HOM analysis and design of its removal system for 3rd harmonic RF cavity in PLS

Pohang Accelerator Laboratory has prepared to SRF 3
^rd
harmonic cavity to increase beam lifetime and to damp orbit instability by lengthening electron bunch in PLS. The SRF cavity was developed and its vertical test was done already with success. Higher order modes were analyzed to optimize its performance in beam orbit. Most of them are not effective to electron beam, while the others have possibility to impact orbit stability. These harmful HOMs can be removed by HOM absorber installed in beam pipe.