TJ-II:Blobs vs streamers
Experimental campaign
2018 Spring
Proposal title
Blobs vs streamers
Name and affiliation of proponent
G. Grenfell, B.Ph. van Milligen
Details of contact person at LNF (if applicable)
B.Ph. van Milligen
Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages)
According to a recent suggestion by Chang[1], turbulence in the edge can be of 'blob type' or 'streamer type'. Chang states: ‘A weak mean Failed to parse (syntax error): {\displaystyle E × B} shear, due to the small effect, allows the formation of the streamer type turbulence.’
We propose studying this effect, not by varying , but rather by varying . To do so, we will scan the edge from negative to positive (crossing zero), either by biasing or by varying the mean density near the spontaneous transition value (Failed to parse (syntax error): {\displaystyle n_e \simeq 0.6 ⋅ 10^{19}} ). Near zero Er, transport across the LCFS should be more streamer-like.
Measurements to make: In this scan, we will measure: Isat decay length in SOL (if possible - this may require several discharges), and omega_S.[2]
We will also attempt to quantify 'blobbiness', in order to detect the transition between 'blob-type' and 'streamer-type' turbulence. This difference might also be reflected in the radial correlation length (or causality, cf. Transfer Entropy). Perhaps there are other ways to quantify the difference between 'blob-type' and 'streamer-type' turbulence.
If applicable, International or National funding project or entity
N/A
Description of required resources
Required resources:
- Number of plasma discharges or days of operation: at least 1
- Essential diagnostic systems: Langmuir probe (2-dimensional), biasing probe
- Type of plasmas (heating configuration): ECRH
- Specific requirements on wall conditioning if any: N/A
- External users: need a local computer account for data access: no
- Any external equipment to be integrated? Provide description and integration needs: N/A
Preferred dates and degree of flexibility
Preferred dates: N/A
References
- ↑ C. Chang et al., Self-organization between the neoclassical and turbulent transports across the separatrix surface, resulting in the regulation of the divertor heat-load width, Synopsis for IAEA Conference (2018)
- ↑ P. Manz, T. Ribeiro, B. Scott, G. Birkenmeier, D. Carralero, G. Fuchert, S. Müller, H. Müller, U. Stroth, and E. Wolfrum. Origin and turbulence spreading of plasma blobs. Phys. Plasmas, 22:022308, 2015