ELFT HÍRADÓ

[<vera.horvath AT eli-alps.hu>]

Időpont:           2020. szeptember 24. 10 óra

Előadó:            Prof. Min Sup Hur (Ulsan Institute of Science and
Technology, Dél-Korea)
Cím:                  Electromagnetic radiation from plasma dipole oscillation

Kivonat:
Plasma oscillation is attractive as a radiation source, since the frequency
can be easily controlled just by changing the plasma density and the amplitude
can be made arbitrarily high (up to the wavebreaking limit) as there is no
damage threshold in plasmas. Unfortunately it is never trivial to convert the
electrostatic plasma oscillation to an electromagnetic wave. There are several
physical reasons for that; for an instance, the plasma oscillation usually
appears as a traveling wave (wakefield or Langmuir wave), which does not
phase-match with the electromagnetic waves inside the plasma. With the aid of
external magnetic field or non-uniformity of the plasma or linear and
nonlinear scattering processes, the energy of the plasma wave can be partially
converted to electromagnetic energy. Recently we reported a totally different
approach to obtain an electromagnetic emission from the plasma oscillation.
The idea is generating a localized bunch of electrons that oscillate in-phase,
which we identify as a plasma dipole oscillator (PDO), by colliding two
detuned laser pulses in plasma. From one-, two- and three-dimensional
particle-in-cell (PIC) simulations, it is verified that the PDO oscillates at
the local plasma frequency and emits a strong dipole radiation at the same
frequency. The electrostatic-electromagnetic energy conversion does not
require any complicated linear and nonlinear processes or external magnetic
field. This property of the PDO makes it useful as a light source in the
terahertz band (Kwon et al., Sci. Rep. 2018) and also as a novel diagnostic
method for non-uniform plasma density (Kylychbekov et al., PSST 2020).  The
PDO in a strongly magnetized plasma has even richer physics; diverse spectral
modes such as upper-hybrid and R, L cutoffs of X-modes exist together, and the
polarization of the radiation also changes with direction of the emission.  As
the spectral density can be made high at a desired frequency, the PDO-THz can
be potentially useful in THz electron acceleration, and other applications
where narrowband THz is required. It is found that the PDO-emission and
coherent cosmic radio bursts share several common features, making the PDO an
interesting subject of lab-spacephysics or lab-astrophysics.

A csatlakozáshoz szükséges link:
https://teams.microsoft.com/l/meetup-join/19%3ameeting_YWIzODU1MmEtOWM1Zi00YWEwLWIyMDYtNzQwOWJlZjVjYTgw%40thread.v2/0?context=%7b%22Tid%22%3a%22b207389a-c5cb-4cb0-a1ad-227b94e96448%22%2c%22Oid%22%3a%22a12feac4-37de-4e24-89e9-c7833f7e5a28%22%2c%22IsBroadcastMeeting%22%3atrue%7d

A szeminárium angol nyelvű. Minden érdeklődőt szívesen látunk.
Horváth Vera