Tube d'essai pour Linac 3 MeV

A scale model llnac cavity (15 cm in diameter) which was used in the linac section of the ISR Department to optimize cavity design for future linacs. This model has a 'cross-bar' structure — the stems supporting alternate drift-tubes are at right angles (for the first drift-tube in the photograph they are horizontal, for the second vertical and so on). By changing the orientation and the size of the stems it is possible to achieve conditions which considerably improve the cavity performance compared with the conventional Alvarez structure. The advantages include making it easier to cope with beam loading, more uniform accelerating fields (dispensing with the need for field flatteners) and less stringent mechanical tolerance.