Development of a 1 MV ultra-fast LTD generator

A 1 MV linear transformer driver (LTD) generator has been manufactured by ITHPP and SEIV, and delivered to CEA/DIF/Polygone d'Expérimentation de Moronvilliers, in order to demonstrate the capability of this technology for flash X-ray radiography applications. This generator is composed of 10 cavities; each cavity includes 16 bricks representing two capacitors (GA 35436, 100kV, 8nF) and one multi-gaps air pressurized switch. To reduce the resistive losses in the switches, the inter-electrode gaps have been reduced from 6 mm in initial design to 4 mm, and the dry air pressure has been slightly increased. Each cavity has been tested individually on an automated testbed using a low inductive resistive load (∼1.2nH) and extensive diagnostics, including a set of sixteen capacitive probes in front of each switch to control their timing sequence. The cavities deliver more than 100kV at ±100kV charging voltage into a matched load of 0.55-0.6Ω in a ∼70-ns FWHM pulse. Around 300 shots have been made on each cavity (to condition the switches) before their integration into the generator.