| | The thermal response of niobium cavities at liquid
helium temperatures remains an active area of research in
order to increase the accelerating gradients of future
accelerators. The effects of plastic deformation on the
thermal conductivity in the phonon transmission regime,
as well as on the Kapitza conductance, have been studied.
The study reveals absence of the phonon peak after
deformation beyond the elastic limit of niobium, with an
almost 80% reduction in the thermal conductivity of
niobium at 2 K. Deformation also reduced the Kapitza
conductance. Low temperature annealing did not recover
the phonon peak that was measured before plastic
deformation. Annealing at the higher temperatures used
during titanification, similar to that carried out on SRF
cavities, recovered the lost phonon peak and increased the
Kapitza conductance by 300%. Thermal conductivity
measurements of single and bi-crystal niobium samples
are also reported in this ongoing research. | |
