Priorities in Fusion Data Compilation

The long-term priorities in A+M and PMI data needs for fusion energy research are regularly reviewed during the IAEA Data Centre Network (DCN) Meeting on "Technical Aspects of A+M Data Processing and Exchange". With regard to data production, both large scale advanced calculations as well as benchmark experiments for validation are needed. The DCN also supports the development of XSAMS (XML Schema for Atoms, Molecules and Solids), a new standard for AM/PMI data exchange, as reliable and convenient tools for data exchange are essential with the development of Internet Technologies. The last DCN meeting was held in September 7-9, 2009 in the IAEA Headquarters in Vienna.

Atomic and Molecular Data

Spectroscopic Data

Transition probabilities for Be, C, N and O and their ions are needed, as well as data for heavy elements like Fe, Cl, Kr, Mo, Cu and W.
Transition probabilities for H, D,T, He, Li, Na, Mg, Al, Si and S are done for all ionization stages at the NIST Data Center for Atomic Spectroscopy. Data compilations for Be, B, Ne, Ar and Cs are in progress.
Energy levels and wavelengths for metallic ions and high-Z impurities are needed.
- W: compilation of some structure data (ionization energies, low lying energy levels etc.) is complete for all ionization stages of W. More detailed data are needed for most ionization stages.
- Xe, Kr and Ar: There are urgent needs of data production for high ionization stages. First compilations for Kr and Xe have been completed, but they are rather incomplete. Argon is of interest for further work.
- Data for Hf and Ta are identified as of possible importance for erosion measurements and for spectral comparisons.
Complete spectroscopic characterizations of heavy noble gas ions are needed. Ne is in good shape and progress is being made on Ar.
The DCN will enhance its expertise to address spectroscopic molecular data priorities. Some of the following data, where needs are identified, may already be available in some molecular databases.
- Spectroscopic characterization of H₂, H₂^*, H₂⁺, H₃⁺ and isotopic variants.
- Impurity plasma edge molecules: CO, CO₂, CH₄, CH, C₂, BeH₂, BH, N₂ and LiH and other hydrocarbons and radicals, including hydrogen isotopic variants.

Collisional Data for Plasma Edge Studies

This section includes neutral particle transport modeling and diagnostics, H-recycling and He-exhaust. All the molecular data are needed for different hydrogen isotopes, including mixed molecules like DT.

Elastic collisions, charge transfer, inelastic collisions of H, H₂, H⁺, H₂⁺, H₃⁺ with H₂ at low and intermediate energies (0 to 10 keV). Much data have been produced, but much more are needed.
H^- + H, H₂ (e.g. detachment, excitation, dissociation)
Electronic excitation and ionization of vibrationally excited H₂^*(v) and H₂⁺(v) in low-energy collisions with e (including dissociative processes and information on energy distribution of reaction products). The NIFS-DATA-73 and the APID vol. 13 (CRP on "Molecular Processes in Fusion Plasmas") are covering a significant part of these needs, as cross sections for H₂⁺ and the rate coefficients for dissociation of H₂^*(v).
Inelastic electronic collision processes of He, He⁺, He²⁺ and excited states of H, He and H₂ at low energies.
Inelastic collision processes of He, He⁺ and He²⁺ with H, H⁺, H₂, H₂⁺ at low energies, including processes with excited H, He and H₂.

Despite considerable progress made in CRP work, there continues to be a need for data production and evaluation for collisional data for hydrocarbons and other molecules relevant to fusion devices:

Further development of the databases for hydrocarbons, H₂O and CO, and Be^-, B^- oxides and hydrides (including their ions).
For hydrocarbons, all processes with electrons and protons should be considered including vibrational excitation.
Particle interchange reactions among primary species, C, O, metals and hydrocarbons. Some data are published in APID 13 on "Molecular Processes in Fusion Plasmas" and NIFS and FZ Julich Reports on hydrocarbons
There is much interest in CH excitation and a need for state resolved data.

Regarding collision processes of high-Z impurities, the CRP on "Atomic Data for Heavy Element Impurities in Fusion Reactors" is addressing some of these issues, concentrating on W and the noble gases. A CRP on tungsten will be initiated in 2010.

Data are needed in priority order for collisions of abundant ions and neutrals of W, Ar, Kr, Xe, Mo and V with e, H⁺, H, H₂. Amongst the W stages, the neutral and singly ionized are of especially high priority.

From previous data priority lists, the following data needs have been addressed. Existing databases appear to be sufficient at this time and no new requests have been made recently:

Elastic and momentum transfer ion-neutral and neutral-neutral collisions in the energy range 0.1 eV - 1 keV/amu, involving H, H⁺, He, He⁺, He²⁺, H₂ and H₂⁺.
Ro-vibrational electronic excitation and attachment for D₂, T₂, DT.
Completion of collisional databases for Be, B and their ions. It includes collision processes of Be^q+, B^q+ with electrons.

Collisional Data for neutral particle beam heating

Data for collision processes of the ions H₂⁺, H₃⁺ with e, H, H⁺, H₂, H₂⁺, He²⁺ from threshold to 1 keV.
Regarding interaction of the neutral beam with the plasma, collisions involving H^* are of importance.
Data for collisional processes H^- on (H^-, e, H, H₂, H₂⁺) in ion beam used (after neutralization) for plasma heating. (Pertinent energy range: from threshold to 1 MeV). Data are needed for loss mechanisms in beams, including stripping.
Charge loss for H^- + H^- collisions at energies from 0 to 20 eV.
Data needed for elastic collisions between negative hydrogen and neutral hydrogen molecule.

Radiative Plasma Cooling

These data are important for determination of ionization balance and radiation losses. It would be very useful to formulate updated and new tables of cooling rates.

Core plasma

Electron impact processes (excitation, ionization, radiative and dielectronic recombination) of medium- and high-Z impurities (W, Ar, Ne, Kr, Xe are highest priority, with V, Ti, Cr, Fe, Ni, Mo of lower priority). Pertinent temperature range is from ~1 keV to ~30 keV. A large amount of data exists for Ti and Fe, but dielectronic recombination rate coefficients are not adequate for L-shell and M-shell ions even for Fe. The CRP on "Atomic Data for Heavy Element Impurities in Fusion Reactors" addressed some of these issues.

Edge plasma

Data are needed for edge temperature (threshold to ~500eV) charge exchange processes among intrinsic impurities and plasma components:

Collisions of Xq+ (X = W, Be, C, He, N, O, Li, B of highest priority, with Cl, V, Ti, Cr, Fe, Ni, Mo of lower priority) with H, H₂, He, H⁺ and H₂⁺ including state selective electron capture.
Data are needed for all processes of N, N₂, Kr, Ne, Ar and Xe with e, H, H⁺, H₂, H₂⁺, He⁺, and H^- (for the proposed radiative cooling scheme of divertors and radiative mantle).

Plasma-Material Interaction

Erosion

Assessment of data needed for Be, BeO, carbon-based materials and medium- and high-Z materials (W, Ti, V, Mo, Nb). Data for physical sputtering yields are known. Energy dependence at normal incidence is satisfactory. Data for angle dependence is not as complete as for normal incidence. Data on sputtered energy (to allow the determination of the mean energy of sputtered atoms) also exist but have not been fitted, and not yet included in database. This can be done through consultancy.
Mixed materials will arise from Be, C and W. Without means of knowing the impurity flux, it is difficult to address this issue, see results from previous CRP on mixed materials. Characterization of the mixed materials is of interest.
Characterization of erosion products such as dust, films, flakes etc.
Need exists for chemical sputtering for carbon based materials. This is being addressed by the ongoing CRP on "Data for Surface Composition Dynamics Relevant to Erosion Processes".
Investigation of erosion and target properties data for materials involved in ELMs and disruptions is important.

Hydrogen isotope reflection, retention and release in fusion materials and codeposited layers

H/D/T permeability, diffusivity, solubility, desorption rate and surface reactions. Materials of interest are W, Be, BeO, Mo, carbon based materials, deposited and codeposited layers of these materials. Data on traps in materials. The CRP on "Tritium Inventory in Fusion Reactors" addressed much of this for Be, C and W.
Angular and energy distribution of H, D, H^-, D^- scattering on surface (particularly on C) at glancing angles and energy from 50 keV to 1 MeV
Charge state as well as electronic and ro-vibrational (molecular) states for reflected and sputtered particles may be important. Many data are now available for reflection of hydrogen isotopes as well as others such as noble gases, in the energy range of ~10 eV - ~100 keV.

Molecular balance on surfaces

There is a strong need of data in this area, emphasizing inclusion of molecular vibration:

Molecule and molecular ion formation and destruction with identification of product charge and quantum state.

Data for hydrocarbons and H^- formation on surfaces, particle sticking, pumping, gettering, and recycling.

Material Properties

Data collection and generation are needed:

Data on size distribution, composition, formation etc for erosion products (dust, flakes etc) containing C, Be, W. A CRP was initiated in 2008 on dust formation and characterization.

Tritium retention in erosion products.

Chemical properties of erosion products.

Mobilization of particles. Good diagnostics will be important.

Neutron induced damage, gas bubble formation in wall material from protons and alpha particles formed by neutron reactions and directly from fusion plasma implantation.