Post coupler studies for Alvarez tanks

Field distributions of drift tube linacs (DTL) with post couplers were measured in three models. They have three different ratios of drift tube-to-wall spacing to one-quarter wave-length (λ/d). As the ratio becomes large, the limited range of post coupler length makes difficult to stabilize the field. But the ratios of post coupler length to λ/4 at stabilization were almost same in each model. The equivalent circuit model of DTL with post couplers were compared with measurements. For another stabilization idea, strip lines were installed in the tank and the field stabilization was observed