Comparison of HELIX TWT Simulation Using 2-D PIC (Magic), 2-D Modal (Gator), and 1-D Modal (Christine) Methods
Abstract
A series of comparisons between three different helix TWT design and simulation codes has been performed. The codes represent various different levels of approximation and speed. All codes utilize the sheath helix approximation. The 2-D PIC code, MAGIC, solves the Maxwell-Lorentz equations directly, in time, through simulations with large numbers of particles. Therefore, it is expected that the PIC code is capable of resolving the space-charge effects accurately. Unfortunately, because of long run times, it is difficult to perform many simulations with many different parameters in a timely manner, allowing a device to be designed and optimized numerically. The 2-D parametric code GATOR solves the envelope equation for the mode amplitude (hence the name "modal") of the electromagnetic field, and models the electron beam as an ensemble of rings of variable radius, making it much faster than the MAGIC code. However, the models to evaluate the DC and AC space-charge fields in GATOR are phenomenological, and typically less accurate over a wide range of parameters than in a PIC code. An important goal of the work reported here is to provide understanding of and possible improvement to the electrostatic model implemented in GATOR. The 1-D parametric code CHRISTINE is the fastest of the three codes, and it includes built-in parametric scan capability. Like GATOR it solves the envelope equation for the field amplitude in time and position, but it tracks only the axial particle motion. Its simple fixed disc model also allows for self-consistent calculation of the AC space-charge field. For a device whose electron beam is well confined by the radial focusing forces, CHRISTINE is able to reproduce accurately the performance of the device. Indeed, all three codes are in excellent agreement in the limit of a very strong solenoid magnetic field. Results of the comparison between MAGIC and GATOR for both a solenoid and PPM focusing cases will be discussed.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1998
- Accession Number
- ADA348847
Entities
People
- B. Levush
- David N. Smithe
- E. Zaidman
- H. Freund
- T. M. Antonsen Jr.