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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

Design and implementation of a multichannel millimeter wave interferometer for the Compact Toroidal Hybrid experiment

A three-channel 1 mm wave interferometer has been designed, assembled, and installed on the Compact Toroidal Hybrid torsatron (CTH). The interferometer design makes novel use of a subharmonic mixer for detection, which simplifies alignment. It employs a single electronically tunable source that is repetitively chirped using a sawtooth waveform of frequency up to 1 MHz. The 15.25 GHz drive oscillator is multiplied in two stages to 122 GHz before a final doubler stage brings it to 244 GHz. Local oscillator (LO) power at 122 GHz is directed through waveguide to the LO input of the subharmonic mixer of each viewing chord, simplifying alignment. Phase detection is performed by directly digitizing the amplified mixer outputs at 50 MHz and processing them with a software algorithm. Initial measurements made with the central chord of the new interferometer agree with those from the existing 4 mm system at low densities. The 1 mm system performs well in current-driven discharges reaching densities over 10{sup 19} m{sup -3}, whereas the lower frequency interferometer is found to be less reliable due to loss of fringes. This is a critical improvement for experiments studying the onset, avoidance, and vacuum magnetic transform dependence of disruptions in the CTH device.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

Advances in compact proton spectrometers for inertial-confinement fusion and plasma nuclear science

Compact wedge-range-filter proton spectrometers cover proton energies {approx}3-20 MeV. They have been used at the OMEGA laser facility for more than a decade for measuring spectra of primary D{sup 3}He protons in D{sup 3}He implosions, secondary D{sup 3}He protons in DD implosions, and ablator protons in DT implosions; they are now being used also at the National Ignition Facility. The spectra are used to determine proton yields, shell areal density at shock-bang time and compression-bang time, fuel areal density, and implosion symmetry. There have been changes in fabrication and in analysis algorithms, resulting in a wider energy range, better accuracy and precision, and better robustness for survivability with indirect-drive inertial-confinement-fusion experiments.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

A compact multichannel spectrometer for Thomson scattering

The availability of high-efficiency volume phase holographic (VPH) gratings and intensified CCD (ICCD) cameras have motivated a simplified, compact spectrometer for Thomson scattering detection. Measurements of T{sub e} < 100 eV are achieved by a 2971 l/mm VPH grating and measurements T{sub e} > 100 eV by a 2072 l/mm VPH grating. The spectrometer uses a fast-gated ({approx}2 ns) ICCD camera for detection. A Gen III image intensifier provides {approx}45% quantum efficiency in the visible region. The total read noise of the image is reduced by on-chip binning of the CCD to match the 8 spatial channels and the 10 spectral bins on the camera. Three spectrometers provide a minimum of 12 spatial channels and 12 channels for background subtraction.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

Compact Kirkpatrick–Baez microscope mirrors for imaging laser-plasma x-ray emission

Compact Kirkpatrick–Baez microscope mirror components for use in imaging laser-plasma x-ray emission have been manufactured, coated, and tested. A single mirror pair has dimensions of 14 × 7 × 9 mm and a best resolution of ~5 μm. The mirrors are coated with Ir providing a useful energy range of 2-8 keV when operated at a grazing angle of 0.7°. The mirrors can be circularly arranged to provide 16 images of the target emission a configuration best suited for use in combination with a custom framing camera. As a result, an alternative arrangement of the mirrors would allow alignment of the images with a fourstrip framing camera.

47 OTHER INSTRUMENTATION↗
DOE OSTI2012

Photo-fusion reactions in a new compact device for ELI

In the last few years significant progress on technological, experimental and numerical studies on fusion process in high density and high temperature plasmas produced by a high intensity laser pulse interaction with clusters in a high external applied magnetic field, enable us to propose a compact photo-fusion magnetic device for high neutron production. For the purpose of the project a pulsed magnetic field driver with values up to 110 Tesla has been developed which allows increasing the trapping time of the high density plasma in the device and improving the neutron yield. Numerical simulations show that the proposed device is capable of producing up to 10{sup 9}-10{sup 10} neutrons per laser shot with an external magnetic field of 150 Tesla. The proposed device can be used for experiments and numerical code validation concerning different conventional and (or) exotic fusion fuels.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2012

Compact steady-state and high-flux Falcon ion source for tests of plasma-facing materials

This paper describes the design and operation of the Falcon ion source. It is based on conventional design of anode layer thrusters. This ion source is a versatile, compact, affordable, and highly functional in the research field of the fusion materials. The reversed magnetic field configuration of the source allows precise focusing of the ion beam into small spot of Almost-Equal-To 3 mm and also provides the limited capabilities for impurity mass-separation. As the result, the source generates steady-state ion beam, which irradiates surface with high heat (0.3 - 21 MW m{sup -2}) and particle fluxes (4 Multiplication-Sign 10{sup 21}- 3 Multiplication-Sign 10{sup 23} m{sup -2}s{sup -1}), which approaches the upper limit for the flux range expected in ITER.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Sensitivity in X-ray grating interferometry on compact systems

The optimization of compact X-ray grating interferometry systems is crucial for the progress of this technique in industrial devices. Here, an analytical formulation for the sensitivity of the phase contrast image acquisition is derived using previous results from noise analyses. Furthermore, experimental measurements of the sensitivity for different configurations are compared, providing further insight into the dependence on polychromatic radiation. Finally, strategies for the geometrical optimization are given.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

Experimental study of a compact P-band coaxial relativistic backward wave oscillator with three periods slow wave structure

A compact P-band coaxial relativistic backward wave oscillator with three periods slow wave structure was investigated experimentally. The experimental results show that the frequency of the P-band coaxial relativistic backward wave oscillator is 897 MHz and the microwave power is 1.47 GW with an efficiency of about 32% in the case in which the diode voltage is 572 kV, the beam current is 8.0 kA, and the guide magnetic field is about 0.86 T. In addition, the device can generate a 3.14 GW microwave radiation as the guide magnetic field increases to 1.2 T at the diode voltage of 997 kV and the beam current of 15.3 kA. The experimental results are in good agreement with those obtained earlier by numerical simulations.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

A compact and miniaturized high resolution capacitance dilatometer for measuring thermal expansion and magnetostriction

We describe the design, construction, calibration, and two different applications of a miniature capacitance dilatometer. The device is suitable for thermal expansion and magnetostriction measurements from 300 K down to about 25 mK, with a resolution of 0.02 A at low temperatures. The main body of the dilatometer is fabricated from a single block of a Be-Cu alloy by electrical discharge milling. This creates an extremely compact high-resolution measuring cell. We have successfully tested and operated dilatometers of this new type with the commonly used physical property measurement system by quantum design, as well as with several other cryogenic refrigeration systems down to 25 mK and in magnetic fields up to 20 T. Here, the capacitance is measured with a commercially available capacitance bridge. Using a piezoelectric rotator from Attocube Systems, the cell can be rotated at T= 25 mK inside of an inner vacuum chamber of 40 mm diameter. The miniaturized design for the one-axis rotation setup allows a rotation of 360 Degree-Sign .

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

Compact high-speed reciprocating probe system for measurements in a Hall thruster discharge and plume

A compact high-speed reciprocating probe system has been developed in order to perform measurements of the plasma parameters by means of electrostatic probes in the discharge and the plume of a Hall thruster. The system is based on a piezoelectric linear drive that can achieve a speed of up to 350 mm/s over a travel range of 90 mm. Due to the high velocity of the linear drive the probe can be rapidly moved in and out the measurement region in order to minimize perturbation of the thruster discharge due to sputtering of probe material. To demonstrate the impact of the new system, a heated emissive probe, installed on the high-speed translation stage, was used to measure the plasma potential and the electron temperature in the near-field plume of a low power Hall thruster.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2012

Gyrokinetic studies of the effect of {beta} on drift-wave stability in the National Compact Stellarator Experiment

The gyrokinetic turbulence code GS2 was used to investigate the effects of plasma {beta} on linear, collisionless ion temperature gradient (ITG) modes and trapped electron modes (TEM) in National Compact Stellarator Experiment (NCSX) geometry. Plasma {beta} affects stability in two ways: through the equilibrium and through magnetic fluctuations. The first was studied here by comparing ITG and TEM stability in two NCSX equilibria of differing {beta} values, revealing that the high {beta} equilibrium was marginally more stable than the low {beta} equilibrium in the adiabatic-electron ITG mode case. However, the high {beta} case had a lower kinetic-electron ITG mode critical gradient. Electrostatic and electromagnetic ITG and TEM mode growth rate dependencies on temperature gradient and density gradient were qualitatively similar. The second {beta} effect is demonstrated via electromagnetic ITG growth rates' dependency on GS2's {beta} input parameter. A linear benchmark with gyrokinetic codes GENE and GKV-X is also presented.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Comparing linear ion-temperature-gradient-driven mode stability of the National Compact Stellarator Experiment and a shaped tokamak

One metric for comparing confinement properties of different magnetic fusion energy configurations is the linear critical gradient of drift wave modes. The critical gradient scale length determines the ratio of the core to pedestal temperature when a plasma is limited to marginal stability in the plasma core. The gyrokinetic turbulence code GS2 was used to calculate critical temperature gradients for the linear, collisionless ion temperature gradient (ITG) mode in the National Compact Stellarator Experiment (NCSX) and a prototypical shaped tokamak, based on the profiles of a JET H-mode shot and the stronger shaping of ARIES-AT. While a concern was that the narrow cross section of NCSX at some toroidal locations would result in steep gradients that drive instabilities more easily, it is found that other stabilizing effects of the stellarator configuration offset this so that the normalized critical gradients for NCSX are competitive with or even better than for the tokamak. For the adiabatic ITG mode, NCSX and the tokamak had similar adiabatic ITG mode critical gradients, although beyond marginal stability, NCSX had larger growth rates. However, for the kinetic ITG mode, NCSX had a higher critical gradient and lower growth rates until a/L{sub T} Almost-Equal-To 1.5 a/L{sub T,crit}, when it surpassed the tokamak's. A discussion of the results presented with respect to a/L{sub T} vs. R/L{sub T} is included.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

A compact stilbene crystal neutron spectrometer for EAST D-D plasma neutron diagnostics

A new compact stilbene crystal neutron spectrometer has been investigated and applied in the neutron emission spectroscopy on the EAST tokamak. A new components analysis method is presented to study the anisotropic light output in the stilbene crystal detector. A Geant4 code was developed to simulate the neutron responses in the spectrometer. Based on both the optimal light output function and the fitted pulse height resolution function, a reliable neutron response matrix was obtained by Geant4 simulations and validated by 2.5 MeV and 14 MeV neutron measurements at a 4.5 MV Van de Graaff accelerator. The spectrometer was used to diagnose the ion temperature in plasma discharges with lower hybrid wave injection and ion cyclotron resonance heating on the EAST tokamak.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

Calibration and operational data for a compact photodiode detector useful for monitoring the location of moving sources of positron emitting radioisotopes

D-Pace has developed a compact cost-effective gamma detector system based on technology licensed from TRIUMF. These photodiode detectors are convenient for detecting the presence of positron emitting radioisotopes, particularly for the case of transport of radioisotopes from a PET cyclotron to hotlab, or from one location to another in an automated radiochemistry processing unit. This paper describes recent calibration experiments undertaken at the Turku PET Centre for stationary and moving sources of F18 and C11 in standard setups. The practical diagnostic utility of using several of these devices to track the transport of radioisotopes from the cyclotron to hotlab is illustrated. For example, such a detector system provides: a semi-quantitative indication of total activity, speed of transport, location of any activity lost en route and effectiveness of follow-up system flushes, a means of identifying bolus break-up, feedback useful for deciding when to change out tubing.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2013

Improvement of extraction efficiency from a compact synchrotron for proton beam therapy by applying particle tracking analysis

Various types of synchrotrons are used for particle beam therapy. In particle beam therapy, especially in proton beam therapy, downsizing of the accelerator system is a major concern. A compact synchrotron dedicated for proton beam therapy is presented. The synchrotron is horizontally weakly focusing and consists of 4 H-type zerogradient dipole magnets and 4 quadrupole magnets. The circumference of the ring is a little shorter than 18 m, and the energies are up to 230MeV. Beam extraction from the synchrotron is performed by RF-driven slow extraction technology. Two sextupole magnets set in adjacent straight sections form a horizontal separatrix which is fixed during the beam extraction. Horizontal RF voltage excites betatron oscillation of the circulating beam, and protons exceeding the separatrix are extracted by an electrostatic deflector and a horizontal septum dipole magnet. To achieve adequately high extraction efficiency, the relationship between the extraction efficiency and the horizontal chromaticity of the ring is analyzed by particle tracking simulation. The horizontal chromaticity with maximum extraction efficiency is half of the theoretical value because of the distortion of the horizontal separatrix for the extraction. With this chromaticity, the spiral-step of the extracted particle is independent of the momentum deviation of the particle, and the separatrix across the electrostatic septum electrodes is superpositioned.

43 PARTICLE ACCELERATORS↗
DOE OSTI2013

Preliminary study on development of 300 Kv compact focused gaseous ion beam system

A new 300 kV compact focused gaseous ion beam (gas-FIB) system with three-stage acceleration lens was constructed at JAEA. The preliminary experiments of formation of the focused gaseous ion beams were carried out to show the availability of the gas-FIB system as a writing tool for 3D proton lithography. As a result of the experiments, it was proved that the focal point was kept at the same position under changing the kinetic energy but with keeping the kinetic energy ratio constant, which was defined as the ratio of kinetic energy in object side to that in image side for the third acceleration lens. This characteristic of the gas-FIB is a good point to advance the 3D proton lithography changing penetration depth in a sample by varying the beam energy.

43 PARTICLE ACCELERATORS↗
DOE OSTI2013

A compact ion source and accelerator based on a piezoelectric driver

Compact ion sources and accelerators using piezoelectric devices for the production of energetic ion beams are being evaluated. A coupled source-accelerator is being tested as a neutron source to be incorporated into oil-well logging diagnostics. Two different ion sources are being investigated, including a piezoelectric transformer-based plasma source and a silicon-based field ion source. The piezoelectric transformer plasma ion source uses a cylindrical, resonantly driven piezoelectric crystal to produce high voltage inside a confined volume filled with low pressure deuterium gas. The plasma generated in the confined chamber is ejected through a small aperture into an evacuated drift region. The silicon field ion source uses localized electric field enhancement produced by an array of sharp emitters etched into a silicon blank to produce ions through field desorption ionization. A second piezoelectric device of a different design is used to generate an accelerating potential on the order of 130 kV; this potential is applied to a deuterated target plate positioned perpendicular to the ion stream produced by either plasma source. This paper discusses the results obtained by the individual components as they relate to the final neutron source.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2013

Compact integrated X-ray intensity and beam position monitor based on rare gas scintillation

We have created and tested a compact integrated X-ray beam intensity and position monitor using Ar-gas scintillation. The light generated inside the device's cavity is detected by diametrically opposed PIN diodes located above and below the beam. The intensity is derived from the sum of the top and bottom signals, while the beam position is calculated from the difference-over-sum of the two signals. The device was tested at Cornell High Energy Synchrotron Source with both 17 keV and 59 keV x-rays. For intensity monitoring, the Ar-scintillation monitor performance is comparable to standard ion chambers in terms of precision. As an X-ray beam position monitor the new device response is linear with vertical beam position over a 2 mm span with a precision of 2 {mu}m.

43 PARTICLE ACCELERATORS↗