Publications [#167646] of Ying Wu

Papers Published

1. J. Li, S. Huang, Y. K. Wu, FEL transverse mode manipulation using an in-cavity aperture system, Proceedings of 2009 Particle Accelerator Conference (2009), pp. 1235-1237
   (last updated on 2011/05/18)

   Abstract:
   The stor­age ring based free elec­tron laser (FEL) os­cil­la­tor serves as a pho­ton driv­er for the High In­ten­si­ty Gam­ma-Ray Source (HIGS) at Duke Uni­ver­si­ty. The FEL cav­i­ty con­sists of two con­cave mir­rors with a large ra­dius of cur­va­ture of more than 27 m. Both cav­i­ty mir­rors see very high in­ten­si­ty in­tra­cav­i­ty FEL power; the down­stream mir­ror also re­ceives high­er har­mon­ic spon­ta­neous UV-VUV ra­di­a­tion of wig­glers. The large heat load by var­i­ous types of ra­di­a­tion can de­form the mir­ror sur­face, caus­ing FEL mode dis­tor­tion. The FEL mir­ror can also be dam­aged by in­tense UV-VUV wig­gler har­mon­ic ra­di­a­tion. To mit­i­gate these prob­lems, a pair of wa­ter-cooled, in-vac­u­um aper­tures have been in­stalled in­side the FEL cav­i­ty. These aper­tures are ideal for ma­nip­u­lat­ing the FEL trans­verse pro­file. This paper re­ports our study on the FEL trans­verse mode shap­ing using these aper­tures, in­clud­ing the char­ac­ter­i­za­tion of the trans­verse mode struc­ture of the FEL beam under a va­ri­ety of op­er­a­tion con­di­tions. These stud­ies allow us to min­i­mize the diffrac­tion loss of the fun­da­men­tal mode of the FEL while ef­fec­tive­ly re­duc­ing the im­pact of off-ax­is UV-VUV wig­gler ra­di­a­tion on the FEL mir­rors.