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Space Charge Simulations in GPT. Simon Jolly Imperial College FETS Meeting, 20/7/05. GPT Space Charge Models. Spacecharge3D - direct relativistic particle-particle interactions. Spacecharge3Dclassic - as above but ignores relativistic effects.
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Space Charge Simulations in GPT Simon Jolly Imperial College FETS Meeting, 20/7/05
GPT Space Charge Models • Spacecharge3D - direct relativistic particle-particle interactions. • Spacecharge3Dclassic - as above but ignores relativistic effects. • Spacecharge3Dmesh - mesh-based relativistic particle interactions using non-equidistant 3D multi-grid Poisson solver. • Spacecharge2Dline - models each particle as a line charge and calculates 2D field. • Spacecharge2Dcircle - models each particle as 2D charged circle.
GPT beam model • 600mm drift length used with no magnetic elements. • Cylindrical beam model: • x/y = 3.3x10-2 mm-mrad (normalised). • x/y = 10mm; x’/y’ = 10mrad (max). • 60 keV, 70 mA (but 10% space charge). • Pulse length from 1 ns - 1 s (infinite for SC2Dline model). • 10,000 particles (1,000 for quick sim.).
ENVEL/LINTRA Models (JP) • Same beam characteristics, similar model to SC2Dline. • Beam cylindrically symmetric, uniform distribution. • After 600mm drift, sims give similar results: • ENVEL: x = y = 20.47 mm, x’ = y’ = 23.28 mrad. • LINTRA: x = y= 20.55mm, x’ = y’ = 23.41 mrad. • Difference: 0.7% spatial and 1.4% angular. • Compare to GPT results…
SC2Dline - v - LINTRA Need to use SDDS and Matlab to do proper x’ and emittance calculations…
SC Models Pros and Cons • SC3D: “exact” solution, but very slow (scales as N2) and needs real beam model. • SC3Dmesh: fast version of SC3D, good for quick models with lots of particles (scales as N), but emittance is pulse-length dependent. • SC2Dline: much better emittance measurements due to “flattened” beam, but as slow as SC3D.