sid_galt said:
What is the basis for Lawson's criterion? How is it derived?
Does it apply to all plasmas or only to magnetically confined plasmas?
Sid,
Lawson's criterion is a rough estimate for the conditions required for
fusion - any basic fusion text will give you the details.
It applies for ALL fusion schemes - regardless of the confinement
mechanism. It's interesting to see how the various fusion schemes
fulfill the Lawson criterion.
Take magnetic confinement. In magnetic confinement, the plasma
densities are fairly low - anyone else would call them a pretty good
vacuum. But the confinement times are on the order of a second or
a few seconds.
At the other end of the spectrum is inertial confinement fusion - also
called "laser fusion". Here there is no attempt made to try to confine
the plasma - only the plasma's own inertia limits its expansion.
Confinement times here are extremely small - on the order of
nanoseconds. However, the densities are extremely high - on the order
of 10,000 grams per cubic centimeter. So the product can also fulfill
the Lawson criterion.
So we have two extremes - low density, but high confinement time
[ magnetic fusion ] or high density, low confinement time [ inertial
confinement fusion ]
Dr. Gregory Greenman
Physicist