Pinch Quality Research Articles

The Investigation of Pre-ionization Effect on the Improvement of Pinch Quality and Increased Hard X-ray Radiation in a Dense Plasma Focus (DPF) Device

The Investigation of Pre-ionization Effect on the Improvement of Pinch Quality and Increased Hard X-ray Radiation in a Dense Plasma Focus (DPF) Device

The effects of the cathode array on emitted hard x-ray from a small plasma focus device

In this study, the effects of the cathode array variations on emitted hard x-rays from a small Mather type plasma focus device (450 J) were investigated. The gradual elimination of the cathode rods inside the cathode array of the device lowered the quality and quantity of the emitted hard x-rays at different pressure values of argon gas. We theorized that the variations of the cathode array were able to change some discharge parameters that could vary the number of the energetic runaway electrons generated during the pinch phase which were responsible for the created features of the emitted hard x-rays. On the other hand, we hypothesized that the removal of the cathode rods could influence the current sheath dynamics during all the phases of a shot including its average axial velocity which was demonstrated by using two axial magnetic probes. We also theorized that cathode rod omission from the cathode array could also increase the initial inductance and the impedance of the system, and the impurities inside the plasma during the pinch phase which could lead to the growth of the instabilities. Moreover, by using the wavelet technique and studying the Mirnov signals, it was shown that the decrease of the cathode rod number increased the plasma magnetic field fluctuations or instabilities (MHD activities) that adversely affected the pinch quality, and reduced the emitted hard x-rays.

Targeting for multiple resources in batch processes

Operating cost of a batch process can be reduced using multiple resources. In this paper, a methodology is proposed to target multiple resources in order to minimize the operating cost of the overall batch process. The proposed methodology is based on the concept of prioritized cost, originally developed for continuous processes. Prioritized cost of a resource depends on the pinch quality, quality of the resource and its cost. The concept of prioritized cost is extended to optimize the operating cost of a batch process. It is proved that to minimize the operating cost a batch process, prioritized cost of a resource in any time interval may not necessarily depends on the pinch quality of that interval. Prioritized cost of a resource in any time interval depends on the highest pinch quality of all the subsequent intervals, including itself. This important result is proved mathematically. The proposed methodology is applicable to fixed-scheduled, fixed-flow batch processes involving single quality.

Cost optimal segregated targeting for resource allocation networks

In this paper, a generalised methodology is proposed to target cost optimal allocation of resources in segregated targeting problems. Cost optimal segregated targeting problems are characterised by the existence of multiple zones; each consisting of a set of demands and using a unique resource with given cost and a single quality index (e.g., emissions factor, contaminant concentrations, etc.). All these zones share a common set of internal sources. This paper presents a rigorous mathematical proof of the decomposition principle that decomposes the problem into a sequence of sub-problems. Decomposition of the original problem is performed based on the prioritised costs for each external resource, attached to a particular zone. Prioritised cost of a resource depends on the pinch quality, quality of the resource and its cost. Applicability of the proposed methodology is illustrated by examples from carbon-constrained energy planning and water allocation networks.

The pulp switch flap: An option for the treatment of loss of the dominant half of the digital pulp

The fingertip has an important role in bi-digital pinch quality, and pulp loss is common and difficult to solve. The pulp switch consists of a pulp island flap with a homodigital neurovascular pedicle, vascularized by the palmar digital artery of the non-dominant pulp transposed to the dominant pulp side. We report the results in 16 patients treated for loss of the dominant half of a digital pulp from January 2000 to December 2008. On review after a minimum of 6 (range 6-18) months, the Weber's test demonstrated an average of 8 mm in static 2 point discrimination test for all digits, except the ring finger. In the monofilament Semmes-Weinstein test, we obtained a score of 3.61 for the thumb and little fingers, and 4.31 for the other fingers. We did not find partial or total necrosis of the flap. The pulp switch flap gave satisfactory functional results for viability, sensitivity, and digital mobility providing a sensate bi-digital pinch with acceptable aesthetic results in a single surgical procedure.

Experimental Study of Current Discharge Behavior and Hard X-ray Anisotropy by APF Plasma Focus Device

Amirkabir (APF) is a new Mather-type plasma focus device (16 kV, 36 μf, and 115 nH). In this work we present some experimental results as variation of discharge current signal respect to applied voltage at the optimum pressure, focusing time of plasma versus gas pressure, and variations of current discharge with different insulator sleeve dimensions. As we prospected optimum pressure tending to increase as we tried to higher voltage levels. The time taken by the current sheath to lift-off the insulator surface and therefore quality of pinched plasma depends on the length of the insulator sleeve. The results show that the insulator diameter can influence on pinch quality. Behavior of hard X-ray (HXR) signals with the pressure and also anisotropy of HXR investigated by the use of two scintillation detectors. The distribution of HXR intensity shows a large anisotropy with a maximum intensity between 22.5° and 45° and also between −22.5° and −67.5°.

Long implosion time (240 ns) Z-pinch experiments with a large diameter (12 cm) double-shell nozzle

Recently, an 8 cm diameter double-shell nozzle has produced argon Z pinches with high K-shell yields with implosion time of 210 ns. To produce even longer implosion time Z pinches for facilities such as Decade Quad [D. Price, et al., “Electrical and Mechanical Design of the Decade Quad in PRS Mode,” in Proceedings of the 12th IEEE Pulsed Power Conference, Monterey, CA, edited by C. Stallings and H. Kirbie (IEEE, New York, 1999), p. 489] (9 MA short circuit current at 300 ns), a larger nozzle (12 cm outer diameter) was designed and fabricated. During initial testing on Double-EAGLE [P. Sincerny et al., Proceedings of the 5th IEEE Pulsed Power Conference, Arlington, VA, edited by M. F. Rose and P. J. Turchi (IEEE, New York, 1985), p. 151], 9 kJ of argon K-shell radiation in a 6 ns full width at half maximum pulse was produced with a 240 ns implosion. The initial gas distributions produced by various nozzle configurations have been measured and their impact on the final radiative characteristics of the pinch are presented. The addition of a central jet to increase the initial gas density near the axis is observed to enhance the pinch quality, increasing K-shell yield by 17% and power by 40% in the best configuration tested.

Initial results for an argon Z pinch using a double-shell gas puff

Recent observations are given for an argon double-shell gas puff imploded with up to 4 MA in 200 ns on the Double Eagle generator [G. B. Frazier et al., Digest of Technical Papers, Fourth IEEE Pulsed Power Conference (IEEE, Piscataway, NJ, 1983), p. 583]. Good K-shell x-ray output with good pinch quality was observed. A novel experimental procedure was used to selectively seed the inner or outer gas plenums with a chlorine tracer. The tracer data provide the first direct experimental evidence that the mass initially closest to the axis is the dominant contributor to the hot core of the radiating pinch.

X-ray results from a modified nozzle and double gas puff z pinch

The nozzle and the anode of the UCI (University of California, Irvine) z-pinch facility were modified to study the influence of the anode-cathode geometrical structure on the stability of the pinch and the x-ray yield of the pinch. The anode was modified from a honey-comb to a hollow cylinder with a 4-cm diameter and a ∼3.5-mm wall thickness, placed 2 cm below the cathode. The cavity in the center of the cathode was enlarged from 6-mm diameter to 36 mm. The design of the cathode and the anode showed a marked improvement of the pinch stability over the previous design. Both zirconium and carbon-carbon nozzle were used for the Kr and Ne z pinches. After a few tens of shots the Zr nozzle was melted at the edge and the pinch degraded, while the carbon-carbon nozzle did not sustain any damage for more than 300 shots. Some shots showed the di/dt at the implosion is ∼5 times higher than the di/dt at the beginning of the discharge, this has never been obtained at UCI before. This ratio of the initial di/dt to pinch di/dt is a measure of the pinch quality. By serendipity it was found that double gas puff z pinch increased the hard x-ray (>1 keV) output by about an order of magnitude. The nozzle was then modified to allow double puff operation. A 3.4-mm-diam hole was opened at the center of the nozzle and a plunger was inserted from the top to control the mass of the gas entering the hole. The diagnostics include di/dt coil, soft, and hard x-ray diodes. Soft and hard x-ray emission are both enhanced by the double gas puff z pinch.