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VERSION:2.0
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BEGIN:VEVENT
DTSTAMP:20260519T022723Z
UID:https://www.ipp.mpg.de/events/45650/10021
DTSTART:20260512T103000Z
DTEND:20260512T113000Z
CLASS:PUBLIC
CREATED:20260507T113141Z
DESCRIPTION: Helicon discharges are widely used to produce high-density\, l
 ow-temperature plasmas and are central in a broad range of applications\, 
 such as plasma-material interaction studies\, electric propulsion\, fundam
 ental plasma physics investigations\, auxiliary heating in tokamaks\, and 
 wake-field particle acceleration. In such plasmas\, helicon wave damping i
 s commonly assumed to be dominated by collisional dissipation. In this wor
 k\, we combine a normal-mode analysis with spatially resolved magnetic fie
 ld measurements using a movable B-dot probe at the Resonant Antenna Ion De
 vice to investigate helicon wave damping over a broad parameter space. Whi
 le collisional models accurately describe most operating regimes\, we iden
 tify a specific parameter window in which the damping of the fundamental h
 elicon mode is reduced by approximately a factor of two relative to collis
 ional predictions. In this regime\, a coherent magnetic-field component at
  the second harmonic frequency 2ω becomes clearly detectable\, contributi
 ng up to ~10% of the total magnetic signal. Using a weakly nonlinear pertu
 rbative framework\, we show that this second-harmonic component arises fro
 m a resonant wave–wave interaction of the form ω + ω → 2ω. Importan
 tly\, the analysis reveals a nonlinear back-coupling from the second harmo
 nic to the fundamental mode\, which quantitatively accounts for the observ
 ed reduction in damping. Although second-harmonic helicon waves have been 
 reported previously\, their role has not been identified as a resonant non
 linear mechanism with a measurable impact on helicon wave dissipation. Bas
 ed on this analysis\, we derive a simple predictive criterion that identif
 ies the parameter range in which this nonlinear interaction is important. 
 Preliminary measurements from the CERN AWAKE Helicon Plasma Source exhibit
  similar harmonic signatures\, suggesting that this mechanism may be robus
 t across different helicon devices.\nVortragende(r): Renat Karimov
LAST-MODIFIED:20260507T113145Z
LOCATION:IPP L5\, Raum: L5 Seminar room
SUMMARY:TOK Seminar: Impact of resonant second-harmonic generation on helic
 on-wave damping
URL;VALUE=URI:https://www.ipp.mpg.de/events/45650/10021
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