Research Needs for Magnetic Fusion Energy Sciences - US Burning ...

gROuP 1a
MEaSuREMEntS FOR MaCHinE
PROtECtiOn anD baSiC COntROL
Plasma shape and position, separatrix-wall
gaps, gap between separatrices
Plasma current, q(a), q(95%)
loop voltage
Fusion power
b n = b tor (ab/i)
line-averaged electron density*
impurity and d, t influx (divertor*, & main
plasma)
surface temperature (divertor & upper plates)*
surface temperature (first wall)
Runaway electrons
halo currents
Radiated power (main plasma, X-pt & divertor)
divertor detachment indicator
(J sat , n e , t e at divertor plate)
disruption precursors (locked modes, m=2)
h/l mode indicator*
z eff (line-averaged)
n t /n d in plasma core
elms
Gas pressure (divertor & duct)
Gas composition (divertor & duct)*
dust
gROuP 1b
MEaSuREMEntS FOR
aDVanCED COntROL
neutron and a-source profile
helium density profile (core)
Plasma rotation (toroidal and
poloidal)*
current density profile (q-profile)*
electron temperature profile (core)*
electron density profile (core and
edge)*
ion temperature profile (core)*
Radiation power profile (core,
X-point & divertor)
z eff profile
helium density (divertor)*
heat deposition profile (divertor)*
ionization front position in
divertor
impurity density profiles*
neutral density between plasma
and first wall
n e of divertor plasma*
t e of divertor plasma
a-particle loss
low m/n mhd activity
sawteeth
net erosion (divertor plate)
neutron fluence
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gROuP 2
PERFORManCE
EVaLuatiOn anD PHySiCS
confined a-particles
tae modes, fishbones*
t e profile (edge)
n e , t e profiles (X-point)
t i in divertor
Plasma flow (divertor)
n t /n d /n h (edge)
n t /n d /n h (divertor)
t e fluctuations
n e fluctuations*
Radial electric field and field
fluctuations
edge turbulence
mhd activity in plasma core
Color coding: Expect performance to meet measurement requirements; maybe/maybe not; expect not to meet requirements.
Indicates at least one primary technique at risk due to mirror degradation.
* Indicates measurement for which US ITER Project has responsibility to provide a primary diagnostic.
Table 1. ITER measurements categorized by role, performance expectation, mirror risk, and US ITER Project
involvement.
Why a new burning Plasma Measurement Program?
The understanding and control of fusion plasma behavior relies on a comprehensive set of measurements.
table 1 shows the diagnostic set currently planned for iteR. a broad variety of issues
challenge designers in providing these needed measurements:
1) There are “acknowledged gaps,” i.e., cases where it is recognized that no compatible
techniques exist to measure a needed plasma parameter. an example is the lack of a qualified
technique for the measurement of lost alpha particles.
2) some presently planned iteR diagnostics are vulnerable due to potential failure of nearplasma
components. an example is degradation of plasma facing diagnostic mirrors due
to plasma-induced deposition or erosion. Failure of such “at-risk” systems could effectively
create more “gaps” in the measurement capability, leading ultimately to reduced effectiveness
of the research program. iteR measurements, indicated by brown shading in table 1, carry
this risk. it would be prudent to develop robust methods to supplement or replace “at-risk”
diagnostics.