# National Institure for Standards and Technology, USA

- Institution
- National Institute of Standards and Technology, USA
- Contact
- Y. Ralchenko http://nlte.nist.gov/FLY/
- Codes
- MCHF, GRASP2K, FLYCHK, NOMAD
- Description
- MCHF and GRASP2K codes are non-relativistic and relativistic atomic structure packages, respectively, and are used to calculate energy levels, transition probabilities, isotope shifts and hyperfine structure. The FLYCHK code is an on-line CR code (non-Maxwellian plasmas, radiation field, opacity effects and mixtures) available at the above web site, and can produce the following output parameters: reaction rates, ionization distribution, power losses and UTA spectra. FLYCHK contains detailed data for hydrogen-, helium- and lithium-like atoms and ions and uses the hydrogenic approximation with screening parameters for other ions. The NOMAD code is similar to FLYCHK, but is more useful for spectroscopic diagnostics - data normally include detailed structure for all relevant ions, as well as non-Maxwellian ions, radiation field, opacity effects and mixtures. This code is applicable to CXRS problems, and there are plans to have a version on-line in the future.

**Atomic and plasma codes at NIST** ^{[1]}

We present a set of atomic structure and plasma kinetics codes that are being developed or hosted at NIST. The most advanced methods in atomic structure theory are implemented in non-relativistic Multiconfiguration Hartree-Fock (MCHF) and relativistic Multiconfiguration Dirac-Fock (MCDF) codes. An example of an MCDF code is provided by the GRASP2K package which is being maintained and improved by C. Froese Fischer in collaboration with several researchers from other countries. C. Froese Fischer also develops the MCHF code. Both these packages as well as some simpler codes are available for free download from the NIST web site. Yu. Ralchenko presented some examples of recent highly accurate results obtained with MCHF and GRASP2K codes for atoms and ions of relevance to fusion research.

The NIST Atomic Spectroscopy Group also develops sophisticated collisional-radiative models for calculation of plasma population kinetics and emission characteristics. The NOMAD code is used for calculation of spectral patterns in the EBIT experiments with highly-charged ions of tungsten and other heavy elements. This detailed code is also used for simulations on neutral beam spectroscopy in fusion machines, e.g., charge exchange recombination spectroscopy and motional Stark effect. Another advanced collisional-radiative code FLYCHK developed by LLNL researchers and available for online calculations on the NIST site is used by hundreds of researchers, including specialists in fusion plasmas for calculations of ionization distribution, radiative power losses and other important parameters.

**References**