Introduction: Three different S-band RF-photoguns have been constructed by Eindhoven University of Technology in the Netherlands: A 1.5-cell, a 100-Hz 1.6-cell, and a 2.6- cell. They share a design concept that differs from the ‘standard’ BNL-gun in many aspects: Individual cells are clamped and not brazed, saving valuable manufacturing time and allowing damaged parts to be replaced individually. The inner geometry employs axial incoupling, inspired by DESY, to eliminate any noncylindrically symmetric modes. Elliptical irises, identical to a 2.6-cell design of Strathclyde University, reduce the maximum field on the irises and thereby reduce electrical breakdown problems. The manufacturing process uses single-point diamond turning based on a micrometerprecise design. The overall precision is such that the clamped cavities are spot-on resonance and have nearperfect field balance without the need for any postproduction tuning.
The new design incorporates
elliptical irises to reduce the field on the cavity walls and thus reduce
Left plot shows the field-distribution near the new elliptical irises. Right plot shows a typical BNL profile.
Experimental progress: The combination of micrometer precise design by Pulsar Physics and micrometer precise manufacture by the central workshop of Eindhoven University resulted in three new rf-photoguns. They are all spot-on resonance, with the desired field-balance.