On page 183/184 of 'Tokamaks (Third Edition)' by John Wesson it says

H-mode confinement

The improved confinement of the H-mode was discovered on ASDEX tokamak and its properties were described in Section 4.13. It was found that when sufficient power was applied the discharge made an abrupt transition in which edge confinement was improved, leading to edge pedestals in the temperature and density. The effect of this was to produce a doubling in confinement time.

What does the author mean here when he said this lead to 'edge pedestals in temperature and density'? If you plot temperature and density as a function of the radius will they have a pedestal shape at the edge? Or does he mean the temperature and density have a structure which supports confinement analogous to a pedestal supporting a statue? Or does he use the word pedestal in the same way you might use the word desirable?


1 Answer 1


Found by googling :

The high confinement regime (H-mode) in a tokamak plasma displays a remarkable edge region. On a small spatial scale of 1-2 cm the properties of the plasma change significantly. Certain parameters vary 1-2 orders of magnitude in this region, called the pedestal.

So it is a specific definition for plasmas in tokamaks, and the whole article is about it.

This google search shows plots, an example :


and justifies the term "pedestal" as, base, foundation.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.