P. Innocente et al., Three-dimensional time-resolved H pellet trajectory reconstruction in RFX by position sensitive detector H-alpha diagnostic, REV SCI INS, 70(1), 1999, pp. 943-946
Hydrogen pellets injected in reversed field pinches (RFPs) experience large
poloidal and toroidal accelerations along magnetic field lines due to the
rocket effect caused by asymmetric ablation processes. The 3D pellet trajec
tory and the global ablation rate is diagnosed in RFX by an absolutely cali
brated multiple position sensitive detector (PSD) system looking at the H-a
lpha radiation coming from the pellet ablation cloud. The design of the dia
gnostic is presented. Then the performance is highlighted by cross-comparis
on between different PSD measurements and with time-integrated images from
a CCD camera. Overall accuracy of the order of a few millimeters is achieve
d, which makes the instrument well-suited to assist transport studies (part
icle deposition), to estimate the radial profile of fast electron tails (de
rived from the modulus of pellet acceleration) and to obtain information on
internal magnetic field pitch (from the direction of pellet acceleration).
(C) 1999 American Institute of Physics. [S0034-6748(99)51201-X].