Precision measurement of the 1<i>s</i>Lamb shift in hydrogenlike argon

Marmar, E.S.; Rice, J.E.; Kallne, K; Källne, J.; LaVilla, R. E.

doi:10.1103/physreva.33.774

Cited by 67 publications

(38 citation statements)

References 7 publications

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“…Absolute wavelength calibration for the tangentially viewing spectrometer was obtained from the potassium Ka lines generated from a KCl fluorescence x-ray source [40]. There was no wavelength calibration for the spectrometer array viewing at +60, so for those measurements all velocities are relative to the pre-RF conditions.…”

Section: Experiments Descriptionmentioning

confidence: 99%

Observations of central toroidal rotation in ICRF heated Alcator C-Mod plasmas

et al. 1998

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IntroductionRotation plays an important role in the transition from L-to H-mode [1][2][3][4].Poloidal rotation in the edge plasma region has been closely associated with the L-H transition [5-7], and toroidal momentum confinement is well correlated with energy confinement [8-11]. While there have been several diagnostic systems designed to measure impurity toroidal rotation in tokamak plasmas [8-33], most of the observations have been made in plasmas with an external momentum source, usually provided by neutral beams. Toroidal impurity rotation in ohmic plasmas (no net momentum input) is consistent with neoclassical predictions [24,33,34]; in ohmic L-mode discharges, impurities rotate in the direction opposite to the plasma current, so in general the assumption that the majority ions and impurities (which are most often measured) rotate in the same way might be questionable [34]. In neutral beam heated plasmas, which have substantial direct momentum input, the toroidal momentum confinement time is much shorter than the neoclassical predic- Experiment DescriptionThe observations presented here were obtained from the Alcator C- Mod [35] tokamak, a compact (major radius R = 67 cm, typical minor radius of 22 cm, and Observations of Toroidal Rotation and ScalingsShown in Fig clockwise, and the solid spectrum is blue-shifted, the argon is rotating clockwise, in same direction as the plasma current during the RF pulse. This is in the direction opposite to the rotation of impurities in ohmic L-mode plasmas [8,24,33,34]. The magnitude of the shift is -. 5 mA, which yields a toroidal rotation velocity of (.5 mA/3731.1 mA) x c = 4.0 x 106 cm/s, in the co-current direction. Since the major radius of Alcator C-Mod is 67 cm, this corresponds to an angular rotation speed of 60 kRad/sec.The toroidal rotation may also be determined from the heliumlike argon forbid-4 den line. Shown in Fig.3a and 3b are spectra recorded from a spectrometer viewing the plasma mid-plane, at an angle of 60 from a major radius, in a slight counter clockwise view. The spectra of Fig.3a were obtained from a 1.1 MA discharge (clockwise current), and there is a blue-shift of .13±.01 ml during the H-mode phase (solid spectrum), when the plasma stored energy increased by .12 MJ. This corresponds to a toroidal rotation velocity increase of (.13 mA/3994.3 mX)/sin(6*)x c = 1.0 x 107 cm/s (150 kRad/sec), in the co-current direction. The spectra of Fig.3b were obtained with the same view from a 1.0 MA discharge with the plasma current in the counter clockwise direction, and there is a red-shift of .07t.01 mA during the 2.7 MW ICRF pulse, indicating that the argon is rotating in the counter clockwise direction, again co-current. This L-mode discharge had a stored energy increase of 45 kJ, when the magnitude of the toroidal rotation velocity increased by 5.3 x 106 cm/s, and still opposite to the rotation direction in ohmic discharges.The phasing of the RF antennas for this case was the same as in Fig.3a. Shown in Fig.3c are spectra recorded from a 6* clockwise ...

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Section: Experiments Descriptionmentioning

confidence: 99%

Observations of central toroidal rotation in ICRF heated Alcator C-Mod plasmas

et al. 1998

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“…Si and Al were also injected into Alcator C plasmas with a laser blow-off system. Lines from hydrogen- [33,34] and helium-like [35][36][37] charge states are taken to have well known wavelengths, either measured or calculated. Experimental wavelengths were determined by performing a least squares fit to observed spectra using gaussian line shapes; measured line widths are dominated by Doppler broadening.…”

Section: Experiments Descriptionmentioning

confidence: 99%

X-ray observations of 2l-nl' transitions and configuration-interaction effects from Kr, Mo, Nb and Zr in near neon-like charge states from tokamak plasmas

Rice

Fournier

Goetz

et al. 2000

J. Phys. B: At. Mol. Opt. Phys.

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“…X-ray spectra were recorded with a von Hamos type x-ray spectrometer [19], whose line of sight is tangent to the plasma major radius, pointing in the counter clockwise direction, as seen from above. Rotation velocities have been determined from the Doppler shifts of the argon Lyman a doublet [20] (1s 'Si. -2p 2 Pa at 3731.1 mA, and is 22 iSi -2p 2 P, at 3736.5 mA) and the 2p' -(2p-)a4dA transition [21] in Mo 3 2+ at 3739.8 mA.…”

Section: Experiments Descriptionmentioning

confidence: 99%

“…Molybdenum is an intrinsic impurity, usually present in all Alcator C-Mod discharges.. Absolute wavelength calibration was obtained from the potassium K, lines generated from a KC1 fluorescence x-ray source [20].…”

Section: Experiments Descriptionmentioning

confidence: 99%

X-ray observations of central toroidal rotation in ohmic Alcator C-Mod plasmas

et al. 1997

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Impurity toroidal rotation has been observed in the center of Alcator C-Mod ohmic plasmas from the Doppler shifts of argon and molybdenum x-ray lines. The rotation is highest (~ 6 x 106 cm/s) in the early portion of the discharges, when the loop voltage is highest and the electron density is lowest, and then typically settles to values < 2 x 106 cm/s during the steady state period. The impurity rotation is in the same direction as the electron toroidal drift, opposite to the plasma current, and reverses direction when the plasma current direction is reversed. Molybdenum and argon ions rotate with the same velocity. These observations are in qualitative agreement with neo-classical theory.

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Precision measurement of the 1sLamb shift in hydrogenlike argon

Cited by 67 publications

References 7 publications

Observations of central toroidal rotation in ICRF heated Alcator C-Mod plasmas

Observations of central toroidal rotation in ICRF heated Alcator C-Mod plasmas

X-ray observations of 2l-nl' transitions and configuration-interaction effects from Kr, Mo, Nb and Zr in near neon-like charge states from tokamak plasmas

X-ray observations of central toroidal rotation in ohmic Alcator C-Mod plasmas

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