COLLECTOR DESIGNS OF TWT IN CST STUDIO

I am looking for a freelancer who can help me with the design of collector designs for a Traveling Wave Tube (TWT) in CST Studio. The specific collector designs I need are a double stage and MDC. As for the requirements, I do not have any specific dimensions or specifications in mind, so I am open to suggestions based on the freelancer's expertise.Only for the people with past experience in CST studio and some knowledge about collectors/twt because of time constraint