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Physics Glossary

.. glossary::
  :sorted:

  alpha_t
    Turbulence characterization parameter used by the separatrix operational space.

  areal_elongation
    Elongation of the confined region computed using the poloidal area inside the last-closed-flux-surface :math:`\kappa_A = S_{pol} / (\pi a^2)`.

  atomic_data
    Dictionary mapping :class:`~cfspopcon.named_options.AtomicSpecies` to datasets giving coronal and non-coronal :math:`L_z` radiated power factors and :math:`\langle Z \rangle` mean charge state curves from `radas <https://github.com/cfs-energy/radas>`_.

  average_electron_density
    Volume-averaged electron density in the confined region :math:`\bar n_e`.

  average_electron_temp
    Volume-averaged electron temperature in the confined region :math:`\bar T_e`.

  average_ion_density
    Volume-averaged ion density in the confined region :math:`\bar n_i`.

  average_ion_mass
    Average mass of fuel ions, with the average weighted by the relative concentration of each species.

  average_ion_temp
    Volume-averaged ion temperature in the confined region :math:`\bar T_i`.

  average_total_pressure
    Sum of electron and ion pressures.

  B_pol_out_mid
    Poloidal magnetic field at outboard midplane separatrix

  B_t_out_mid
    Toroidal magnetic field at outboard midplane separatrix

  beta_poloidal
    Ratio of plasma pressure to magnetic pressure provided by the poloidal magnetic field.

  beta_toroidal
    Ratio of plasma pressure to magnetic pressure provided by the toroidal magnetic field.

  beta_total
    Ratio of plasma pressure to magnetic pressure provided by the total magnetic field.

  bootstrap_fraction
    Fraction of the plasma current due to the bootstrap current.

  breakdown_flux_consumption
    From a point model estimate given by :cite:`Sugihara`, this expression gives the required flux for ionization.

  change_in_dilution
    Change in the fuel-ion dilution, resolved per impurity species.

  change_in_zeff
    Change in the effective charge, resolved per impurity species.

  confinement_power_scaling
    A :class:`~cfspopcon.named_options.ConfinementPowerScaling` indicating which confinement mode power-threshold scaling to use.

  confinement_threshold_scalar
    Scalar value applied to the confinement threshold (:math:`P_{LH}` or :math:`P_{LI}`), used to study the effect of increasing or decreasing the threshold.

  confinement_time_scalar
    Usually denoted :math:`H`, scalar applied to the energy confinement time calculated from a scaling such that :math:`\tau_e = H \tau_{e,scaling}`.

  core_impurity_species
    A :class:`~cfspopcon.named_options.AtomicSpecies` indicating which species should be used as the core radiator

  core_radiated_power_fraction
    Fraction of input power radiated from the confined region before it reaches the separatrix.

  critical_alpha_MHD
    Critical value of :math:`\alpha_{MHD}` used in the separatrix operational space.

  current_relaxation_time
    Time constant for the radial current diffusion.

  cylindrical_safety_factor
    Analytical approximation of safety factor at :math:`\rho=0.95` (confusingly, still has some shaping corrections despite being called the 'cylindrical' safety factor).

  density_profile_form
    A :class:`~cfspopcon.named_options.ProfileForm` indicating which sort of assumed profile shape we should use for the density profiles.

  dilution
    Fuel-species concentration as a fraction of the electron density :math:`n_{DT}/n_e`.

  edge_collisionality
    Collisionality at the separatrix.

  edge_impurity_concentration
    Concentration of the edge radiator (impurity density relative to the electron density) in the edge.

  edge_impurity_concentration_in_core
    Concentration of the edge-radiator impurity in the core, after applying a compression/enrichment factor.

  edge_impurity_enrichment
    Ratio of concentration of the edge radiator in the core to in the edge, :math:`f_e = n_{edge}/n_{core}`.

  edge_impurity_species
    A :class:`~cfspopcon.named_options.AtomicSpecies` indicating which species should be injected into the plasma to increase the power radiated from the confined region.

  effective_collisionality
    Estimate of collisionality used for computing the expected density peaking.

  ejima_coefficient
    Empirical linear scaling factor of the product of major radius and plasma current at flattop correlated with resistive flux at start of flattop :math:`C_E`.

  electron_density_peaking
    Ratio of the peak ion density to the volume-averaged electron density.

  electron_density_peaking_offset
    Scalar offset of the electron density peaking relative to the density peaking scaling.

  electron_density_profile
    A 1D profile of the electron density as a function of :math:`\rho_{pol}`.

  electron_temp_profile
    A 1D profile of the electron temperature as a function of :math:`\rho_{pol}`.

  elongation_psi95
    Usually denoted :math:`\kappa_{95}`, the elongation at the :math:`\psi_N=0.95` surface.

  elongation_ratio_areal_to_psi95
    Ratio of areal elongation to elongation at the :math:`\psi_N=0.95` surface, :math:`\kappa_{A}/\kappa_{95}`.

  elongation_ratio_sep_to_areal
    Ratio of separatrix elongation to areal elongation :math:`\kappa_{sep}/\kappa_A`.

  energy_confinement_scaling
    Which :math:`\tau_e` energy confinement scaling should be used. Should match a confinement scaling in `cfspopcon.formulas.energy_confinement::energy_confinement_scalings.yaml`.

  energy_confinement_scaling_for_L_mode
    Which :math:`\tau_e` energy confinement scaling should be used if :math:`P_{SOL} < P_{LH}`. Should match an L-mode confinement scaling in `cfspopcon.formulas.energy_confinement::energy_confinement_scalings.yaml`.

  energy_confinement_time
    A characteristic time which gives the rate at which the plasma loses energy. In steady-state, :math:`\tau_e=W_p / P_in`.

  external_flux
    The flux from the time integration of the voltage due to the external inductance of the plasma. The general formula is the time integration of :math:`- L_e\frac{dI_p}{dt} - Ip\frac{dL_e}{dt}`
    Note, time-independent POPCON makes the simplification that :math:`L_e` is constant over the ramp-up.

  external_inductance
    The self-inductance associated with the LCFS of the plasma.

  f_shaping
    Shaping factor used to compute :math:`q_*`.

  fieldline_pitch_at_omp
    The magnetic field pitch :math:`B_{tot} / B_{pol}` at the 'upstream' end of a flux tube in the scrape-off-layer, used to convert from poloidal to parallel heat flux density.

  flux_needed_from_CS_over_rampup
    The amount of flux needed from the CS over ramp up.

  fraction_of_external_power_coupled
    Fraction of supplied external heating absorbed by the plasma: :math:`f_{coupled}=P_{external} / P_{launched}`.

  fraction_of_P_SOL_to_divertor
    fraction of the total power going towards the most-loaded divertor target.

  fuel_ion_density_profile
    A 1D profile of the fuel ion density as a function of :math:`\rho_{pol}`.

  fusion_reaction
    A `str` indicating which fusion reaction should be used, should match a class name in `cfspopcon.formulas.fusion_reaction.fusion_data`

  fusion_triple_product
    The product of the energy confinement time, the core ion temperature and core ion density, used as a metric for fusion performance.

  greenwald_density_limit
    The highest volume-averaged density which can be achieved before a density-limit disruption is triggered.

  greenwald_fraction
    Ratio of the average electron density to the Greenwald density limit :math:`f_{G}=\bar n_e / n_G`.

  heavier_fuel_species_fraction
    Fraction of fuel ions which are the heavier species. i.e. for DT fusion, this is :math:`f_T = n_T/(n_T+n_D)`.

  impurity_charge_state
    The mean charge state of a non-fuel species.

  impurity_concentration
    Concentration of each impurity species, relative to the electron density.

  impurity_residence_time
    The average time an impurity ion stays in the scrape-off-layer before it recycles on the wall.

  impurity_species
    A :class:`~cfspopcon.named_options.AtomicSpecies` indicating which impurity to use for a calculation.

  inductive_plasma_current
    Plasma current driven by the central solenoid (i.e. excluding the contribution of the bootstrap current).

  internal_flux
    The flux from the time integration of the voltage due to the internal inductance of the plasma. The general formula is the time integration of :math:`- L_i\frac{dI_p}{dt} - \frac{Ip}{2}\frac{dL_i}{dt}`
    Note, time-independent POPCON makes the simplification that :math:`L_i` is constant over the ramp-up.

  internal_inductance
    The self-inductance of the plasma from the center to the plasma edge.

  internal_inductivity
    Also known as normalized internal inductance, for a general geometry, is :math:`\frac{\langle B^2_{\theta} \rangle _V}{\langle B_{\theta}(r=LCFS) \rangle}` but is approximated in POPCON for a cylindrical plasma.

  intrinsic_impurity_concentration
    Concentration of each intrinsic impurity species, relative to the electron density.

  inverse_aspect_ratio
    Ratio of minor to major radius :math:`\epsilon= a / R_0`.

  invmu_0_dLedR
    :math:`\frac{1}{\mu_0}\frac{\partial L_e}{\partial R}` (eq.21 in :cite:`Barr_2018`) which is a part of the hoop force and therefore appears in the :term:`vertical_magnetic_field_equation` which counteracts the outward toroidal forces.

  ion_density_peaking
    Ratio of the peak ion density to the volume-averaged ion density.

  ion_density_peaking_offset
    Scalar offset of the ion density peaking relative to the density peaking scaling.

  ion_heat_diffusivity
    A heat diffusion constant which gives a heat flux corresponding to an ion temperature gradient.

  ion_temp_profile
    A 1D profile of the ion temperature as a function of :math:`\rho_{pol}`.

  ion_to_electron_temp_ratio
    Ratio of electron and ion temperatures, :math:`T_i/T_e`.

  ionization_volume
    Volume available above the target for ionization

  ionization_volume_density_factor
    factor that relates the target density to an averaged density across the ionization volume

  kappa_e0
    Electron heat conductivity constant, such that :math:`q_{e,\parallel,cond}=\kappa_{e0}T_{e}^{5/2}\nabla_\parallel T_e`.

  kappa_ez
    finite z correction factor to the electron heat conductivity.  per :cite:`Goldston_2017`

  lambda_q
    The near-scrape-off-layer heat-flux-density decay length.

  lambda_q_factor
    A scaling factor :math:`C` which can be used to increase or decrease :math:`\lambda_q=C \lambda_{q,scaling}`.

  lambda_q_scaling
    A :class:`~cfspopcon.named_options.LambdaQScaling` indicating which scaling to use for calculating :term:`lambda_q`.

  lengyel_overestimation_factor
    A constant calibration factor applied to the impurity concentration calculated by the Lengyel model such that its value approximately matches the value calculated by higher fidelity modelling such as SOLPS.

  loop_voltage
    inductive loop voltage

  magnetic_field_on_axis
    Magnetic field at the geometric magnetic axis :math:`B_0 = BR / R0`.

  major_radius
    The major radius of the geometric magnetic axis.

  max_flattop_duration
    Given the loop voltage at flattop, and how much flux from the CS has been consumed over the ramp-up, this defines how long your flattop can be.

  maximum_P_LH_factor_for_P_SOL
    If P_SOL is larger than this factor times the P_LH threshold, core impurities will be seeded to reduce P_SOL to th

  mean_ion_charge_state
    Mean charge state of the ions (:math:`n_e / \sum_j n_j`)

  min_P_radiation
    The minimum amount of power which must be radiated from the confined region. If power radiated by the intrinsic impurities
    is less than this, a core radiator will be injected until this level is reached.

  minimum_core_radiated_fraction
    Minimum fraction of :math:`P_{in}` which should be radiated from the confined region, below which we will inject an additional core radiator to increase the radiated power up to this value.

  minor_radius
    Horizontal minor radius of the plasma :math:`(R_{max,LCFS}-R_{min,LCFS})/2`

  n_points_for_confined_region_profiles
    The number of points to use for the confined region profiles.

  neoclassical_loop_resistivity
    Plasma loop neoclassical resistivity.

  nesep_over_nebar
    Ratio of the separatrix electron density to the volume-averaged electron density :math:`n_{e,sep} / \bar n_e`.

  neutral_flux_density_factor
    Conversion factor from neutral pressure at duct to neutral recycling flux at the target.  From :cite:`Kallenbach_2018`

  neutron_power_flux_to_walls
    Neutron power per unit area to the wall.

  neutron_rate
    Number of neutrons produced per second.

  normalized_beta
    Ratio of plasma pressure to magnetic pressure provided by the total magnetic field, normalized to :math:`\beta_{max} = I_MA / a B_0` (Troyon limit).

  normalized_inverse_temp_scale_length
    Inverse normalized electron temperature gradient scale length :math:`a / ( T_e / \nabla T_e )`, which defines the shape of the :class:`~cfspopcon.named_options.ProfileForm.prf` profiles.

  nu_star
    The normalized collisionality.

  P_alpha
    Fusion power released as alpha particles integrated over the plasma volume.

  P_auxiliary_absorbed
    auxiliary heating absorbed by the plasma integrated over the plasma volume.

  P_auxiliary_launched
    External heating supplied to the plasma (entering the volume, but not necessarily absorbed by the plasma) integrated over the plasma volume.

  P_external
    External heating absorbed by the plasma (ohmic plus auxiliary) integrated over the plasma volume.

  P_fusion
    Total power generated by fusion integrated over the plasma volume. For DT fusion, this is the sum of the power going to the alpha particles and to the neutrons.

  P_in
    Total input power to the plasma. Sum of ohmic, auxiliary and alpha power.

  P_LH_thresh
    Power required to cross the L-H transition.

  P_LI_thresh
    Power required to cross the L-I transition.

  P_neutron
    Fusion power released as neutrons integrated over the plasma volume.

  P_ohmic
    Power deposited in the plasma due to resistive ohmic heating.

  P_rad_bremsstrahlung
    Power radiated due to Bremmsstrahlung from all species.

  P_rad_hydrogen_bremsstrahlung
    Power radiated due to Bremmsstrahlung from hydrogen.

  P_rad_impurity
    Power radiated by impurities in the plasma.

  P_rad_synchrotron
    Power radiated due to synchrotron radiation.

  P_radiation
    Power radiated from the confined region due to Bremmsstrahlung, synchrotron and impurity excitation-relaxation processes.

  P_radiation_from_core_seeded_impurity
    The power radiated by the core radiator.

  parallel_connection_length
    Parallel length (along a field-line) of a scrape-off-layer flux tube, from an 'upstream' position (usually the outboard midplane) to the divertor target.

  PB_over_R
    :math:`P_{SOL}B_0/R`, a metric used to estimate how challenging heat exhaust will be.

  PBpRnSq
    :math:`P_{SOL}B_{pol}/(R n_{sep}^2)`, a metric used to estimate how challenging heat exhaust will be. This metric is approximately :math:`q_\parallel/n_{e,sep}^2`, which in the Lengyel model gives the impurity concentration required for detachment.

  peak_electron_density
    Peak electron density

  peak_electron_temp
    Peak electron temperature

  peak_fuel_ion_density
    Peak fuel ion density (i.e. product of fuel dilution, ion peaking factor and average electron density).

  peak_ion_temp
    Peak ion temperature

  peak_pressure
    Peak total pressure in the core.

  plasma_current
    Current carried by the plasma :math:`I_p`.

  plasma_stored_energy
    Thermal energy in the plasma.

  plasma_volume
    Plasma volume inside the last-closed-flux-surface.

  poloidal_circumference
    Plasma poloidal circumference of the LCFS.

  poloidal_field_flux
    The surface flux contribution from the vertical magnetic field required for radial force balance (which arises from the poloidal field coils).

  poloidal_sound_larmor_radius
    The sound Larmor radius using the poloidal magnetic field.

  power_crossing_separatrix
    Power crossing the separatrix and entering the scrape-off-layer.

  pumping_duct_neutral_pressure
    Neutral pressure at the baratron position in pumping duct.

  Q
    Fusion power thermal gain factor.

  q_parallel
    The parallel heat flux density entering a scrape-off-layer flux tube.

  q_perp
    The poloidal heat flux density entering a scrape-off-layer flux tube.

  q_star
    Analytical approximation of safety factor at :math:`\rho=0.95`.

  radas_dir
    A path to the `radas <https://github.com/cfs-energy/radas>`_ working directory.

  radas_version
    Version of radas used to construct the atomic data files.

  radiated_power_method
    A :class:`~cfspopcon.named_options.RadiationMethod` indicating how we should calculate the power radiated from the confined region.

  radiated_power_scalar
    An enhancement factor :math:`C` to modify the radiated power :math:`P_{rad} = C P_{rad,calculated}`.

  ratio_of_divertor_to_duct_pressure
    ratio between divertor neutral pressure and pressure at pumping duct

  ratio_of_molecular_to_ion_mass
    Ratio between neutral molecule mass and ion mass

  ratio_of_P_SOL_to_P_LH
    The ratio of the power crossing the separatrix to the LH transition threshold power.

  ratio_of_P_SOL_to_P_LI
    The ratio of the power crossing the separatrix to the LI transition threshold power.

  reattachment_time
    Time duration for detachment front to reach the target in response to a transient.  Per :cite:`Henderson_2023`

  reference_electron_density
    A constant upstream electron density used when evaluating the :math:`L_Z` impurity radiation curve (due to the reasonably weak dependence of :math:`L_Z` on :math:`n_e`, this approximation shouldn't be too harmful).

  reference_ne_tau
    A constant :math:`n_e\tau` (upstream electron density times impurity residence time) used when evaluating the :math:`L_Z` impurity radiation curve.

  resistive_flux
    Usually this is the magnetic flux induced by the resistance of the plasma. However, given that POPCON calculates this with the empirical :math:`C_E`, it may also hold information about flux induced coupling with the wall. :math:`\psi_{res} = C_E\mu_0R_0I_p`.

  resistivity_trapped_enhancement_method
    A flag to indicate which method should be used when calculating the enhancement of resistivity due to trapped particles.

  rho
    The square-root of the normalized poloidal flux :math:`\rho_{pol}=\sqrt{\psi_N}`, used as a flux surface label.

  rho_star
    The ratio of the sound Larmor radius to the major radius for the average ion temperature.

  safety_factor_on_axis
    On-axis safety factor

  separatrix_electron_density
    The electron density at the 'upstream' end of a scrape-off-layer flux-tube (usually at the outboard midplane).

  separatrix_electron_temp
    The electron temperature at the 'upstream' end of a scrape-off-layer flux-tube (usually at the outboard midplane).

  separatrix_elongation
    Elongation of the last-closed-flux-surface :math:`(Z_{max,LCFS} - Z_{min,LCFS}) / (R_{max,LCFS} - R_{min,LCFS})`.

  separatrix_power_transient
    Transient increase to power crossing the separatrix.  Per :cite:`Henderson_2023`

  separatrix_triangularity
    Separatrix triangularity (average of upper and lower triangularity).

  SepOS_density_limit
    Less than 1 if an L-mode is below the density limit, according to the separatrix operational space.

  SepOS_LH_transition
    Less than 1 if in L-mode and greater than 1 if in H-mode, according to the separatrix operational space.

  SepOS_MHD_limit
    Less than 1 if below the ideal MHD limit, according to the separatrix operational space.

  sheath_heat_transmission_factor
    Sheath heat transmission coefficient per equation 2.89 in :cite:`Stangeby_2000`

  SOC_LOC_ratio
    Ratio of the energy confinement time from the chosen saturated ohmic confinement (SOC) scaling and the chosen linear ohmic confinement (LOC) scaling.

  SOL_conduction_fraction
    Fraction of power carried by heat conduction in the scrape-off-layer.

  SOL_momentum_loss_function
    Fraction of momentum entering a scrape-off-layer flux tube which is lost before reaching the divertor target.

  SOL_power_loss_fraction
    Fraction of power entering a scrape-off-layer flux tube which is lost (radiated or cross-field transported) before reaching the divertor target.

  spitzer_resistivity
    Plasma loop collisional resistivity.

  summed_impurity_density
    Density of non-fuel ions.

  surface_area
    Area of the last-closed-flux-surface, i.e. the surface defined by toroidally revolving the poloidal last-closed-flux-surface.

  surface_inductance_coefficients
    The set of coefficients from Hirshman :cite:`hirshman` or Barr's :cite:`Barr_2018` paper on external flux which are used to fit analytic expressions, dependent on plasma geometry, to the external inductance and vertical field mutual inductance of the plasma.

  sustainment_power_in_electron_channel
    The power in the electron channel required to maintain the electron temperature at the separatrix.

  sustainment_power_in_ion_channel
    The power in the ion channel required to maintain the ion temperature gradient at the separatrix.

  target_angle_of_incidence
    Angle of incidence between magnetic field vector and surface normal vector at divertor target.

  target_electron_density
    The electron density at the divertor target.

  target_electron_flux
    The rate of electrons per unit area reaching the divertor target.

  target_electron_temp
    The electron temperature at the divertor target.

  target_gaussian_spreading
    Gaussian spreading coefficient, S, representing diffusive transport between x-point and divertor target

  target_neutral_pressure
    Neutral pressure at the divertor target.

  target_q_parallel
    The parallel heat flux density at the divertor target.

  temp_profile_form
    A :class:`~cfspopcon.named_options.ProfileForm` indicating which sort of assumed profile shape we should use for the temperature profiles.

  temp_scale_length_ratio
    The ratio of the electron and ion temperature scale lengths at the separatrix :math:`T_i / T_e * \lambda_{T_e} / \lambda_{T_i} = L_{T_e} / L_{T_i}`.

  temperature_peaking
    Ratio of the peak (electron or ion) temperature to the volume-averaged temperature.

  toroidal_flux_expansion
    Ratio of the divertor target major radius to the 'upstream' (usually outboard midplane) major radius for the two point model :math:`R_{target} / R_{upstream}`.

  total_flux_available_from_CS
    The amount of flux available from the central solenoid over the entire pulse.

  trapped_particle_fraction
    Global average of the fraction of trapped electrons used in the calculation of global plasma resistivity.

  triangularity_psi95
    Usually denoted :math:`\delta_{95}`, average of upper and lower triangularity at the :math:`\psi_N=0.95` surface.

  triangularity_ratio_sep_to_psi95
    Ratio of separatrix triangularity to triangularity at the :math:`psi_N=0.95` surface :math:`\delta_{sep}/\delta_{95}.`

  troyon_max_beta
    The Troyon beta limit.

  two_point_model_error_nonconverged_error
    Indicates whether the two-point-model should raise an error or return NaN if its iterative solver does not converge.

  vertical_field_mutual_inductance
    This unitless mutual-inductance quantity provides the coupling between the plasma surface and the vertical magnetic field.

  vertical_magnetic_field
    Vertical magnetic field derived from the necessary force to balance the hoop force :math:`B_V`

  vertical_magnetic_field_equation
    Which vertical magnetic field equation to select from :cite:`mit&taka`, :cite:`Barr_2018`, :cite:`Jean`, :cite:`MFEF`

  vertical_minor_radius
    Vertical minor radius of the plasma :math:`(Z_{max,LCFS}-Z_{min,LCFS})/2`

  wall_temperature
    Temperature of neutral gas at the wall

  z_effective
    The "effective charge" of the ions, defined as :math:`\sum_j Z_j^2 n_j / n_e`.