ISSN:0094-243X    

DOI:10.1063/1.2949208

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The review of X‐pinch investigations in high current diode of BIN facility (250 kA, 100 ns) is presented. The main purposes were to investigate pinch forming processes and hot dense plasma properties. X‐pinch is also considered as a source for multiple charged ions spectroscopy and for X‐ray optics testing. The set of diagnostics applied in these experiments allowed us to investigate the pinch forming processes in different configurations of crossed wires loads. High spectral and space resolved measurements of plasma radiation in 1–200 Å range, absolute energy measurements and electron beam registration were provided. Plasma parameters were obtained from relative intensities and shapes of multiple charged ions spectral lines. Electron density of plasma with the temperatureTe = 0.2–1 keVvariated from 1023cm−3in hot spot to 1018cm−3during plasma expansion. In recombining plasma, an inversion of Al He‐like ions levels population was registrated. Total radiation output of 0.5 mm pinch reached hundreds Joules in 2–100 Å range during 100 ns.

ISSN:0094-243X    

DOI:10.1063/1.2949209

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Observations of a Vacuum Spark discharge plasma are presented when driven from a 1.5&OHgr; 120ns Coaxial line at peak current up to 180kA. The line may be operated with the line gap shorted allowing the Hybrid Vacuum Spark mode, or with the line gap operational giving a rectangular voltage pulse. In both cases the rate of rise of the current is 1–2×1012A/s, however the initial voltage conditions are different. A Nd:YAG laser may be focused onto either the Anode or onto the Cathode to initiate the discharge. With the Laser focused onto the Anode intense electron beams are generated, with the formation of a low density gap plasma, except near the anode where the density is much higher and where filamentary density structures are observed. On applying the laser to the Cathode in the Hybrid mode, the additional formation of a very dense narrow pinch near the cathode at peak current is seen. For currents in excess of 90kA, Hot Spots form in this channel and are associated with the generation of energetic electron beams. The observations presented here differ with comparable work in the initial conditions required for the formation of dense Hot Spots, in their position and in their reproducibility. The electron density in the channel is measured at 1019cm−3over 0.5mm, whereas the Hot Spots have dimensions of 50 &mgr;m and temperatures of approximately 700eV.

ISSN:0094-243X    

DOI:10.1063/1.2949210

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Aluminum wire x‐pinch and z‐pinch experiments were conducted using the XP pulsed power generator at Cornell University. Time resolved measurements of plasma expansion and sausage instability growth along the wires were made using a sub‐nanosecond pulsed nitrogen laser and x‐ray backlighting. Rapid (0.9 to 2.9 cm/&mgr;s) unstable expansion of a coronal plasma formed around both x‐pinch and z‐pinch wires was observed, while a dense core plasma expanded more slowly (0.1 to 0.8 cm/&mgr;s) and uniformly. The x‐pinch cross point is an intense, compact L‐shell and K‐shell radiation source. The cross region imploded to a minimum radius just before the intense emission of soft x‐rays. Time resolved characteristics of the K‐shell radiation implied electron densities as high as 1022cm−3and temperatures of a few hundred eV for 12 to 75 &mgr;m wires and 185 to 360 kA peak current. Z‐pinches showed pinch points along the full wire length.

ISSN:0094-243X    

DOI:10.1063/1.2949212

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The results are presented dealing with the working out and study of the plasma source of soft X‐ray (SXR) of the new type.Experimental set up included compact low‐inductance vacuum spark (LIVS) with initial energy supply equal up to 2.5 kJ and glass‐capillary concentrator (GCC) of SXR. The characteristics of SXR of vacuum spark and properties of SXR were studied using diagnostic complex. The coefficient of conversion of initial energy supply into SXR (&eegr;) amounted to 0.01 in range 1.2nm. Value &eegr; had peak dependence on atomic number of anode Za. The spectra were recorded belonging to Ne‐like, F‐like ions of Fe, Cu ions and He‐like, H‐like ions of Al, Ti, Fe.Glass capillary concentrator consists of about several hundreds glass capillaries Flux density of SXR in focusing spot was up to 105–106Wt/cm, density of energy is up to 20–30 mJ/cm2at diameter of SXR focusing spot equal to about 2–3mm in the range 0.7–1.0 nm.The plasma source of the new type is intended for X‐ray microscopy, study of influence of SXR on the surface of solid state. It allows to carry out experiments making only on electron synchrotronic sources of SXR.

ISSN:0094-243X    

DOI:10.1063/1.2949213

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

There are presented the implications of the interferometric, schlieren and spectroscopic diagnostics in the diode pulse discharge in nitrogen between two cone‐shaped electrodes (discharge energy 0.5 kJ, max. current 50 kA, 1 st discharge period 4 &mgr;s, gas pressure 5 kPa).In this discharge, there are formed two jets with the filamentary structure due to the inertial force of the ions of the current layer. These jets accelerate the ions evaporated from the electrodes and the ions from the breakdown current layer into the central part of the discharge. The filaments and the shape of both jets are relatively stable during the first halfperiod of the discharge current.The space and time development of electron density, density gradient and temperature were measured and results were used for the calculation of the jets' and filaments' stationary regime conditions.

ISSN:0094-243X    

DOI:10.1063/1.2949214

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Gas‐puff Z‐pinch research at the IPP Prague is briefly reviewed. The XUV and soft x‐ray measurements, performed with elements from carbon to argon, are summarized. Coupling of driver and load parameters for optimum generation of K‐shell radiation of the mentioned elements is discussed using simple considerations.

ISSN:0094-243X    

DOI:10.1063/1.2949215

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The soft X‐ray emission of intermediate and high Z elements from a low inductance vacuum spark, has been analyzed by space‐resolved spectroscopy and modeling of the emission. In the case of intermediate Z elements, the observed spatial extent and the estimated plasma parameters of the regions emitting L‐shell ions transitions are consistent with the predictions of the radiative collapse model of the spark. For high Z elements, the estimated characteristics of the plasma emitting radiation of the M‐shell ions seem to indicate that in this case too a radiative collapse may take place, triggered by the intense line emission of Ni‐like ions.

ISSN:0094-243X    

DOI:10.1063/1.2949216

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The discharge development of a triggered pulsed hollow cathode discharge is investigated with respect to two regimes of operating pressure: the high pressure regime at ∼ 10−2mbar and the low pressure regime at ∼ 10−5mbar. The hollow cathode discharge studied here is performed with the UMFX device powered by either eight 2700 pF door‐knob capacitors connected in parallel and discharged at 40 kV or a single 1.85 &mgr;F capacitor discharged at 20 kV. The characteristics of the discharge is monitored by using magnetic probe for dI/dt measurement; PIN diodes and XRD for time‐resolved X‐ray signals; and pinhole camera for time‐integrated X‐ray imaging. At the high operating pressure regime, X‐rays are observed to be emitted from the tip of the anode only. At the low operating pressure regime, however, the heating of the plasma by the main capacitor discharge is significantly enhanced. In the case of low energy discharge (with 22 nF capacitor bank), a plume‐like plasma emitting in the soft X‐ray region is observed to be formed attached to the tip of the anode. The pre‐breakdown electron beam, which is a well‐known phenomenon in this type of discharge, is also observed to be significantly enhanced. For the case of discharges performed with the 1.85 &mgr;F capacitor, dense plasma spots are observed at low operating pressure of 10−4mbar or lower. These dense plasma spots are not observed for discharges operated at pressures higher than 10−4mbar

ISSN:0094-243X    

DOI:10.1063/1.2949217

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The vapor phase separating the initial solid state from the final plasma state of wire loads in pulse power devices is often assumed to be very short lived and of no consequence to the subsequent load implosion for fast current pulses. However, researchers have attributed Cu K&agr;radiation and load stability to a persistent solid core in experiments with Cu wires or frozen D2fibers, respectively. The spatial structure of Al Z‐Pinch loads has been studied with streaked absorptiongrams, holographic interferometry, gated multiple pinhole cameras, and debris collectors to address this issue. A coronal plasma surrounding a neutral rich inner region is seen 310 ns into a current pulse having a quarter period of 1.5 &mgr;s. The observations made of the coronal plasma separating from the neutral inner region in two wire experiments has ramifications for multiple wire arrays. This phenomenon may account for pre‐cursor plasma formation, softened implosion, a small fraction of the mass radiating in the K shell and straggling in the load assembly on the axis. The results indicate that the initial plasma formation process on individual wires of an array is very important to the subsequent load implosion and must be modeled realistically.

ISSN:0094-243X    

DOI:10.1063/1.2949218

出版商:AIP    

年代:1994

数据来源: AIP