Synthetic ECE

[eldond]

Electron Cyclotron Emission is the basis for a diagnostic that measures electron temperature. The measurement locations are not fixed in space in general but depends on magnetic field, which can change with plasma pressure and current. To find the location, calculate the total field, taking into account the externally applied magnetic fields and the magnetic field of the plasma. If parameter scans in the SOLPS model are not too great, this will be approximately the same as in the gEQDSK file; Br and Bz can be obtained from psi(R,Z) (without normalizing) and Bt can be obtained from using OMFIT's AuxQuantities.

Once the measurement locations are known, it's simple to sample electron temperature from the SOLPS model.

SynthDiag list on SPARC sharepoint

• Read the IMAS schema to find out how to specify the setup for ECE (the frequency that each channel reads)
• Try to find out reasonable guesses for SPARC ECE or make up values that will do something close to useful to use as defaults. Can ask Jeremy Lore and ORNL team if they know anything about this.
• Create src/default_ece.json and populate it with reasonable guesses for ECE setup. The key field to populate is ece.channel[:].frequency. Please see other default*.json files in src/ for examples of how to structure these.
• Create src/ece.jl and have it read required information from the SOLPS state, which will be stored in IMAS in the edge_profiles IDS.
  • The electron cyclotron frequency is omega_ce = e B / m_e where e is the electron charge, B is the total magnetic field strength, and m_e` is the electron mass.
  • The magnetic field components are in the equilibrium IDS in IMAS. For simplicity, it would be possible to get started by using these approximations: B = B_toroidal and B_toroidal = B_0 * R_0 / R, where R is major radius and B_0 and R_0 are stored in the edge_profiles IDS (search for R0B0)
  • Using the map from omega to B and from B to R, obtain the R location where each channel collects data
  • Sample T_e from the edge_profiles IDS at the R,Z locations (the ECE array should have a Z location): this is the nominal measurement for each channel
  • Advanced (do after the above works well): Check for cutoff. Ask Max Austin, x4192 how to simulate cutoff.