Purpose/Aim
Particle accelerators use fast pulsed magnet systems (kickers) for injection, extraction and disposal of beam. Kicker systems at CERN are usually under vacuum devices pulsed to levels of up to 80 kV and 5 kA as fast as 100 ns. Newly built, in vacuum equipment, for the SPS accelerator, experienced significant issues during high voltage DC conditioning and high voltage pulse tests. Ceramic insulators are used to electrically isolate the high voltage parts e.g. from the housing or vacuum tank and ground structures.
Experimental/Modeling methods
Subsequent inspection revealed ceramic insulators with traces of electrical breakdowns. New qualification methods have been introduced to better understand the root cause of the observed insulation faults and to qualify new samples. For detailed analysis, computed tomography, microscopy, partial discharge tests, electrical breakdown tests, and electrical stress tests have been conducted.
Results/discussion
Internal voids, cracks and inhomogeneities in the material structure have been identified resulting in the weak performance. The insulators were produced from an extruded alumina bar. A new batch of insulators was produced with isostatic pressure to ensure better material density and homogeneity with much better performance.
Conclusions
Qualification of insulators before installation is critical to system reliability. With the newly introduced tests poor insulators can be identify from the beginning and the risk of failure during operation is reduced.
 

INSULATOR,ULTRA-HIGH VACUUM,ACCELERATOR MAGNETS,FAST PULSED