J. Plasma Fusion Res. SERIES, Vol.4 (2001) 138-145

Static and Dynamic Behaviors of Detached Plasmas inDivertor Simulator NAGDIS-||TAKAMURA S.*, OHNO N., UESUGI Y.', NISHUIMA D., OHSUMI K., MOTOYAMA M.,
HATTORI N., EZUMI N.2, KRASHENINNIKOV S.3, PIGAROV A.3 ANd WENZEL U.4
Department of Energy Engineeing and Science, Graduate School of Engineering,tCenterfor Integrated Research in Science and Engineering, Nagoya University, Nagoya 464-860j, Japan
2Nagano National College of Technology, Nagano 381-8550, Japan3(Jniversity of Califurnia at San Diego, La Jolla, Calffornia 92093-0411, USA
aMax-Planck-Institut

fiir Plasmaphysik, EUMTOM Association, D-1011 Berlin, Germany(Received: 5 December 2000 / Accepted: 18 August 2001)

Abstract
Comprehensive investigations on the stationary behaviors in detached recombining plasmas in thelinear divertor plasma simulator, NAGDIS-II, are summarized in relation to the phenomena observed intokamaks with magnetic divertor. Structural dynamics due to injection of ELM-like plasma heat pulse
produced by whistler wave heating into the detached helium plasma have been clarified in terms ofquenching of plasma recombination, transport of plasma heat and particles, and recovery ofrecombination. Several time scales and specific energies are proposed to characterize the impact ofELM
on the detached recombining plasmas and to understand the underlying physics. The identification oforigin of the so-called inverse ELM and the role of highly excited Rydberg atoms are summarized.

Keywords:
structural dynamics, plasma detachment, recombining plasma, edge localized mode, divertor

stationary characteristics of plasma detachment t2-lll.
Recently, we are focusing our research on the dynamic
behaviors of detached recombining plasmas against

1. lntroduction
The plasma detachment is a key concept to solve
heat and particle control in magnetically confined fusion
experimental reactors. It should be realized together
with a good core confinement. The ELM (Edge
Localized Mode) heat pulse associated with the good

ELM-like plasma heat pulses generated by radiofrequency plasma heating ll2,l3l, in which thetransitions from detached to attached plasma or fromrecombining to ionizing plasmas and vice versa havebeen identified. Enhanced ionization of highly excitedconfinement should be tolerable in terms of criticalpulse energy depending on the target material.
Compatibility of plasma detachment with the good
confinement of high density plasma and a mitigation of

atoms generated by plasma recombination was found to

make a prompt ion flux to the target. The so-called

inverse ELM observed in diverted tokamaks was
explained with collisional radiative atomic model of

ELM energy deposition is one of urgent issues to solve
for a future successful realization of fusion experimental

recombining as well as ionizing plasmas.
In this work, we would like to focus on the detailed

reactors [1].
The divertor plasma simulator NAGDIS-II has been
providing a lot of basic knowledge concerning the*C o rr e sp ondin g autho r' s e - mail : t akamura @ nue e. na g oy a - u. a c.j p

138@2001 by The Japan Society of Plasma
Science and Nuclear Fusion Research

Takamura S. et aI., Static and Dynamic Behaviors of Detached Plasmas in Divertor Simulator NAGDIS-II

description of what is going on when injecting ELMlike heat pulse into the detached recombining plasmas.

because the electron-ion energy coupling is essential for

Especially, structural dynamics along the magnetic fieldcharge exchange with neutrals. Such a density thresholdthe electron cooling since the ion energy is lost throughline is the main concern in terms of quenching ofplasma recombination, transport of plasma heat andparticles to the target and recovery of recombination.
Several time scales and characteristic energies areproposed to characterize the ELM impacts on thewas confirmed by using 2-D fluid 82 code to calculate
the field aligned structure [2]. A strong anomaly of
single Langmuir probe characteristics observed indetached low-temperature plasmas was reported to give
us a considerably high Z" compared with the value
determined spectroscopically. The reason has been
discussed in terms of I" gradient along the B field
associated with the parallel electron transport [5].

detached recombining plasmas. They are also keys tounderstand the underlying physics. The interesting
response against a train of many short pulses is also

Detailed evaluation of Z" and n" of detachedrecombining plasmas by two different spectroscopic

represented.

2. Stationary Behaviors

methods, using continuum emission and a series of line

The NAGDIS-II device [2-13] shown schemaricallyemission from highly excited levels was carried out,
showing a typical roll-over of n" with increase in gas

in Fig. I has a vacuum chamber of 2.5 m in length and0.18 m in diameter with the magnetic field intensity up
to 2.5 kG. The neutral gas pressure in the plasma test
region can be controlled from I to 30 mtorr to rcalize
attached as well as detached plasmas by feeding apressure and a subsequent decrease, observed in divertor
plasmas of tokamaks 1]. The different evaluation of Z"[

was discussed based on the presence of energetic
electrons. All the above studies concern the plasma

secondary gas and/or changing the pumping speed neardetachment due to electron-ion recombination (EIR)
including three-body and radiative recombinations.

the target plate. Fast scanning probes to measure theplasma parameters are installed at X = 0.25 m

Another recombination process associated with(entrance), 1.06 m (upstream), 1.39 m (midstream) and1.72 m (downstream) from the plasma emanating anodemolecular reactions, that is, molecular activatedrecombination (MAR) involving a vibrationally excitedwith its aperture of 24 mm in diameter. The ion fluxhydrogen molecule such as H2(v) + e -+ H- + H
followed by H- + A* -+ H + A, and Hr(v) + A* -+(AH)* + H followed by (AH)+ + e -+ A + H, where A+
and A are the hydrogen helium or other impurity ion

under only detached conditions and the floating voltage
are measured at the target plate located at X = 2.05 m.

Spectra of light emissions are detected at the above
three locations. This device can generate high density
plasma r4e up to 1020 m-3 for He and 10le m-3 for H inand atom, respectively existing in divertor plasmas, waspointed out in theory and modelling tl4-161. MAR was

steady state relevant to the divertor plasmas in fusion

clearly observed for the first time in NAGDIS-II [6].

devices. The electron temperature Q is ranged from 5 toHydrogen gas puffing into a He plasma strongly reduced
the ion flux along the B field, although the conventional

l0 eV.
The discharge current of 80 A produces He plasma

EIR was quenched. Careful comparison of the observed
He Balmer spectra with collisional radiative (CR)with n" = 4.0 x lOle m-3 and Z" - 8.5 eV at the entrance.

At an increased He neutral pressure P11" of 6.5 mtorr, theatomic molecular data indicates that the enhanced
population distribution over the atomic levels withrelatively low principal quantum numbers can be well
explained by taking the MAR into account. Structuraldifference of detached plasma between EIR and MAR
was identified in the modellingl4,Tl and experiment [8]in helium/hydrogen mixture plasmas. MAR in purehydrogen plasma was discussed for a necessary plasma
condition to obtain plasma detachment through MAR or

plasma detachment just starts. In the pure He plasmas, aminimum density to have a detachment is identified [3]entrance
X-Om 0.25m

up

mid

down

1.06m

1.39m

1,72m 2.05m

Plasma T*

EIR in tokamak divertor conditions [10].

TargetPlate

Recent experiments show a coexistence of He andhydrogen Balmer series spectra indicating EIR rootwhen a small amount of H, gas was introduced into theFig. 1 Schematic configuration of divertor simulator
NAGDIS-II.

He plasma [17,18]. When more H, gas is introduced andr39

Takamura S. et al.. Static and Dynamic Behaviors of Detached Plasmas in Divertor Simulator NAGDIS-I

the partial hydrogen gas pressure exceeds a criticallevel, both continuum and series of line emission
disappear, that is, EIR does not occur at all in theplasma, suggesting a transition to MAR [6]. Therefore,
we can identify the boundary for EIR-MAR transition in
the parameter space of He plasma density and H2 gas
injection rate.

parameters as follows: ?s1y is the ELM pulse duration;f,coNv = Ll(aC) or LzlD whete s-0.2 is the convection

3. Dynamic Behavior of Plasma Detachment

Table I, we have four categories. In the first casetime for the upstream plasma to flow into therecombining region with the chracteristic scale of L, Cg

is the sound speed and D is the parallel diffusion
coefficient. Es1p,a is the total ELM energy for each pulse;
EqurNcH is the energy necessary for perfect quenching ofrecombination in the recombining region' According to

3.1 Background
First of all, we remind you the importance of ELMlike heat pulse in view of the erosion of divertor target

Wun = 12 -l7lfiilt t 7"-'*rr-

plate in steady state fusion experimental reactor. Figure

2 shows a schematic of the ELM energy transport
through SOL (Scrape-off Layer) and detachedrecombining plasma onto the divertor target plate. There
have been strong worries about the tolerance of ELM

energy into the divertor plate made of graphite ortungsten [19]. We have to know what happens in the

I Energr? I DepositionWidth?
I Duration ? I Frcquency ?
I Conduction or Convection ?

ELM transport through SOL and divertor plasma. Timedependent analysis with proper atomic physics isnecessary, taking conductive and convective transport

PlasmaFig.2 ELM energy transport across the separatrix,
through SOL and detached plasma, finally onto

into account.

the divertor target plate.

3.2 Generation of Heat Pulse
The rf heating has been employed to generate theelectron heat pulse. The antenna consists of 25 cm x 2

t2(a)folded bar along the magnetic field, driven with thefrequency of 13.56 MHz located between ion andelectron cyclotron frequencies, corresponding to thefrequency range of whistler wave. Figure I gives a

fi

J-3

"'-'.r.,j ii{zschematic of experimental configuration. Figure 3(a)shows the results of 82 fluid simulation on the field-

2Laligned structure of He plasma density n" andB2 P = l0mTorr\i0temperature 2". The e-i collisional damping of the wave
is so strong as shown in Fig. 3(b) that the wave energy
may be completely absorbed in a very low temperature

10

.4

I

8_
6a
4fi
2
0

12

i- 10

high-density recombining plasma. Some direct

(b)

Tr

acceleration of electrons by the antenna near field along
the magnetic field would have an effect on thephenomena.

&6bo

The employed heat pulse may have a very similar
character to the real ELM heat pulse coming from theelectron heat conduction rather than the convection of=,plasma through SOL.

Wave Dampingoo'

Axial Position [m]3.3 Categorization of Heat Pulse
Here we would try to give a categoization of ELM

Fig. 3 (a) Field-aligned structure of detached plasma

according to the pulse duration time and the totalenergy, as shown in Table I. We define the basic

obtained by 82 fluid simulation and (b) spatial
profile of wave damping rate.

140

Takamura S. et al., Static and Dynamic Behaviors of Detached Plasmas in Divertor Simulator NAGDIS-II

corresponding to top-left cell, we have a partial
quenching of EIR due to an insufficient energy,
followed by a convection of upstream warm plasma
after ELM event due to short pulse duration comparedrecombining plasma is discussed. Figure 4 shows some
responses of He Balmer series emissions He(23p-n3D) tothe heat pulse with ?p11q of 50 ps and ppp of 200 W at

the He gas pressure P"" of 9 mtorr, where a welldetached He plasma is formed without heat pulse.

with r.o*y, and finally a slow recovery of EIR. This
would be the case in the present experiment. We will
come back again to this categorization after having

Careful look at the time evolutions of Balmer series
emissions suggests an apparent temporal development as

explained the main results.

follows: During the heat pulse the intensities mainly
determined by recombining component go down

3.4 Structural Dynamics of Divertor plasma

indicating a weakening of recombination. They retain

In the following, a structural dynamics of detached1.4

while. However, large reductions follow, having
minimums at / = 0.18 - 2.20 ms. It seemed to us that----ltx
.il:

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1.0

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the target during pulse

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S{)l" emrur dtrcei to fbe t8rg4

dptrgpob€
starts

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llet coduetfrxr oIELM &Downstream

,2

1.2

e

* Rydberg atoms play a role just at the beginning of heat pulse.t .r2

7.

recombining to ionizing+ o followed by slow convection
after pulse- . Recovery of EIR (Recombining)

upstr€m wam plasmat.^s. Complete transition fromduring ELM

&r ri
;:

Heat conduction of ELM energy= . dir€ct
to

Tcoo"

,b-.

lil!*x

a-

i:.'.
iii:

t2 .tw
ile
'
'i8

:

ti.

tP-3iD):(a) H

it#trr

Enu > Eou"n"l(Perfect Quenching of EIR)(Partial Quenching of EIR)

i

tit

.:

ir^ir
tX&

0.2

Table I Classification of ELM.
Erru < Equ"n"h

lia
j:

tll

0.4 r

0.8

PgsfmTorrl.Fr9o*,0.8 -ir:t.

the level or tend to come back to the original level for a

I
a'

;
:

'l

:

r

g"*q D)
0
0.1

tr

2 -zt

a'

tr)

>-

a'

!,

a

-30

:
:

0.2

N

0

03

Time [msJ

Fig. 4 Partial quenching of recombination and apparent

0.1 A.2 0.3
Time [ms]0.4

Fig. 5 Response of ion saturation current and floating"reheating" in detached plasma, viewed throughpotential detected with Langmuir probe to the

He Balmer series emissions.

heat pulse.

t4l

Takamura S. et al., St^tic and Dynamic Behaviors of Detached Plasmas in Divertor Simulator NAGDIS-II

is well represented by V1 measurements at several
locations along the field line, as shown in Fig. 6' insuch great reductions come from a kind of plasma

heating, which we call "reheating" phenomenon.

which the timings of Vs minimum is really delayed as"Reheating" is also detected in somewhat different waysby the floating potential V6 measurement with aLangmuir probe as shown in Fig. 5. A drop of Vp usually

the location approaches the target. Figure 5 also shows aslow increase in ion flux to the probe, indicating aplasma flow into the recombining region so that themeans a heating of plasma or an appearance of energetic

electrons at this probe location. The minimums of Vi
appear at t = 0.12 - 0.15 ms, that is, 50 - 80 ps earlier
than those of line emissions. A real "reheating" is very
difficult to be explained by, for example, a long
confinement of hot electrons or a transport of heatedplasma along the B field. Finally, we found that the
upstream warm plasma flows into the recombining
region to compensate a partial quenching of plasma

mystery of "reheating" is now supposed to be resolved.
After the "reheating", a slow recovery of plasma

recombination due to heat pulse. The time evolutions of
Vs and emission intensities are different because theplasma density is so low that their influence appear
drastically because their flux could be comparable to or
greater than the ion flux.

recombination takes place in the time scale of 0.5 to 1.0
ms.

Fieure 7 shows a schematic of structural dynamics
a""ordilng to the heat pulse. We note that a sharp drop of
V1 during rf heat pulse comes from the arrival of suprathermal electrons to the recombining region where theformer is determined by the balance of ion and electron

flux to the probe, and the latter is done by the balance of

3.5 Response to Heat Pulse Train
A series of heat pulse with each duration of only 20
ps and the rf power of 200 W, and at a rather fast
repetition of 10 kHz was injected into the originallydetached recombining plasma. The responses ofemission intensities, ion flux to the probe and floating
potential are shown in Figs. 8, 9 and 10, respectively.

ionizing and recombining components in CR processes.
The idea standing for the transport of upstream plasma

Floating Potential-8-12

We note that the probes were moving during the pulse
injection (6 mm/4 ms). That is the reason why the ion
flux and floating potential without rf are apparently
changing in time. Even a short pulse destroys gradually
the plasma recombination, introducing the upstream
warm plasma into the downstream recombining region.
increasing the ion flux and decreasing % there although
there are only little effects on the upstream plasma.
During the whole pulse train, the ion flux and Vp havequasi steady values in about 1.0 ms. After the pulse train
the recovery of them takes a time of 0.4 - 0.5 ms- The

F -ro
-20
-24

Time [mslFig. 6 Transport of upstream warm plasma into therecombining region to compensate the partial

quenching.

convection of Recombining Region
warm plasma
Cloud of Rydberg stoms
Frrduenching
RF antenna

Energetic electrons

(9

g
t'{

Absorption of RF wave

TFig. 7 Structural dynamics of detached plasma along the magnetic field when the heat pulse is injected.

r42

Takamura S. et al., Static and Dynamic Behaviors of Detached Plasmas in Divertor Simulator NAGDIS-il

Pg=9mTorr, PrF20OW l)ownstream

t.2

,a)

I
=
6 0.8

["'

0.6

I

0.4

(E

ti
li

r

L

physics point of view, the population on the lowquantum pricipal numbers make a quick transition
between recombining and ionizing, while those on
highly excited levels are influenced more by therecombining component. It means that the highly
excited levels are occupied by the recombining
component during an initial inflow of upstream warmIilililil1 ilililil

0.2
G'
(D
!{|

\

t-t^-

rA

tr
q)

-33n:1emission intensities from low excited levels (n = 3 and4) have a relatively short time constant of O.2 - 0.3 ms
as shown in Fig. 8(a), while those with high excitedlevels (r = 5 through 8) shown in Fig. 8(b) have a long
characteristic time of about 0.6 ms. From the atomic-z3P< 3D;t

1.2

I

plasmas. Slow recovery of recombination after the pulse

train comes from slow cooling and recombination rates.

zo 0.8

3.6 Other Dynamic Behaviors

0.6

A fairly strong heat pulse with P,r = 2 kW and thepulse width of 0.5 ms makes a transition fromrecombining to ionizing during the pulse and then aback-transition from ionizing to recombining. These

o.4
0.2

transitions are characterized by the so called negatively

Time [mslpeaked double inverse ELM observed in tokamaks with

Fig. 8 Responses of He Balmer series emissions to theheat pulse train.

30

t ,streen-16

qF frr

a0

(a)

N

q20

RF. o\

hrhil
\

ttl
FI

;10

g8

F

74 d

.F6

.a

l,til'-ur'l !!'FTr-.rlA ltr

r

\

f-{

2
0

h

.-*inlFffi

Fonlllliltl llilfltl
a8
L- ,., Rtr' )ff(Drrrcw 6tretm-t2b) Dow ltlrculll

on..

RF ol

-24 at ftilr1

lililtr llllilill

0
10 -[

#
#,
(a)ur strermt:

RF rff-idivertor 120,211. The physical origin was explained with

Ffrbt,

Eli

L

rh

-16

f -24

RF offlililrilt ltililill

rtflrl{{

-:i

f-*

0

Time [msllonlllillrl lilililtl

-24

0r234

"t, -ir' ffi
tq

3

4

Tine [mslFis. 10 Responses of floating potential of Langmuirprobe to the heat pulse train.

Fig. 9 Responses of ion current to the heat pulse train.

r43

Takamura S. et al., Static and Dynamic Behaviors of Detached Plasmas in Divertor Simulator NAGDIS-II

0-10

to the target show similar behaviors, which means thatthe electron impact excitation and ionization from the

0.03
d

-20
F -30

ground state are increased due to the energetic electrons
produced by the rf heating. The floating voltage also
starts to drop at / = 0.06 ms, see Fig. l1(c). The prompt
increase of the ion flux at the beginning of rf pulse,

ont <

= -40
>

%

0.01 E

-50
-60

-c)

however, can not be explained by the electron imapct
excitation from the ground state. A strong candidate forpossible explanation is that highly excited Rydberg
atoms produced by EIR are ionized by the energetic
electrons because the ionization cross section of He
atoms in highly excited levels was found to to be quite
large. Such Rydberg atoms play an important role in the
net recombination, which could be related to the rapid
increase of the ion flux to the target, a negative spike
tl7,18l or quiet behavior in the emission intensities and

IE

4. Conclusion

0

10

0.02

0
-10

Zao

o.ol

€

>* -30

0

40
-t2

0

4 EE
€aE

-16

-t -zo

* -2t

, #E

-ze

a delayed drop in V1.

Hts]

32

We have performed comprehensive investigationon the static as well as dynamic behaviors in detachedrecombining plasmas in the linear divertor plasma
simulator, NAGDIS-II. For the stationary plasma
detachment, contribution of MAR and EIR to the plasma
detachment and a EIR-MAR transition were introduced

0
102

:4
.t)

G'

6l-

h
10r a

E

q)

rd2
{)
100

€l
X

?0

by showing the key references.
We focus on the dynamic behaviors of detachedrecombining plasmas under the ELM-like heat pulse
irradiation. Structural dynamics have been discussed
basing on the experimental observations in terms ofquenching of plasma recombination, compensating flowof upstream warm plasma into the recombining region.
and recovery of recombination. Dynamic behaviors
associated by the transition between recombining andionizing plasmas was also identified. Heat pulses are
categorized due to the heat pulse duration and the total
pulse energy, in which several characteristic time scales
and energies are defined. The role of highly excited

€€)
N
cl

F

0.2 0.4

Time [ms]

0-l
0.6

z

Fig. 11 Dynamic behaviors of ion currents and floating

potential at the upstream, downstream and theend plate. He Balmer series emissions at
downstream are also shown.

a CR model [12]. Such an ELM corresponds to thebottom-right cell of Table I. Under the same heat pulse
condition, we observed that the ion flux to the target
plate increased very quickly to be about seven times aslarge as the value before the heat pulse as shown in
Figs. ll(c) and (d). The great increase in the ion flux
lasts for only 0.06 ms. In this interval the emission
intensity of He (23P-53D;T) line becomes weak or theemission He (23P-33D:T) is quiet first and then increases
at t = 0.06 ms. Some modest increase in ion flux to theprobe is observed at upstream as well as downstream asshown in Figs. ll(a) and (b). After r = 0.1 ms, the time
evolution of these emission intensities and the ion flux

Rydberg atoms generated by plasma recombination was
discussed under the presence of energetic electrons dueto heat pulse in relation to the dynamic behaviors of theion flux to the target and its floating potential. Thesefundamental research would contribute theunderstanding of real ELM behaviorsin in fusion
devices.

tll

References
ITER Physics Expert Group on Divertot et al.,Nucl. Fusion 39,2391 (1999).

t2l N. Ohno, S. Mori, N. Ezumi, M. Takagi, S.
t44

Takamura S. et al., Static and Dynamic Behaviors of Detached Plasmas in Divertor Simulator NAGDIS-II

Takamura and H. Suzuki, Contrib. Plasma Phvs.
36,339 (1996).

Y. Uesugi, S. Takamura, U. Wenzel, J. Plasma
Fusion Res. SERIES 3,2O2 (2OOO).
[13] Y. Uesugi, N. Hattori, D. Nishijima, N. Ohno andt3l N. Ezumi, S. Mori, N. Ohno, M. Takagi, S.
Takamura, H. Suzuki and J. Park, J. Nucl. Mater.

S. Takamura, J. Nucl. Mater. 290-293, ll34

24r-243,349 (1997).
t4l D. Nishijima, N. Ezumi, K. Aoki, N. Ohno and S.
Takamura, Contrib. Plasma Phys. 38, 55 (1998).
t5l N. Ezumi, N. Ohno, K. Aoki, D. Nishijima and S.
Takamura, Contrib. Plasma Phys.38, 3l (1998).

(2001).

[4] S.I. Krasheninnikov et al., Phys. Lett. A214,285(ree6\.
[15] D.E. Post, J. Nucl. Mater. 220-222,143 (1995).
[16] A.Yu Pigarov, et al.,pbys. Lett. A 222,251(1996).
t17l S. Takamura, N. Ohno, Y. Uesugi, D. Nishijima,
M. Motoyama, N. Hattori, H. Arakawa, N. Ezumi,
S. Krasheninnikov, A. Pigarov and U. Wenzel,
Proc. lSth IAEA Fusion Energy Conf Sorrento,
Italy, 4 to l0 october,20oo,IAEA-CN-77 tBxp4l

t6l N. Ohno, N. Ezumi, S. Takamura, S.I.

Krasheninnikov and A. Yu Pigarov, Phys. Rev.

Lett.6t,8l8 (1998).

t7l N. Ohno, N. Ezumi, D. Nishijima and S. Takamura,
Czech. J. Phys.48, 127 (1998).

t8l D.Nishijima, N. Ezumi, H. Kojima, N. Ohno, S.

29.

Takamura, S.I. Krasheninnikov and A.Yu Pigarov,
J. Nucl. Mater.266-269, 116l (1999).

t18l N. Ohno, D. Nishijima, S. Takamura, Y. Uesugi,
M. Motoyama, N. Hattori, H. Arakawa, N. Ezumi,
S. Krasheninnikov, A. Pigarov, U. Wenzel, Nucl.
Fusion 41, 1055 (2001).
[19] A. Loarte et al., "Predicted ELM Energy Loss andPower Loading in ITER-FEAT", Proc. ISth IAEA

t9l N. Ohno, M. Tanaka, N. Ezumi, D. Nishijima, S.
Takamura, S.I. Krasheninnikov, A.Yu Pigarov andJ. Park, Phys. Plasmas 6,2486 (1999).

t10l N. Ezumi, D. Nishijima, H. Kojima, N. Ohno, S.

Fusion Energy Conf. Sorrento, Italy, 4 to 10
october, 2000, IAEA-CN- 77 II tERlz-ITERp/l l.

Takamura, S.I. Krasheninnikov and A.Yu Pigarov,
J. Nucl. Mater. 266-269, 237 (1999).

tl ll D. Nishijima, U. Wenzel, M. Motoyama, N. Ohno,
S. Takamura and S.L Krasheninnikov, J. Nucl.

[20] A. Loarte, R.D. Monk er a/., Nucl. Fusion 38, 331

Mater. 290-293, 688 (2001 ).
ll2l N. Ohno, D. Nishijima, M. Motoyama, N. Hatuori,t2ll U. Wenzel et al., J. Nucl. Mater. 266-269, 1252

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