Abstract
Abstract
ITER diagnostics include an extensive set of
laser and microwave diagnostics to give access to a wealth of information on the
core and edge plasma and to support high performance operation of ITER. For
example, Core and Edge Thomson scattering systems build detailed density and
temperature profiles on time scales much faster than τ
E
to follow transient
events; ECE and reflectometry add time resolution to follow MHD
events. Implementing these diagnostics is challenging, needing a panoply of
technologies to keep them functioning reliably for thousands of hours despite
extreme events such as disruptions and wall conditioning cycles. Shielding,
shutters and cleaning systems protect the forward elements of most optical
systems from the build-up of deposits and damage. Still, plasma-facing mirrors
must survive laser loads and endure erosion, deposition and in-situ RF
cleaning. Calibration and monitoring systems ensure accurate and drift-free
operation. These support systems are also not straightforward and required
specific R&D. Access also drives the design: to deal with the neutron
and gamma sources yet allow maintenance of activated components, ITER uses
large, multi-purpose ports that couple otherwise distinct systems into modules
for maintenance. Machine movement requires provisions to maintain alignment and
calibration, from these port plugs, shown in figure 1, to the
accessible areas 10–50 m away. A final complication comes from the difficulty of
employing electronics near the plugs. Extensive qualification for radiation
resistance is needed. This paper examines design adaptations that ITER adopted
for its near-reactor environment, consider the lessons learnt from the ITER
design activity specifically for laser and microwave systems and lays out some
possible evolution paths for the reactor diagnostician that must follow a more
industrial approach.