The CS Insert Coil (CSIC), a well-instrumented 140 m long Nb_3Sn solenoid wound one-in-hand and installed in the bore of the CS Model Coil, was tested during the summer of 2000 at JAERI Naka, Japan, within the framework of the International Thermonuclear Experimental Reactor large projects [1]. The maximum transport current in the CSIC was 40 kA and the peak background field was 13 T. The coils were cooled by forced flow HeI nominally at 4.5 K and 0.6 MPa. An inductive heater was used to study stability and quench propagation in the CSIC. In this first of two companion papers we concentrate on the conductor stability tests, while a second paper is dedicated to the analysis of quench propagation [2]. The stability margin of the conductor was measured for different transport currents, helium mass flow rates and temperature margins, and the corresponding results will be presented and discussed. In the analysis, a major uncertainty comes from the assessment of the actual energy input and its partition between jacket and cable. Therefore, an electromagnetic model of the inductive heater was developed and validated. Using this input, the stability margin is computed with the Mithrandir code and compared with experimental results, showing good agreement.
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