I always choose cryod when I ordered my 9000es Modwright when it still alive. No problem. The laser gave up.
Cryogenic Treatment of Tubes, and why you should not.
Came across this paper while ago on cryo treating tubes and thought iI'd share it here. There is some other great information on tubes on the site as well.
Cryogenic Treatment of Tubes: An Engineer’s Perspective - Effectrode