Method for determining hydrogen mobility as a function of temperature in superconducting niobium cavities
A method for determining the mobility of hydrogen as a function of temperature in superconducting niobium cavities comprising: 1) heating a cavity under test to remove free hydrogen; 2) introducing hydrogen-3 gas into the cavity; 3) cooling the cavity to allow absorption of hydrogen-3; and 4) measuring the amount of hydrogen-3 by: a) cooling the cavity to about 4° K while flowing a known and regulated amount of inert carrier gas such as argon or helium into the cavity; b) allowing the cavity to warm at a stable rate from 4° K to room temperature as it leaves the chamber; and c) directing the exit gas to an ion chamber radiation detector.
1. A method for determining the mobility of hydrogen as a function of temperature in superconducting niobium cavities comprising:
a) heating a cavity under test to remove free hydrogen;
b) introducing hydrogen-3 gas into the cavity;
c) cooling the cavity to 4° K for a period sufficient to allow hydrogen exchange between the introduced hydrogen-3 and any residual hydrogen; and
d) measuring the amount of hydrogen-3 absorbed by the cavity by:
i) warming the cavity to about 4.22° K while flowing a known and regulated amount of helium carrier gas into the cavity;
ii) allowing the cavity to warm at a stable known rate from 4.22° K to room temperature as the carrier gas leaves the chamber as an exit gas; and
iii) directing the exit gas to an ion chamber radiation detector to measure the level of radiation in the exit gas, which level of radiation correlates with the concentration of hydrogen-3 devolved from the niobium cavity as a function of the temperature of the cavity.
2. The method of claim 1 wherein about one part in ten of an organic gas is added to the exit gas as it exits the niobium cavity.
3. The method of claim 2 wherein the organic gas is methane.