Physics Glossary

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 \(\kappa_A = S_{pol} / (\pi a^2)\).

atomic_data

Dictionary mapping AtomicSpecies to datasets giving coronal and non-coronal \(L_z\) radiated power factors and \(\langle Z \rangle\) mean charge state curves from radas.

average_electron_density

Volume-averaged electron density in the confined region \(\bar n_e\).

average_electron_temp

Volume-averaged electron temperature in the confined region \(\bar T_e\).

average_ion_density

Volume-averaged ion density in the confined region \(\bar n_i\).

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 \(\bar T_i\).

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 [2], 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 ConfinementPowerScaling indicating which confinement mode power-threshold scaling to use.

confinement_threshold_scalar

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

confinement_time_scalar

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

core_impurity_species

A 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 \(\alpha_{MHD}\) 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 \(\rho=0.95\) (confusingly, still has some shaping corrections despite being called the ‘cylindrical’ safety factor).

density_profile_form

A 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 \(n_{DT}/n_e\).

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, \(f_e = n_{edge}/n_{core}\).

edge_impurity_species

A 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 \(C_E\).

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 \(\rho_{pol}\).

electron_temp_profile

A 1D profile of the electron temperature as a function of \(\rho_{pol}\).

elongation_psi95

Usually denoted \(\kappa_{95}\), the elongation at the \(\psi_N=0.95\) surface.

elongation_ratio_areal_to_psi95

Ratio of areal elongation to elongation at the \(\psi_N=0.95\) surface, \(\kappa_{A}/\kappa_{95}\).

elongation_ratio_sep_to_areal

Ratio of separatrix elongation to areal elongation \(\kappa_{sep}/\kappa_A\).

energy_confinement_scaling

Which \(\tau_e\) 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 \(\tau_e\) energy confinement scaling should be used if \(P_{SOL} < P_{LH}\). 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, \(\tau_e=W_p / P_in\).

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 \(- L_e\frac{dI_p}{dt} - Ip\frac{dL_e}{dt}\) Note, time-independent POPCON makes the simplification that \(L_e\) 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 \(q_*\).

fieldline_pitch_at_omp

The magnetic field pitch \(B_{tot} / B_{pol}\) 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: \(f_{coupled}=P_{external} / P_{launched}\).

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 \(\rho_{pol}\).

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 \(f_{G}=\bar n_e / n_G\).

heavier_fuel_species_fraction

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

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 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 \(- L_i\frac{dI_p}{dt} - \frac{Ip}{2}\frac{dL_i}{dt}\) Note, time-independent POPCON makes the simplification that \(L_i\) 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 \(\frac{\langle B^2_{\theta} \rangle _V}{\langle B_{\theta}(r=LCFS) \rangle}\) 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 \(\epsilon= a / R_0\).

invmu_0_dLedR

\(\frac{1}{\mu_0}\frac{\partial L_e}{\partial R}\) (eq.21 in [3]) which is a part of the hoop force and therefore appears in the 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 \(\rho_{pol}\).

ion_to_electron_temp_ratio

Ratio of electron and ion temperatures, \(T_i/T_e\).

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 \(q_{e,\parallel,cond}=\kappa_{e0}T_{e}^{5/2}\nabla_\parallel T_e\).

kappa_ez

finite z correction factor to the electron heat conductivity. per [4]

lambda_q

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

lambda_q_factor

A scaling factor \(C\) which can be used to increase or decrease \(\lambda_q=C \lambda_{q,scaling}\).

lambda_q_scaling

A LambdaQScaling indicating which scaling to use for calculating 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 \(B_0 = BR / R0\).

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 (\(n_e / \sum_j n_j\))

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 \(P_{in}\) 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 \((R_{max,LCFS}-R_{min,LCFS})/2\)

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 \(n_{e,sep} / \bar n_e\).

neutral_flux_density_factor

Conversion factor from neutral pressure at duct to neutral recycling flux at the target. From [5]

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 \(\beta_{max} = I_MA / a B_0\) (Troyon limit).

normalized_inverse_temp_scale_length

Inverse normalized electron temperature gradient scale length \(a / ( T_e / \nabla T_e )\), which defines the shape of the 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

\(P_{SOL}B_0/R\), a metric used to estimate how challenging heat exhaust will be.

PBpRnSq

\(P_{SOL}B_{pol}/(R n_{sep}^2)\), a metric used to estimate how challenging heat exhaust will be. This metric is approximately \(q_\parallel/n_{e,sep}^2\), 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 \(I_p\).

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 \(\rho=0.95\).

radas_dir

A path to the radas working directory.

radas_version

Version of radas used to construct the atomic data files.

radiated_power_method

A RadiationMethod indicating how we should calculate the power radiated from the confined region.

radiated_power_scalar

An enhancement factor \(C\) to modify the radiated power \(P_{rad} = C P_{rad,calculated}\).

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 [6]

reference_electron_density

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

reference_ne_tau

A constant \(n_e\tau\) (upstream electron density times impurity residence time) used when evaluating the \(L_Z\) 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 \(C_E\), it may also hold information about flux induced coupling with the wall. \(\psi_{res} = C_E\mu_0R_0I_p\).

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 \(\rho_{pol}=\sqrt{\psi_N}\), 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 \((Z_{max,LCFS} - Z_{min,LCFS}) / (R_{max,LCFS} - R_{min,LCFS})\).

separatrix_power_transient

Transient increase to power crossing the separatrix. Per [6]

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 [7]

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 [8] or Barr’s [3] 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 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 \(T_i / T_e * \lambda_{T_e} / \lambda_{T_i} = L_{T_e} / L_{T_i}\).

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 \(R_{target} / R_{upstream}\).

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 \(\delta_{95}\), average of upper and lower triangularity at the \(\psi_N=0.95\) surface.

triangularity_ratio_sep_to_psi95

Ratio of separatrix triangularity to triangularity at the \(psi_N=0.95\) surface \(\delta_{sep}/\delta_{95}.\)

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 \(B_V\)

vertical_magnetic_field_equation

Which vertical magnetic field equation to select from [9], [3], [10], [11]

vertical_minor_radius

Vertical minor radius of the plasma \((Z_{max,LCFS}-Z_{min,LCFS})/2\)

wall_temperature

Temperature of neutral gas at the wall

z_effective

The “effective charge” of the ions, defined as \(\sum_j Z_j^2 n_j / n_e\).