. n n > I illif fllV

NIFS—346

JP9507179

Helium I Line Intensity Ratios in a Plasma for the Diagnostics of Fusion Edge Plasmas

S. Sasaki, S. Takamura, S. Masuzaki, S. Watanabe, T. Kato, K. Kadota

(Received - Jan. 6, 1995 ) NIFS-346 Mar. 1995

NAGOYA, JAPAN This report was prepared as a preprint of work performed as a collaboration research of the National Institute for Fusion Science (NIFS) of Japan. This document is intended for information only and for future publication in a journal after some rearrange­ ments of its contents. Inquiries about copyright and reproduction should be addressed to the Research Information Center, National Institute for Fusion Science, Nagoya 464-01, Japan. Helium I line intensity ratios in a plasma for the diagnostics of fusion edge plasmas

S. Sasaki *

Advanced Engineering Group, Keihin Product Operations, Toshiba Corporation. Suehiro-cho.

Tsurumi-ku, Yokohama 230, Japan

S. Takamura, S. Masuzaki, and S. Watanabe

Department of Energy Engineering and Science, Nagoya University, Nagoya 464-01. Japan

T. Kato

National Institute for Fusion Science, Nagoya 464-01, Japan

K. Kadota

Plasma Science Center, Nagoya University, Nagoya 464-01, Japan

Electron temperature and density are measured, and the hot electrons in

a plasma are investigated using the He I line intensity ratios in the NAGDIS-

I linear device (Nagoya University Divertor Simulator) [S. Masuzaki, and S.

Takamura, Jpn. J. Appl. Phys. 29, 2835, (1990).]. He I line intensity

ratios have been calculated with the collisional radiative model using new

atomic data allowing for the presence of hot electrons, and summarized for

the electron temperature and density measurements especially for the edge or

diveitor plas>mas in the fusion device. (PACS numbers: 52.70, 34.80.D, 50.20.H, 07.20.D)

Keyword: Helium I line intensity ratios, Te and ne measurements, hot electrons, fusion edge plasma, collisional radiative model.

"E-mail address: [email protected]

1 I. INTRODUCTION

Study of edge plasma and especially divertor plasma is one of the urgent and crucial issues in the nuclear fusion research. An active spectroscopic method, which utilizes atomic beams injected into plasma, is a promising technique for the space- and time- resolved electron density. ??e, and temperature. Te, measurements in the fusion edge plasmas [1-3].

As a probe atom, helium has various advantages such as well-known atomic data, strong visible lines, and an intrinsic species in the fusion burning plasma. The Tt measurement using He 1 line intensity ratio, 492.2 nm / 471.3 nra. was proposed by Cunningham [4]. and has been applied for plasma diagnostics with various discussions and improvements [5-11].

Recently ne measurement using 667.8 nm / 72S.1 nm and 501.4 nm / 504.S nm line intensity ratios is proposed and applied in TEXTOR tokamak [10], and PSI-1 linear device [11].

In the present work. Te and ne measurements using He I line intensity ratios are improved to extend to high density fusion edge plasmas which sometimes contain hot electrons. The line intensity ratios are obtained from "effective emission rate coefficients". C*{7f(\)'s. based on the collisional radiative (C.R.) model including the excited states with principal quan­ tum number up to 20 [12]. New recommended cross section data represented in analytic expressions arc employed for the calculation of the C*£/(\) [13.14].

The Te and ne measurements are demonstrated in the helium discharge of the NAGDIS-1

11 -3 linear device [15.16]. In the low density plasma (ne ss 10 cm ). Te measurement and the investigation of hot electron are performed. The hot electrons, which are often produced in the RF (radio frequency) heated plasmas [17], would modify the plasma edge properties such as sheath potential [IS]. An effect of resonance scattering on 501.6 nm (3'P - 2'5), which is attractive both for Te and ne measurements, is discussed using the optical escape factor [19,20], and compared to the experimental result. The simultaneous ne and Te (Teh)

n 13 -3 measurements are demonstrated in the high density plasma (??c = 10 - 10 cm ), which corresponds to the ne of fusion edge plasma.

An "'effective ionization rate coefficient", Se^', in the C.R. model is presented for the

9 application of beam probe spectroscopy. The C£f/(A)'s and Seff of helium atom are impor­ tant quantities for the investigation of the "helium ash" in the divertor plasma in the fusion device. So far. the 0*£f(\)'s and S6^ of carbon atom, which is also an important impurity specie, have been discussed and ST mmarized elsewhere [21].

II. PRINCIPLE OF THE METHOD

A. Effective emission rate coefficients in the C.R. model

The effective emission rate coefficient Cl{J(\) is obtained by the numerical code devel­ oped by Fujimoto [12]. with substituting new excitation rate coefficient data for the excited states with principal quantum number up to 7 [14]. Energy level diagram of He atom consid­ ered in this work is shown in Fig. 1. We calculate the line intensities of 501.S nra (^5 - 21P),

501.6 nm (3*P - 2*5), 492.2 nm (4lD - 21P), and 471.3 nm (435 - 23P). whose wavelengths are close each other. In the finite density plasmas, ionization and excitation/dc-cxcitation from the excited states cannot be neglected. In the C.R. model, the rate equation of the population density n(i) under the ionizing plasma condition is expressed as.

C n C ~= UeY, ji U) + T,AMJ)) ~ K£ u»(0 + £^»(0) -neS,n(t) = 0, (1) ttt \ j# J» I \ &i •>'<« J where Aij, d-, and 5,- are the transition probability, the excitation/de-excitation rate coeffi­ cient from (z) to (j), and the ionization rate coefficient from (?'). Here, plasma and working gas are assumed to be optically thin. The n(i) is obtained from the set of simultaneous equations. The CeJJ{\) [cm3/s] for the line with wavelength A (i —* j transition) is defined as,

C'JiM = -4®%r = !^. (2)

neEfc n(k) nenHe where n//e is the density of helium atoms.

-3 Figure 2 (a) shows Te dependence of C|^/(A) at the low density limit (ne = 1 cm ).

In such a low density plasma, Cl(J{X) is close to the value in the corona model. The e l Cf '7{/(501.6 nm) increases toward higher T, up to 200 eV because \ S - :VP excitation hears the characteristics of an allowed transition. Since the excitations for the 304.S nm and 492.2

f nm lines are optically forbidden transitions, the Ce ,{/(A)*s for these lines decrease toward higher Te. For the triplet line. C£f/(471.3 nm). rapidly decreases toward higher Te because of its spin change forbidden nature.

Figure 2 (b) shows the ne dependences of C,f,{/(A)"s at Tr = 20 eV. The C^{/(A)"s are slightly larger than the emission rate coefficients in the corona model within a factor of

10 V, even in the low nF plasma, since the cascade contribution is neglected in the corona model. The ne dependences of C/,{/(A)'s for singlet and triplet lines show different features. For the singlet lines, C^J(\ys for 504.S nm, 501.6 nm and 492.2 nm have almost constant

10 13 -3 e values in ne < I0 , 10 and 10" cm , respectively. In the higher ne plasmas. C'f T{/(A)'s

7 decrease as ??e increases because ??(/) s arc saturated to ;?f. which comes from frequent

c electron collisions on the excited states. For the triplet line, the C( ,{/(471.3 nm) slightly

n -3 increases in an intermediate nr plasma. 10' < ;if < 10 cm , because of the increase of

3 2 S mctastable state population. In the higher nc plasma, the frequent electron collisions makes r?(?) saturated to »e resulting in the decrease of (?£,{/(471.3 nm).

The accuracy of C^IJ[\) depends on the atomic data. The ,4,j has a good accuracy less than a factor of 5 '/,. The accuracy of CtJ is estimated to be within a factor of 20 '/, for T,

< 50 cV with including the analytical fitting error [13,1 1]. For Tc > 50 cY. Cn has higher accuracy because of less uncertainty of al} for high electron impact energy especially for the allowed excitation.

B. Electron temperature and density measurements using line intensity ratios

c c// The line intensity ratio R "{\x / A2) is obtained as, /? (A,/A2) = C;{/(A1)/Q,{/(A2), by assuming the constant sensitivity of the optical detection system for A( and A2. Figure

e 3 shows the /? ^(At/A2)*s for several singlet-triplet line pairs at, the low density limit (ne

= 1 cm-3). The singlet-triplet line pairs are suitable for 7^ measurement, because of strong

4 ef T, dependence of R J(\1/\2), coming from the different Tt dependences of Cfm(A)"s. In

eJ} such low density plasmas, R (Xi/X2) is close to the value in the corona model. The

Cunningham's result of 492.2 nm / 471.3 nra in the corona model is compared to the present

work in Fig. 3 [4], which has a discrepancy about a factor of two. His result is based on

the experimental cross section data, where an error in its absolute-intensity calibration has been pointed out [5].

e Figure 4 (a) shows 7^ dependence i? ^(A1/A2)'s for singlet-triplet line pair of at ne =

12 -3 10 cm corresponding to the nr in the fusion edge plasmas. In such a high ?if plasma.

f ^ ^(^i/^2)'s in the high n£ plasma have a large difference to those in the low ??f plasma.

e The n€ dependences of R ^[Xi/X2)'s for these line pairs are shown in Fig. 4 (b). The line

e intensity ratios in the corona model are compared to i? ^(Aj/A2)'s in this figure, which

e 4 -3 coincide to i? ^(Ai/A2)'s within a factor of 10 % in the low ?je region, vf < 10 cm . In

4 u -3 cfI ! the intermediate 7?c plasma, 10 < ne < 10 cm , the R (X-l/X2)' s for these line pairs arc

small compared to those in the low ne plasma because of the increase of C^(471.3 nm) as

u 12 -3 r// 1 shown in Fig. 2 (b). In the high n£ plasma with ne > 10 - 10 cm , 7? (Ai/A2) s have

e strong ne dependences. The /? ^(501.6 nm / 471.3 nm) has a strong nc dependence in ne >

u -3 10 cm , because of the different ne dependences of C^/(501.6 nm) and Cj,{/(471.3 nm).

e 2 (b). The R ^(50l.S nm / 471.3 nm) is attractive for Te measurement in the fusion edge

11 14 -3 plasmas with nr. « 10 - 10 cm because of its strong Te dependence and relatively weak

ne dependences.

r For the purpose of ne measurement, strong ??e and weak Te dependences of y? ^^(At/A2)

c are desired. Figure 5 shows R M(Xl/\2)'s for the singlet-singlet line pairs, which are suitable

e for nt, measurement. By using the strong ne dependence of R U{X\/ X2), ne measurement is

u -3 available for rie > 10 cm . However, we should note only 10 7. of the experimental error

of the line intensity ratio results in the error of ne as much as a factor of two. The result

of Behrcndt for Rt^(o0l.6 nm / 504.8 nm) is compared to the present work in Fig. 5 (b)

[11]. which shows a discrepancy within 50 '/,. This may come from the different atomic data

and the less number of excited states included in the model (principal quantum number <

5 e 5). The weak Te dependences of /? ^(Ai/A2)"s for these singlet line pairs. Fig. 5. suggest that the ambiguity of Te does not result in the serious error in the reproduced ne. On the

e contrary, the strong ?ie dependences of i? ^^(A1/A2)*s for the singlet-triplet line pairs. Fig.

4(b), means we must know 7?e for the Te measurement. Therefore. ne and Te are alternatively determined by iterations from the singlet-singlet and singlet-triplet line pairs by using the initial valu? of 7ie determined from the singlet-singlet one.

The reliability of Re^[\\/\2) depends both on the accuracy of CV/s and the C.R. model.

11 -3 11 -3 In the plasmas with 7?f < 10 cm for singlet lines and ne < 10 cm for triplet lines. Cu's are important since the accuracy of Cf7{/(A) is dominantly determined by Cn's. However in the higher 7?e plasma, the reliability of the C.R. model is important. It may depend on the atomic processes and the number of atomic levels included in the model. The number of the excited states (principal quantum number < 20) is considered to be sufficient. The resonance scattering, which enlarges the population densities - ' nl P excited states, should be considered in the plasma with high base pressure of He gas

C. Effects of hot electrons on the line intensity ratio

Sometimes an electron velocity distribution function, f{ve), is not represented by a

Maxwellian, but has a hot (tail) component. Such is the often case for the RF heated

plasmas. We approximate f(rc) of the hot component to be a Maxwellian with high Tr.

Then, f(ve) is expressed as a superposition of two Maxwellian distribution functions for

cold and hot components, i.e. fc(ve) with electron temperature of Tec, and jh{ve) with 7^:

f(ve) = (l-a)fc{ve) + afh(ve), (3)

where a is the abundance of the hot component, defined as a = 7je/l/77e, with 77e/, the electron

density of the hot component. Then, Ctj is expressed as,

/•oo 2 Ch = / ot]vef(ve)4iTV edve, = (1 - a)Ch(Tec) + aCtJ(Teh), (4) JO

6 with cru the excitation/de-excitation cross section. The CtJ{Tfc) and CtJ{Tfh) are the CtJ at

Tec and Teh., respectively.

e The i? -^(492.2 nm / 471.3 nm) in the presence of hot electrons with Tch — 20 eV and

n -3 40 eV at ne = 10 cm is shown in Fig. 6 (a). This figure shows that the presence of hot electrons gives rise to a substantial modification of the line intensity ratio. The #'°^-''(A1/A2) at low Tec. where (1 — a)C,j(Tcc) < aCtj{Trh). is rather close to the value in the mono

c electron temperature plasma with T^. The ne dependence of /? -^( 492.2 nm / 471.3 nm) in the presence of hot electrons with Teh = 40 eV and a = 10 '/, is shown in Fig. 6(b). The line intensity ratio in the corona model is also shown for comparison, which is very close to

eff -3 the value of R (492.2 nm / 471.3 nm) at nc = 1 cm .

III. EXPERIMENTAL RESULT

NAGDIS-I is a linear plasma device with a PIG type discharge using a LaB6 hot cathode, operated at the axial magnetic field of < 0.15 T [15]. The vacuum vessel has a column length of 250 cni and a radius of 13.S cm. The plasma has Te and ne profiles in a trapezoid shape with a diameter of «10 cm in FWHM. The optical detection system consists of a lens, an optical fiber, a monochromator. and a photomultiplier. The sensitivity of the optical system is almost constant over the wavelengths of 504.S nm, 501.6 nm. 492.2 nm and 471.3 nm.

These line emissions are observed through a chord passing the plasma center. A numerical simulation is performed to compare the observed line intensity ratios as chord averaged values and the intensity ratios in the plasma center. Because of the large plasma column and the low ??e in the edge region, the observed line intensity ratio can be approximated as that in the plasma center. The plasma parameters Tec, 7\hl and a at the plasma center, are measured by the Langmuir probe. The Te measurement and the investigation of the hot

11 -3 electron aie performed in the low density plasma (ne a* 10 cm ), where the ne dependences

e of /? ^(Ai/A2)'s are weak. The simultaneous nc and Te (Tih) measurements are performed

11 13 -3 in the high density plasmas (??e = 10 - 10 cm ).

i A. Electron temperature measurement and investigation of hot electrons

The electron temperature and the abundance of hot electrons are varied by the filling gas pressure in the "low 7?e- experiment". The ion gauge shows the pressure in the vacuum vessel without the discharge is several 10_1 Torr. Since the pressure gauge does not represent a real value during the discharge because of the plasma pumping effect, the flow rate of the filling lie gas is used as an indi.-n.tion of the pressure. The discharge voltage V"/ is regulated to maintain a fixed discharge current at Id — 1U A. The \',j in the low gas pressure is ss ISO

V and that for high pressure is ss 100 V as shown in Fig. 7 (a). This figure also shows ne

11 -3 measured by the Langmuir probe. nc(L.P.). The value of »t « 1 x 10 cm is considered as the upper limit where the corona model is valid (except for the triplet lines).

The electron temperatures obtained by the Langmuir probe and by the He I line intensity ratio (lie I method) are compared in Fig. 7 (b). Observed line intensities and those ratios,

492.2 nm / 471.3 nm and 501.6 nm / 492.2 nm. are shown in Fig. S. In this condition, the numerical simulation suggests that the observed line intensity ratios are slightly smaller than those in the plasma center by 2-3 '/„ which are small compared to the experimental error (ss ± 5 '/,). Then, the experimental en or of Tt in the He I method is within 3 eV. In the low pressure condition (< 10 ccm), the Langmuir probe result shows that the plasma has a mono- electron temperature with Tec > 10 - 20 eV. though /(ry) somewhat deviates from the Maxwellian. Here, 7'fc(L.P.) from (he Langinuir probe; is in good agreement with

Te(Ilc 1) from the He I method. In the high pressure condition (> 15 ccm). hot component is separated from the cold component: Tffi(L.P.) « 20 - 40 cV. o « 10 ± 3 °L Tf«,(L.P.) < 10 eV. Then, TP (He I), which neglects the effect of hot electrons, is larger than Trc (L.P.) as suggested by Fig. 6. In both pressure ranges, numerically obtained /?cJ^(492.2 nm / 471.3 nm) is consistent with the experimentally obtained line intensity ratio by using TC,,(L.P.).

71=/, (L.P.) and a = 10 ± 3 1 as shown in Fig. S (b). The determination of* Tfi, from the line intensity ratio is available if a and Tcc arc known. The Trh derived from the line intensity ratio, Tch{Uc 1), using Tee(L.P.) and o = 10 ± 3 °/.. is consistent with y^L-P.). Here, the

8 large deviation of re/i(He I) comes from the ambiguity of o. Although the quantitative measurements of Teh and a are difficult, the He 1 method can show the evidence of the existence of hot electrons if we know Ttc. It is often the case of RF experiments where the hot electrons are produced but the change of T(C is small.

l l The line of 501.6 nm (3 P - 2 S) has attractive features both for Tc and 7if measurements as discussed before. In the present experiment, however, the effect of resonance scattering enlarges the 501.6 nm line intensity as shown in Fig. S (a), and disables Tt and ue mea­ surements. Here, the effect of resonance scattering is investigated using the "optical escape factor" [9.19,20] from the viewpoint of experimental applications. The optical escape factor

A for the line center of 53.7 nm resonance line (3'P - \lS) is obtained from the optical depth r [20]. The values of A and r for the He gas with temperature of 300 K are shown

-2 as functions of a column density nnt x L cm in Fig. 9. Here. A = 1 means the He gas is

1 1 -2 optically opaque for 53.7 nm photons. In our experiment. n^t xi = 10 ' cm corresponds the He gas pressure of 2 X 10-"1 Torr. where L is the radius of the vacuum vessel [L — 13.S

1 1 2 cm). The value of A = 0.07 at ??e x L = 10 ' cm' means we cannot neglect this effect under the present condition. We employ a simple model including three states, i.e. the ground state (1). the 2lS metastable state (2), and the 31 P excited state (3). As suggested by Fig.

2(b). the corona model approximation is still valid for the singlet lines. 501.6 nm and 492.2

11 3 nm. at ne % 1 x 10 cm" . The rate equation for H(3) using A is approximated as.

^77^ = n£C13n(l) - AA31n(3) - A32»(3) = 0. (5) at Then, the emission rate coefficient for A = 501.6 nm can be derived as,

C™(501.6nm) = C13---^» (6) /i32 -r A/131

Equation (6) explains the small value of A enlarges the 501.6 nm line intensity. Numerical result of 501.6 nm / 492.2 nm line intensity ratio is in a good agreement with the experimental one as shown in Fig. S (c). Here, nfjt x I is assumed to be proportional to the gas flow-

e rate. The ambiguity of n//e gives a large error har on 7? ^(501.6 nm / 192.2 nm). Further

9 discussions including the finite population density of the 2lS metastatic state and the effects of collisions with neutral He atoms are necessary for the detailed quantitative investigation.

The small values of A malces the population densities of n1 P large, and this may give influence on ^S and nxD excited states. It is concluded, from the practical use. the effect of resonance scattering on the line of 501.6 nm can be avoided for He gas pressure below

10-5 Torr for L = 13.8 cm. A beam probe technique solves this problem by reducing the

He gas density njie and the column radius L.

B. Simultaneous electron density and temperature measurement

The electron density is varied by the discharge current Ij. while the flow rate of He gas is fixed at 30 ccm in the "'high ne experiment". In this condition, Tec is almost constant at ss 5 eV, although Teh and a vary by Id. A fast scanning Langmuir probe technique is

employed for 7?e and Tec measurements to avoid the thermal damage to the probe tip [16].

Unfortunately, Teh and a cannot be measured by the probe due to the very noisy signal.

The experimental result of line intensity ratios of 504.8 nm / 471.3 nm. 492.2 nm / 471.3 nm

and 492.2 nm / 504.8 nm are shown in Fig. 10 (a). The former two are for Te measurement

and the latter one is for ne measurement. Measured 7?e and Te arc shown in Figs. 10 (b)

and (c), respectively. In the present condition, the numerical simulation suggests that the observed line intensity ratios are smaller than those in the plasma center bv within 10 %

in this plasma, which is mainly due to the large spatial variation of 7?e. The experimental

error in the observed line intensity ratios is estimated as within ± 10 '/,. Only 10 'I, of the

experimental error on the 492.2 nm / -504.8 nm line intensity ratio results in the error in the

electron density, 7?e(He I), as much as a factor of two. Here, ne(He I) is obtained with the

aid of !Tec(L.P.), Teh(He I) and assuming a = 10 ± 3 %. The ??e obtained by the Langmuir

probe, 7ie(L.P.), also has a large experimental error within a factor of two. Although, both

ree(He I) and 77e(L.P.) have large experimental errors, they are consistent each other within

the error bars, and have the similar Id dependence. The Te(He I) from the 504.8 nm /

10 471.3 nm and 4!)2.2 nm / 471.3 mn line intensity ratios are large compared to Ttc (L.P.) because of the neglection of hot electrons. The ± 10% of the experimental error in the line intensity ratios results in the error of reproduced Te within 5 eV. Since T£C is small at « 5

e eV, R H{\\/\2) is rather close to the value at mono temperatme of Teh as suggested by Fig.

6. It is remarkable that Te and Tell obtained by the different line intensity ratios are close each other, although they have quite different Te and ?;e dependences. Here, the accuracy of

e nr is important since 7? ^(A1/A2)'s for singlet-triplet line pairs have strong ne dependence.

The Tf;,(He I) is obtained using rcc(L.P.) and assuming a = 10 ± 3 %. which is the Langmuir probe result at the gas flow rate of 30 ccm and the discharge current I,i = 10 A in the low ne experiment. In the low Ij region (< 15 A), l\h has a value of 30 - 50 eV, while Teh decreases down to 10 - 30 eV where /,/ > 15A. Here the nc and Te (Te/J measurements using the He I line intensity ratios arc demonstrated as the powerful tool for the diagnostics of fusion edge plasmas.

IV. APPLICATION AND DISCUSSION

An "effective ionization rate coefficient" Se^ in the C.R. model is a useful quantit}' for various applications. The quantity of Se^ is defined as,

e The Te and ne dependences of S ^ arc shown in Fig 11. Since 5,-'s (from the excited states)

e are much larger than Si (from the ground state), S ^ increases in the high ne plasmas,

e 4 14 -3 where n(i) of the excited states are large. The S ^ in the nE range of ne = 10 - 10 cm ,

-3 is large compared to the value at ne = 1 cm , which comes from the ne dependence of

1 1 -3 e the metastable popidation densities. As ne exceeds 10 ' cm , S ^ increases due to the ionization from the higher excited states. In the beam probe application, the spatial range of the measurement is determined by the beam penetration depth tp, which is defined as

e Cp = VHe/(neS M) with u//e the velocity of helium beam. The Cp of the 300 K thermal helium

11 12 -3 beam is estimated as 21 rm in the plasma with Tt = 20 eV and nc = 1 x 10 cm . Then, the thermal He beam penetrates the scrape-oiT layer in the small or medium size tokamak.

cIJ The S has rather st rong Tc dependence compared to the nc dependence, which is an

e advantage for an another type of Te measurement utilizing the strong Te dependence of S -^

[2]-

The recombination of He ions in the low Te and/or high nc plasmas influences on the population balances of the excited states. The population density »(?') is expressed as a sum of a pure ionizing component n(/);D71, and a pure recombining component n(i)Tecom^.

A i.e. n(i) = n(i),-„„. 4- n[i)recom.- Figure 12 shows an example of n(i)rCcom./n(i) for the A D excited state obtained by the C.R. model including the recombination at n//e+ / H//c = 0.1.

The value of 7?//e+/nj/e = 0.1 is the maximum value, which is experimentally estimated in

the NAGDIS-I helium discharge. Since Te % 8 - 20 eV in this plasma, it corresponds to

the ionizing plasma. For the beam probe application, the influence of recombination can be neglected since the small amount of helium atom is injected perpendicularly to the magnetic

field.

The existence of the metastable states, 2XS and 23,5'. enlarges the relaxation times of

the population densities. As suggested by the ne dependence of C|,{/(A)"s, the contributions of the 2'S on the singlet lines are relatively small compared to those of the 23£' state for

the triplet lines. Then the relaxation times for the singlet lines are considered as ~ l/A.,j

with the order of several tens nanoseconds. Triplet lines are. however, strongly influenced

by the 235 metastable state. Since An for 23S - llS transition is very small (1.7 x 10-4

s~l) [22], collisional processes determine the relaxation time. The ionization is the dominant

process for the population balance on the 235' state because of large S, from 23.9. The large

3 relaxation time of 2 5 metastablc state (ss 100 /«s) in the present low ne experiment can

influence the population balance of the triplet state, since the transit time of 300 K lie atoms

across the vessel radius (L = 13.8 cm) is the similar value (« 100 (is). Further discussion

including the movement of He gas in the vessel and the atomic processes on the material

surface is necessary for the detailed investigation.

12 ACKNOWLEDGMENTS

The authors are grateful to Prof. T. Fujimoto (Kyoto University) for his valuable dis­ cussions and for the numerical code of the collisional radiative model. This work was partly supported by a Grant-in-Aid of the Scientific Research from the Japan Ministry of Educa­ tion, Science and Culture (.ISPS Fellowship. No. 3293).

APPENDIX A: FURTHER RESULTS DERIVED FROM THE COLLISIONAL

RADIATIVE MODEL

The excitation rate cocilkient CM and the effective emission rate coefficient CljJ(\) are summarized. The CM to the excited states with principal quantum number up to 5 is shown in Fig. Al. The CM is numerically calculated using the cross section presented by Kato et al. [14]. The C^/{\) is shown as a function of 1\ in Fig. A2.

3 Line radiation power rate coefficient Pr„/ [eVcm /s] is an important quantity for the

e investigation of power balance in the divertor plasmas. The Pr u/ is obtained as,

peff = E.MOEjo-Ajfl.,)^ (A1) "t»He where E;3 is the energy of the line. The line radiation power per unit volume is given by

3 f neP^-Jnjje [eVcm~ /s]. Figure A3 depicts the Te and ne dependences of Pr //. It should be noted here that this quantity is obtained for the ionizing plasma condition. Details in the line radiation power rate coefficient is described and discussed in the reference for carbon atom [21].

Two metastable states, 215 and 23S, influence on the ionization and line emission pro­ cesses of helium atom. Normalized population densities, n{i)lnjje = n{i)/T,kn(k), for the nietastable states obtained by the C.R. model are shown in Fig. A4. The ne dependences of these metastablc states are consistent with the results of C*fJ(\Ys, Sc" and P^„i.

13 APPENDIX B: APPLICATIONS

The ratio of Se^ / C^/(\) is a useful quantity for the determination of beam density in the beam probe spectroscopy technique [2,3], and for the atomic impurity measurement

e c such as carbon [21]. The ratio of S ^ / Ce //(A) is shown as a function of Te in Fig. Bl.

Line intensity ratios for ne and Te measurements are summarized for the experimental

11 14 -3 use. The figures are drawn in the ??c range of 10 - 10 cm and Te range of 5 - 50 eV. Here we present the line intensity ratio* of UY2/2 nm / 50-1.8 nm. 504.8 nm / 471.3 nni. and

492.2 nm / 471.3 nm. The former one is for ne measurement and the latter two are for Te

e measurement. The ne dependence of i2 ^(492.2 urn / 504.8 nm) are shown in Fig. B2 (a),

eff which has a small Te dependence. The ne dependences of R (o04.S nm / 471.3 nm) and Reff (492.2 nm / 471.3 nm) are shown in Fig. B2 (b) and (c), respectively. Since these line intensity ratios have strong nc and Te dependences, we must, know ne for Te measurement

11 -3 e in the high density plasma with ne > 10 cm . 'The Te dependences of r? ^(504.S nm /

e 471.3 nm) and R ^ (492.2 nm / 471.3 nm) are summarized for Te measurement in Fig. B3 and B4, respectively.

14 [1] K. Kadota. K. Tsuchida. V. Kawasumi, and J. Fujita, Plasma Phys. 20, 1011 (19

[2] A. Pospieszczyk. F. Aumayr. H. L. Bay. E. Hintz P. Leismann. Y. T. Lie. G. G. Ross. D.

Rusbult. R. P. Schorn. B. Schweer. and II. Winter. J. Nucl. Mater. 162-164, 571 (19S9).

[3] S. Sasaki, Y. Uesugi. S. Takamura. H. Sanuki. and K. Kadota. Phys. Plasmas 1, 1089 (1994).

[4] S. P. Cunningham. Conference on Thermonuclear Reactors, Liveimore. U.S. Atomic Energy

Commission Report. No.279. p.289 (1955).

[5] A. II. Gabriel, and D. \V. 0. Heddle, Proc. Roy. Soc. (London) A258, 124 (1960).

[6] C. C. Lin. and R. M. St. John, Phys. Rev. 128, 1749 (1962).

[7] R. J. Sovie. Phys. Fluids 7, 613 (1964).

[8] R. F. de Vries, and R. Mewe, Phys. Fluids 9, 414 (1966).

[9] N. Brenning. J. Quant. Spectrosc. Radiat. Transfer 24, 319 (1980).

[10] B. Schweer, G. Mank, A. Pospieszczyk, B. Brosda, B. Pohlmeyer, J. Nucl. Mater. 196-198,

174 (1992).

[11] H. Behrendt, W. Bohmeyer, L. Dietrich. G. Fussmann, II. Greuncr, H. Grote, M. Kammeyer.

P. Kornejew, M. Laux, E. Pasch, 21st EPS Conference on Controlled Fusion and Plasma

Physics, Montpellier, France. Ill p. 1328 (1994).

[12] T. Fujimoto, J. Quant. Spectrosc. Radiat. Transfer 21, 439 (1979).

[13] F. J. de Heer, R. Hoekstra, A. E. Kingston, and H. P. Summers, Nucl. Fusion Suppl. 3, 19

(1992).

[14] T. Kato, and R. K. Janev, Nucl. Fusion Suppl. 3, 33 (1992).

[15] S. Masuzaki, and S. Takamura, Jpn. J. Appl. Phys. 29, 2835 (1990).

15 [1G] S. Masuzaki. N. Ohno. M. Takagi. and S. Takamura. Trans. IEE of .Ipn. 112-A. 91-3 (1992)

(in Japanese).

[17] S. Takamura, A. Sato. Y. Shen, and T. Okuda. J. Nucl. Mater. 149, 212 (1987).

[18] K. Shiraishi, and S. Takamura. J. Nucl. Mater. 176-177, 251 (1990).

[19] T. Holstein. Phys. Rev. 72, 1212 (1947).

[20] U. W. Dtawin. and F. Emard. Beitr. PWnaphyMk 30a, 143 (1973).

[21] S. Sasaki, Y. Ohkouclii. S. Takamura, and T. Kato. J. Phys. Soc. .Ipn. 63, 2942 (1994).

[22] C. D. Lin. W. R. JOIMSOII, and A. Dalgarno, Phys. Rev. A, 15, 154 (1977).

16 Figure captions

FIG. 1. Energy level diagram of helium atom included in C.R. model.

FIG. 2. Effective emission rate coefficients obtained by the C.R. model. C*{J(X). (a) Te depen­

-3 dence of C*/,/(X) at the low density limit (ne = 1cm ). (b) ne dependence of C*f,/(X) at Tf = 20 eV.

f TIG. 3. Line intensity raMos. R ^{XijX>). for TL measurement at low density limit (nt =

lcm~3). which are close to the values in the corona model. The result by Cunningham is shown

for comparison.

e FIG. 4. Line intensity ratios, R ^{X\/X2) for singlet-triplet line pairs, suitable for Te measure­

c 12 -3 ment in the fusion edge plasmas, (a) Te dependnnce of R ^(Xi/Xi) at 7?e = 10 cm , (b) ne

e// dependence of tf (Ai/A2) at 7; = 20 eV.

( FIG. 5. Line intensity ratios. R ^(X\/X2) for singlet-singlet line pairs, suitable for ve measure­

e 12 -3 ment in the fusion edge plasmas, (a) Te dependence of R ^(Xi / A2) at ne = 10 cm . (b) ne

e dependence of R ^(X\ / A2) at Te — 20 eV. The result by Behrendt is shown for comparison.

FIG. 6. Line intensity ratio 7?c-^(492.2 nm / 471.3 nm) in the presence of hot electrons, (a)

f// n -3 C 7? (Ai/A2) at Tth = 20 eV and 40 eV. nt = 10 cm , (b) R ^(XX/X2) for T,h = 40 eV in the

high ??f plasmas. The result in the corona model is shown for comparison.

FIG. 7. Tf measurement and investigation of hot electrons in the low ne experiment, (a) Dis­

charge voltage Vd and electron density ne. (b) Electron temperatures obtained by the Langmuir

probe. Tec(L.P.) and Te/,(L.P.), and by the 492.2 nm / 471.3 nm line intensity ratio. re(He I) and

7^/,(He I). The effect of hot electrons is neglected in Te (He I), while it is included in Tf/, (He I).

17 FIG. S. (a) Experimental result of the line intensities in the low n, experiment, (b) Line intensity ratio of 492.2 nm / 471.3 nm. The numerical result (Calc.) well reproduces the experimental result by including the effect of hot electrons, (c) Line intensity ratio of 501-6 nm / -192.2 nm.

1 The numerical result using the optica escape factor A(ne X L) (Calc.) is consistent with the experimental one.

FIG. 9. Optical depth of the 53.7 nm photon r and optical escape factor \ for He gas temperature of 300 K.

FIG. 10. Te and ne measurements in the high ne experiment, (a) Experimentally observed line intensity Tatios. (b) Electron densities obtained from the 492.2 nm / 504.8 nm line intensity ratio.

?ie(He I), and by the Langmuir probe, ne(L.P.). (c) Electron temperatures obtained from the 504.8 nm / 471.3 nm and 492.2 nm / 471.3 nm line intensity ratios, Te(He 1). and Te/,(lle 1), and by the

Langmuir probe. Tec(L.P.)

FIG. 11. Effective ionization rate coefficient S6^ obtained by the C.R.- model.

1 FIG. 12. Contribution of the recombining component on the population density of 4 D, n(i ),eram.

ls / n(i). The ratio of ion to atoms n^e / riHe 0.1, which is the maximum value in the NAGDIS-I helium discharge.

IS FIG. Al. Excitation rale coefficient from the ground state C'u. (a) V$ — nKS, (b) l1S,-n1/>, (c) ^S-n'D. (d) VS-iPS. (e) ll5-n3P. (f) llS-n3D.

e FIG. A2, Effective emission rate coefficient Cf ,{/(A) for (a) 504.8 nm, (b) 501,6 nm, (c) 492.2 nm. and (d) 471.3 nm.

FIG. A3, (a) Tr- and (b) nr- dependences of the line radiation power rate coefficient

Prld defined for the ionizing plasma condition.

FIG. A4. (a) Te- and (b) ne- dependences of the normalized population densities n(?)/";/r- for the 215 and 235 mctastable states.

FIG. 131. Ratio of effective rate coefficients for ionization to emission, Sc^(C^{\). for

(a) 504.S nm, (b) 501.6 nm, (c) 492.2 nm, and (d) 471.3 nm.

e FIG. B2. The ne dependence of i? -^(Ai/A2) summarized for experimental use. (a)

e// e// JR (492.2 nm / 504.8 nm) for ve measurement, (b) i? (504.S nm / 471.3 nm) for Tt measur ement. (c) #e//(492.2 nm / 471.3 run) for 7; measurement.

e FIG. B3. The Te dependence of /? "(504.8 nm / 471.3 nm) for Te measurement (a) ne

u 12 3 12 13 3 13 14 3 = 10 - 10 cm" , (b) ne = 10 - 10 cm' , (c) ne = 10 - 10 cm" .

FIG. B4. The Te dependence of #"(492.2 nm / 471.3 nm) for Te measurement (a) ne

11 12 3 12 13 3 13 14 3 = 10 - 10 cm" , (b) ne = 10 - 10 cm" , (c) ne = 10 - 10 cm" .

19 p 1D 1F+ 3S 3P 3D 3F+ mmmmwrnm wmmmmm:

492.2nm 471.3nm

Metastable

l=24.54eV Singlet Triplet |1 j .Ground , , , , ,

Fig. 1 Effective emission rate Effective emission rate coefficient Cf" [cm3/s] coefficient Cf!l [cm3/s] —1. Or ai X X —L x O o I o o• o o 1 _i. ro o 00 ro o T- o - i; §" •* 1 1 mMM^ s m -* 1 1 CD • 1 O 13 1 1 !'• (D H- - • r-ro n f CD CD" ° 1 X - ^ $> ai Oi 11 " II " w 1 -A o •-, ^ "*i _. . NCDO I \ » roO -- —"^^^ * O CD -*• rv> -»• 4o* '.CD

Cmp e D " co ho b) 00 1 :<" ^-. 3 : a ~ i , 1 ' "" - D 1 CD _,. 1 1 O - ^ /,;' / - \\\ UJ co i y / _ c" CD —* q kr 0 • \\l o ro H \N\ 'i O -3 CD " \\\ • 2**— *"*".^* 3 .1 Q.O - 1 •v \ co en - — TT-—*^**^ • CD =3 - CD fl, ' \\ i • - Sr^ "" - ^ t „ / V '• q _I__J • •""* • » »••••• r-» 00 n =1cnrv3 (Low density limit)

t • I i i 1111 j •• i i ri — 504.8/471.3 [nm] ,'' 501.6/471.3 492.2/471.3 ,'

(Cunningham) 492.2/471.3

• • *»• • 1 10 100

Electron temperature Te [eV] Fig. 3 5 C I I I I I I I T I • 1i •i I I . (a)n _mi=102 12cnrr3 "e o CO ^ 1 •1—» << w T— c: <^ CD C CD C _J 0.1 0.05 1 10 100 Electron temperature Te [eV] 50 r~i—'—i—i—i i i—i—i—i—i—i—i—r • (b) Te=20eV .o V-» 492.2/471.3 [nm] "•CO5 10 r 1— 504.8/471.3 f / cvj 7/

1— 501.6/471.3 0 "55 CE CD

Corona model 0.1 • • « • i i i i i i i i—i—«— 102 105 108 1011 1014 1017 3 Electron density ne [cm ]

Fig.4 10 i i i 111 • • i i i i 11111. 12 3 ; (a)ne=10 cnr

1 r

0.1 • * ' • • • • • i • • i • i • i 1 10 100 Electron temperature Te [eV] 50 r-T ~i—i—i—n— i—i—i—r (b) Te=20eV 492.2/504.8 [nm] 10 r 501.6/504.8 501.6/492.2

1 F

(Behrendt et al.) Corona ----501.6/504.8 model 0.1 I I I I I 1 I I I i i I L. 102 105 108 1011 1014 1017 3 Electron density ne [cm ] Fig. 5 1.0 • i • 1111111111111111111 n 11111111 (a) n =1011cnrr3

0.5 a=0%

a=10%, Teh=20eV

a=10%, Teh=40eV

0 * • * • * * • • * * • • * • * • • • • * • • * • * • • • • * • • • * 4 i i i i | i i i i [ i i i i i i i i i i i i i i i n i i | i i i i . (b) Teh=40eV .,• 1cm3 , a=10% \ 1111 om-3 \ 10 cm 1012cm-3 "1013cnrr3

Corona model 0 • • * • • • • * • • • • * • • • • * • • • * * • • • * * • • 10 15 20 25 30 35 40 Electron temperature of cold component Tec [eV] Fig. 6 Discharge voltage Electron temperature T , T [eV] VdM ec e no ro ro CO oi o oi o oi Ol 01 o ro o o o o o o 11 \ 11 o 01 oo Ul rr- T1" fa'b"M"'H

CJI

O ro oi

GO o

CO I.I. ryim .I.I.I.I o-»• ro co 4^ cn C5)-NJ oo oooooooo o en Ol Electron temperature Bectron dens|ty [eV] 11 ne[10 cm-3] 14 2 nHex L=1xl0 [crrr ] 20 F i i i i I i i i i | i i i i | i i i i | i i i :(a) 501.6 nm w c rs © CO 10 — CD 471.3 nm c 5 £ PB 8 8888888 492.2 nm ° 0 • • • • * • • • • * • • • • * • • * * * • • • • * • • • ge 1.2 11111 11 i I i i i i | i i i i | i i i i | i i i Kb) • Experiment ^1-0 o Calc. without Teh w^: 0.9 1 $ Calc. with Teh © E 0.8 ? ?f¥fi?S o o o o o o o o •JJ0.5 • !•••• I . t . . I • • • . I • • • . I . . . • .2 E 5 illiir 4 .•(c)" riTfft >-cvi n [] 3 [] [] u " n If 2 n Experiment li oCalc.(A=1) — CD 1 CD * »Calc.(A(nHexL)) 'OOp O OOOO.OOO —I IT) 0 I I I I 10 15 20 25 30 35 Gas flow [ccm] Fig. 8 100 0 I I I I IT 0.5

o cc 0.1 CD Q. CC O CO CD .9

"•*-• i0.01 Qd.

J l__l I I I I. 0.005 14 15 1013 10 10 2 Column density nHe x L [cnrr ]

Fig. 9 10 . (a) 492.2/504.8 [nm] ^ • • • • • : co • • 492.2/471.3 [nm] : o o o o o " c 1 r o o u - CD n 504.8/471.3 [nm] : CD 1 1 I I I I I T—r & 10">3t.(b) nJHe I) "co c: .— CD c? "° E c o1012t- 1> 11 2 -© nB(LP.)

LU 1Q11I-. .T.i • • • • • ' ~ 50 .(c) Te (He I) 504.8 nm/471.3 nm T a) 40 - •Te * eh 492.2nm/471.3nm CO liny eh cV 30 Eo • • •*— (D ch 20

o "["..(LP.L ) » i_ ec( -P) S 10 I Mi;

0 J-J_L • ' 5 10 50 100 Discharge current Id [A]

Fig.10 T—I I llll|— 1—i—i rrrr -1018 cm'3 13 3 8 •10 cm" 10" ion cm-3 1 cm3

10 •9

10,-1 0 J i i r / /lit J i i i i i i ii 1 10 100

Electron temperature Te [eV] Fig. 11

i i i 1111 i • IIIIII njjnHe"'Hu e =0.1 \ \^-1-1012cnrr3 ^ \^ 1014cm3 10-1 \^>^ ""V-1016crrr3 \ v~ \ 10i8 cm-3 10- \ X

10- 3 I ill Ml LI I ll • • * * • '' 1 10 100

Electron temperature Te [eV]

Fig. 12 Excitation rate coefficient Excitation rate coefficient C-, J [cm3/s] C,j[cm3/s] O O o O O O I O o I IV) i o i o I CO ro CD CD 00 I 1111 ll| I I 11111IJ I I llllllj | I Mill T • I I lllll T I I I III! I I Mllll| 1I I •llll m 'ST j CD O «—i- o CD O Tl 3 T3 CD »-+

CD Ol ^ GO N> IF "0 "0 "0 "0

o iii o Uil JJOU o 10~'u b iii iniij i iii mi) i i 111 iij I (c)-n1D c

10"9 b III lllll| I I I I IIM| I I I 1114 I (d) -n3S CcD O -10 4-^•^ 10 CD O in O CO 10 -11 [c m rat e c T— o o •*-> CO 12 •»-» 10- o X LU 53s 13 i a — I I Mill 10- M« • i ml I 'I 'I iI i'HJLIII „ 1 10 100 1000 Electron temperature Te [eV] Fig. A1 -Q 10 p—* 1 1111 HI I I III llll I I I iIIX (e) -n3P c CD 10 'o io- L *^- CD _ Ow CJOO O

.9 O S"co 10"12 o x LU 10"13 1 10 100 1000 Electron temperature Te [eV]

10' b III 1 11ll| I I I 1 11111 I I I Mill : (f)-n3D c CD

fi c 10-11 CD O CO O CO CD E 10-12 CC u, n 3 0 O 3 D •»—• CO 3 S•*—> 10-1 !jl 43D 0 X 111 53D

4 IO-1 ''•*•• 1' m" l I 1 1 1 1 ml ' •••••• 1 10 100 1000

Electron temperature Te [eV] Fig. A1 Effective emission rate coefficient Effective emission rate coefficient Cf« (A.) [cm3/s] C|« (X) [cm3/s] o o o o O o o I i • I i CO I ro ni| • CO i i i i nii| I i I I ini| •I Mill (b ) 50 1 1 1 ED I 3 • 1 i 1 J 1 0 O I 01 o i 1 i o _JL o .6n m •M 3 O O S? o o o o CO bo L 3 A co iu -i ^ CO Z3 • 0 3 3 : "D N CD \ 0-^) - \ ' - «—t- \ c - —1 \ - 0 \ H • \ • CD • • ID ^^^r nil ^ , 1 i I I I III Effective emission rate coefficient Effective emission rate coefficient 3 C|£ (X) [cm3/s] Of" (X) [cm /s]

O O O O i o • o i I oo o GO r\o 1 II 11 III i i i iini| i i i i • • • 11 i I I /mi "V 1 J <"""V 1 1 r-, ' o i 3 m • 1 i i " '. CD 3 —L o J~-~- ^ . CO «• _i -vl r-4- § ! : CD o 1 -n CO *->. ^***^ o o o r ] O O O O O •* ^^ °"^ 00 -X -X —1. _1 " "" » •>. ZJ 1 «-•• -r* oo ro -*• CD ^ 3 J k^ \ 3 : 3 N \ > •o '- \ \ CD \ \ \ —r \ 0) \ «—y \ 1 1 1 1 III c \ 1 —1 11/ CD 1 \ 1 l • 1 / H / 1 - CD : / / " ii-ii "cF O I I MINI ,t. i >• i 111 o Line radiation power rate coefficient Line radiation power rate coefficient Pe« [eV cm3/s] P lf f [eV cm3/s] rad r d O O O o • i CO 00 I wmmml O 1 1 lllllll F • i •iHI o m • S CD . ^^^^^m^m^- _± O ^s^»w o •-+ 3 ^•t^T^^w i —n 03 O " ""^r^^^ij^^N. 13 "sVV t-t- * ^ ••" CD \ VX "S ° i : > % \\ CD -». • ! i i \\\ , «-•• • i i „ L _L —1. _J. m c o o o o \v\A CDCD m ^a a_i _Mi _xa - o o o o H VAT • CD •333ii i 3 , 03 CO 03 03 * 'AH i mm "j ^^^^^^^^^^J^^^^^^^^^^^^^^^^^^^^^^^^J^^^^ O 1 1 lllllll —_-^ « oo ro Normalized population density Normalized population density n(i)/nHe n(i)/nHe

Tl (p' > 4^ 105 1 (a) 504.8nm _ _ 1< -3 -10 Hem ]:

4 ^ 10 r 13 f —-10 ___ - - '. — -Z

CO 10" 103 r

1 " 102 • • 1 10 100

Electron temperature Te [eV] 4 10 • • T, -n—|. ri ni[ • i- i i i i 111 I (b) 501.6nm

1Q14 1Q11 [cm-3] J

1013 1012 3=E CDcD £" 103 CD CO

2 10 •t J- A J I • I 11 • 10 100

Electron temperature Te [eV] Fig. B1 4 10 i i 11 I I I I I U (c) 492.2nm

103 Q

CD CO 102

1 10 1 • • • I 1 • • 1 10 100

Electron temperature Te [eV] 5 10 p i i i i 111| i i i i i 11y i (d)471.3nm i4[cm-3L 104 r 10 <<: ---1013^" ^§ £• 103 CD CO

102

101 1 10 100

Electron temperature Te [eV] Fig. B1 Line intensity ratio Ljne intensity ratio Line intensity ratio Reff(492.2 nm / 471.3 nm) Reff(504-8 nm! 471 -3 nm) Reff(492.2 nm / 504.8 nm)

. , o o o o -* -* , -Lrooo4^tno)^ioocDo- '0 |>0004^(Jl0)-v|00CDO

i • i • i' i' i • i • • ° -!-| ttl • 1 • 1 • ,_,..,, r T-|-i-|-r- 1 • rf*^*S W . V- *"—' m • CD 4* • " CO • oi-*- vv —* • ro : : v » o ro n: =3 ^ \\» *"*««^. ~n Q. i Ol CQ 0 V *• o • Zi « 4^ . 03 CO 1 : oo: ro «-»• • x » *< 1 ! 13 L V". 0 ^ k± ,—, 4^ p co tf." o " CD 00 (j, \v 3 • < CD^ CD \ • CO < < « : .I.I.I. J 1111 i.l.,i IV Line intensity ratio Line intensity ratio Line intensity ratio Reff(504.8 nm / 471.3 nm) Reff(504.8 nm / 471.3 nm) Reff(504.8 nm / 4713 nm) Line intensity ratio |jne intensity ratio Line intensity ratio eff Reff(492.2 nm / 471.3 nm) Reff(492.2 nm / 471.3 nm) R (492.2 nm / 471.3 nm) Recent Issues of NFS Series

NIFS-302 K. Nishimura, R. Kumazawa, T. Mutoh, T. Watari, T. Seki, A. Ando, S. Masuda, F. Shinpo, S. Murakami, S. Okamura, H. Yamada, K. Matsuoka, S. Morita, T. Ozaki, K. Ida, H. Iguchi, I. Yamada, A. Ejiri, H. Idei, S. Muto, K. Tanaka, J. Xu, R. Akiyama, H. Arimoto, M. Isobe, M. Iwase, O. Kaneko, S. Kubo, T. Kawamoto, A. Lazaros, T. Morisaki, S. Sakakibara, Y. Takita, C. Takahashi and K. Tsumori, ICRF Heating in CHS; Sep. 1994 (IAEA-CN-60/A-6-I-4)

NIFS-303 S. Okamura, K. Matsuoka, K. Nishimura, K. Tsumori, R. Akiyama, S. Sakakibara, H. Yamada, S. Morita, T. Morisaki, N. Nakajima, K. Tanaka, J. Xu, K. Ida, H. Iguchi, A. Lazaros, T. Ozaki, H. Arimoto, A. Ejiri, M. Fujiwara, H. Idei, A. liyoshi, 0, Kaneko, K. Kawahata, T. Kawamoto, S. Kubo, T. Kuroda, O. Motojima, V.D. Pustovitov, A. Sagara, C. Takahashi, K. Toi and I. Yamada, High Beta Experiments in CHS; Sep. 1994 (IAEA-CN-60/A-2-IV-3)

NIFS-304 K. Ida, H. Idei, H. Sanuki, K. Itoh, J. Xu, S. Hidekuma, K. Kondo, A. Sahara, H. Zushi, S.-l. Itoh, A. Fukuyama, K. Adati, R. Akiyama, S. Bessho, A. Ejiri, A. Fujisawa, M. Fujiwara, Y. Hamada, S. Hirokura, H. Iguchi, O. Kaneko, K. Kawahata, Y. Kawasumi, M. Kojima, S. Kubo, H. Kuramoto, A. Lazaros, R. Liang, K. Matsuoka, T. Minami, T. Mizuuchi, T. Morisaki, S. Morita, K. Nagasaki, K. Narihara, K. Nishimura, A. Nishizawa, T. Obiki, H. Okada, S. Okamura, T. Ozaki, S. Sakakibara, H. Sakakita, A. Sagara, F. Sano, M. Sasao, K. Sato, K.N. Sato, T. Saeki, S. Sudo, C. Takahashi, K. Tanaka, K. Tsumori, H.Yamada, I. Yamada, Y. Takita, T. Tuzuki, K. Toi and T. Watari, Control of Radial Electric Field in Torus Plasma; Sep. 1994 (IAEA-CN-60/A-2-IV-2)

NIFS-305 T. Hayashi, T. Sato, N. Nakajima, K. Ichiguchi, P. Merkel, J. Nuhrenberg, U. Schwenn, H. Gardner, A. Bhattacharjee and C.C.Hegna, Behavior of Magnetic Islands in 3D MHD Equilibria of Helical Devices; Sep. 1994 (IAEA-CN-60/D-2-II-4)

NIFS-306 S. Murakami, M. Okamoto, N. Nakajima, K.Y. Watanabe, T. Watari, T. Mutoh, R. Kumazawa and T. Seki, Monte Carlo Simulation for ICRF Heating in HeliotronlTorsatrons] Sep. 1994 (IAEA-CN-60/D-P-I-14)

NIFS-307 Y. Takeiri, A. Ando, O. Kaneko, Y. Oka, K. Tsumori, R. Akiyama, E. Asano, T. Kawamoto, T. Kuroda, M. Tanaka and H. Kawakami, Development of an Intense Negative Hydrogen Ion Source with a Wide- Range of External Magnetic Filter Field; Sep. 1994 NIFS-308 T. Hayashi, T. Sato, HJ. Gardner and J.D. Meiss, Evolution of Magnetic Islands in a Heliac; Sep. 1994

Ni FS-309 H. Amo, T. Sato and A. Kageyama, Intermittent Energy Bursts and Recurrent Topological Change of a Twisting Magnetic Flux Tube; Sep.1994

NIFS-310 T. Yamagishi and H. Sanuki, Effect of Anomalous Plasma Transport on Radial Electric Field in Torsatron/Heliotron; Sep. 1994

NIFS-311 K. Watanabe, T. Sato and Y. Nakayama, Current-profile Flattening and Hot Core Shift due to the Nonlinear Development of Resistive Kink Mode; Oct. 1994

NIFS-312 M. Salimullah, B. Dasgupta, K. Watanabe and T. Sato, Modification and Damping of Alfven Waves in a Magnetized Dusty Plasma; Oct. 1994

NIFS-313 K. Ida, Y. Miura, S -I. Itoh, J.V. Hofmann, A. Fukuyama, S. Hidekuma, H. Sanuki, H. ldei, H. Yamada, H. lguchi, K. Itoh, Physical Mechanism Determining the Radial Electric Field and its Radial Structure in a Toroidal Plasma; Oct. 1994

NIFS-314 Shao-ping Zhu, R. Horiuchi, T. Sato and The Complexity Simulation Group, Non-Taylor Magnetohydrodynamic Self-Organization; Oct. 1994

NIFS-315 M.Tanaka, Collisionless Magnetic Reconnection Associated with Coalescence of Flux Bundles; Nov. 1994 NIFS-316 M.Tanaka, Macro-EM Particle Simulation Method and A Study of Collisionless Magnetic Reconnection; Nov. 1994

NIFS-317 A. Fujisawa, H. Iguchi, M. Sasao and Y. Hamada, Second Order Focusing Property of 210° Cylindrical Energy Analyzer; Nov. 1994

NIFS-318 T. Sato and Complexity Simulation Group, Complexity in Plasma -A Grand View of Self- Organization; Nov. 1994

NIFS-319 Y. Todo, T. Sato, K. Watanabe, T.H. Watanabe and R. Horiuchi, MHD-Vlasov Simulation of the Toroidal Alfven Eigenmode; Nov. 1994

NIFS-320 A. Kageyama, T. Sato and The Complexity Simulation Group, Computer Simulation of a Magnetohydrodynamic Dynamo II: Nov. 1994

NIFS-321 A. Bhattacharjee, T. Hayashi, C.C.Hegna, N. Nakajima and T. Sato, Theory of Pressure-induced Islands and Self healing in Three- dimensional Toroidal Magnetohydrodynamic Equilibria; Nov. 1994

NIFS-322 A. liyoshi, K. Yamazaki and the LHD Group, Recent Studies of the Large Helical Device; Nov. 1994

NIFS - 3 23 A. liyoshi and K. Yamazaki, The Next Large Helical Devices; Nov. 1994

NIFS-324 V.D. Pustovitov Quasisymmetry Equations for Conventional Stellarators; Nov. 1994

NIFS-325 A. Taniike, M. Sasao, Y. Hamada, J. Fujita, M. Wada, The Energy Broadening Resulting from Electron Stripping Process of a Low Energy Au~ Beam; Dec. 1994

NIFS-326 I. Viniar and S. Sudo, New Pellet Production and Acceleration Technologies for High Speed Pellet Injection System "HIPEL" in Large Helical Device; Dec. 1994

NIFS-327 Y. Hamada, A. Nishizawa, Y. Kawasumi, K. Kawahata, K. Itoh, A. Ejiri, K. Toi, K. Narihara, K. Sato, T. Seki, H. Iguchi, A. Fujisawa, K. Adachi, S. Hidekuma, S. Hirokura, K. Ida, M. Kojima, J. Koong, R. Kumazawa, H. Kuramoto, R. Liang, T. Minami, H. Sakakita, M. Sasao, K.N. Sato, T. Tsuzuki, J. Xu, I. Yamada, T. Watari, Fast Potential Change in Sawteeth in JIPP T-IIU Tokamak Plasmas; Dec. 1994

NIFS-328 V.D. Pustovitov, Effect of Satellite Helical Harmonics on the Stellarator Configuration; Dec. 1994

NIFS-329 K. Itoh, S-l. Itoh and A. Fukuyama. A Model of Sawtooth Based on the Transport Catastrophe; Dec. 1994

NIFS-330 K. Nagasaki, A. Ejiri, Launching Conditions for Electron Cyclotron Heating in a Sheared Magnetic Field; Jan. 1995

NIFS-331 T.H. Watanabe, Y. Todo, R. Horiuchi, K. Watanabe, T. Sato, An Advanced Electrostatic Particle Simulation Algorithm for Implicit Time Integration; Jan. 1995

NIFS-332 N. Bekki and T. Karakisawa, Bifurcations from Periodic Solution in a Simplified Model of Two- dimensional Magnetoconvection; Jan. 1995

NIFS-333 K. Itoh, S.-l. Itoh, M. Yagi, A. Fukuyama, Theory of Anomalous Transport in Reverse Field Pinch; Jan. 1995 NIFS-334 K. Nagasaki, A. Isayama and A. Ejiri Application of Grating Polarizer to 106.4GHz ECH System on Heliotron-E; Jan. 1995

NIFS-335 H. Takamaru, T. Sato, R. Horiuchi, K. Watanabe and Complexity Simulation Group, A Self-Consistent Open Boundary Model for Particle Simulation in Plasmas', Feb. 1995

NIFS-336 B.B. Kadomtsev, Quantum Telegragh : is it possible?; Feb. 1995

NIFS-337 B.B.Kadomtsev, Ball Lightning as Self-Organization Phenomenon; Feb. 1995

NIFS-338 Y. Takeiri, A. Ando, O. Kaneko, Y. Oka, K.Tsumori, R. Akiyama, E. Asano, T. Kawamoto, M. Tanaka and T. Kuroda, High-Energy Acceleration of an Intense Negative Ion Beam; Feb. 1995

NIFS-339 K. Toi, T. Morisaki, S. Sakakibara, S. Ohdachi, T.Minami, S. Morita, H. Yamada, K. Tanaka, K. Ida, S. Okamura, A. Ejiri, H. Iguchi, K. Nishimura, K. Matsuoka, A. Ando, J. Xu, I. Yamada, K. Narihara, R. Akiyama, H. Idei, S. Kubo, T. Ozaki, C. Takahashi, K. Tsumori, H-Mode Study in CHS; Feb. 1995

NIFS-340 T. Okada and H. Tazawa, Filamentation Instability in a Light Ion Beam-plasma System with External Magnetic Field; Feb. 1995

NIFS-341 T. Watanbe, G. Gnudi, A New Algorithm for Differential-Algebraic Equations Based on HIDM; Feb. 13, 1995

NIFS-342 Y. Nejoh, New Stationary Solutions of the Nonlinear Drift Wave Equation; Feb. 1995

NIFS-343 A. Ejiri, S. Sakakibara and K. Kawahata, Signal Based Mixing Analysis for the Magnetohydrodynamic Mode Reconstruction from Homodyne Microwave Reflectometry; Mar.. 1995

NIFS-344 B.B.Kadomtsev, K. Itoh, S.-l. Itoh Fast Change in Core Transport after L-H Transition; Mar. 1995

NIFS-345 W.X. Wang, M. Okamoto, N. Nakajima and S. Murakami, An Accurate Nonlinear Monte Carlo Collision Operator; Mar. 1995