29th Symposium on Fusion Technology (SOFT 2016)

P4.158 State of the art and perspective of high-speed pellet injection technology

8 Sep 2016, 14:20

1h 40m

Foyer 2A (2nd floor), 3A (3rd floor) (Prague Congress Centre)

Board: 158

Poster H. Fuel Cycle and Breeding Blankets P4 Poster session

Speaker

Francesca Bombarda (FSN Department)

Description

The injection of cryogenic pellets from the low field side (LFS) has long been in use for core fueling of fusion devices. However, with higher plasma temperatures and bigger sizes, this technique becomes increasingly inadequate to ensure effective core particle deposition; injection from the high field side (HFS) has shown better results, despite the severe limitations imposed to the pellet speed (≤ 300 m/s) by inboard accessibility. For future burning plasma reactors, an alternative approach may be that of injecting high-speed pellets from the HFS, through suitable “free-flight” paths, eliminating curved transfer systems [1]. Furthermore, the expected length of the plasma discharges will require steady-state repetitive systems, capable of firing pellets at frequency no less than 10 Hz. ORNL and ENEA have been collaborating on high-speed injectors since 1990; they successfully realized a high-speed repeating pellet injector (2.55 km/s at 1 Hz), by combining an existing ORNL D2 piston extruder, and an ENEA two-stage gun [2]. Since then, good progress has been achieved on both fronts of steady-state extruders [3], and operation and reliability of two-stage guns [4]. A comprehensive R&D program is therefore proposed, including several innovative techniques, to investigate how far speed limits and repetition rates of combined two-stage guns and steady-state extruders technologies can be extended. Simulation results are presented to determine optimized pellet injection locations on the basis of the expected plasma parameters for future devices, either under construction such as JT60SA or being proposed. [1]   A. Frattolillo et al,. this Conference [2]   A. Frattolillo et al., Rev. Sci. Instrum. 67, 1834-1841(1996). [3]   S. J. Meitner et al., Advances in Cryogenic Engineering, AIP Conf. Proc. 1573, 1475-1482 (2014) [4]  A. Frattolillo et al., Proc. of the 42nd EPS Conf. on Plasma Physics, Lisbon, Portugal, http://ocs.ciemat.es/EPS2015PAP/pdf/P2.155.pdf, (2015).