ELFT HÍRADÓ

[RMKI PFO szeminarium-koordinator <szeminarium AT rmki.kfki.hu>]

                                MEGHIVO


Az MTA KFKI RMKI Plazmafizikai Foosztaly szeretettel meghiv minden
kedves erdeklodot az alabbi eloadasra:


        Pellet ablation dependence on magnetic field intensity


Eloado: Lovasz Bela
        ELTE, negyedeves fizikus hallgato


Idopont: 2010. majus 11. (kedd) 14:00


Helyszin: KFKI Campus, III epulet, 1. emelet, 105 teazo
          1121, Budapest, Konkoly Thege Miklos ut 29-33.
          Az intezet megkozelitheto a 90-es autobusszal:
          http://www.bkv.hu/busz/90-90a_1.html


Videokonferencia:
H.323 kapcsolat: 0036100309910 (előadás és fóliák)


Az eloadas kivonata:

Nowdays well established fuelling and ELM control method for fusion 
devices are pellet injections. Pellets are small frozen portions of 
mostly hydrogen isotopes. An important parameter for injection of 
pellets is the penetration depth. At the first experimental fusion 
reactor called ITER, ELM pacing pellets have to pierce far into the 
pedestal area, whereas fuelling pellets have to even penetrate to the 
pedestal top of the hot fusion plasma.

When a hydrogen isotope pellet is shot in into the plasma, ablation sets 
in immediately. That means that high energy particles, mostly electrons, 
from the plasma are clashing into the surface of the pellet and are 
detaching material from the surface. Little energy is needed for 
deuterium to sublimate so a neutral cloud is formed and evolves quikly 
around the pellet. This cloud dilats gaslike. An electron flux from the 
plasma is streaming into the cloud raising the total energy of the 
cloud. Through heat conduction energy is getting to the surface of the 
pellet, detaching further particles. This flux causes a charge 
difference between cloud and plasma and this leads to an electric 
shielding. The shielding limits the electron flux so lesser electrons 
and lesser energy gets into the cloud per area. Thus the cloud size will 
determine the whole electron and energy getting into the cloud. The size 
of the ionized cloud is determined by the magnetic field strength, 
because average pathlength of the particles becomes smaller if the 
magnetic field lines get denser. When the cloud energy got high enough, 
ionisation of the cloud sets in, and a channel flow of the ionized cloud 
begins along the magnetic field lines. The ablation process is treated 
by the Hybrid ablation code.[1]

Theory expects a smaller ionized cloud and a slower ablation of the 
pellet with increasing magnetic field strength because the energy flux 
is smaller and greater penetration depth for the pellet. However, 
experiments at ASDEX Upgrade showed that the penetration depth is 
inversely proportional to the magnetic field strength.[2] This 
presentation compares the devitions of the theory and the experiments in 
detail with the hybrid ablation code.

References:

[1] K. Gal et al., Nuclear Fusion 48, 085005 (2008)
[2] E. Belonohy et al., Nuclear Fusion 48, 065009 (2008)


Udvozlettel,
Szepesi Tamas


--
-------------------------------------------------------
Tamas Szepesi, RMKI PFO seminar coordinator
KFKI - Research Institute for Particle and Nuclear Physics
EURATOM Association
Web: http://www.rmki.kfki.hu/pfoszeminarium
Letters: P.O. Box 49, H-1525, Budapest-114, Hungary
Phone: (36 1) 3922222 / 1467
Fax: (36 1) 3922598, 3959151
E-mail: 
szeminarium AT rmki.kfki.hu,
 
szepesi AT rmki.kfki.hu
-------------------------------------------------------