PFC/RR-90-5
DOE/ET-51013-281
Ignitor Scale-Up Studies (DIGNITOR)*
Leslie Bromberg, P. Titus**, D. R. Cohn
Plasma Fusion Center
Massachusetts Institute of Technology
Cambridge, MA 0213-
Mnd-
C. W. Bolton
Office of Fusion Energy
U. S. Department of Energy
Germantown, Maryland
April 12,1990
*This work was supported by the U. S. Department of Energy Contract No.
DE-AC02-78ET51013. Reproduction, translation, publication, use and
disposal, in whole or part, by or for the United States government is
permitted.
**Permanent address: Stone & Webster Engineering Corporation
Abstract
An analysis of a scaled-up version of IGNITOR (to a major radius of 2.16 m)
is discussed. The design, referred to as DIGNITOR, is a direct extrapolation of
IGNITOR. The consequences from the increased size are discussed (mainly due to
decreased temperature excursions). A summary of comprehensive calculations of
the stresses (documented in an accompanying paper) are presented. The case of a
divertor plasma configuration is analyzed. The implications of a CIT-like vacuum
vessel are also discussed.
1
Introduction
The purpose of the work was to study the implications of increasing the size
of the IGNITOR device [1] to a size comparable to the CIT. We will refer to the
extrapolated device as DIGNITOR. Previous work (done for the IGNITOR design
in 1988) calculated the reactions to the Lorentz, mechanical and thermal loads of
the toroidal and poloidal field systems; fine-tuned the equilibrium; and studied the
sensitivity of the stresses to non-ideal conditions (non-zero gaps, moduli variations,
preloading variations, etc) [2]. The previous work showed that the IGNITOR
configuration was relatively robust to non-ideal conditions [2].
IGNITOR uses a magnet design (bucking and wedging) that maximizes the
magnetic field for a given coil stress level. In bucking and wedging the radial loads
of the toroidal field coil are supported by both the toroidal field coil (wedging) and
by a poloidal field coil/bucking post (bucking). In IGNITOR the wedging takes
about 30% of the radial loads and bucking takes the remaining 70%. The implane
stresses are minimized for this distribution of loads [4], although the minimum is
insensitive to distribution of the radial loads (due to the presence of the vertical
loads). The wedging, however, is necesary to support the out-of-plane loads. If
there is not enough wedging, shear carrying capacity between the turns of the
toroidal field coil would not be sufficient to support the out-of-plane loads. This
concern was addressed at length in the previous study and it was found that the
IGNITOR configuration was indeed robust to the non-ideal conditions studied.
No structural failure conditions were found. Substantial gaps (of the order of 1
mm) could be tolerated.
In this report we present results of extensive calculations of the plasma equilibria, for the scenarios indicated in Table I.
In this report only a summary of the stress calculations are presented for the
case of full current (18.5 MA). This case results in the largest loads, and backing
away from it (i.e., reducing the plasma current while holding the toroidal field
constant) will result in a more benign stress situation. Extensive details of the
stress calculations are presented in an accompanying paper [3].
2
We did not deal with the issues of the vacuum vessel and the first wall of
DIGNITOR. Instead we chose to look at a range of vacuum vessels determined from
either scaling up the IGNITOR vacuum vessel/first wall or using the CIT vacuum
vessel/first wall. We have not calculated the disruption loads for DIGNITOR.
The first column shows the parameters of CIT. The first DIGNITOR column
corresponds to a DIGNITOR plasma with 18.5 MA and with a IGNITOR-like vacuum vessel (directly scaled from the IGNITOR). The plasma current was adjusted
in order to operate at a value of q (~ 5BTa 2 K/IpR) comparable to that of CIT.
The second case corresponds to a divertor plasma, with an x-point at the location of the first wall (also with a IGNITOR-like vacuum vessel). The last column
corresponds to a divertor with a CIT-like vacuum vessel (TF-plasma gap equal to
that of CIT).
Figure 1 shows the IGNITOR geometry. We have scaled the major radius
to 2.16 m. There are large compression rings on the outer leg of the device, both
at the top and bottom. The purposes of these rings are to decrease the vertical
load of the throat and to provide sufficient hoop stresses in the region near the
top and bottom of the inner leg to react the out-of-plane shears in these regions.
There is a bucking post through the center of the OH transformer. The bucking
post supports of OH transformer and toroidal field coil when the inwardly directed
radial load of the TF solenoid is larger than the outwardly directed OH load. Also,
it is designed to carry some vertical load through a preload.
When scaling the size of the device (at constant magnetic field), the current densities (j) in the magnets scale as the inverse of the scaling constant
A =
RDIGNITOR/RIGNITOR
rate then scales as A-
2.
(in this case, A = 1.76).
The volumetric heating
For constant temperature excursions (which varies and
Jx
), then the characteristic times (start-up, flat-top, ramp-down) scale as
-r
A2 . The relative current penetration and the temperature excursions would
be the same for both IGNITOR and DIGNITOR if these scaling rules are utilized.
In this work, however, we have assumed a flat top time of 7 s, the same as
CIT. This results in much lower temperature than both CIT and IGNITOR at the
end of pulse and much lower power supply and stored energy requirements than
3
CIT. Releasing the temperature constraint can be used to the advantage of DIGNITOR power supply equipment, by decreasing the ramp-up times or increasing
the pulse length. We have, indeed, assumed slower ramp-rates than a straight
scale-up of IGNITOR (-r
-
A'). The temperature excursions of both the toroidal
and the poloidal field system, however, are still small.
In section II of this report the equilibria for a limiter and several divertor
cases are presented. Calculation of the PF scenario (temperature, energy and
power of the toroidal field and poloidal field systems) are also shown.
Section III shows the results for the electrical/thermal parameters for the
toroidal field coil.
Section IV summarizes the results from the stress calculations.
Section V extrapolates the results to other intereating regions of parameter
space, including divertor operation. Limits of pulse length, implication of a more
CIT-like vacuum vessel, and other tradeoffs will be performed parametrically in
this section.
Section VI briefly discusses some of the impacts on physics of a CIT-sized
IGNITOR.
Finally, section VII summarizes the results.
II. Equilibria and PF considerations
The equilibria that was used for the analysis of the standard DIGNITOR
plasma was scaled from the IGNITOR equilibria. The IGNITOR equilibria is
shown in Figure 2. The currents in the PF coils for DIGNITOR (with 18.5 MA
plasma current), the energy stored and dissipated, and the resistive and inductive
power and the coil temperatures are shown in Figure 3. The temperature excursions are small, with the maximum temperature in the PF coil systen (in PF1) of
125 K. The toroidal field coil and the central solenoid are started at 50 K.
The summary of the energy and power of the poloidal field system for this
case are shown in Table II. The energy and power requirements are less than those
4
for CIT.
The case of a divertor was analyzed next. We have done preliminary optimization of a divertor configuration for such a machine. However, due to the low
elongation, we have found that it is very hard to pull the x-point. The best results
that we have obtained are shown in Figure 4. The size of the coils is proportional
to the current that they carry. The current of the divertor coil (PF5) is 12.9 MA.
Figure 5 shows the PF coil temperature, the inductive and resistive PF system
power, the stored and dissipated energy and the coil temperatures. There is substantial temperature excursion of PF5. Since this coil is relatively out of the way,
it would be possible to increase its size to decrease the current density and the
temperature rise. We have not done this in this work. Substantial decreases in
the energy could be obtained by increasing the size of PF5.
The flux linkage between the PF system and the plasma has been decreased
for the divertor cases, in order to take into account the diminished plasma flux
requirements due to the lower plasma current.
We have investigated the possibility of running a divertor discharge and
accomodating a more CIT-like vacuum vessel. The main parameters are shown in
the last column of Table I. The plasma minor radius has been reduced by about
9 cm (to 0.69 m).
This would allow use of CIT vacuum vessel and gaps. The
possible need for a thicker vacuum vessel due to larger fields and currents (and
therefore, disruption loads) has not been included, since we have not calculated
the disruption loads for DIGNITOR. Any comparison with CIT should be done
cautiously.
The resulting plasma equilibrium is shown in Figure 6. The plasma current
is decreased to 15 MA, corresponding to q = 1.65. The current in the divertor coil
(PF5) has been dramatically decreased. This is because of the increased plasma
elongation.
There is a large corresponding decrease of the energy, power and
temperature excursion of the coils, as shown in Figure 7. Table II contains the
results for the divertor case.
5
III. Toroidal field coil: temperature and energy considerations
The model used to calculate the toroidal field temperature, the Lorentz loads,
the energy and the power requirements was designed such that the model nodal
points corresponds to the nodal points in the FEM analysis.
The power, energy requirements and maximum temperature for the toroidal
field coil are shown in Figure 8. The temperature excursions in the toroidal field
coil are also substantially smaller than for both IGNITOR and CIT.
In order to provide larger radial loads during the startup (when the toroidal
field coil is not fully charge but the OH transformer is), we investigated charging
the toroidal field magnet earlier. At start-up, the current in the toroidal field coil
was increased by 22%. This has the additional advantage that the toroidal field
coil is more constant during the plasma start-up phase, simplifying the plasma
heating if resonant waves are used. The net effect is an increase in temperature of
about 10 K, with a corresponding increase of TF power of about 50 MW.
IV. Stress summary
In this section, a summary of the stress calculations for DIGNITOR is presented. The full details are given in another report [3].
The stress calculations were performed for a plasma current of 18.5 MA and
a toroidal field of 12 T. Qualification of this level of operation would qualify some
family of lesser loading with the provision that OH and TF loading was either
sufficiently reduced or was matched as in the fully loaded case.
It has been suggested that the allowable for externally supported coils (such
as the ones in DIGNITOR) be 0.75 o,, where o,, is the yield stress. The yield
stress is temperature adjusted.
The maximum average stress in the TF is about 233 MPa at both beginning
of flat top (BOFT) and end of flat top (EOFT). This is slightly above 2/3 of yield
ay = 340 MPa (close to the allowable for not-confined coils). The OH coil sees
a maximum of 250 MPa average stress or 0.67 of yield (a. = 370 MPa at 60 K).
6
Again, the OH transformer is below the allowable for confined coils and close to
the allowable for not-confined coils..
In table III the limiting peak stresses are shown and are compared with yield.
The toroidal field packing fraction is 90%, while the central PF transformer
is 80%.
Like IGNITOR, DIGNITOR employs two preload mechanisms, the large
outer shrink ring and second, the center tiebolt (shown in Figure 1). The Tiebolt
also serves as a bucking post when the TF loads over-come the OH loads and
put the machine core in radial compression. DIGNITOR has benefitted from the
scale-up in terms of the lower temperatures of the coils.
Active control of the
tiebolt preload is not needed in DIGNITOR to relieve end-of-pulse compressive
stresses. The preloads assumed for the precompression systems are 90 MN for the
tiebolt load and 1600 MN for the total ring radial load.
The tiebolt produces only a small percentage of the vertical pre-compression.
The ring load is large, but radial pressures to achieve these large loads are modest, approximately 50 MPa (7 kpsi) average. This would allow for many jacking
schemes such as the wedge type jacks used in IGNITOR or freezable hydraulic
bladders.
Next the issue of fatigue of the magnets is addressed. Equivalent alternating
stresses of approximately 200 MPa have been calculated based on a proposed
multiaxial fatigue model [3]. Equivalent mean stresses were compressive and thus
will improve fatigue behavior over that predicted from a conventional R=-1 S-N
diagram. But based on this type of diagram , the number of cycles of the coils
would be over 10000 cycles. This is based on mean performance characteristics,
with reasonable credit taken for the better performance of the cold-worked coppers,
and improved liquid nitrogen fatigue life. More tests of the specific material chosen
for the coils would be appropriate to quantify the statistical uncertainty in fatigue
performance. This evaluation is exclusive of initial flaw/crack propagation effects,
and detailed fracture mechanics calculations are also needed to allow a reasonable
inspection program. These calculations have not yet been performed.
The fatigue life will be affected by microplasticity during repeated load cy-
7
cles (cyclic softening).
This has the effect of reducing the yield stress in work
hardened copper. In DIGNITOR, stresses remain within the elastic region of the
stress-strain curve throughout the machine. Cyclic softening will not be an issue
for all but the most highly stressed areas. Without detailed stress strain curves
for liquid nitrogen temperatures it is difficult to assess the possibility of noticeable
cyclic softening. The more highly stressed areas typically represent small percentages of the total coil volume and thus would behave as strain controlled regions
with constraint provided by increases in stress in low stress regions. For a tokamak design like DIGNITOR, which utilizes external structure, the effect of small
amounts of cyclic softening and creep would be to make stresses more uniformly
distributed and increase the load share taken by other regions of the coil and the
external structure. External structures will be made from materials which do not
exhibit cyclic softening.
The shear capacity of a TF inter-plate bond is a function of face compression. Based on assumed performance of insulator shear capacity, and the wedge
pressures in the TF, the calculated shear capacity is larger than the shear stress.
The minimum excess shear capacity is near zero near the intended design boundary between wedged and the the unwedged region of the TF horizontal leg. In
this region the out-of plane loads are taken by C-Clamp wedges in between the
TF legs. At the equatorial plane, at EOFT, on the plasma side of the TF, the
peak torsional shear stress is 49.8 MPa. The hoop wedge pressure is 180 MPa
and the bond strength without compression is 13.8 MPa. The shear capacity is
.3x 180+13.8=67.8 MPa. In a manner similar to the TF shear stress evaluation,
the shear stresses in the OH can be calculated and compared with the shear capacity. Typical results are shown in Table IV.
V. Discussions
In this section we summarize the work of the previous sections and speculate
about the implications of using a more CIT-like vacuum vessel.
As defined by the parameter q = 5BTa2 n/IpR), the DIGNITOR configu-
8
rations that we have analyzed have comparable q's to CIT, as shown in Table
I.
The case of the DIGNITOR small divertor plasma has comparable distance
between the plasma and the toroidal field coil and CIT. Therefore it is possible to
fit in a CIT-like vacuum vessel and first wall.
We have briefly studied the out-of-plane loading on the toroidal field coil in
the small divertor configuration of DIGNITOR (last column in Table I). This was
done to explore whether divertor operation resulted in larger shears. However,
in part because the plasma current is substantially decreased in the case of the
divertor, the induced shears are smaller in the case of the divertor that in the case
of the 18.5 MA non-diverter plasma. Since the toroidal field has been kept at 12
T, the shear capacity is not changed. Details of these calculations can be found
in the accompanying report [3].
Table V summarizes the energy, power and temperatures of the poloidal field
system for the designs shown in Table I. These numbers are substantially smaller
than those for CIT, mainly due to the increased copper coatent in the throat (for
both TF and PF systems).
The flat-top time in Table V is 7 s with the exception of the last column,
where it has been increased to 10 s. Increasing the pulse length requires additional
energy and larger temperatures at the end of the pulse (the power is mainly determined by start-up consideration). We have not calculated the stresses for the
longer pulse option. However, since the temperatures are still relatively low for
the case of the small divertor, it is expected that for moderate increments of the
flat top time the stress distribution will not change.
VI. Physics
The ignition margin based on Goldston scaling for tokamaks of similar elongation and q's is
I.M.~ B 2 a.
26
Ro. 5
where I.M. is the ignition margin (a measure of nr), B is the toroidal field, a is
9
the minor radius and R is the major radius.
In making relative comparisons between DIGNITOR and CIT, the Goldston
scaling is the most pessimistic. This is because the other scalings have possitive
toroidal field and density scaling that would be to the advantage of DIGNITOR.
To compare CIT and DIGNITOR we take the CIT-like device listed in Table
I. Using these versions of small-divertor for DIGNITOR and CIT from Table I,
DIGNITOR (with elongation of 2) would have 1.5 times larger margin than CIT.
However, the DIGNITOR transformer is capable of driving up to 18.5 MA so that
if operation at lower q or slightly larger minor radius is possible, then DIGNITOR
would have up to 1.9 times the ignition margin of CIT.
Because of the inertial cooling of the coils, the pulse length of this class of
ignition devices is limited. In CIT the flat top pulse length is limited to about 7
seconds. In DIGNITOR the flat top pulse length is about 15-20 seconds (depending
on the level of neutron power heating the magnet). For DIGNITOR, the energy
confinement time is estimated ~ 0.7 seconds. With 20 MW of heating power,
DIGNITOR is expected to be heated in about 3-4 seconds. The 10-20 seconds
flat top therefore gives adequate time to explore the ignited domain. We have
not calculated the stress distribution in DIGNITOR for the case of longer pulse
lengths.
VII. Conclusions
This work has studied the possibility of using the IGNITOR magnet configuration for a CIT-size device. We have not found any failure mechanism due to
non-ideal behaviour for the magnet. The stresses in the toroidal field coil are below
yield and below the allowables for a fully confined coil. The shear carrying capacity is sufficient for a performance level of the insulation and bonding strength
consistent with that proposed for CIT. And the low temperature excursions of
the coil remove the need for dynamically loading of the tiebolt. The result is a
machine with at least 50% more ignition margin, lower power supply and stored
energy requirements, longer pulse length (up to 20 seconds at full field), sufficient
number of pulses and appropriate diagnostic access.
1~
References
[1] "IGNITOR PROJECT: Phase I Design Report", EURATOM-ENEA Association on Fusion Research, Centro Ricerche Energia Frascati, Jan 1989
[2] P.H. Titus and A. Deluzio, "Structural Analysis of the IGNITOR Reactor:
Investigation of the Structural Characteristics and Material Property Sensitivity Studies for In-Plane and Out-of-Plane Loads Analysis", MIT Report
PTP-89/15 (October, 1988)
[3] P.H. Titus et al., "Structural Analysis of the DIGNITOR Reactor," MIT
Plasma Fusion Report, to be published.
[4] D.B. Montgomery, J. Chen and H. Becker, "Structural Support and Conductor
Configurations for CIT", CIT Engineering Report G-870810-PPL-01-ER.
11
Table I
Scaled Ignitor (Jan, 1989) by 1.76 (linear dimension)
CIT
DIGNITOR
DIGNITOR
DIGNITOR
(large
divertor)
(small
divertor)
Major radius (m)
2.16
2.16
2.16
2.16
Minor radius (m)
0.66
0.78-0.80
0.78-0.80
0.69
Toroidal field (T)
10
12
12
12
Plasma current (MA)
12
18.5
16.4
15.1
2(95%)
1.8
1.6(95%)
1.85(95%)
q (5BTa It/IR)
1.68
1.64
1.65
1.62
flat top (pulse length) (s)
7
7
7
7
7
20
20
20
0.17
0.081
0.081
0.17
0.37x 1.02
0.47x 1.4
Elongation
2
max flat top t (s)
TF-plasma gap (m)
Port size (m xm)
t Determined by maximum temperature excursion.
12
Table II
DIGNITOR PF SYSTEM PARAMETERS
Large
Small
Divertor
Divertor
16.4 MA
15.1 MA
18.5 MA
Time of Max. Energy (s)
19.3
27.7
19.3
Stored Energy (MJ)
1634
1165
1305
Dissipated Energy (MJ)
2394
1084
1280
Total Energy (MJ)
4028
2250
2585
Max. Stored Energy (MJ)
1634
1421
2430
Max. Dissipated Energy (MJ)
3646
1375
1690
Time of Peak Power (s)
12.3
20.7
5.4
Magnetic Power (MW)
530
225
615
Resistive Power (MW)
156
70
82
Peak Power (MW)
686
295
605
Start-Up Flux (V-s)
35.5
35.5
47.6
EOFT Flux (V-s)
-41.6
-41.6
-43.2
Limiter
Maximum Energy Stored and Dissipated
Peak Power
Flux Swing
13
Table I
Scaled Ignitor (Jan, 1989) by 1.76 (linear dimension)
CIT
DIGNITOR
DIGNITOR
DIGNITOR
(large
divertor)
(small
divertor)
Major radius (m)
2.16
2.16
2.16
2.16
Minor radius (m)
0.66
0.78-0.80
0.78-0.80
0.69
Toroidal field (T)
10
12
12
12
Plasma current (MA)
12
18.5
16.4
15.1
2(95%)
1.8
1.6(95%)
1.85(95%)
1.68
1.64
1.65
1.62
7
7
7
7
5
20
20
20
0.17
0.081
0.081
0.17
0.37x 1.02
0.47x 1.4
Elongation
q (5BTaIIpR)
flat top (pulse length) (s)
max flat top I (s)
TF-plasma gap (m)
Port size (m xm)
t Determined by maximum temperature excursion.
13 a
Table III
DIGNITOR Stress Levels Evaluated With Respect to Yield
Time
Location
Von Mises
Temp
Stress
Yield
F.S
Stress
Based on
Yield
PRECHARGE
EOFT
OH I.D. (PF1)
(K)
(MPa)
300
58.9
374
1.25
284
95
367
1.29
212
167
335
1.58
TF Nose
Equatorial Plane
EOFT
(MPa)
TF Plasma Side
Equatorial Plane
14
Table IV
DIGNITOR OH Shears Stress Levels Evaluated With Respect
Shear Carrying Capability
Time
Location
Total
Inter-pancake
Shear
Shear capacity
(MPa)
(MPa)
BOFT
TI Top
12
21.6
BOFT
T1 Mid Height
25.57
46.8
EOFT
TI Mid Height
29.7
48.3
EOFT
TI Equator
31
49.8
15
Table V
Power, energy and temperature for several
DIGNITOR plasmas scenarios
limiter
large
small
small
divertor
divertor
divertor
7
7
7
10
18.5
16.4
15.1
15.1
pre-start up
650
400
400
400
end of start up
550
650
470
470
PF energy (GJ)
2.6
4.0
1.95
2.5
PF peak temperature (K)
125
360(PF5)
115
155
TF power (MW)
450
450
450
450
TF energy (GJ)
6.2
6.2
6.2
6.9
TF temperature (K)
180
180
180
190
Flat top (s)
Plasma current (MA)
PF power (MW)
16
RZW1. 062
4n.W 3
R1 110 59
R1649.
7
F2
S2
i
Lm-40IN
-'FIF
*SM4TF 33
A5 3
I
si
"I .~n
2
L
PLASMA
L.
eq
0 11611or
0 oa.e boundary
Fig 1
1 bound.ary
11005
viewIGNITOR
of
1Elevation
Fig
Elevation view of IGNITOR
design; from reference [1]
17
~FaI. :.020
-4
14A4
-0.000
I (Not 0.000
: ("a).c0.s
$S
..,:
NAI- -S.:90
I m-1.850
I(MAI -10.000
Ip
--
- -
- -
-
= 12MA
- -
1
(NM1 -10.000
I lMA)
-1.850
I NAl - 0.000
i
I
I (MAI0.8s
I (Al
. a. 000
I IMRI -1.020
Fig 2
IGNITOR Equilibria, high
beta.
18
-a-.
190
F
----.--3--
2500
PF Total
.- PFI,U+L
PF2,U+L
I
I
II
1.0
P 3,U+L
4,U+L
7,U+L
56U+L
7,U+L
-
2000
0.5
C.,
1500
i
-I
0.0
-..
.7
I-
1000
--
42
4z
500
A,-
-
I-/
-
0
5
PF2,U+L
sPF5,U+L
-4-PF6,U+L
-7-
"-A*-v
I
15
Time (a)
10
PF otal
PFI,U+L
--
-PF3,U+L
PF4,U+L
-4--
-0.5
1
0
-
--
---
I
-5001
---
20
25
-1.0
30
0
5
10
15
PF7,U+L
20
25
30
Time (s)
140
I
PF
- ..-PFIU
PF2,U
-4-PFZU
- -s- -PF3,U
*,
--
---
7-7---
-
-
PF4,U
PF7,U
- *-
10
-- -
- ----
+
-
.-
-
s
.
PF 6,U
PF 7,U
-- 4-
120
IU
PF;2,U
PF:3,U
PF~4,U
PF 5,U
4--
-7-
U
,-
100 I-
z
CU
S
.
0
13
.
96,
0
5-
4
-~
80
U-
-10
9-
-
--
60
4-
40
-20
0
5
10
15
20
25
30
0
5
15
20
Time (s)
Time (s)
Fig 3
10
Total energy, total power,
coil currents and coil
temperature for DIGNITOR.
18.5 MA, high beta.
19
25
30
500
480
460
*.(cm)
=215 96
-(cm)
= 80 32"
- 12.0
- 16 44.
Beta(%) - 1.77
q(axis) - 0 948(0)
-p(MA)
440
420
400
380
360
q(edge) -
2 44
Kappa
-
Delta
li/2
a
-
1.57
0.3r
0.3L
Beta pals 0.22
Rx(cM) =167 62
Zx(cm) =143.79
Flux(Vs)u 42 05
340
320
300
280
260
00
240
220
00-
-0
0
200
180
160
140
-0
000
aoc
aoc
120
100
60
40
e8P
was
20
0
aa
a
a
Fig 4
a
a
a
a
a
a
a
a
Equilibria for DIGNITOR
with divertor.
16.4 MA plasma current
20
a
a
a
a
a
aa
I
C
C
0
0
C.,
C
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(v1q) SI 3HI
21
MHOO Jd
0 04)O
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500
Re(cre)
a(cm)
3215.97
= 68.811
460
8(0)
-
440
lp(MA)
1
t5.00J
57
ete(%) 0.96
q(axis) q(edqe) 2.54
a 1.86
Kappa
Delta
a
-3
0.33
Ii/2
480
420
400
380
360
12.00-
Seto pais 0 21
Rx(cM) =168.00~
340
320
-
300
Zx(cm)
iFlux(Vs)=
=144 0042.01_
280
260
00 a
240
00
220
0
000/
200
180
160
140
0
0
age
ees
ese
120
100
80
60
00
00
was
-,,
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40
was
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U,.
wa,
.
I
UB
20
0
a
CD
a3
S
CO C3
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0
a
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a
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w~s a
ce*
a
a
0
C3 a
10
0
a
a
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a2
10
a a
40
Fig 6 Equilibria for small divertor
in DIGNITOR.
15.1 MA plasma
current
22
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a
r4
a3 a
s
10
C3
a
3
j
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71
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to 0
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Sn
o00
S
(r)q) JUJOU3
23
xv'
Sn
I
0
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I
(VW) S.N3H~Efl3 1103 Ad
Sn
-
I
0
N
i't-4
0)
00
I'
C2
)
C
- ....-
I
....
.1
6 - -----------------------------------------------------
-------------------- --- ------------------------------ ..........
- --------- _------------- ---------- -
- ----------------------------------------------
- ------------- -----4 - ------------ ----------- ..... ...................
-----------------------------------------------------
...... ......
:3
Cf)
C3
3 - ------------- ----------- ....................... ------------ ......
W
CO
2 - ------------- ----- ----------- ------------------ ------------ ..........
0
(r
Uj
z
Uj
......
........................... -----------
Cr
Uj
3.
a.
__j
cc
CD
2 - --------------I----------- --------------------- --------------------------
--------- -----------------
......... ................................
- ------------- ----------- .................. ................. ...........
-------------- _---
10
10
0.
0.
10
1.0
1.5
T -me (5ec)
2.0
0.
2.5
1.80 7 t
0.
i e
t 1
1.0
10
-----------------
1.60
2.0
(Secl
.. . .. ..........
? 1- !e
1!
t - 1-
......................... .............. ........
1 .70
1.5
Time
----------
---- ---------- - -------------
1 .50 7 ............ ........... ............ .. .....
---
---------- ............
cc I . 40 7 ------------------------------- .... ............... ....................
cc
-----------------.................................
W 1.30
------------I
CL
---------------
1.20
1.
------- -- --------- I----- _
----------
10
---------
CX 1.00
---------
.......
.........
------- ---------
..............
90
.70
0
........... -- -------.....
-----------
----------- -------------------- _
----------------------------------11
1
1
10
..........
I I I .
1.0
T me
Fig 8
----------- --------------------------------
------------
I?
---- ------------ ..........
I
1.5
2.0
2.5
( sec I
Total energy, total power
and maximum temperature
of TF coil.
12 T field at 2.1 m.
24
2.5