niobium quarter-wave resonator development for a heavy ion re ...

RF Test on β = 0.041 QWR
• Vertical test with cavity immersed in liquid helium.
• Multipacting barriers at low field, were able to
get through them rapidly.
• Observed x-rays at high field (9 R/hour at max
field); did some RF conditioning, but not able
to eliminate the field emission.
• Did not observe thermal breakdown.
• Max fields: E p ≈ 80 MV/m, B p ≈ 140 mT,
V a ≈ 2.2 MV.