1 / 3

UCLA PARMELA (c. 1998)

SIGNIFICANT PHYSICS CHANGES Particle Loading/Noise Mitigation Hammersley sequence particle loading “quiet start” [from J. Gonichon, MIT], now adopted into LAACG release; Dithering of time step to reduce numerical microbunching;

jolie
Download Presentation

UCLA PARMELA (c. 1998)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. SIGNIFICANT PHYSICS CHANGES Particle Loading/Noise Mitigation Hammersley sequence particle loading “quiet start” [from J. Gonichon, MIT], now adopted into LAACG release; Dithering of time step to reduce numerical microbunching; “Realistic” particle loading, incorporating spatial and temporal density modulations and particle loading by direct sampling from a video image of the laser mode pattern. RF and Static Field Representation Arbitrary 3D Electromagnetic (or static) fields, via 40x40x100 point maps of (Ex,Ey,Ez,Bx,By,Bz), quadratically interpolated (nearest, linear and cubic interpolation also supported), supporting two simultaneous frequencies and arbitrary extent (N.B. Fringe fields of cavities may be represented); 1D (Bz(z)) and 2D (Br(r,z), Bz(r,z)) static magnetic fields, quadratically interpolated; PPM magnetic field representation (PCM, Sturrock, Offset-pole). E. Colby, SLAC/ARDB March 16, 2000 UCLA PARMELA (c. 1998)

  2. E. Colby, SLAC/ARDB March 16, 2000 • Space Charge and Image Charge Representation • Fully 3D space charge fields with arbitrary aspect ratio ellipsoidal charge clouds; • Partial port of Carlsten’s line-by-line algorithm incorporating coherent synchrotron radiation effects in bends. • Wakefield Effect Estimation (non-self consistent) • Loading and application of W||(z) and W(z) maps from ABCI, Xwake, etc. implemented as point transformations at element exits. • Corrected Physics Errors from Los Alamos 1995 Version • Removal of bizarre field-weighting at cathode that caused serious underestimation of image charge effects (RZ Mesh method for space charge); • Correction of error in exit fringe field term of BEND card (T313 element missing 1/r). • Diagnostics • Addition of many diagnostics for computing emittances, dumping RF, static magnetic and space charge fields, particle distributions, trajectories, etc.

  3. E. Colby, SLAC/ARDB March 16, 2000 Significant Non-physics Changes • PVM implementation of PARMELA with automatic job generation and semi-automated data analysis to perform large parameter scans quickly; • All output is in columnar ASCII files, not a binary TAPE2 file; • Development of a large library (>200 scripts and functions) of Matlab code for post-processing and displaying output from PARMELA. Physics Errors in PARMELA • Integration is non-symplectic (Euler method) • EM fields and space charge fields not self-consistently calculated in a common framework • Space charge calculation is electrostatic (no radiative effects included; no internal magnetic fields even at cathode where velocity sheer is substantial); • Cathode image charge treatment is relativistically incorrect (images placed at “present” rather than “retarded” positions, underestimating the induced energy spread) • 3D space charge evaluation technique is noisy

More Related