TJ-II:Plasma fueling experiments: influence of gas puffing distribution on plasma behaviour

Experimental campaign

2019 Autumn

Proposal title

Plasma fuelling experiments: influence of gas puffing distribution on plasma behavior

Name and affiliation of proponent

Macarena Liniers Vázquez (Laboratorio Nacional de Fusión)

Details of contact person at LNF (if applicable)

Enter contact person here or N/A

Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages)

Gas puffing in TJ-II is usually performed by means of a piezoelectric valve located in sector A8. The resulting gas pressure distribution, as measured by four Fast Ion Gauges symmetrically distributed around the torus, is highly non-symmetric for such gas pulses. This is due to the strong helicity of the vacuum chamber, which has a significant impact on the gas transport dynamics. The characteristic time of gas transport between two machine periods is of the order of the plasma pulse duration (100 ms). In fact, the gas puffing system of TJ-II includes four piezoelectric valves symmetrically distributed around the machine. The influence of the fuel sources distribution on plasma performance may be studied by using different combinations of piezo valves. The effect of the assymetries on the confinement may be readily observed. Some improvement in the L-H transition conditions has been reported at Heliotron-E (S. Kobayashi, oral presentation at TJ-II, 26/03/2108): a lower power threshold was found as well as improved confinement, when using a toroidally distributed gas puffing.

If applicable, International or National funding project or entity

Proyecto Plan Nacional FIS2017-89326-R

Description of required resources

Required resources:

• Number of plasma discharges or days of operation: 1 day of operation
• Essential diagnostic systems:Plasma density, Temperature, NPA (tangential), IR Thermography, Fast Ion gauges, Halpha, Plasma Energy
• Type of plasmas (heating configuration):ECH+NBI
• Specific requirements on wall conditioning if any:stable condition
• External users: need a local computer account for data access: yes/no
• Any external equipment to be integrated? Provide description and integration needs:

Preferred dates and degree of flexibility

Preferred dates: 16-12-2019(format dd-mm-yyyy)

References

S. Kobayashi,"Recent experimental results of Heliotron J:H mode and recent topics", Oral presentation at TJ-II Group meeting,CIEMAT, Spain, 23d March 2108

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