Analysis of the pinch characteristics in a miniaturized repetitive plasma focus device
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ORIGINAL PAPER
Analysis of the pinch characteristics in a miniaturized repetitive plasma focus device S Goudarzi*, H Babaee and A Esmaeli Plasma and Nuclear Fusion Research School, Nuclear Science and Technology Research Institute, Atomic Energy Organization of Iran, Tehran, Iran Received: 03 December 2018 / Accepted: 09 August 2019
Abstract: In this article, the experimental results of pinch characteristics in a miniaturized (20 J) repetitive Mather-type plasma focus device (SORENA-1) have been presented. Argon, neon and deuterium were used as working gases, and variations of pinch characteristics such as pinch time tp, negative spike height hp, pinch duration dt with working conditions (different gases, initial pressures and discharge voltages) were described and analyzed. Keywords: Miniaturized plasma focus; Pinch characteristics; Current derivative PACS No.: 52.59.Hq; 52.58.Lq
1. Introduction Plasma focus (PF) devices were developed independently in the 1960s in two different models by Filippov in Soviet Union [1] and Mather in the USA [2]. At PF discharges, short-duration (tens to hundreds of nanoseconds), hightemperature (* keV) and high-density (* 1025 m-3) plasma columns (pinch) are formed, which can emit highenergy ions, electrons, soft and hard X-rays and neutron pulses (when deuterium is used) [3–5]. With respect to interesting applications (industrial, medical, research and educational) predicted for plasma focus devices and the simplicity of their structure and operation, high research activities have been made on them in different laboratories all over the world [6–12]. The energy of PF devices that were made up to beginning of twenty-first century was between hundreds of Joules and some Mega Joules [6]. These types of PFs can only work single shot [9], and some very small PF devices in the early twenty-first century have been designed and constructed. Different laboratories in recent years have worked on very small PFs, due to their interesting characteristics (such as repetitive performance with high frequencies (up to 50 Hz) [9], portability, little variations in
the beam emission in discharges with similar conditions and low cost) [9–15]. At PF discharges, a negative spike in current derivative signal is the sign of pinch formation, and the amplitude of this spike (pinch height) shows the strength of the pinch [4, 13]. In order to achieve the best efficiency, the pinch time should be coincident with peak of discharge current [7]. Also, most of the beams are generated in pinch duration. Hence, investigation of the pinch characteristics such as pinch time, pinch height and pinch duration is important for analyzing the performance of a device. In this article, the pinch formation and its characteristics (pinch time, pinch height and pinch duration) in the experiments with a miniaturized (20 J) Mather-type repetitive PF device at different working conditions have been investigated and analyzed carefully.
2. Experimental setup Using the experimental fact that the plasma energy density parameter an
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