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TJ-II: Validation of neutral beam current drive: Difference between revisions
TJ-II: Validation of neutral beam current drive (view source)
Revision as of 15:49, 21 January 2022
, 21 January 2022→Description of the activity
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== Description of the activity == | == Description of the activity == | ||
The goal of the experiment associated to this proposal is to measure the toroidal current driven by each of the two neutral beams. To this end, it is important to achieve long NBI plasmas with stable density. | The goal of the experiment associated to this proposal is to measure the toroidal current driven by each of the two neutral beams (NBCD). To this end, it is important to achieve long NBI plasmas with stable density. | ||
Long pulses are needed to approach the current stabilization phase and stable density ensures that the time dependence of the toroidal current is mainly due to its | Long pulses are needed to approach the current stabilization phase and stable density ensures that the time dependence of the toroidal current is mainly due to its | ||
electrodynamic evolution and is not caused by a different coupling of the beam power issued from variations in the thermal plasma parameters. Additional ECRH power can be used for | electrodynamic evolution and is not caused by a different coupling of the beam power issued from variations in the thermal plasma parameters. Additional ECRH power can be used for | ||
density control purposes. Plasmas with co-NBI (NBI1) and counter-NBI (NBI2), as well as plasmas with balanced injection (NBI1+NBI2), will be explored. The level of optimum ECRH power will be determined depending | density control purposes. Plasmas with co-NBI (NBI1) and counter-NBI (NBI2), as well as plasmas with balanced injection (NBI1+NBI2), will be explored. The level of optimum ECRH power will be determined depending | ||
on the operation conditions considering that moderate electron temperature (below 800 keV) are desirable to favour shorter stabilization times. Using off-axis ECRH injection may also help to reduce L/R time. | on the operation conditions considering that moderate electron temperature (below 800 keV) are desirable to favour shorter stabilization times. Using off-axis ECRH injection may also help to reduce L/R time. | ||
Since both bootstrap and NBCD are contributing to the toroidal plasma current, the validation of NBCD needs first an estimation of the bootstrap contribution. Validating bootstrap current is a long standing | |||
issue in TJ-II ECRH plasmas. Experimental proposals devoted to this task (http://fusionwiki.ciemat.es/wiki/TJ-II:Validation_of_bootstrap_predictions) have been unsuccessful because of the difficulties encountered to achieve pulses long enough to observe current stabilization. | |||
The measured toroidal current will be compared to the computational/numerical estimates of the toroidal current generated by both neutrals beams once the bootstrap current contribution is removed. | The measured toroidal current will be compared to the computational/numerical estimates of the toroidal current generated by both neutrals beams once the bootstrap current contribution is removed. | ||
== International or National funding project or entity == | == International or National funding project or entity == | ||