Measurements of Escaping Alphas in the TFTR DT Experiments PDF Download
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Author: G. Y. Fu
Publisher:
ISBN:
Category : Alpha rays
Languages : en
Pages : 6
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Author: G. Y. Fu
Publisher:
ISBN:
Category : Alpha rays
Languages : en
Pages : 6
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Author: S. J. Zweben
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Category :
Languages : en
Pages : 0
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Author:
Publisher:
ISBN:
Category : Alpha rays
Languages : en
Pages : 6
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Alpha particle loss to the wall of TFTR has been measured during the initial TFTR DT run period. These measurements were made with the same lost alpha scintillator detector system used previously for DD fusion products, except for a switch of the scintillator material from zinc sulfide (P31) to yttrium aluminate (P46) to insure a linear response up to the maximum alpha flux expected in DT. The alpha loss signals in DT are (almost equal to) 100 times larger than the DD fusion product loss signals, as expected from the neutron rates and the relative sensitivity to DT vs. DD fusion products.
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Languages : en
Pages :
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Radially resolved confined alpha particle energy and density distributions are routinely measured on TFTR using two diagnostics: PCX and[alpha]-CHERS. The Pellet Charge-eXchange (PCX) diagnostic uses the ablation cloud formed by an impurity pellet (Li or B) for neutralization of the alphas followed by analysis of the escaping helium neutrals. PCX detects deeply trapped alpha particles in the energy range 0.5 - 3.8 MeV. The[alpha]-CHERS technique, were the alpha signal is excited by charge-exchange between alphas and the deuterium atoms of one of the heating beams and appears as a wing on the He[sup+] 468.6 nm line, detects mainly passing alphas in the range of 0.15 - 0.7 MeV. Studies of alpha losses during DT experiments on TFTR have also been conducted using lost alpha detectors located on the walls of the plasma chamber. All of these diagnostics were used for investigating the influence of sawtooth crashes on alphas in high power D-T discharges in TFTR. Both PCX and[alpha]-CHERS measurements show a strong depletion of the alpha core density and transport of trapped alphas radially outwards well beyond q= 1 surface after a sawtooth crash. Lost alpha detectors measure bursts of alpha loss of the previously confined alphas (
Author: Giuseppe Gorini
Publisher: Springer Science & Business Media
ISBN: 1461303699
Category : Science
Languages : en
Pages : 631
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This book of proceedings collects the papers presented at the Workshop on Diagnostics for ITER, held at Villa Monastero, Varenna (Italy), from August 28 to September 1, 1995. The Workshop was organised by the International School of Plasma Physics "Piero Caldirola. " Established in 1971, the ISPP has organised over fifty advanced courses and workshops on topics mainly related to plasma physics. In particular, courses and workshops on plasma diagnostics (previously held in 1975, 1978, 1982, 1986, and 1991) can be considered milestones in the history of this institution. Looking back at the proceedings of the previous meetings in Varenna, one can appreciate the rapid progress in the field of plasma diagnostics over the past 20 years. The 1995 workshop was co-organised by the Istituto di Fisica del Plasma of the National Research Council (CNR). In contrast to previous Varenna meetings on diagnostics, which have covered diagnostics in present-day tokamaks and which have had a substantial tutorial component, the 1995 workshop concentrated specifically on the problems and challenges of ITER diagnostics. ITER (the International Thennonuclear Experimental Reactor, a joint venture of Europe, Japan, Russia, and the United States, presently under design) will need to measure a wide range of plasma parameters in order to reach and sustain high levels of fusion power. A list of the measurement requirements together with the parameter ranges, target measurement resolutions, and accuracies provides the starting point for selecting a list of candidate diagnostic systems.
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Languages : en
Pages :
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Alpha particle loss was measured during the TFTR DT experiments using a scintillator detector located at the vessel bottom in the ion grad-B drift direction. The DT alpha particle loss to this detector was consistent with the calculated first-orbit loss over the whole range of plasma current I=0.6-2.7 MA. In particular, the alpha particle loss rate per DT neutron did not increase significantly with fusion power up to 10.7 MW, indicating the absence of any new ''collective'' alpha particle loss processes in these experiments.
Author: George R. McKee
Publisher:
ISBN:
Category : Alpha rays
Languages : en
Pages : 296
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Author: TFTR Team
Publisher:
ISBN:
Category : Alpha rays
Languages : en
Pages : 4
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Category :
Languages : en
Pages :
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An escaping alpha collector probe has been developed for TFTR's DT phase. Energy distributions of escaping alphas have been determined by measuring the range of [alpha]-particles implanted into nickel foils located within the alpha collector. Results at 1.0 MA of plasma current are in good agreement with predictions for first orbit alpha loss. Results at 1.8 MA, however, show a significant anomalous loss of partially thermalized alphas (in addition to the expected first orbit loss), which is not observed with the lost alpha scintillator detectors in DT plasmas, but does resemble the anomalous delayed loss seen in DD plasmas. None of the candidate explanations proposed thus far are fully consistent with the anomalous loss observations. An experiment designed to study the effect of plasma major radius shifts on [alpha]-particle loss has led to a better understanding of [alpha]-particle dynamics in tokamaks. Intuitively, one might suppose that confined marginally passing [alpha]-particles forced to move toward higher magnetic field during an inward major radius shift (i.e., compression) would mirror and become trapped particles, leading to increased alpha loss. Such an effect was looked for during the shift experiment, however, no significant changes in alpha loss to the 90[degree] lost alpha scintillator detector were observed during the shifts. It is calculated that the energy gained by an [alpha]-particle during the inward shift is sufficient to explain this result. However, an unexpected loss of partially thermalized [alpha]-particles near the passing/trapped boundary was observed to occur between inward and outward shifts at an intermediate value of plasma current (1.4 MA). This anomalous loss feature is not yet understood.
Author: R. V. Budny
Publisher:
ISBN:
Category : Alpha rays
Languages : en
Pages : 56
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