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cryogenics

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MOP92 Simulation of the RF Coupler for TRIUMF ISAC-II Superconducting Quarter Wave Resonators coupling, simulation, impedance, acceleration 234
 
  • V. Zvyagintsev
    TRIUMF, Vancouver
  The inductive RF coupler for the TRIUMF ISAC-II 106 MHz superconducting accelerating quarter wave resonators was used as a basis for the simulation model of stationary transmission processes of RF power and thermal fluxes. Electromagnetic simulation of the coupler was done with ANSOFT HFSS code. Transmission line theory was used for electromagnetic wave calculations along the drive line to the Coupler. An analogy between electric and thermal processes allows the thermal calculations to be expressed in terms of electrical circuits. The data obtained from the simulation are compared to measured values on the RF coupler.  
 
TUP71 Highly Sensitive Measurements of the Dark Current of Superconducting Cavities for TESLA Using a SQUID Based Cryogenic Current Comparator pick-up, electron, shielding, feedback 432
 
  • W. Vodel, R. Neubert, S. Nietzsche
    FSU, Jena
  • K. Knaack, M. Wendt, K. Wittenburg
    DESY, Hamburg
  • A. Peters
    GSI, Darmstadt
  This contribution presents a Cryogenic Current Comparator (CCC) as an excellent tool for detecting dark currents generated, e.g. by superconducting cavities for the upcoming TESLA project (X-FEL) at DESY. To achieve the maximum possible energy the gradient of the superconducting RF cavities should be pushed close to the physical limit of 50 MV/m. The undesired field emission of electrons (so-called dark current) of the superconducting RF cavities at strong fields may limit the maximum gradient. The absolute measurement of the dark current in correlation with the gradient will give a proper value to compare and classify the cavities. The main component of the CCC is a highly sensitive LTS-DC SQUID system which is able to measure extremely low magnetic fields, e.g. caused by the dark current. For this reason the input coil of the SQUID is connected across a special designed toroidal niobium pick-up coil for the passing electron beam. A noise limited current resolution of nearly 2 pA/√(Hz) with a measurement bandwidth of up to 70 kHz was achieved in the laboratory. Design issues of the CCC and the application in the CHECHIA cavity test stand at DESY as well as experimental results will be discussed.  
 
THP12 Superconducting RFQs in the PIAVE Injector feedback, linac, rfq, target 623
 
  • G. Bisoffi, G. Bassato, G. Bezzon, A. Calore, S. Canella, F. Chiurlotto, A. Lombardi, P. Modanese, A.M. Porcellato, S. Stark
    INFN/LNL, Legnaro, Padova
  The PIAVE superconducting RFQs were installed on the linac line and connected to the TCF50 cryogenic system. First results on the on-line resonator performance (e.g. Q-curves, amplitude and phase locking) are described as well as the behaviour of the fast tuners.