Space and time resolved emission of hard X-rays from a plasma focus

Harries, W. L.; Lee, J H; Mcfarland, D. R.

doi:10.1088/0032-1028/20/9/409

Cited by 13 publications

(7 citation statements)

References 3 publications

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“…Harries et al [13], investigating x-ray emission from plasma focus, reported that the low energy x-rays are emitted from the plasma while the high energy x-rays are emitted from the anode surface. The low energy emission was found to be consistent with a thermal plasma of a few keV energy.…”

Section: Introductionmentioning

confidence: 99%

Comparative study of ion, x-ray and neutron emission in a low energy plasma focus

Zakaullah

Akhtar

Waheed

et al. 1998

Plasma Sources Sci. Technol.

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In a low energy (2.3 kJ) Mather-type deuterium plasma focus, neutron and x-ray emission is investigated by time integrated and time resolved detectors. CR-39 nuclear track ion detectors are employed for measuring charged particle angular distribution. Correlation of charged particles with neutron and x-ray emission is also investigated. The neutron emission profile is found to be composed of two pulses, the intensity and anisotropy of which vary with the filling pressure. The charged particle flux is maximum with high fluence anisotropy for the pressure range 2.5-3.0 mbar which is also the optimum pressure for high neutron emission with low fluence anisotropy (∼1.5). The high neutron emission with low fluence anisotropy is attributed to the presence of trapped deuterons in an anomalous magnetic field. The relevant pressure range generates favourable conditions for plasma density and pinch filament diameter. X-ray emission is generally high at low pressure. For the pressure range of 2.5-4.0 mbar, the axial neutron detector registers a hard x-ray pulse, which may escape through a half inch thick Cu flange. These results suggest that at low pressures, the collapsing current sheath interacts with the anode end and causes intense low energy (≤10 keV) x-ray emission, but the neutron emission remains low. X-rays are dominantly Cu Kα. In the narrow pressure regime 2.5-3.0 mbar, the current sheath forms a pinch filament leading to high neutron yield with low fluence anisotropy.

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Section: Introductionmentioning

confidence: 99%

Comparative study of ion, x-ray and neutron emission in a low energy plasma focus

Zakaullah

Akhtar

Waheed

et al. 1998

Plasma Sources Sci. Technol.

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“…Such a technique was reported by Bernstein and Hai (1970) on a plasma focus. Harries, Lee and McFarland (1978) extended the technique to look at hard X rays from the plasma focus with limited spatial resolution. The temporal resolution was limited to tens of nanoseconds in both experiments.…”

Section: Discussion and Summariesmentioning

confidence: 99%

“…Four-pinhole X-ray photograph of the plasma column and the hot spots; the four images are obtained through filters of (a) 3 jum Al, (b) 8;zm Fe, (c) 10-5 jum Ti and (d) 12-5 nm Cu. (Harries et al 1978). Analyses of the signals indicate that the radiation detected originate from a high temperature argon plasma ionized to helium-and hydrogen-like stages (Deeney 1988).…”

Section: Time Integrated and Space Integrated X-ray Measurementsmentioning

confidence: 99%

Studies of the spatial and temporal evolution of a dense plasma focus in the X-ray region

1989

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The dynamics of the plasma evolution in a dense plasma focus has been studied using a streak camera system in the soft X-ray region. The experiments were performed on a medium energy plasma focus operating with a hydrogen-argon admixture. The streak camera system employed provides nanosecond resolution and allows the plasma to be viewed simultaneously through two different filters to achieve energy resolution. Observations are made in the radial direction and along the pinch axis. Collimated X-ray PIN diodes suitably filtered were used to provide additional information on the structure of the X-ray emitting regions of the plasma. The plasma focus is observed to be totally dynamical and continuously evolving in nanosecond time scale. Hot spots are observed to form among the moving plasma at various times. Such continuous nanosecond time scale evolution of the focus pinch in the X-ray region have not been reported previously. IntroductionThe plasma focus device has long been the favorite device for investigation owing to the anomalously high neutron yield and the favorable neutron scaling with discharge current (Decker et al. 1980). The exact mechanism for neutron production is still under discussion. On large machines with W 0 >250kJ, the results indicate that, for properly optimized electrode dimensions, the neutron emission starts at the beginning of or during maximum compression (Pecorella et al. 1977;Jerzykiewicz et al. 1985;Herold et al. 1985). These reports have dispelled the concept that most neutrons are generated by beam-target interaction resulting from the much quoted m = 0 instability as originally suggested by Anderson (1958) in a conventional Z-pinch. Some early measurements on smaller machines suggested that the neutron production is due to the m = 0 instabilities (Schonbach et al. 1974). These machines were operating mainly in the 15-30 kV region, with capacitor bank energy W o below 20 kJ. More recent experiments on small machines, but operating at voltage of 60 kV or higher, indicate that a first period of neutron production which is independent of the m = 0 instabilities is also present (Hirano et al. 1985;Herold et al. 1988). The spatial and temporal evolution of the hot dense plasma is therefore of great importance in the quest to understand the basic mechanisms responsible for the neutron yield observed in these devices.In this paper, we report on experiments to study the evolution of the hot plasma with

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“…Space and time resolved HXR emission was dis cussed by Harries et al [13]. Time delay of the HXR and neutron emission studied by Kubez et al [14].…”

Section: Introductionmentioning

confidence: 99%

Study of the electrode material and insulator length effect on high-energy X-rays emitted by a 4-kJ plasma focus device

Habibi

2012

Plasma Phys. Rep.

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In this paper, behavior of hard X ray (HXR) anisotropy and its intensity along the anode bar of the APF plasma focus device (16 kV, 36 µF, 115 nH) with different anode tip materials is studied. The signals obtained by scintillation detectors by a special arrangement at each angular position show that the employ ment of higher Z anode insert materials not only increases the intensity of HXR signal, but also results in the high degree of HXR emission isotropy. The highest HXR intensity was observed with a conic W anode insert and the lowest, with a flat Al anode insert. The side on emitted intensity along the anode bar has been studied by moving the scintillation detector in the direction of the central electrode axis. For Pyrex and quartz insu lators, the lengths of 40 and 50 mm, respectively, would seem optimal to produce the maximum HXR inten sity. Also the Pyrex insulator would cause a higher HXR intensity than the quartz insulator.

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Space and time resolved emission of hard X-rays from a plasma focus

Cited by 13 publications

References 3 publications

Comparative study of ion, x-ray and neutron emission in a low energy plasma focus

Comparative study of ion, x-ray and neutron emission in a low energy plasma focus

Studies of the spatial and temporal evolution of a dense plasma focus in the X-ray region

Study of the electrode material and insulator length effect on high-energy X-rays emitted by a 4-kJ plasma focus device

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