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PRODID:-//Memento EPFL//
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SUMMARY:"A hydrogen pellet injector for the TJ-II stellarator: Testing\, m
 odelling and first experiments"
DTSTART:20141205T103000
DTEND:20141205T113000
DTSTAMP:20260609T230405Z
UID:7c2216ebd299fcdea59d8b56e227cfe72f10c9908790e80484b3d5d9
CATEGORIES:Conferences - Seminars
DESCRIPTION:I. Arapoglou (CIEMAT\, Spain)\nThe new compact four-barrel pel
 let injection system that has been recently installed on the TJ-II stellar
 ator\, is equipped with a cryogenic refrigerator for in situ hydrogen pell
 et formation and will be used as a fuelling and diagnostic tool. This syst
 em has been modelled and tested in order to predict and study particle abl
 ation and deposition along the pellet path through the plasma\, together w
 ith the resulting evolution of the background plasma. A pellet ablation mo
 del\, based on the NGS model\, has been developed and adjusted to the pell
 et path inside the standard magnetic configuration of TJ-II. After verifyi
 ng the validity of the model\, it was implemented into a transport code as
  a subroutine adapted to provide a pellet source term in the equations. Th
 e obtained results showed relatively good agreement with the subsequent fi
 rst experiments. Injecting pellets into TJ-II plasmas\, besides verifying 
 the successful installation and operation of the system\, confirmed pellet
  injection to be a useful central fuelling tool and also the wide range of
  applications of the system was apparent. Better particle and plasma energ
 y confinement was observed due to the injected pellet. Furthermore\, the p
 resence of plasma current\, that can modify the topology of the magnetic s
 urfaces and shift the filaments of very fast electrons in the plasma\, whi
 ch cause the sudden\, almost instantaneous\, ablation of the pellet. Thus\
 , it was found that pellet injection could also be used to explore magneti
 c configurations\, and identify and locate these populations of fast elect
 rons inside the plasma.
LOCATION:PPB 019
STATUS:CONFIRMED
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