J. Plasma Fusion Res. SERIES, Vol.7 (2006) 352-355

Atomic and Molecular Data Activities for Fusion Research at JAERIKUBO Hirotaka, SATAKA Masao and SHIRAI Toshizo∗
Japan Atomic Energy Research Institute∗∗ , Ibaraki 311-0193, Japan（Received: 4 October 2004 / Accepted: 21 September 2005）

Abstract
This paper gives an overview of recent atomic and molecular data activities for fusion research at Japan
Atomic Energy Research Institute: JAERI. Cross sections for atomic and molecular collisions relevant tofusion research have been compiled and evaluated. Analytical formulas have been derived from the evaluatedcross section data to facilitate practical use of the data. Regarding spectral data, wavelengths, energy levels,
oscillator strengths, transition probabilities and ionization energies have been critically compiled for highly
ionized atoms, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Kr, and Mo, that can occur as impurities in fusion plasmas. In
addition to data compilation and evaluation, atomic and molecular data required for fusion research have also
been produced.
Keywords:
atomic and molecular data, cross section, spectral line, fusion research, JAERI, hydrogen, helium, impurity
1．Introduction
In fusion reactors, heat and particle control is essential for obtaining high fusion performance and preventing damage of the plasma-facing materials. Plasma
modeling considering atomic and molecular processes
is necessary for establishment of such control [1].
Atomic and molecular processes are also applied to various plasma diagnostics [2]. Atomic and molecular dataof fuel hydrogen, helium produced by the fusion reactions and impurities produced from plasma-facing materials by plasma-surface interaction or injected for heat
control or plasma diagnostics are required for plasma
modeling and diagnostics.
Recently, roles of atomic and molecular collisions
have been intensified by emphasis on cold divertor plasmas, which are attractive for mitigating severe problemsof concentrated power loading of divertor plates. Therefore, the need of cross sections is becoming larger forcollisions that are important in cold divertor plasmas. In
cold divertor plasmas, collisions of neutral or low ionized atoms and molecules at low collision energies areimportant. On the other hand, spectroscopic data, wavelength, transition probabilities, energy levels and ionization energies, are basic and essential quantities forplasma diagnostics and modeling. Spectroscopic data
for light atoms are fairly available [3]. However, spectroscopic data for heavy atoms are not suﬃcient at thepresent and their compilation and production is important.

This paper gives an overview of recent atomic andmolecular data activities for fusion research at JAERI.
We have been compiling cross section data for atomic
and molecular collisions and spectral data relevant tofusion research. We have also been producing atomic
and molecular data required for fusion research.
2．Compilation and evaluation of cross section
dataWe have been compiling cross sections for atomicand molecular collisions and deriving analyticalformulas from the evaluated data to facilitate practical use of the data [4]. The databases of Japanese
Evaluated Atomic and Molecular Data Library,
JEAMDL, are available for ∼900 collision processes through the Web at the URL www-jt60.naka.
jaeri.go.jp/JEAMDL/index.html. Cross sections for thefollowing fusion-relevant processes were evaluated:charge transfer of H atoms and ions colliding withgaseous atoms and molecules [5], charge transfer of H
atoms and ions colliding with metal vapor [6], stateselective electron capture of C6+ and O8+ ions colliding
with H atoms [7], collisions of H, H2 , He and Li atoms
and ions with atoms and molecules [8-11], collisions of
H+ , H2 + , H3 + , H, H2 and H− with H2 molecules [12],electron collisions with CO, CO2 and H2 O molecules[13], electron collisions with hydrocarbon molecules(CH4 , C2 H6 , C2 H4 , C2 H2 , C3 H8 and C3 H6 ) [14]. The
databases include many processes for the species andCorresponding author’s e-mail: kubo.hirotaka@jaea.go.jp* Deceased.
** Present: Japan Atomic Energy Agency

C 2006 by The Japan Society of Plasma

Science and Nuclear Fusion Research352

Atomic and Molecular Data Activities for Fusion Research at JAERI

they cover wide collision energy ranges, typicallyfrom near the threshold energies to around 1 keV. The
charge-transfer cross sections are required for modelingand diagnostics of fusion plasmas and development of
neutral beam heating systems. The cross sections ofstate-selective electron capture of C6+ and O8+ ions colliding with hydrogen atoms are particularly importantfor charge exchange recombination spectroscopy [2].
Compilation of molecular data is recently emphasized,
since low-temperature divertor plasmas have beenrealized and molecular processes are becoming more
important [15,16]. Recently, we have been evaluating
cross sections for electron collisions with N2 , which has
been injected for heat control [17] and cross sectionsfor He atoms and ions.
Figure 1 shows an example of the complied crosssection data: total ionization cross sections of CH 4 byelectron collisions [14]. The data points indicate measured cross sections, and the curve indicates an analytical fitting. The fitted formula is expresses as

analytical formulas are useful for plasma modeling.
3．Compilation and evaluation of spectral data
We have published a monograph on spectral data forhighly ionized atoms, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Krand Mo, in collaboration with National Institute of Standards and Technology [18]. In the monograph, criticallyevaluated data for wavelengths, energy levels, oscillator strengths, transition probabilities and ionization energies are tabulated. Both observed and calculated data
are compiled. The data tables include data for all ionization stages from Ca-like through H-like, except for Krand Mo that start at Ge-like and Rb-like, respectively.
Forbidden lines, i.e., mainly magnetic dipole and electronic quadrupole transitions, are also included. The
metallic atoms can be produced from plasma-facing
materials of fusion devises by plasma surface interaction. For study of heavy impurity transport, measurement of ion temperature and enhancement of radiative
losses for heat control, Kr gas has been injected in several tokamaks [19]. The highly ionized atoms can occur
as impurities in main plasmas with high temperatures.
Recently, we have been compiling spectral data for
Ar, Ga and W ions [20]; compilation for W I and II
has been completed [21]. Argon injection has been
performed to enhance radiation losses for heat control
and to improve energy confinement at high densities[22]. Gallium is a candidate material for liquid divertors, which are innovative divertors to solve the problem of the divertor heat load [23]. Tungsten is one of
the candidate plasma-facing materials for future fusion
devises due to its low sputtering yield and good thermal properties. In ITER, the International Thermonuclear Experimental Reactor, tungsten is considered tobe used for the divertor baﬄes [24]. Many spectral lines
have been identified for neutral and low ionized (Z ≤ 6)
W atoms until now. However, identification of spectral
lines is not suﬃcient for highly ionized W atoms. Further study is required for spectral data of highly ionized
W atoms.

σ(E) = 10−16 a1 [ln (E/Eth ) + a2 ]/[Eth E(1 + (a3 /(E − Eth ))a4 )] cm2 ,where σ is the cross section, E is the incident electronenergy and Eth is the threshold energy of the ionization.
Here, Eth = 1.300 × 10−2 keV, a1 = 3.539 × 10−3 , a2 =3.600×10−2 , a3 = 3.730×10−2 , a4 = 9.060×10−1 . Such

4．Production of cross section data and spectral data
Cross sections for various hydrocarbon molecules
have been measured in collaboration with universities.
The cross sections are required to model behavior ofhydrocarbon molecules produced from carbon-based
plasma-facing materials by chemical sputtering [15].
Cross sections for charge transfer by C, Ne and Ar ionswith various hydrocarbon molecules were measured at
keV energies, and their dependence on the ionization
potentials, the total number of electrons and the num-Fig. 1 Total ionization cross sections of CH4 by electron
collisions [14]. The data points indicate the measured cross sections and the curve indicates ananalytical ﬁtting.
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Atomic and Molecular Data Activities for Fusion Research at JAERI

bers of the bonds of the hydrocarbon molecules wasfound [25,26]. Cross sections for electron collisions
with C2 H6 and C2 H4 molecules were measured in a collision energy range below 100 eV. Charge transfer crosssections of impurity ions produced from the plasmafacing materials, Be, B, C, Cr, Fe and Ni ions, withgaseous atoms and molecules have also been measured[27].
The spectral lines of C IV n = 5 − 6 (466.0 nm) andn = 6 − 7 (722.6 nm) sometimes appear bright in divertor plasmas due to charge exchange between C4+ ionsand excited H atoms: H∗ (n = 2). These visible lines
are useful to observe behavior of such highly ionized
C atoms in divertor plasmas [28]. Cross sections ofstate-selective electron capture in collisions of C 4+ ionswith the excited H atoms have been calculated using
a molecular-bases close-coupling method in a collisionenergy range of 60 - 6000 eV/amu [29]. The calculation showed that electrons are dominantly captured into
C3+ (n = 6) states.
Spectral lines of highly ionized Xe atoms have notbeen identified suﬃciently at the present. In JT-60U, Xe
has been injected for study of heavy-impurity transport.
We observed spectra in a wavelength range of 4 − 7
nm and we are analyzing spectral lines for n = 3 − 3transitions of highly ionized Xe ions. Calculation with
an impurity transport code showed that the Xe atoms
were dominantly ionized around 36 times at the plasma
center, where the electron temperature was ∼3 keV.

ties at JAERI are pursued with many collaborators: Drs.
W. L. Wiese, J. Reader, A. Kramida, C. Sansonetti (National Institute of Standards and Technology), Profs. M.
Imai, A. Itoh (Kyoto Univ.), T. Kusakabe (Kinki Univ.),
N. Shimakura (Niigata Univ.), T. Tabata (Osaka Prefecture Univ.), H. Tanaka (Sophia Univ.), Y. Itikawa (Inst.
of Space and Astronautical Science), Drs. A. Sasaki
and K. Moribayashi (JAERI). The authors would like toexpress their thanks to Dr. T. Ozeki of JAERI for his
support and encouragement.

[1]

[2]

[3]

[4]

5．SummaryWe have been compiling and producing cross section
data and spectral data for fusion research. Cross sections for atomic and molecular collisions relevant to fusion research have been evaluated and analytical formulas have been derived from the evaluated data. Spectral
data have been critically evaluated for highly ionizedatoms that can occur as impurities in fusion plasmas.
We have also been producing atomic and molecular datarequired for fusion research. Compilation and production of cross sections for collisions that play importantroles in cold divertor plasmas and spectroscopic data forheavy atoms are significant subjects of our present andfuture activities. The species in the scope of our data
activities are typically limited to the field of fusion research. However, the compiled databases are also useful for astrophysics, atomic physics and plasma engineering and so on, since they are comprehensive for thespecies.

[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]

Acknowledgements
At the present, the atomic and molecular data activi-

[15]
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