Physics of fusion power
1 / 11

Physics of fusion power - PowerPoint PPT Presentation

  • Uploaded on

Physics of fusion power. Lecture 3: Lawson criterion / Approaches to fusion. Ignition condition. Ignition is defined as the state in which the energy produced by the fusion reactions is sufficient to heat the plasma. n-T-tau is a measure of progress.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about 'Physics of fusion power' - amy

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Physics of fusion power

Physics of fusion power

Lecture 3: Lawson criterion /

Approaches to fusion

Ignition condition
Ignition condition

  • Ignition is defined as the state in which the energy produced by the fusion reactions is sufficient to heat the plasma.

N t tau is a measure of progress
n-T-tau is a measure of progress

  • Over the years the n-T-tau product shows an exponential increase

  • Current experiments are close to break-even

  • The next step ITER is expected to operate well above break-even but still somewhat below ignition

Some landmarks in fusion energy research
Some landmarks in fusion energy Research

  • Initial experiments using charged grids to focus ion beams at point focus (30s).

  • Early MCF devices: mirrors and Z-pinches.

  • Tokamak invented in Russia in late 50s: T3 and T4

  • JET tokamak runs near break-even 1990s

  • Other MCF concepts like stellarators also in development.

  • Recently, massive improvements in laser technology have allowed ICF to come close to ignition: planned for last year but didn’t happen.

Quasi neutrality

  • Using the Poisson equation

  • And a Boltzmann relation for the densities

  • One arrives at an equation for the potential

Positive added charge Response of the plasma


  • The solution of the Poisson equation is

Potential in vacuum Shielding due to the charge screening

The length scale for shielding is the Debye length which depends on both Temperature as well as density. It is around 10-5 m for a fusion plasma

Vacuum and plasma solution

Quasi neutrality1

  • For length scales larger than the Debye length the charge separation is close to zero. One can use the approximation of quasi-neutrality

  • Note that this does not mean that there is no electric field in the plasma

  • Under the quasi-neutrality approximation the Poisson equation can no longer be used to calculate the electric field

Divergence free current
Divergence free current

  • Using the continuity of charge

  • Where J is the current density

  • One directly obtains that the current density must be divergence free

Also the displacement current must be neglected
Also the displacement current must be neglected

  • From the Maxwell equation

  • Taking the divergence and using that the current is divergence free one obtains

  • The displacement current must therefore be neglected, and the relevant equation is

Quasi neutrality2

  • The charge density is defined to be equal to zero (but a finite electric field does exist)

  • This equation replaces the Poisson equation. (we do not calculate the electric field from Poisson’s equation, which would give zero field)

  • Additionally, the displacement current is neglected.

  • Length scales of the phenomena are larger than the Debye length, time scales longer than the plasma frequency.

  • The current is divergence free.