Fast Alpha Diagnostics Using Pellet Injection

Fisher, R. K.; Leffler, J.S.; Howald, A. M.; Parks, P.B.

doi:10.13182/fst88-a25133

Cited by 29 publications

(26 citation statements)

References 9 publications

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“…Several diagnostics designed to measure confined ␣ particles in large tokamaks recently began operation; namely, charge exchange spectroscopy, 1 microwave scattering, 2 and energetic neutral particle analysis with the use of low-Z impurity pellets. 3,4 The last method, called pellet charge exchange ͑PCX͒, was developed in a collaboration between General Atomics, the A. F. Ioffe Physical-Technical Institute, and the Princeton Plasma Physics Laboratory and is now operated routinely on TFTR during D-T experiments. PCX diagnostic results were reported on measurements of rf-driven energetic helium-3, 5 hydrogen, 6 and tritium 7 minority ion tails, the energy distribution of fast confined ␣ particles and tritons, 8,9 and the influence of magnetic field ripple and sawtooth oscillations on the behavior of the alpha energy spectra and radial density distributions.…”

Section: Introductionmentioning

confidence: 99%

Design and operation of the pellet charge exchange diagnostic for measurement of energetic confined α particles and tritons on the Tokamak Fusion Test Reactor

Medley

Mansfield

Roquemore

et al. 1996

Review of Scientific Instruments

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Radially resolved energy and density distributions of the confined ␣ particles in D-T experiments on the Tokamak Fusion Test Reactor ͑TFTR͒ are being measured with the pellet charge exchange ͑PCX͒ diagnostic. Other energetic ion species can be detected as well, such as tritons produced in D-D plasmas and H, He 3 , or tritium rf-driven minority ion tails. The ablation cloud formed by injected low-Z impurity pellets provides the neutralization target for this active charge exchange technique. Because the cloud neutralization efficiency is uncertain, the PCX diagnostic is not absolutely calibrated so only relative density profiles are obtained. A mass and energy resolving E ʈ B neutral particle analyzer ͑NPA͒ is used which has eight energy channels covering the energy range of 0.3-3.7 MeV for ␣ particles with energy resolution ranging from 5.8% to 11.3% and a spatial resolution of ϳ5 cm. The PCX diagnostic views deeply trapped ions in a narrow pitch angle range around a mean value of v ʈ /vϭϪ0.048Ϯ10 Ϫ3 . For D-T operation, the NPA was shielded by a polyethylene-lead enclosure providing 100ϫ attenuation of ambient ␥ radiation and 14 MeV neutrons. The PCX diagnostic technique and its application on TFTR are described in detail.

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Section: Introductionmentioning

confidence: 99%

Design and operation of the pellet charge exchange diagnostic for measurement of energetic confined α particles and tritons on the Tokamak Fusion Test Reactor

Medley

Mansfield

Roquemore

et al. 1996

Review of Scientific Instruments

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“…Electron impact ionization is included in the present work but was omitted from the original calculations. 2 Electron recombination is negligible. In Eqs.…”

Section: A Description Of Charge Changing Reactionsmentioning

confidence: 99%

“…1 Fisher et al have proposed the pellet charge-exchange ͑PCX͒ method to measure the confined alpha particle energy distribution function. 2 This technique has been implemented on the Tokamak Fusion Test Reactor ͑TFTR͒ 3 and is presently the only proven method for measuring the energy distribution function of alpha particles with energies greater than 1 MeV.…”

Section: Introductionmentioning

confidence: 99%

The interaction of fast alpha particles with pellet ablation clouds

et al. 1997

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Articles you may be interested inMeasurements of the deuterium ion toroidal rotation in the DIII-D tokamak and comparison to neoclassical theorya) Phys. Plasmas 19, 056107 (2012); 10.1063/1.3694656 Local pellet based and line-integrated nonperturbing charge exchange measurements with a compact neutral particle analyzer on Large Helical Device Rev. Sci. Instrum. 77, 10F119 (2006); 10.1063/1.2336472 Modeling of beryllium deposition from a beryllium-seeded deuterium plasma J. Appl. Phys. 97, 064912 (2005); 10.1063/1.1862309 Pellet charge exchange measurements of confined alphas in deuterium-tritium plasmas (invited) (abstract) Rev. Sci. Instrum. 70, 974 (1999); 10.1063/1.1149453 Nonperturbing meaurement of energy distribution function of confined D-T fusion alpha particles in Joint European Torus plasmas using impurity induced neutralization (abstract) Rev. Sci. Instrum. 70, 932 (1999);The energy spectra of energetic confined alpha particles are being measured using the pellet charge exchange method ͓R. K. Fisher, J. S. Leffler, A. M. Howald, and P. B. Parks, Fusion Technol. 13, 536 ͑1988͔͒. The technique uses the dense ablation cloud surrounding an injected impurity pellet to neutralize a fraction of the incident alpha particles, allowing them to escape from the plasma where their energy spectrum can be measured using a neutral particle analyzer. The signal calculations given in the above-mentioned reference disregarded the effects of the alpha particles' helical Larmor orbits, which causes the alphas to make multiple passes through the cloud. Other effects such as electron ionization by plasma and ablation cloud electrons and the effect of the charge state composition of the cloud, were also neglected. This report considers these issues, reformulates the signal level calculation, and uses a Monte-Carlo approach to calculate the neutralization fractions. The possible effects of energy loss and pitch angle scattering of the alphas are also considered.

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“…Several diagnostics designed to measure confined alphas in large tokamaks were used in the TFTR experiments; namely, charge exchange recombination spectroscopy [4] microwave scattering [5], and energetic neutral particle analysis with the use of low-2 impurity pellets [6,7]. The last method, which we call Pellet Charge exchange (PCX), was operated routinely on TFTR during D-T experiments [8].…”

Section: Confined Trapped-alpha Behaviourmentioning

confidence: 99%