Spin push for TaperedPL#1433
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cemitch99 merged 5 commits intoMay 7, 2026
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ax3l
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Apr 24, 2026
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Thanks @carlandreaslindstrom . This one is just awaiting a benchmark test, which is almost ready and being finalized now. |
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@ax3l Actually, the benchmark that I had in mind requires implementing the spin push in |
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| // compute multipole magnetic field normalized by q/mc: | ||
| amrex::ParticleReal gamma_ref = refpart.gamma(); | ||
| T_Real const Bx = m_g * ( y + m_taper * x * y ) * gamma_ref * m_beta; | ||
| T_Real const By = -m_g * ( x + m_taper*0.5_prt * (powi<2>(x) + powi<2>(y)) ) * gamma_ref * m_beta; | ||
| T_Real const Bz = 0_prt; |
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Codex:
The magnetic field signs look opposite to the phase-space kick. The
ordinary push applies:dpx = -g * A;dpy = -g * B;
Following the convention used in Multipole.H, the normalized fields should be proportional to Bx = dpy * beta*gamma and By = -dpx * beta*gamma, so I’d expect: Bx = -m_g * (y + m_taper * x * y) * gamma_ref * m_beta; By = m_g * (x + 0.5_prt * m_taper * (powi<2>(x) + powi<2>(y))) * gamma_ref * m_beta; As written, the spin precession for taper=0 corresponds to the field sign of a defocusing plasma lens while the particle kick is focusing for m_g > 0.
Co-authored-by: Axel Huebl <axel.huebl@plasma.ninja>
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I see CI is failing. Merging #1454 now which will fix it. |
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This PR will be tested using #1452 |
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This PR adds the spin push for the thin tapered plasma lens element. Close #1154
Follow-up: add spin push for ChrPlasmaLens and benchmark against TaperedPL (with taper=0) for consistency check