TJ-II:Turbulence properties near a rational surface: Difference between revisions
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== Description of the activity == | == Description of the activity == | ||
In previous work, we have established that the intermittence parameter C(1) varies in a systematic way near rational surfaces<ref>B. Carreras, L. García, J. Nicolau, B. van Milligen, U. Hoefel, M. Hirsch, and the TJ-II and W7-X Teams. ''Intermittence and turbulence in fusion devices''. Plasma Phys. Control. Fusion, 62:025011, 2020.</ref>. This was found to be the case both in a numerical model of resistive MHD turbulence, and confirmed using data from the W7-X stellarator. Hence, the intermittence parameter provides an indirect diagnostic of the magnetic configuration. | In previous work, we have established that the intermittence parameter C(1) varies in a systematic way near rational surfaces<ref>B. Carreras, L. García, J. Nicolau, B. van Milligen, U. Hoefel, M. Hirsch, and the TJ-II and W7-X Teams. ''Intermittence and turbulence in fusion devices''. [[doi:10.1088/1361-6587/ab57f9|Plasma Phys. Control. Fusion, 62:025011, 2020]].</ref>. This was found to be the case both in a numerical model of resistive MHD turbulence, and confirmed using data from the W7-X stellarator. Hence, the intermittence parameter provides an indirect diagnostic of the magnetic configuration. | ||
In more recent work, the iota scan experiments of 2013<ref>B.Ph. van Milligen et al., Parallel and perpendicular turbulence correlation length in the TJ-II stellarator. Nucl. Fusion, 53:093025 (2013)</ref> were revisited, and a remarkably detailed confirmation of this phenomenon was obtained<ref>B. P. van Milligen, B. Carreras, L. García, and C. Hidalgo. ''The localization of low order rational surfaces based on the intermittence parameter in the TJ-II stellarator''. Nucl. Fusion, 60:056010, 2020.</ref>. The latter paper also suggested that a radial electric field (i.e., poloidal rotation) may affect the intermittence parameter significantly. | In more recent work, the iota scan experiments of 2013<ref>B.Ph. van Milligen et al., ''Parallel and perpendicular turbulence correlation length in the TJ-II stellarator''. [[doi:10.1088/0029-5515/53/9/093025|Nucl. Fusion, 53:093025 (2013)]]</ref> were revisited, and a remarkably detailed confirmation of this phenomenon was obtained<ref>B. P. van Milligen, B. Carreras, L. García, and C. Hidalgo. ''The localization of low order rational surfaces based on the intermittence parameter in the TJ-II stellarator''. [[doi:10.1088/1741-4326/ab79cc|Nucl. Fusion, 60:056010, 2020]].</ref>. The latter paper also suggested that a radial electric field (i.e., poloidal rotation) may affect the intermittence parameter significantly. | ||
In the present experiment, we therefore plan to repeat the iota scan experiments while applying a radial electric field, induced via probe biasing. | In the present experiment, we therefore plan to repeat the iota scan experiments while applying a radial electric field, induced via probe biasing. | ||
The plan is to scan iota between configurations 100_40 and 100_44, while the B and D Langmuir probes are located at | The plan is to scan iota between configurations 100_40 and 100_44, while the B and D Langmuir probes are located at <math>\rho \simeq 0.85-0.90</math> (the reason being that this scan will move the important 8/5 rational surface across the Langmuir probe location, based on the results from the latest paper cited). The applied voltage to the biasing probe will be [-300, -150, 0, 150, 300], making 5 discharges at each voltage to verify reproducibility<ref>B.Ph. van Milligen, B.A. Carreras, L. García, G. Grenfell, I. Voldiner, C. Hidalgo, and the TJ-II Team. ''The impact of radial electric fields and plasma rotation on intermittence in TJ-II''. [[doi:10.1088/1361-6587/ac54e9|Plasma Phys. Control. Fusion, 2021]].</ref>. | ||
Apart from intermittence, we will quantify all other turbulence parameters that can be measured by the probes: <math>V_f, I_{\rm sat}, E_r, E_\theta, v_\theta, \Gamma</math>, the RMS of various quantities, long-range correlations between probes B and D, cross phase (between <math>E_\theta, I_{\rm sat}</math>), etc.<ref>B. van Milligen, B. Carreras, I. Voldiner, U. Losada, C. Hidalgo, and the TJ-II Team. ''Causality, intermittence and crossphase evolution during confinement transitions in the TJ-II stellarator''. Phys. Plasmas, 28:092302, 2021.</ref> | Apart from intermittence, we will quantify all other turbulence parameters that can be measured by the probes: <math>V_f, I_{\rm sat}, E_r, E_\theta, v_\theta, \Gamma</math>, the RMS of various quantities, long-range correlations between probes B and D, cross phase (between <math>E_\theta, I_{\rm sat}</math>), etc.<ref>B. van Milligen, B. Carreras, I. Voldiner, U. Losada, C. Hidalgo, and the TJ-II Team. ''Causality, intermittence and crossphase evolution during confinement transitions in the TJ-II stellarator''. [[doi:10.1063/5.0057791|Phys. Plasmas, 28:092302, 2021]].</ref> | ||
== International or National funding project or entity == | == International or National funding project or entity == | ||
N/A | |||
== Description of required resources == | == Description of required resources == | ||
Required resources: | Required resources: | ||
* Dynamic iota scan between configurations 100_40 and 100_44 | * Dynamic iota scan between configurations 100_40 and 100_44 | ||
* Biasing at fixed voltage [-300, -150, 0, 150, 300] | * OH current control | ||
* Biasing at fixed voltage [-300, -150, 0, 150, 300] V | |||
* Number of plasma discharges or days of operation: 30 discharges, 1 day | * Number of plasma discharges or days of operation: 30 discharges, 1 day | ||
* Essential diagnostic systems: Langmuir probes | * Essential diagnostic systems: Langmuir probes | ||
* Desirable diagnostic systems: Doppler reflectometer, HIBP (at similar radial positions as the Langmuir probes) | * Desirable diagnostic systems: Doppler reflectometer, HIBP (at similar radial positions as the Langmuir probes) | ||
* Type of plasmas (heating configuration): ECRH heated, density constant, below critical density (<math>n_e \simeq 0.6\cdot 10^{19} {\mathrm m}^{-3}</math>) | * Type of plasmas (heating configuration): ECRH heated, density constant, below critical density (<math>n_e^{\rm crit} \simeq 0.6\cdot 10^{19} {\mathrm m}^{-3}</math>) | ||
== Preferred dates and degree of flexibility == | == Preferred dates and degree of flexibility == | ||
Latest revision as of 11:52, 11 March 2022
Experimental campaign
Spring 2022
Proposal title
Turbulence properties near a rational surface
Name and affiliation of proponent
B.P. van Milligen, I. Voldiner, B.A. Carreras, C. Hidalgo
Details of contact person at LNF
N/A
Description of the activity
In previous work, we have established that the intermittence parameter C(1) varies in a systematic way near rational surfaces[1]. This was found to be the case both in a numerical model of resistive MHD turbulence, and confirmed using data from the W7-X stellarator. Hence, the intermittence parameter provides an indirect diagnostic of the magnetic configuration.
In more recent work, the iota scan experiments of 2013[2] were revisited, and a remarkably detailed confirmation of this phenomenon was obtained[3]. The latter paper also suggested that a radial electric field (i.e., poloidal rotation) may affect the intermittence parameter significantly. In the present experiment, we therefore plan to repeat the iota scan experiments while applying a radial electric field, induced via probe biasing.
The plan is to scan iota between configurations 100_40 and 100_44, while the B and D Langmuir probes are located at (the reason being that this scan will move the important 8/5 rational surface across the Langmuir probe location, based on the results from the latest paper cited). The applied voltage to the biasing probe will be [-300, -150, 0, 150, 300], making 5 discharges at each voltage to verify reproducibility[4]. Apart from intermittence, we will quantify all other turbulence parameters that can be measured by the probes: , the RMS of various quantities, long-range correlations between probes B and D, cross phase (between ), etc.[5]
International or National funding project or entity
N/A
Description of required resources
Required resources:
- Dynamic iota scan between configurations 100_40 and 100_44
- OH current control
- Biasing at fixed voltage [-300, -150, 0, 150, 300] V
- Number of plasma discharges or days of operation: 30 discharges, 1 day
- Essential diagnostic systems: Langmuir probes
- Desirable diagnostic systems: Doppler reflectometer, HIBP (at similar radial positions as the Langmuir probes)
- Type of plasmas (heating configuration): ECRH heated, density constant, below critical density ()
Preferred dates and degree of flexibility
Preferred dates: N/A
References
- ↑ B. Carreras, L. García, J. Nicolau, B. van Milligen, U. Hoefel, M. Hirsch, and the TJ-II and W7-X Teams. Intermittence and turbulence in fusion devices. Plasma Phys. Control. Fusion, 62:025011, 2020.
- ↑ B.Ph. van Milligen et al., Parallel and perpendicular turbulence correlation length in the TJ-II stellarator. Nucl. Fusion, 53:093025 (2013)
- ↑ B. P. van Milligen, B. Carreras, L. García, and C. Hidalgo. The localization of low order rational surfaces based on the intermittence parameter in the TJ-II stellarator. Nucl. Fusion, 60:056010, 2020.
- ↑ B.Ph. van Milligen, B.A. Carreras, L. García, G. Grenfell, I. Voldiner, C. Hidalgo, and the TJ-II Team. The impact of radial electric fields and plasma rotation on intermittence in TJ-II. Plasma Phys. Control. Fusion, 2021.
- ↑ B. van Milligen, B. Carreras, I. Voldiner, U. Losada, C. Hidalgo, and the TJ-II Team. Causality, intermittence and crossphase evolution during confinement transitions in the TJ-II stellarator. Phys. Plasmas, 28:092302, 2021.