A. Frattolillo et al., Acceleration of large size deuterium pellets to high speeds using a small two-stage pneumatic gun, REV SCI INS, 70(5), 1999, pp. 2355-2364
The technology of two-stage pneumatic pellet injectors represents by far th
e most reliable way to perform deep plasma fueling, with pipe gun devices c
apable of routinely launching small or medium size (up to 4 mm) D-2 pellets
at speeds in excess of 3 km/s, using rather small two-stage guns. It is st
ill an open question, however, if scaling of the pellet size to the Interna
tional Thermonuclear Experimental Reactor relevant values (6-8 mm) will or
will not require a somewhat proportional increase in the physical size of t
he two-stage gun. In order to investigate this question, an extensive study
was carried out at ENEA Frascati, using numerical simulation codes. It cle
arly indicated that a "compact'' two-stage gun may have the potential to ac
celerate large size pellets at speeds up to 5 km/s. A low cost experiment w
as also scheduled. A spare pipe-gun cryostat of the single-shot two-stage p
neumatic injector, previously used for high-speed pellet fueling of the Fra
scati tokamak upgrade, was modified in order to accommodate larger bore (up
to 6 mm) launching barrels. In this article, we will mainly discuss the re
sults of numerical simulations. A very early experimental campaign, carried
out in 1996, will also be briefly reported, during which intact 6 mm D-2 p
ellets were launched at speeds up to 2.5 km/s. (C) 1999 American Institute
of Physics. [S0034-6748(99)01105-3].