Study of Pyrex and quartz insulators contamination effect on the X-ray intensity in a 4-kJ plasma focus device
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LASMA RADIATION
Study of Pyrex and Quartz Insulators Contamination Effect on the Xray Intensity in a 4kJ Plasma Focus Device1 M. Habibi*, R. Sharifi, and R. Amrollahi Department of Energy Engineering and Physics, Amirkabir University of Technology, Tehran, Iran *email: [email protected] Received December 23, 2012; in final form, June 20, 2013
Abstract—The variation of the Xray intensity has been investigated with the Pyrex and quartz insulators sur face contamination in a 4kJ plasma focus device with argon gas at 11.5kV charging voltage. Elemental anal ysis (EDAX) showed that the Cu evaporated from the electrode material and was deposited on the sleeve sur face improves the breakdown conditions. A small level of sleeve contamination by copper is found to be essen tial for good focusing action and high HXR intensity. The SEM imaging showed the graintype structure of Cu formed on the surface and it changed the surface property. Resistance measurements of original and coated Pyrex surface proved that the copper deposition on the sleeve surface will reduce its resistance as com pared to the almost infinitely large resistance of the uncontaminated sleeve. As the contamination is surpassed to some critical level, the HXR intensity from the device is deteriorated. DOI: 10.1134/S1063780X14020056 1
1. INTRODUCTION
Plasma focus (PF) device belongs to Zpinches series that are dominantly pulsed working. These devices are generally capable of producing hot (1–2 keV) and dense plasma (1025–1026 m–3) by means of electromagnetic compression and acceleration [1, 2]. PF is a simple functional device with high neutron and Xray yields. This device can generate 1018–1020 neutron/s and Xrays of intensity up to 107–109 W/cm2.To examine the scope of PF in the fusion programme as well as its other applications, it seems essential that different machine parameters be investigated systematically and in a comprehensive manner. As Herold et al. [3] suggested, in the optimization of PF facilities, differ ent parameters are involved, such as the geometry and structure of the inner and outer electrodes, the dimen sions of the electrodes, the material and configuration of the insulator, and the initial pressure. These param eters are interrelated in a complicated way and no gen eral relations have been found so far. The pinch formation in a PF discharge shows a particular dependence between the driver device char acteristics which determine the current sheath struc ture and its subsequent evolution: dynamic compres sion, thickness, homogeneity, and temperature. Moreover, a recognized initial current sheath feature on the insulator surface seems to be an important con dition in order to create efficient plasma and to obtain the expected Zpinch [4]. The most important condi tion for efficient acceleration and radial compression is the homogeneity of the current layer formed in the 1 The article is published in the original.
breakdown phase. This layer should be completely symmetric, thin and not diffused. Otherwise,
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