated in quasi‐stedy‐state approximation. The worked out code allows to study a discharge plasma consisted fromK‐,L‐,M‐,N‐shell ions. With using of developed code the possibility of [Ne]‐like ions creation in hollowZpinch that implodes on a target placed on an axis have been investigated. The current amplitude is 0.5 MA, the timerise is 200 ns. It is assumed that a target is very massive and is described by undisturbed, nonconductive cylinder. The series of computations was carried out forKrandFefilling plasma. For typical variant the detailed consideration of implosion is presented.

ISSN:0094-243X    

DOI:10.1063/1.2949140

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The implosion dynamics of argon plasma is investigated using 1D two‐temperature radiation MHD code ZARYA. A detailed configuration atomic model has been employed to calculate the line emission. The model includes effects of line opacity, Doppler effect due to ions motions and ionic state variation. The state populations are calculated using a set of time‐ dependent atomic rate equations for electron collisional excitation and de‐excitation, dielectronic and radiative recombination, photoexcitation and others processes. The ionization state of the plasma is calculated self‐consistently with line and continuum radiation transport. Perfect gas equations of state taking into account the energy of ionization are used for electrons and ions pressure and internal energy calculations.Anomalous resistivity mechanism phenomenologically considered is low‐ hybrid drift instability model. Microturbulence effects are included by increasing the resistivity coefficients. Finally, a comparison is made with calculations using Braginskii transport coefficients. We find that numerical results taking into account anomalous collisions are more closed to the experimental data.

ISSN:0094-243X    

DOI:10.1063/1.2949141

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The main results of a new, essentially classical method for the analytic description of inelastic atomic processes, both radiative and collisional, caused by electrons of low and moderate energies, which are typical for most plasmas including hot dense plasmas with multiply charged ions (MCI), are presented. The results are to be used as building blocks in the numerical modeling of high‐complexity plasmas.

ISSN:0094-243X    

DOI:10.1063/1.2949143

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A qualitative model is proposed for the enhanced‐rate propagation of the magnetic field along the anode. For infinite inertia of ions and homogeneous electron density, the scaling laws are obtained for the characteristic dimensions of magnetic field front propagating along the anode.

ISSN:0094-243X    

DOI:10.1063/1.2949145

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Two‐dimensional “cold‐start” resistive MHD computations of formation and evolution of deuterium‐fiber‐initiated Z‐pinches have been extended to include separate ion and electron energy equations and finite‐Larmor‐radius ordered terms. In the Ohm's Law (magnetic field evolution) equation, Hall and diamagnetic pressure terms have been added, and corresponding terms have been added to the energy equations. Comparison is made of the results of these computations with previous computations and with experiment.

ISSN:0094-243X    

DOI:10.1063/1.2949146

出版商:AIP    

年代:1994

数据来源: AIP