nb 3 sn cavity erl1-4 history of erl1-4 – nb 3 sn coating, just hpr test shows relatively flat q...
TRANSCRIPT
Nb3Sn Cavity ERL1-4• History of ERL1-4
– Nb3Sn coating, just HPR• Test shows relatively flat Q vs E up to
quench at ~13 MV/m, Q~1e10
– 5x HF rinse, HPR• November test shows Q-slope
– 120 K Torture• Test shows no degradation
– Remove coating with BCP• Baseline test: good performance up
to 20 MV/m
– Recoat with same parameters• Test shows performance is repeatable
0 5 10 1510
9
1010
1011
Q0
Eacc
[MV/m]
First Coating, 2.0 KFirst Coating, 4.2 KSecond Coating, 2.0 KSecond Coating, 4.2 K
Measuring DC Flux Penetration Field
• Nick made a 1760-winding NbTi solenoid
• Get cavity to a few MV/m, then apply DC field, watch Pt (or Pr)
• When RF field drops, flux from DC field has penetrated to RF surface
• Hall probe measures magnetic field
Flux penetration
T = 6.3 K
0 50 100 150 200 250 3000
50
100
150
200
T2 [K2]
10 x Power Supply I [A]Hall Probe B [mT]
Approximate Bsh of Nb with correction for field at hall probe
Flux penetration as a function of T2
Lines with x-intercept matching Tc of Nb or Nb3Sn and y-intercepts fitted by eye
From Nick’s thesis:
Ratio of X’s gives magnetic field correction for hall probe