Inner-shell Ionization

We also present calculations of inner-shell ionization of neutral Fe [7], which are compared to ionization measurements made from thin targets [21]. Although these calculations are not as directly relevant to fusion modeling efforts, we present them to highlight the capability of the Los Alamos Atomic Physics Codes to perform fully relativistic structure and collisional calculations. Such approaches may prove useful in modeling ionization and excitation from heavy, highly charged ions such as W, which is expected to play a crucial role in ITER.

Fig. 4 shows the K-shell ionization of neutral Fe. Fully relativistic distorted-wave calculations [7] are compared to measurements [21]. The fully relativistic capability in the Los Alamos suite of codes has been under development over the past 15 or so years [22]. The calculations begin with the RATS structure code, which is based on the Dirac-Fock-Slater approach of Sampson et al. [23]. Fully relativistic calculations of excitation and ionization are performed using appropriate options within the ACE and GIPPER codes, respectively, which are based on the distorted-wave approach of Zhang et al. [24, 25]. The calculations are in excellent agreement with the measurements. A further semirelativistic calculation (shown as the dashed line) is lower than the measurements, indicating the need for a fully relativistic approach when considering ionization at high energies from heavy targets.

FIG. 4. K-shell electron-impact ionization of neutral Fe. We compare our current calculations with the measurements of [21].

4. CONCLUSIONS

We have presented a brief overview of recent efforts made using the Los Alamos suite of atomic physics codes to compute collisional data of interest to fusion modeling. For ions that are twice or more ionized, the perturbative approaches used in the Los Alamos codes are expected to be accurate. In the future, it is expected that the atomic data needs for fusion modeling will be primarily focused on tungsten, due to its importance in the divertor region of ITER. The strength of the Los Alamos codes is the ability to compute large quantities of accurate atomic data in an efficient manner. In particular, it is straightforward to compute collisional data for excitation between, and ionization from, large numbers of configurations and/or levels, for a large number of ion stages of a given element. Thus the Los Alamos

103 Atomic Physics Codes are capable of generating many of the data needs for future fusion modeling.

ACKNOWLEDGMENTS

The Los Alamos National Laboratory is operated by Los Alamos National Security, LLC for the National Nuclear Security Administration of the U.S. Department of Energy under Contract No. DE-AC5206NA25396.

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