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28ghz_ecrh_icc10c.pdf2010-03-16 08:04:48Paul Woskov

28 GHz Gyrotron ECRH on LDX

Author: Paul P Woskov
Requested Type: Poster Only
Submitted: 2009-12-04 14:16:05

Co-authors: J. Kesner, P. C. Michael, D. T. Garnier, M. E. Mauel

Contact Info:
167 Albany Street
Cambridge, MA   02139

Abstract Text:
A 10 kW, CW, 28 GHz gyrotron has been implement on LDX to increase the plasma density to more fully explore the potential of high beta plasma stability in a dipole magnetic configuration. This represents over a 50% increase in the 17 kW ECRH used in the past from sources at 2.45, 6.4, and 10.5 GHz. Plasma density has been observed to increased linearly with ECRH power and the added gyrotron power is expected to increase peak density to over 10^12 cm^-3. Fundamental and harmonic electron cyclotron (EC) resonance surfaces at 28 GHz span the entire plasma profile in the high magnetic field gradient regions above and below the floating coil (F-coil). The gyrotron beam is directed downward at 24^o from a horizontal axis about 1 m above the F-coil and 2 m from the dipole axis by a Vlasov antenna. The diverging linearly polarized beam illuminates the entire upper plasma region and is incident to the resonant magnetic fields at angles having a large parallel component. In this orientation absorption coupling occurs to both the elliptically polarized x and o modes. Coupling to the fundamental x-mode and upper hybrid resonance, normally cutoff from the outside can occur by reflection off the F-coil to redirect first pass unabsorbed radiation from the high field side. The presence of hot electrons ~100 keV can also cause some absorption in the lower EC harmonics. The gyrotron beam is transmitted to LDX in 32.5 mm diameter waveguide in the TE01 mode using one 90^o bend and a ~5 m straight waveguide run. A custom horizontal port was installed in the upper domed region of LDX vacuum vessel to simplify the transmission line to requiring only one bend. A water cooled resonant fused quartz vacuum window is being evaluated for eventual minute plasma operations.

Characterization: A2,A5

Please place with other Dipole Experimental Posters: Sorting order is 1) Garnier, 2) Kesner, 3) Davis, 4) Woskov, 5) Kardon, 6) Worstell, 7) Grierson.

Princeton University

Innovative Confinement Concepts Workshop
February 16-19, 2010
Princeton, New Jersey

ICC 2010