Theory Weekly Highlights for June 2003

June 27 2003

A plan has been implemented to replace the existing MDSplus data server for the DIII-D community. The exiting server is a 5-year old single processor workstation that slows down considerably during DIII-D operation resulting in a factor of 10 reduction in data retrieval rates by the scientific team. The new server being ordered is a 4-processor Linux server offering over 20 times faster data retrieval under the heaviest load. The current MDSplus server has total storage of 520GB, of which 300GB are used. The new server will come with 730GB effective internal storage, which will keep up with the increasing storage need for the analyzed data until year 2006 at the projected data growth rate.

June 20 2003

An analytic kinetic theory of the transition process between circulating and trapped electrons has been developed in a unified gyro-fluid model and incorporated into the GLF2003 theory based transport model. The GLF2003 gyrofluid equations were fit to the kinetic theory. The loss of bounce averaging as the mode frequency exceeds the bounce frequency has an important impact on the Landau damping. One especially interesting consequence of the bounce average loss effect is in reducing the fraction of trapped particles that can bounce average when the parallel wavenumber of the toroidal drift wave instability is increased. The new model greatly improves the fidelity of GLF2003 to the fully kinetic linear stability results.

June 13 2003

In recent work to appear in Physical Review E, neoclassical transport coefficients were re-derived for the case of small toroidal rotation using the method of matched asymptotic expansions. This alternative derivation resulted in a full set of transport equations written in a transparent form for large aspect ratio flux surfaces. The method has now been extended to the case of large toroidal rotation velocity. For this purpose, a new formulation of the large rotation theory based on the drift kinetic equation is used, and a complete set of transport equations for both the electron and the ion channels is again obtained. In particular, the new derivation for the angular momentum flux, using the inverse aspect ratio as a small parameter, justifies the previous variational principle approach. All transport coefficients are found to be significantly enhanced by rotation. These coefficients are useful as limits to compare with existing and future numerical results as well as the formulas presently used in transport codes.

June 06 2003

The DOE/MICS-appointed National Fusion Collaboratory (NFC) Review Committee carried out a 2 day review of the NFC, 18 months into this three year SciDAC project. The review was attended by representatives of the NFC Fusion Science partners (GA, MIT, PPPL), and the Computer Science partners (ANL, LBNL, Princeton University and University of Utah Computer Science departments); the committee as well was composed of representatives from Fusion and Computer Science. The initial findings of the review committee were very positive, as illustrated by these excerpts from the committee's preliminary report:

  • Overall the results of the project are very impressive, especially at the half-way point.
  • Grid-based TRANSP transition to be THE production service [for US tokamak experiments] is a tremendous success – a real impact!

The review covered in detail all three major aspects of the NFC project: remote and distributed computation, security, and visualization. The final report will be posted to the project website, Fusion Grid, when it becomes available.

These highlights are reports of research work in progress and are accordingly subject to change or modification