Vertical cryostats for cavity tests
Vertical cryostats for cavity tests

Vertical cryostat CV1

Context

Low power RF characterization tests of superconducting cavities at low temperature down to T = 1.8 K.

Two buried vertical cryostats (CV1 and CV2) shielded against earth magnetic field allow one to measure accelerating gradient and surface resistance of superconducting cavities. They can accommodate cavities up to Φ = 0.45 m diameter and l = 1 m long in CV1, and Φ = 0.7 m diameter and l = 1.9 m long in CV2.

 

 

 

 


 

 

 

 

 

 

Technical means

  • Liquid Helium cooling: a refrigerator unit producing 140 l/h and 2000 l buffer tanks for each vertical cryostat, allowing one to provide helium at 4.2 K or 1.8 K by pumping on the helium bath. 500 l liquid helium are consumed for a typical cavity test in CV1, and 1500 l in CV2.
  • RF sources with adjustable frequency and power (80-90 MHz 50 W; 170-180 MHz 500 W; 700-1500 MHz 200 W; 704 MHz 1 kW), controlled via PLL based closed circuit loop.
  • Measurement of incident, transmitted and reflected RF power; estimation of heat losses via helium consumption (level drop or flowmeter).
 
Vertical cryostats for cavity tests

Elliptical cavity on insert

Vertical cryostats for cavity tests

Vertical cryostat CV1 and CV2 bunkers

 

 

Achievements, related projects

  • Single cell cavities to prototype new cavity preparation methods (etching, rinsing, heating, doping, ….),
  • XFEL, SPL, ESS elliptical cavity prototypes,
  • 12 Spiral2 quarter-wave cavities qualification,
  • IFMIF half-wave cavities qualification.
 

 

 

Technical steps, expertise

  • Mounting of the cavity on vertical insert, vacuum leak tests, installation of thermal probes,
  • Positioning of the insert into the cryostat, connection to pumping lines and RF coax lines,
  • Leak checks and low power RF checks at room temperature,
  • Cooling down to 4.2 and / or 1.8 K, with fast ramps (3 K / min) from 150 to 50 K,
  • Control of the cavity frequency, the field ramp in the cavity by injecting increasing RF power and concurrent measurement of quality factor deduced from Pi, Pt, Pref.
 
Vertical cryostats for cavity tests

ESS 5 cell high beta cavity

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#3995 - Last update : 08/07 2017

 

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