Speakers
Ms
Nina Sorokina
(Budker Institute of Nuclear Physics, Novosibirsk State Technical University)
Dr
Sergey Polosatkin
(Budker Institute of Nuclear Physics, Novosibirsk State Technical University, Novosibirsk State University)
Description
A project of a new linear device for confinement of fusion plasmas is under development in the Budker Institute of Nuclear Physics, Novosibirsk. The new facility named GDMT utilizes several physical effects discovered and studied in the last decade on the GOL-3 and GDT devices. In the GDMT device, plasmas with fast sloshing ions will be confined in an axially-symmetric solenoid with multi-mirror sections attached at both ends. The multi-mirror end sections are 5 m long and composed of superconducting coils with magnetic field up to 7.5 T.
Quasi-stationary operation of the facility with increased confinement time of plasma may lead to impurities accumulation that can cause increase of radiation cooling, scattering and forced losses of fast ions. Expected sources of impurities and its influence to plasma confinement are discussed in the paper. For several elements such as oxygen, tungsten and molybdenum we estimate expected influx to a plasma, dynamics of ionization and confinement in the trap, and related radiation losses and increase of effective charge.
Main expected source of light impurities in plasma is contamination of neutral beams. Ordinary, ion beams, generated by ion sources of beam injection system, contain fraction of accelerated water ion $H_2O^+$, that dissociates in charge-exchange target and results in contamination of neutral beam by fast oxygen atoms. Decrease of oxygen content in a neutral beam below 1% is a challenge. Therefore, it is possible to estimate oxygen ion flux $5\times10^{19}$ $s^{-1}$ and concentration of oxygen ions in plasma ($n_O=3\times10^{11}$ $cm^{-3}$ with radiation loss power about 15 kW and increase of Zeff to about 1,5.
Physical sputtering of a limiter and unipolar arcing are considered as sources of heavy impurities. Physical sputtering by plasma ion bombardment is a fundamental process, which determines minimal erosion rate and impurities production from plasma-facing components. Lower-bound estimate of heavy impurities flux to plasma from the limiter is $5\times10^{17}$ $s^{-1}$ that cause radiation loss power 40 kW. Unipolar arcs accompanies with release of $~10^{17}$ atoms of limiter material to a plasma. Every such events will cause to increase of effective charge to a value about 4 with dramatic loss of population of fast ions in plasma.
Primary author
Ms
Nina Sorokina
(Budker Institute of Nuclear Physics, Novosibirsk State Technical University)
Co-authors
Prof.
Aleksandr Burdakov
(Budker Institute of Nuclear Physics, Novosibirsk State Technical University)
Dr
Alexander Ivanov
(Budker Institute of Nuclear Physics, Novosibirsk State University)
Dr
Alexei Beklemishev
(Budker Institute of Nuclear Physics, Novosibirsk State University)
Dr
Andrey Anikeev
(Budker Institute of Nuclear Physics, Novosibirsk State University)
Dr
Ivan Ivanov
(Budker Institute of Nuclear Physics, Novosibirsk State University)
Dr
Sergey Polosatkin
(Budker Institute of Nuclear Physics, Novosibirsk State Technical University, Novosibirsk State University)
Dr
Stanislav Sinitsky
(Budker Institute of Nuclear Physics, Novosibirsk State University)
Dr
Vitaly Astrelin
(Budker Institute of Nuclear Physics)
Dr
Vladimir Postupaev
(Budker Institute of Nuclear Physics, Novosibirsk State University)
