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VERSION:2.0
PRODID:-//Memento EPFL//
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SUMMARY:Higher-order guiding-centre motion  in VENUS-LEVIS
DTSTART:20150618T103000
DTEND:20150618T113000
DTSTAMP:20260414T175430Z
UID:ffd7865cfee7c44428d95a6239600cc22fb6e8b84882f18539e4a175
CATEGORIES:Conferences - Seminars
DESCRIPTION:Samuel Lanthaler\, ETH-Z\nStarting from the full Lagrangian fo
 r a charged particle in a magnetic field\, Lie perturbation methods can be
  used to give a rigorous derivation of Hamiltonian guiding-centre equation
 s which are valid to any desired order in the Larmor radius. This geometri
 c perturbation approach has been used to obtain an analytic derivation of 
 the guiding-centre Lagrangian to second order. Over the past weeks\, the r
 esulting equations have been implemented in the VENUS-LEVIS code. The VENU
 S-LEVIS orbit-solver is designed to investigate fast ions in general 3D ma
 gnetic fields. It combines flexibility in the choice of coordinate system 
 with a strict Hamiltonian formulation of guiding-centre and full-orbit equ
 ations\, switching between the two in the event of strong field variation 
 (gradient\, curvature and torsion).\nI will show how the consistent use of
  Lie perturbation methods yields a natural switching between full and guid
 ing-centre orbits. In fact\, the availability of both push-forward and pul
 l-back operators would in principle allow for any quantity (e.g. a distrib
 ution function) given in terms of full orbit particle coordinates to be tr
 ansformed to the corresponding quantity in terms of guiding-centre coordin
 ates\, and vice versa. The new availability of these operators in VENUS-LE
 VIS should therefore enhance its flexibility in the future.\nGoing from fi
 rst to second order in the guiding-centre approximation has several additi
 onal benefits. Among them:\n• the coordinate transformation at second or
 der yields an improved switching between full and guiding-centre orbits\,\
 n• the inclusion of second order terms\, such as the Banos drift\, which
  are important to reproduce matching particle and guiding-centre trajector
 ies\,\n• improved conservation properties (e.g. invariance of the magnet
 ic moment at second order)\, which are necessary for the consistency of th
 e guiding-centre approximation\,\n• the resulting Lagrangian allows for 
 the inclusion of the gyrophase in addition to the guiding-centre position 
 and velocity in a straightforward way.
LOCATION:PPB 019
STATUS:CONFIRMED
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