A Method to Produce Lithium Pellets For Fueling and ELM Pacing in NSTX-U
Authors: D. Andruczyk, A.L. Roquemoroe, P Fiflis, D. Mansfield and D.N. Ruzic
Abstract:
A device has been developed that produces spherical lithium pellets for the controlled
excitation, or pacing, of ELMs and replenishing lithium coating on PFCs during a plasma
shot. The device is based on a dripper design, where the lithium is forced through a small
orifice with gas pressure. It is envisaged to use the dripper in two ways: first it is used in
conjunction with the lithium granular injector developed at PPPL for ELM pacing and the
second for replenishing lithium PFC coatings during a plasma discharge by “dripping”
liquid lithium drops into the plasma edge and vaporization will redistribute the lithium to
recoat the PFC during the shot. A theory has been developed for the drop formation and
frequency using high-pressure gas. Experiments have been performed initially with
Wood’s metal and subsequently lithium. Using Wood’s metal at a backing pressure of ΔP
> 600 torr, frequencies up to f = 1200 Hz have been achieved with droplet diameters d >
600 μm. These agree well with theory. Measurements using lithium also show that the
frequency does not quite match the theory with ΔP = 450 torr, a frequency of f = 2 kHz
and but the diameters are in good agreement with d = 0.8 mm.
__________________________________________________
Submitted to: SOFE 2013 Proeedings (June 0213) 25th Symposium on Fusion Engineering, San Francisdco, CA (June 10-14, 2013)
__________________________________________________
Download PPPL-4893 (pdf212 MB 8 pp)
__________________________________________________