• S. Ghatak, A.S. Dhavale, K.C. Mittal
  BARC, Mumbai

BARC is in­volved in the de­vel­op­ment of su­per­con­duct­ing cav­i­ties for Ac­cel­er­a­tor Driv­en Sub-crit­i­cal Sys­tem (ADSS). The per­for­mance of su­per­con­duct­ing RF struc­ture can be great­ly af­fect­ed due to mul­ti­pact­ing. Hence 2D and 3D mul­ti­paction sim­u­la­tion stud­ies have been car­ried out for a medi­um ve­loc­i­ty (β=0.49) el­lip­ti­cal Nio­bi­um cav­i­ty op­er­at­ing at 10⁵⁰ MHz. An in-house code has been de­vel­oped which uses fi­nite el­e­ment method based soft­ware to cal­cu­late elec­tro­mag­net­ic field of the struc­ture. Leap frog method al­go­rithm has been used to solve Lorenz force equa­tion for tra­jec­to­ry track­ing of elec­trons which are launched in­side from dif­fer­ent ini­tial po­si­tions. Elec­tron tra­jec­to­ries are tracked until they hit the sur­face. An in­ter­po­la­tion func­tion is used to cal­cu­late SEY at dif­fer­ent im­pact en­er­gies. By re­peat­ing the pro­cess at dif­fer­ent field level for dif­fer­ent pri­ma­ry elec­trons mul­ti­pact­ing field lev­els are iden­ti­fied. The study re­vealed that the cav­i­ty struc­ture is not mul­ti­pact­ing prone up to 17 MV/m av­er­age ac­cel­er­at­ing field. Two point first order mul­ti­pact­ing is ob­served at the equa­to­ri­al re­gion of the cav­i­ty when the ac­cel­er­at­ing field is be­tween 18 MV/m and 28 MV/m.