Torr Deuterium Research Articles

Damage Study of Irradiated Tungsten using fast focus mode of a 2.2 kJ plasma focus

In this work, damage results of four 12 mm × 12 mm × 5 mm PLANSEE double forged tungsten target samples exposed in INTI PF device at different distances from anode operating in the fast focus mode at 12 kV, 2.5 Torr deuterium are presented. SEM and EDX images and analysis show the extent of damage on the exposed tungsten surface. Micro-cracks up to 300 nm and 500 nm to 5 μm holes together with signs of melting are found on the tungsten exposed surfaces depending on their distances from the anode top. Current waveforms fitting using Lee Model Code show yields of 3 × 106 neutrons and 8.5 × 1014 ions per shot with average ion energy of 56 keV per ion at pinch exit, generating heat flux of 1.8 × 1014 Wm−2 and damage factor (also called heat flux factor) of 1.6 × 1010 Wm−2s0.5 on a target at pinch exit.

Fast Faraday cup for fast ion beam TOF measurements in deuterium filled plasma focus device and correlation with Lee model

In this work, the design and construction of a 50 Ω fast Faraday cup and its results in correlation with the Lee Model Code for fast ion beam and ion time of flight measurements for a Deuterium filled plasma focus device are presented. Fast ion beam properties such as ion flux, fluence, speed, and energy at 2–8 Torr Deuterium are studied. The minimum 34 ns full width at half maximum ion signal at 12 kV, 3 Torr Deuterium in INTI PF was captured by a Faraday cup. The maximum ion energy of 67 ± 5 keV at 4 Torr Deuterium was detected by the Faraday cup. Ion time of flight measurements by the Faraday cup show consistent correlation with Lee Code results for Deuterium especially at near to optimum pressures.

Neutron emission characterisation at the FN-II Dense Plasma Focus

Plasma foci are efficient plasma based neutron sources, when deuterium is used as the filling gas. The dense plasma focus FN-II is a small device (4.7 kJ), in which the emission of deuterium fusion neutrons (2.45 MeV) are studied. The system produces an average neutron yield of (5.3 ± 0.5) × 108 neutron/shot in 4π sr at ~ 350 kA peak discharge current and 2.75 torr deuterium operation. Three methods are currently used; silver activation counters and CR-39 nuclear track detectors, for time integrated and angular distribution studies, and BC 400 scintillators coupled to photomultiplier tubes for spectra studies. In the latter case, we compare signals due to neutron reflections in the laboratory with those obtained with a collimated beam in a paraffin shielded detector. Regarding the angular distribution of the neutron emission, it has been found to have isotropic and anisotropic components, the former giving the largest contribution. Also, the neutron spectrum, measured at 90° of the axis device, is broadened, peaking at energies slightly larger than 2.45 MeV. These can be interpreted as the consequence of coexisting neutron generation mechanisms, which will be discussed in this work. The correlation between neutron and hard X-ray yields is also discussed, and a possible interpretation in terms of different neutron generation mechanisms is attempted. There has also been a dosimetric study of the laboratory with TLD dosimeters, which will be presented in this paper.

A 160 kJ dual plasma focus (DuPF) for fusion-relevant materials testing and nano-materials fabrication

This paper summarizes PF-160 Dual Plasma Focus (DuPF) numerical experiments using the Lee Model code and preliminary 3D design drawings using SolidWorks software. This DuPF consists of two interchangeable electrodes enabling it to be optimized for both Slow Pinch Mode (SFM) and Fast Pinch Mode (FFM); the latter using a speed factor (SF) of 90 kA cm-1 Torr-0.5 for FFM in deuterium [S Lee et al, IEEE Trans Plasma Science 24, 1101-1105 (1996)]; and the former with SF of less than half that value for SFM. Starting with available 6 × 450 µF capacitors rated at 11kV (10% reversal), numerical experiments indicate safe operation at 9 kV, 6 Torr deuterium with FFM anode of 5 cm radius; producing intense ion beam and streaming plasma pulses which would be useful for studies of potential fusion reactor wall materials. On the other hand operating at 5 kV, 10 Torr deuterium with SFM anode of 10 cm radius leads to long-duration, uniform large-area flow which could be more suitable for synthesis of nano-materials. The dual plasma focus design is illustrated here with two figures showing FFM and SFM electrodes.

Neutron production with mixture of deuterium and krypton in Sahand Filippov type plasma focus facility

This Letter reports the order of magnitude enhancement in neutron yield from Sahand plasma focus device with krypton seeded deuterium operation. The highest average neutron yield of 2.2×109 neutrons per shot was achieved at 1.00 Torr deuterium with 3% krypton which is higher than the best average neutron yield of 3.18×108 neutrons per shot for pure deuterium operation. Estimation of average neutron energy showed that the maximum and minimum average energies are 2.98±0.6 MeV at 16 kV in 0.25 Torr deuterium with 3% Kr and 2.07±0.2 MeV at 18 kV operation in 0.5 Torr deuterium with 3% Kr, respectively. The anisotropy of neutron emission from Sahand DPF showed that the neutrons are produced mainly by beam–target mechanisms.

Dimensions and lifetime of the plasma focus pinch

In spite of intensive studies of the plasma focus, scaling laws, with the exception of those for neutron yield, are not well known. This paper points out that Mather-type plasma focus devices operated in the neutron-optimized regime have remarkably little variation in a drive parameter, (I/sub p//s)//spl rho/p/sub 0//sup 1/2/, the peak drive current per unit anode radius divided by the square root of the fill density; this quantity having the value of 89 kA/cm per torr deuterium equivalent of fill gas with a standard deviation of less than 10%. This parameter controls the speed of the plasma in both the axial and radial phases; and its constancy over a wide range of plasma focus devices really indicates that these devices all operate at the same axial and radial speeds, and hence by inference they all have the same temperatures in the axial and radial phases. Using a simple dynamical model the linear dimensions and time scales of the gross plasma focus pinch are shown to be related to the anode radius of the plasma focus device. The results of experiments performed with a 3-kJ device using different anodes are in good agreement with the theoretical predictions.

An investigation of the ion beam of a plasma focus using a metal obstacle and deuterated target

The results of an experimental study of the ion beam properties of a 3.3-kJ, 15-kV plasma focus are reported. The plasma focus is operated at 3 torr deuterium, and neutron yield measurements are made with a copper obstacle or deuterated target placed at various axial positions from the end of the anode. It is found that in the normal operation of the focus without an obstacle or target, less than 15% of the neutrons are produced within the pinch column, and that more than 85% of the neutrons arise from the deuterium-ion-beam bombardment of the deuterium gas in the region 20-60 mm from the end of the anode. The neutron production is highest between 30-40 mm from the anode. The results are valid only for a small focus.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Direct observations of the deuterium-induced surface reconstruction of the Ni(110) plane.

The reconstruction of the Ni(110) plane induced by the adsorption of deuterium has been investigated in atomic detail with the field ion microscope. Small clusters of Ni atoms were observed to rearrange from a bulk-terminated structure to a ``missing-row'' structure upon exposure to ${10}^{\mathrm{\ensuremath{-}}8}$-Torr deuterium at 165--175 K. The observed structure is inconsistent with the ``paired-row'' structure deduced from low-energy electron diffraction and ion-scattering measurements.

Proposal for a sensitive leak test telescope

A proposal for an in-vessel movable leak sensor, called a leak test telescope, is described for leak localization inside two of the largest thermonuclear fusion devices (TFTR and JET). To improve sensitivity and source identification beyond the present state of the art, a differential sensor head employing two actively pumping collimators, a continuously rotating shutter, and a quadrupole mass spectrometer as sensor is proposed. With the use of phase-lock signal processing this detector should be capable of detecting a leak of 1×10−6 Torr l/s from a distance of 0.5 m in a typical fusion environment with backgrounds &amp;gt;1×10−7 Torr deuterium–tritium.

High field laser heated solenoids

A 10 kJ pulsed CO 2 laser and 3.8 cm bore, 15 T, 8 μs rise time, 1-m long fast solenoid facility has been constructed to demonstrate the feasibility of using long wavelength lasers to heat magnetically confined plasmas. The most critical physics requirement is the necessity of creating and maintaining an on-axis electron density minimum to trap the axially directed laser beam. Satisfaction of this requirement has been demonstrated by heating 1.5 Torr deuterium fill plasmas in 2.7 cm bore plasma tubes to line energies of approximately 1 kJ/m.

Neutron-, ion-, and electron-energy spectra in a 1 kJ plasma focus

The neutron energy spectrum (4 Torr deuterium) was determined from 30 m flight histograms.—An average energy of approximately 100±20 keV of the neutron producing deuterons within an assumed cone angle of approximately 40 degrees along thez-axis was calculated by means of the target beam model.—Shadow bar techniques reveal that only 10% of the neutrons are produced in the ≈1 cm long focus.—Experimental time of flight analysis confirms that the ion spectrum extends from less than 70 to greater than 400 keV. The electron spectrum in 8 Torr hydrogen follows a ≈3 keV Boltzmann distribution, but demonstrates the presence of nonthermal >100 keV electrons.

X-Ray Analysis for Electron Beam Enhancement in the Plasma Focus Device*

AbstractThe plasma focus device, a form of linear pinch discharge, produces an intense x-ray and neutron (D2) burst from a magnetically heated dense plasma. Rapidly changing magnetic fields at pinch time generate large axial electric fields which accelerate electrons and ions. In the experiments reported here the x-ray production during the plasma pinch of a 96 kilojoule (at 20 kV) plasma focus device was measured.The purpose of these experiments was to evaluate the energy in accelerated electrons in the plasma focus device and to learn how to enhance these electron hursts. Well focused, megampere electron beams at a few hundred kilovolts, lasting less than 10 nanoseconds have applications in fusionable pellet heating experiments. (1) X-rays were monitored to evaluate these electron bursts using a defocusing bent crystal spectrometer, doubly diffused silicon (PIN) detectors, with Ross filters, thermoluminescent dosimeters (TLDs) with filters, and x-ray pinhole photography.Thermoluminescent dosimeters indicated maximum x-ray yields of 140 joules above 3 keV at 57.3 kilojoules stored energy (16 kV) for a conversion efficiency to x-rays of 0.2%. 40 joules are above 60 keV and 15 joules above 80 keV. The hard x-ray pulse typically rises in 3 ns and frequently has a pulse width less than 10 ns. The low energy x-ray spectrum consists almost entirely of lines from the high Z anode insert, and the high energy spectrum is characteristic of a nonthermal power law distribution with an exponent of 2.2 ± 0.8. Peak hard x-ray production is obtained at 1 torr deuterium in contrast to peak neutron production (3 x 1010) at 5 torr. The addition of argon reduces total x-ray yield and increases the relative fraction of soft x-rays.These measurements suggest that the plasma focus produces 1200 joules of electrons with an average energy of 150 keV, in 10 nanoseconds with a stored energy of 57.3 kilojoules. This is a power of 1.2 × 1011 watts and power density of 1.5 × 1013 watts cm−2.

THE STUDY OF θ-PINCH PLASMA USING A MACH-ZEHNDER INTERFEROMETER ILLUMINATED BY A GIANT PULSED RUBY LASER

The plasma electron density, shape and instability of the 23 kJ θ-pinch have been studied through the use of a Mach-Zehnder interferometer with a giant pulsed ruby laser illumination. The axial interferograms in the range of 45-120 m Torr deuterium pressures gave two-dimensional electron density distributions for the dicharge and established peak plasma electron densities in the range of 6-1016-2.3·1017 cm-3 for the plasma at peak pinch. The time of the peak pinch was about 1/3 of the first half-cycle of the main compressive magnetic field. The plasma characteristic time of containment (time required for the number of particles to be reduced to 1/e) close to peak pinch was 1.8-4.3μs. The interferograms with reverse bias magnetic field showed that the bias magnetic field was trapped in the plasma, and revealed that radial hydromagnetic oscillation of the plasma occurred between the trapped magnetic field and the main compressive magnetic field. The interferograms also showed that the plasma is essentially stable during the first half-cycle of the main compressive magnetic field in the range 45-80 m Torr deuterium pressures.