SLIDE 1
Effect of the cavity cooldown
- n the quality-factor
Vitaliy Goryashko
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Effect of the cavity cooldown on the quality-factor Vitaliy FREIA, - - PowerPoint PPT Presentation
Effect of the cavity cooldown on the quality-factor Vitaliy FREIA, - - PowerPoint PPT Presentation
Effect of the cavity cooldown on the quality-factor Vitaliy FREIA, Uppsala 2016-02-08 Paradigm of slow cooling 2 Vitaliy Goryashko Thermal currents Normal cooldown Cycling, slow cooldown 3 Vitaliy Goryashko Thermal currents: contd
SLIDE 2
SLIDE 3
Vitaliy Goryashko
Normal cooldown Cycling, slow cooldown
Thermal currents
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SLIDE 4
Vitaliy Goryashko
Temperature along the cavity at the onset of the SC phase transition (Δ) and residual resistance for the cooldown and thermal cycles.
Thermal currents: cont’d
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SLIDE 5
Vitaliy Goryashko
The effect of thermal cycling
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SLIDE 6
Vitaliy Goryashko
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The conclusion of this and similar studies was that the cavity cooldown should be as slow as possible in the vicinity of the transition temperature in order to avoid thermocurrents and associated with them trapping of magnetic fluxes. That was also the recommendation of SRF2013. But a year later the Fermilab group made a discovery…
SLIDE 7
Vitaliy Goryashko
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SLIDE 8
Vitaliy Goryashko
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SLIDE 9
Vitaliy Goryashko
Expulsion effect
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SLIDE 10
Vitaliy Goryashko
The propagating phase boundary sweeps out the magnetic flux.
Nucleation of SC phase
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SLIDE 11
Vitaliy Goryashko
Temperature gradient for a one-cell cavity
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SLIDE 12
Vitaliy Goryashko
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SLIDE 13
Vitaliy Goryashko
Cooling in the presence of a strong magnetic field
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SLIDE 14
Vitaliy Goryashko
Cooling rate and thermal gradient
The cooldown rate is not the key parameter The temperature difference at the phase front is the main factor. The gradient along the cavity surface must be more than 0.1 K/cm.
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SLIDE 15
Vitaliy Goryashko
Summary There is still a lot of room in this field of research and it might be of interest for us to look into this effect.
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