1 research outputs found
Development and first operation of a Cavity Ring Down Spectroscopy diagnostic in the negative ion source SPIDER
The Neutral Beam Injectors of the ITER experiment will rely on negative ion
sources to produce 16.7 MW beams of H/D particles accelerated at 1 MeV. The
prototype of these sources was built and is currently operated in the SPIDER
experiment (Source for the Production of Ions o Deuterium Extracted from an RF
plasma), part of the Neutral Beam Test Facility of Consorzio RFX, Padua. In
SPIDER, the H-/D- ion source is coupled to a three grids 100 kV acceleration
system. One of the main targets of the experimentation in SPIDER is to
uniformly maximize the extracted current density; to achieve this it is
important to study the density of negative ions available in proximity of the
ion acceleration system. In SPIDER, line-integrated measurements of negative
ion density are performed by a Cavity Ring Down Spectroscopy (CRDS) diagnostic.
Its principle of operation is based on the absorption of the photons of a laser
beam pulse by H-/D- photo-detachment; the absorption detection is enhanced by
trapping the laser pulse in an optical cavity, containing the absorbing medium
(i.e. negative ions). The paper presents and discusses the CRDS diagnostic
setup in SPIDER, including the first measurements of negative ion density,
correlated to the main source parameters.Comment: 5 pages, 7 figures. Contributer paper for the HTPD 2020 conference.
Accepted manuscrip