Bohm_diffusion

plasmapy.formulary.misc.Bohm_diffusion(T_e: Unit('K'), B: Unit('T'))

Return the Bohm diffusion coefficient.

The Bohm diffusion coefficient was conjectured to follow Bohm model of the diffusion of plasma across a magnetic field and describe the diffusion of early fusion energy machines [Bohm, 1949]. The rate predicted by Bohm diffusion is much higher than classical diffusion, and if there were no exceptions, magnetically confined fusion would be impractical.

\[D_B = \frac{1}{16} \frac{k_B T}{e B}\]

where \(k_B\) is the Boltzmann constant and \(e\) is the fundamental charge.

Aliases: DB_

Parameters:

• T_e (Quantity) – The electron temperature.

• B (Quantity) – The magnitude of the magnetic field in the plasma.

Warns:

UnitsWarning – If units are not provided, SI units are assumed.

Raises:

• TypeError – T_e is not a Quantity and cannot be converted into one.

• UnitConversionError – If T_e is not in appropriate units.

Examples

>>> import astropy.units as u
>>> T_e = 5000 * u.K
>>> B = 10 * u.T
>>> Bohm_diffusion(T_e, B)
<Quantity 0.00269292 m2 / s>
>>> T_e = 50 * u.eV
>>> B = 10 * u.T
>>> Bohm_diffusion(T_e, B)
<Quantity 0.3125 m2 / s>

Returns:

D_B – The Bohm diffusion coefficient in meters squared per second.

Return type:

Quantity