D-D fusion experiments using fast Z pinches

Spielman, R.B.; Baldwin, George Thomas; Cooper, G. W.

doi:10.2172/661646

Cited by 12 publications

(12 citation statements)

References 7 publications

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“…Deuterium gas-puff experiments were carried out on the z-pinch at the University of California in Irvine (200 kA peak current, 600 ns rise-time [12] or 500 kA, 1.5 µs [13]), on the Angara-5-1 generator (2-3 MA, 100 ns [14,15]), on the Saturn generator (7 MA, 60 ns [16]), on the Z machine (17 MA, 100 ns [17,18]) and on the S-300 generator (2 MA, 100 ns [19,20]). The plasma dynamics of these deuterium z-pinches seemed to be very similar to the radial and pinch phase of dense plasma foci (see [21] and references herein).…”

Section: Plasma Physics and Controlled Fusionmentioning

confidence: 99%

Efficient generation of fast neutrons by magnetized deuterons in an optimized deuterium gas-puff z-pinch

Klír

Shishlov

Kokshenev

et al. 2015

Plasma Phys. Control. Fusion

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Z-pinch experiments with deuterium gas puffs have been carried out on the GIT-12 generator at 3 MA currents. Recently, a novel configuration of a deuterium gas-puff z-pinch was used to accelerate deuterons and to generate fast neutrons. In order to form a homogeneous, uniformly conducting layer at a large initial radius, an inner deuterium gas puff was surrounded by an outer hollow cylindrical plasma shell. The plasma shell consisting of hydrogen and carbon ions was formed at the diameter of 350 mm by 48 plasma guns. A linear mass of the plasma shell was about 5 µg cm −1 whereas a total linear mass of deuterium gas in single or double shell gas puffs was about 100 µg cm −1 . The implosion lasted 700 ns and seemed to be stable up to a 5 mm radius. During stagnation, m = 0 instabilities became more pronounced. When a disruption of necks occurred, the plasma impedance reached 0.4 Ω and high energy (>2 MeV) bremsstrahlung radiation together with high energy deuterons were produced. Maximum neutron energies of 33 MeV were observed by axial time-of-flight detectors. The observed neutron spectra could be explained by a suprathermal distribution of deuterons with a high energy tail. Neutron yields reached 3.6 × 10 12 at a 2.7 MA current. A high neutron production efficiency of 6 × 10 7 neutrons per one joule of plasma energy resulted from the generation of high energy deuterons and from their magnetization inside plasmas.

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Section: Plasma Physics and Controlled Fusionmentioning

confidence: 99%

Efficient generation of fast neutrons by magnetized deuterons in an optimized deuterium gas-puff z-pinch

Klír

Shishlov

Kokshenev

et al. 2015

Plasma Phys. Control. Fusion

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“…Neutron yields from deuterium gas puff Z-pinches. 18, 21,22,27 We left out the peak neutron yield at 2-3 MA on the Angara-5-1 (Ref. 19) because it was achieved with a strong axial gradient of linear density.…”

Section: Neutron Yield Scaling With Currentmentioning

confidence: 99%

“…With a hollow gas puff, similar neutron yields of 2 Â 10 12 were achieved at significantly higher currents of about 8 MA on the Saturn generator. 21 The "saturation" of a neutron yield at a value of % 10 12 was overcome first on the Z machine with a double-shell deuterium gas-puff at a 17 MA current. 22,23 With regard to the overall neutron yield of 4 Â 10 13 , MHD (Ref.…”

Section: Introductionmentioning

confidence: 99%

Deuterium gas puff Z-pinch at currents of 2 to 3 mega-ampere

et al. 2012

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Deuterium gas-puff experiments have been carried out on the GIT-12 generator at the Institute of High Current Electronics in Tomsk. The emphasis was put on the study of plasma dynamics and neutron production in double shell gas puffs. A linear mass density of deuterium (D2) varied between 50 and 85 μg/cm. Somewhat problematic was a spread of the D2 gas at a large diameter in the central anode–cathode region. The generator operated in two regimes, with and without a plasma opening switch (POS). When the POS was used, a current reached a peak of 2.7 MA with a 200 ns rise time. Without the POS, a current rise time approached 1500 ns. The influence of different current rise times on neutron production was researched. Obtained results were important for comparison of fast deuterium Z-pinches with plasma foci. Average DD neutron yields with and without the POS were about 1011. The neutron yield seems to be dependent on a peak voltage at the Z-pinch load. In all shots, the neutron emission started during stagnation. At the beginning of the neutron production, the neutron emission correlated with soft x-rays and a significant fraction of neutrons could be explained by the thermonuclear mechanism. Nevertheless, a peak of the neutron emission occurred 40 ns after a soft x-ray peak. At this very moment, hard x-rays above 1 MeV were detected and a rapid expansion with a velocity of 3×105 m/s was observed. In the case of the POS, 1 MeV widths of radial neutron spectra implied that there are deuterons with the energy above 200 keV moving in the radial direction. On the basis of D2 gas puff experiments in the 0.3–17 MA region, the neutron yield dependence on a current as Y∝I3.0±0.2 was proposed.

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“…Dan Spielman [30] has observed that it is possible to improve on the n k time bound of a naive search algorithm for learning parity using k log n examples:…”

Section: Anõ(n K/2 ) Time Attribute Efficient Algorithmmentioning

confidence: 99%

Toward Attribute Efficient Learning of Decision Lists and Parities

Klivans

Servedio

2004

Learning Theory

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Abstract. We consider two well-studied problems regarding attribute efficient learning: learning decision lists and learning parity functions. First, we give an algorithm for learning decision lists of length k over n variables using 2Õ . This is the first algorithm for learning decision lists that has both subexponential sample complexity and subexponential running time in the relevant parameters. Our approach is based on a new construction of low degree, low weight polynomial threshold functions for decision lists. For a wide range of parameters our construction matches a lower bound due to Beigel for decision lists and gives an essentially optimal tradeoff between polynomial threshold function degree and weight. Second, we give an algorithm for learning an unknown parity function on k out of n variables using O(n 1−1/k ) examples in poly(n) time. For k = o(log n) this yields the first polynomial time algorithm for learning parity on a superconstant number of variables with sublinear sample complexity. We also give a simple algorithm for learning an unknown size-k parity using O(k log n) examples in n k/2 time, which improves on the naive n k time bound of exhaustive search.

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D-D fusion experiments using fast Z pinches

Cited by 12 publications

References 7 publications

Efficient generation of fast neutrons by magnetized deuterons in an optimized deuterium gas-puff z-pinch

Efficient generation of fast neutrons by magnetized deuterons in an optimized deuterium gas-puff z-pinch

Deuterium gas puff Z-pinch at currents of 2 to 3 mega-ampere

Toward Attribute Efficient Learning of Decision Lists and Parities

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