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SUMMARY:"Suprathermal ion transport in turbulent magnetized plasmas"
DTSTART:20150202T103000
DTEND:20150202T113000
DTSTAMP:20260510T131504Z
UID:8e188efdf466e434ecddf06d07b9834ad987633da380d30f83bec8d1
CATEGORIES:Conferences - Seminars
DESCRIPTION:Dr. A. Bovet\, CRPP-EPFL\nSuprathermal ions\, which have an en
 ergy greater than the quasi-Maxwellian background plasma temperature\, are
  present in many laboratory and astrophysical plasmas. In fusion devices\,
  they are generated by the fusion reactions and  auxiliary heating. In sp
 ace\, suprathermal ions include energetic solar particles and cosmic rays.
  The understanding of the acceleration and transport mechanisms of these p
 articles is still incomplete. Basic plasma devices allow detailed measurem
 ents that are not accessible in astrophysical and fusion plasmas\, due to 
 the difficulty to access the former and the high temperatures of the latte
 r. The basic toroidal device TORPEX offers an easy access for diagnostics\
 , well characterized plasma scenarios and validated numerical simulations 
 of its turbulence dynamics\, making it the ideal platform for the investig
 ation of suprathermal ion transport. We present three-dimensional measurem
 ents of a suprathermal ion beam injected in turbulent TORPEX plasmas. The 
 combination of uniquely resolved measurements and first-principle numerica
 l simulations reveals the general non-diffusive nature of the suprathermal
  ion transport. A precise characterization of their transport regime shows
  that\, depending on their energies\, suprathermal ions can experience eit
 her a superdiffusive transport or a subdiffusive transport in the same bac
 kground turbulence.  The transport character is determined by the interac
 tion of the suprathermal ion orbits with the turbulent plasma structures\,
  which in turn depends on the ratio between the ion energy and the backgro
 und plasma temperature. Time-resolved measurements reveal a clear differen
 ce in the intermittency of suprathermal ions time-traces depending on the 
 transport regime they experience. Conditionally averaged measurements unco
 ver the influence of field elongated turbulent structures\, referred to as
  blobs\, on the suprathermal ion beam. A theoretical model extending the B
 rownian motion to include non-Gaussian (Lévy) statistics and long-range t
 emporal correlation is developed.  This model successfully describes the 
 evolution of the radial particle density from the numerical simulations an
 d provides information on the microscopic processes underlying the non-dif
 fusive transport of suprathermal ions.
LOCATION:PPB 019
STATUS:CONFIRMED
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