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Rybarcyk, Lawrence J.

Publications and source records attributed to Rybarcyk, Lawrence J..

3 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Hot filament performance in a Freeman ion source

Here, we report on the simulation results of the hot tungsten filament behavior in a Freeman ions source installed in the LANL electro-magnetic isotope separator (EMIS). The Freeman source enables us to ionize and extract high intensity single-charge ion beams from different gases as well as from various solid materials in order to purify the content of a selected isotope. We have modified our LANSCE H– Ion Source Filament Model to calculate the ion source working parameters during a beam production cycle and estimate the ion source filament lifetime. Two main mass erosion processes of the hot cathode in a Freeman ion source are included: thermal evaporation and plasma sputtering. The initial working temperature of the ion source filament was estimated to be in range of 2400 to 2500 K. The filament model shows that the plasma sputtering rate is several magnitude of order higher than the thermal evaporation rate. The results of ion source modeling were compared with recorded data during the EMIS beam production runs using krypton noble gas.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

RF Gap Transformation in PARMILA

The PARMILA (Phase And Radial Motion in Ion Linear Accelerators) code is used to design ion linacs and simulate the beam dynamics therein. The original code was developed in the 1960’s and later the Los Alamos Accelerator Code Group developed a PC version that has been used worldwide. Recently, in an effort to modernize the code and use it as the basis for a high-performance beam dynamics simulator with the LANSCE linac, the details of the code have come under additional scrutiny. PARMILA is a “z code” that uses various transformations to approximately represent the effect of the beam line element on the beam. In the case of the RF gap, it treats the particle dynamics inside the gap as a combination of drift + kick at the mid-plane + drift. Recently, we uncovered an undocumented keyword “off-exact” in PARMILA that enables the code to use the full modified-Bessel functions instead of low-order approximations in the RF gap transformation. This change improved the accuracy of the transformation for off-axis particles. However, a discrepancy between the analytical formula and the code was found for the transformation of the transverse coordinates. The purpose of this tech note is to document the derivation of the gap transformation and the related DTL cell length calculation used in the PARMILA code.

43 PARTICLE ACCELERATORS↗