Transcript H1Overview_ITERWS_Poster

H-1NF: The National Plasma Fusion Research Facility
B.D. Blackwell , D.G. Pretty, J.H. Harris, T.A.S.Kumar, D.R. Oliver, J. Howard, M.G. Shats, S.M. Collis,C.A. Michael and H. Punzmann
Configuration Studies
ECH plasma
The H-1 heliac is a current-free stellarator with a helical magnetic axis which twists around the machine axis (a 1m circular ring
conductor,) three times in one toroidal rotation. It is a “flexible” heliac composed almost entirely of circular coils with the
exception of the helical control winding, which also wraps around the ring conductor, in phase with the magnetic axis of the
plasma. Control of this current produces a range of rotational transform  from 1 to 1.5: (B0 =1T, r > 0.15-0.2 m), and 0.7 to 2.2
for B0 ~ 0.5 T, r > 0.1 m, allowing almost independent control of two of the three parameters: , magnetic well (–2% to +6%)
and shear in rotational transform., which can be positive (stellarator-type) negative (tokamak-like), or near zero (<0.1).
The figure shows an ECH produced plasma (200kW 28GHz
gyrotron, 2CE at 0.5T). With a 10ms pulse, and rf preionization
of ~11017m-3, a diamagnetic temperature of 100-200eV was
observed provided gas feed was carefully controlled (p < 210-6
Torr). A highly localised ionization rate was observed in the
emission from argon doping, and at higher gas fills, a peak
density in excess of 31018 was obtained, with a lower
temperature. Impurity levels, estimated by comparison of spectral
line intensities, were lower than in the rf discharges.
At 0.5 tesla, RF (20 ~150kW,  ~ cH) produces plasma in H:He and H:D mixtures at densities up to <ne> ~ 21018m-3, with
temperatures initially limited to < 50eV by low-Z impurities. ECH ( = 2ce) produces considerably higher temperatures and
centrally-peaked density profiles.
The flexibility of the heliac configuration and the precision
programmable power supplies provide an ideal environment for
studies of magnetic configuration. The main parameter varied in
this work is the helical core current ratio, kH which primarily
varies the rotational transform iota. Magnetic well and shear
also vary .
Configuration Mapping:
Electron Beam Wire Tomography
A low energy (20eV, 100nA) electron beam traces out the
magnetic geometry, and is intercepted by a rotating grid of 64
molybdenum wires, 0.15mm diameter. The data, similar to Xray
CAT scan data can be inverted to obtain images of the electron
transits, shown below in blue. The advantage of this technique is
that the exact position of the electron transit can be determined to
within <1mm, allowing the magnetic geometry of the H-1 heliac to
be precisely checked.
Magnetic Fluctuations
high temperature conditions:
H, He, D; B ~ 0.5T;
ne ~ 1e18; Te<50eV
i,e << a,
mfp >> conn
• spectrum in excess of 100kHz
• mode numbers not yet accurately
resolved, but appear low: m ~ 1- 8,
n>0
• b/B ~ 2e-5
• both broad-band and
coherent/harmonic
nature
• abrupt changes in spectrum for no
apparent reason
• some Alfvénic scaling with ne, iota
Poloidal mode number measurements
phase
Expected for
m =2
Microwave Source:
Major/minor radius
Vacuum chamber
Aspect ratio
Magnetic Field
Heating Power
by Ding-fa Zhou
14000Amp bus
conductor and cooling
(Kyoto-NIFS-ANU collab.)

28 GHz gyrotron

230 kW ~ 40ms
Point by point comparison with
computation
RF configuration scans
The density and time-evolution of RF produced plasma
varies markedly with configuration as seen here, where kH is
varied between 0 and 1.
magnitude
“bean-shaped” 20 coil Mirnov array
(Argon)
Coil number
• Phase vs poloidal angle is not simple
“fish-eye” view of corrugated ECH waveguide to H-1 on left.(H.Punzmann)
– Magnetic coords
– External to plasma
• Propagation effects
• Large amplitude variation
Density (x1018m-3 )
5 tonne support
structure
Helical
plasma
n
T

1m/0.1-0.2m
33m2 good access
5+
toroidal
1 Tesla (0.2 DC)
0.2MW 28 GHz ECH
0.3MW 6-25MHz ICH
3e18
<200eV
0.2%
2-4
Time (seconds)
12MW Pulsed Magnet Power Supply
2-4
Below is the density at 50 ms for a similar range in kH.
DC-DC Convertor/Regulator: ABB Aust. /Technocon AG
24 Pulse Rectifier: Cegelec Australia
Transformers/Reactors: TMC Australia
Switchgear: Holec Australia and A-Force Switchboards, Sydney
Consultant Engineers: Walshe & Associates, Sydney
  65
Helical
conductor
control
winding
24 pulse
rectifier
switchgear
+
11kV 3
f
permanent
harmonic filter
(11kV, 2.5MVAr)
Rotating 64 wire electron
beam tomography system
Pentagonal central support
column
Diamagnetic energy
monitor
Rotating 55 view Doppler
tomography system
  75
2kHz PWM
+
Photos: Tim Wetherell
  43
11kV ::
800V
transformer
+
H-1
800VDC
14,000A
10 ea. 1MW
DC-DC convertor
SVC switched
power factor
adjustment
1-4MVAr, 800V
critical accuracy
time window
1 second
Sudden changes in density associated with resonance at zero shear
Points are matched one by one, allowing matching of
rotational transform to better than 1 part in 104. Small
deviations from the computation can by quantified in terms
of small errors in construction ~1-2mm. Super computer
modelling allows these errors to be tracked down. In this
example, a better fit was obtained by more accurate
modelling of the vertical field coil pair.
Mostly 0-3
3-8
4-5,
4-5,
7-87-8
mode numbers related to rationals
Data Mining, Alfvénic Scaling: The figure to the left
shows Fourier fluctuation data a), and b) after data mining by SVD
analysis, grouping of SVDs by spectral content, and clustering the
groups according to phase similarity. The cluster marked with the
red lines in the lower figure exhibits scaling in rotational transform
with the shear Alfvén eigenmode frequency (although a scale factor
of 3 is unaccounted for). This is clarified by normalization to ne in
c) and the cluster is enlarged below.