Fast snapshots that produce time-domain output without slowing down the ODE solverIn previous versions, time-domain output had to be generated with the tout keyword. Internally, tout instructs the GPT ODE solver to decrease its stepsizes in such a way that the particle coordinates are calculated exactly at the specified times. The tout algorithm starts to make small adjustments to the stepsizes ahead of the requested output time in order to end correctly. As a result, tout slows down the ODE solver. GPT version 3.1 has a new snapshot command that is completely decoupled from the stepping algorithm. The new snapshot keyword also writes the phase-space coordinates at the specified simulations times, but it does so using high-order interpolation instead of slowing down the ODE solver. For a series of time domain outputs with dense spacing this results in a significant performance increase without any loss in accuracy.
The new snapshot command is particularly useful when the CPU time is dominated by the calculation of the electromagnetic fields and not by the tracking itself, such as is the case in a molecular dynamics simulation of a diffraction experiment.
Perfect screens without interpolation error
Using the same interpolation algorithm as described above, the screens in GPT version 3.1 do not contain interpolation errors. That is to say, the interpolation error is always less than the tracking error. This allows the use of screen output in regions with very high field gradients. Without loss of accuracy it is now possible to position a large number of screens very densely together in a high-field region, even if particles pass several screens during one timestep.
A selection of the common features of GPT is listed below. Please contact us whenever you have any questions about the capabilities of GPT related to your project.
| Equations of motion 5th order embedded Runge-Kutta Adaptive stepsize control Best accuracy over 10-10 Any number and any type of particles Additional differential equations |
Windows User Interface* Fully integrated set-up editor On-line help Plots of raw GPT output Plots of all data-analysis results Plots of particle trajectories Multiple synchronized windows Wizards for custom elements |
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| Output At specified simulation times At 3D planes (nondestructive screens) Coordinates and electromagnetic fields Trajectory output |
Space-charge 3D particle-in-cell 3D point-to-point 1) 2D point-to-ray 2D point-to-circle |
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| Data-analysis Fully hierarchical Standard macroscopic quantities RMS, 90% and 100% Emittance Courant-Snyder parameters Histograms Color-density plots Support for files >>4 GB |
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Scanning and solving Automatic parameter scans Multi-dimension root-finder Multi-dimensional optimizer MPI scans over several PC's 2) |
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| Collector design Multiple-scattering plate, pipe, cone, torus, sphere, iris Current/Power density plots |
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| Beam line components barmagnet, bend, bz, bzsolenoid, circlecharge, drift, ecyl, erect, ezcell, linecharge, magline, magplate, magpoint, multislit, platecharge, pointcharge, quadrupole, rectcoil, rmax, sextupole, solenoid, trwcell, trwlinac, trwlinbm, undueqfo, unduplan, xymax Custom elements |
Interfaces with other codes 2D and 3D electrostatic field-maps 2D and 3D magnetostatic field-maps 2D TM cavity field-map Poisson/ Superfish interface Tabulated ascii input and output DXF output for 3D drawing software SDDS conversion utility |
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1) GPT version 3.0 contains a fast O(N log N)
point-to-point space charge model. The 2.8 release contains an O(N2)
version.
2) Platform dependant, see the GPT versions page for details.