TJ-II:Investigation of the mechanism of decoupling between energy and particle transport channels: Proposal for joint experiments in TJ-II and H-J
Experimental campaign
2017 Spring
Proposal title
Investigation of the mechanism of decoupling between energy and particle transport channels:Proposal for joint experiments in TJ-II and H-J
Name and affiliation of proponent
Bing Liu and Ulises Losada
Details of contact person at LNF (if applicable)
Ulises Losada
Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages)
Motivation It has been known for years that energy and particle transport channels in magnetic fusion plasmas can sometimes response differently to external actions. One example is the response of transport channels to the resonant magnetic perturbations (RMP) used for EML-control in H-mode. It has been observed that when RMP is applied, density profile is strongly modified while temperature profile modification remains modest [1]. Another example is the decoupling of energy and particle transport channels in the I-mode observed in Alcator C-Mod [2] and ASDEX-Upgrade [3]. I-mode is characterised by a temperature pedestal similar to H-mode, while particle confinement remains as in L-mode level. Understanding the physical mechanism of the decoupling of energy and particle transport channels is crucial for the extrapolation of present ELM free plasma operation scenarios (e.g. I-mode) and ELM-control technique (e.g. RMP) to the next generation devices, such as ITER and DEMO.
Decoupling between energy and particle transport has also been observed in stellarator/heliotron devices. In TJ-II, external biasing has only minor modifications in the electron temperature but strong modifications in plasma density [4], and H-mode transition is accompanied by an augmentation in energy and particle content, being larger in the particle channel [5]. Recently, in H-J HIGP triggered H-mode transition, when the HIGP exceeded certain threshold, a particle transport barrier is form rapidly at the edge with improvement of energy confinement but without formation of energy transport barrier [6].
Objectives We propose a joint experiment in TJ-II and H-J for the investigation of possible physical mechanisms that could lead to the development of such decoupled energy/particle transport channels. Characterization of plasma regimes with particle / energy transport decoupling: (1) In TJ-II: H-mode transition, electrode biasing; (2) In Heliotron J, HIGP triggered H-mode transition. Characterization of density, potential and electron temperature fluctuation levels and cross-phases in plasma regimes with and without particle / energy decoupling Characterization of long-range correlations (as proxy of zonal flows) in plasma regimes with and without particle / energy decoupling
Diagnostics:
TJ-II:
Profiles: YAG Thomson scattering system for electron density and temperature profiles, CXRS for ion temperature profile
Fluctuation and cross phase at the edge: a 2D Langmuir probe array (a new probe is already built).
Long-range correlation: dual-Langmuir probe system (Sector D/B); dual-HIBP system
Heliotron J Profiles: YAG Thomson scattering system for electron density and temperature profiles, CXRS for ion temperature profile Fluctuation and cross phase at the edge: a 2D Langmuir probe array (we need to build a new one). We will try to build the probe in a compact size and make it possible to access the plasma. This 2D probe will be installed at a less sensitive port 8.5. Long-range correlation: two probes, the 2D at 8.5, and a rake at 11.5 Core fluctuations and cross-phase between electron density fluctuation and electron temperature fluctuation: CECE/reflectometor?
If applicable, International or National funding project or entity
Enter funding here or N/A
Description of required resources
Required resources:
- Number of plasma discharges or days of operation:
- Essential diagnostic systems:
- Type of plasmas (heating configuration):
- Specific requirements on wall conditioning if any:
- 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: (format dd-mm-yyyy)
References
- ↑ G. R. McKee et al, Nucl. Fusion 53, 113011 (2013)
- ↑ D. G. Whyte et al, Nucl. Fusion 50, 105005 (2010)
- ↑ F. Ryter et al, Nucl. Fusion 57, 16004 (2017)
- ↑ C. Hidalgo et al., Plasma Phys. Control. Fusion 46, 287 (2004)
- ↑ B. P. Van Milligen et al., Phys. Plasmas 23, (2016)
- ↑ S. Kobayashi et al, in IAEA (2016), EX/P8-17