9 research outputs found
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Low-energy electron capture by Ne2+ ions from H(D)
Using the Oak Ridge National Laboratory (ORNL) ion-atom merged-beams apparatus, the absolute, total single-electron-capture cross section has been measured for collisions of Ne2+ with deuterium (D) at center-of-mass (c.m.) collision energies of 59ā949 eVāu. With the high-velocity ion beams now available at the ORNL Multicharged Ion Research Facility, we have extended our previous merged-beams measurement to lower c.m. collision energies. The data are compared to all four previously published measurements for Ne2++H(D) which differ considerably from one another at energies ā²600 eVāu. We are unaware of any published theoretical cross-section data for Ne2++H(D) at the energies studied. Early quantal rate coefficient calculations for Ne2++H at eV/u energies suggest a cross section many orders of magnitude below previous measurements of the cross section at 40 eVāu which is the lowest collision energy for which experimental results have been published. Here we compare our measurements to recent theoretical electron-capture results for He2++H. Both the experimental and theoretical results show a decreasing cross section with decreasing energy
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Rotating Dual-Wire Beam Profile Monitor Optimized for use in Merged-Beams Experiments
A rotating dual-wire beam proļ¬le monitor based upon a National Electrostatics Corporation Model BPM80 beam proļ¬le monitor is described. The device can measure beam proļ¬les in two perpendicular directions (horizontal and vertical) in each of two pseudoplanes that are situated along the beam axis and are separated by a distance of 5.4 cm. The output signal from the device is analyzed in real time to yield horizontal and vertical beam proļ¬les and to calculate the divergence of a particle beam that traverses the device. This set-up is well-suited for merged-beams experiments where one beam is tuned to saved proļ¬les from a second beam in order to minimize the merge angle and beam divergences while maximizing the beamābeam overlaps
A high-performance 14C accelerator mass spectrometry system
Author Posting. Ā© Arizona Board of Regents on behalf of the University of Arizona, 2010. This article is posted here by permission of Dept. of Geosciences, University of Arizona for personal use, not for redistribution. The definitive version was published in Radiocarbon 52 (2010): 228-235.A new and unique radiocarbon accelerator mass spectrometry (AMS) facility has been constructed at the
Woods Hole Oceanographic Institution. The defining characteristic of the new system is its large-gap optical elements that
provide a larger-than-standard beam acceptance. Such a system is ideally suited for high-throughput, high-precision measurements
of 14C. Details and performance of the new system are presented
A high-performance C-14 accelerator mass spectrometry system
A new and unique radiocarbon accelerator mass spectrometry (AMS) facility has been constructed at the Woods Hole Oceanographic Institution. The defining characteristic of the new system is its large-gap optical elements that provide a larger-than-standard beam acceptance. Such a system is ideally suited for high-throughput, high-precision measurements of C-14. Details and performance of the new system are presented
Development of fast helium beam emission spectroscopy for tokamak plasma density- and temperature diagnostics
Development of fast helium beam emission spectroscopy for tokamak plasma density- and temperature diagnostics
Overview of JET results
High density and high confinement operation in ELMy H-mode is confirmed at or above the normalized parameters foreseen for the ITER operating point (H98(y,2) 3c 1, n/nGW 3c 1, \u3b2N > 1.8 at q95 3c 3). The scaling of the ELMy H-mode with \u3b2N could be more favourable than that predicted by the IPB98(y,2) scaling. In ELMy H-mode, ion cyclotron current drive (ICCD) control of large sawteeth stabilized by fast particle has been demonstrated and the underlying neo-classical tearing modes (NTMs) and sawtooth physics is being refined. At high-density, Type I ELMy H-modes show trends that would lead to marginally acceptable ELMs on ITER. Type II ELM regime has been produced, though under very restrictive conditions. Type III ELMy operation with radiation fractions up to 95% has been demonstrated by seeding of N2 in H-modes and could extrapolate to Q = 10 ITER operation, albeit at high current (17 MA). The mitigation of Type I ELMs, nevertheless, remains a challenge. Considerable progress has been obtained in internal transport barrier (ITB) plasmas, with operation at central densities close to the Greenwald density or/and low toroidal rotation or/and high triangularity. Demonstrations of full current drive and successful simultaneous real time control of safety factor and temperature profiles have been achieved in ITB plasmas. Physics of resistive wall modes (RWMs) has been compared with theory, showing favourable scaling for ITER. High \u3b2N 3c 2.8 operation of hybrid modes (also called improved H-modes) has been obtained with dominant neutral beam heating. Hybrid modes with dominant ion cyclotron resonance heating (ICRH) have also been achieved. Trace tritium experiments yielded valuable information on particle transport in H-mode, ITB and hybrid regimes. In Type I ELMy plasmas, successful tests of the conjugate-T ICRH scheme have been achieved as well as lower hybrid coupling at ITER-relevant 10\u201311 cm distances. Reduced D and T fuel retention has been observed, which could relate to operation with vertical targets in the divertor and/or lower (ITER-like) vessel temperature. It is confirmed that erosion occurs predominantly on the main chamber surfaces, with possible benefits for T retention in ITER, although consequences for the metallic first wall lifetime need to be assessed. Disruption and ELM studies indicate that transient power deposition could be less constraining than expected for the ITER divertor, but more challenging for the metallic first wall. Alpha particle tomography and direct observation of alpha particle slowing down have been made possible by \u3b3 -spectroscopy. Measurements of Alfve \u301n cascades have been improved by a new interferometric technique. Promising tests of ITER relevant neutron counting detectors have been conducted