Disclosed herein is a mounting mechanism such as a drift tube mounting mechanism for mounting a drift tube provided in a drift tube accelerator vessel 10 via an elongate holding element 14. The mounting mechanism comprises a biasing mechanism comprising one or more disc spring members 46 for axially biasing the elongate holding element 14 with respect to the vessel towards a mounting position. The mounting mechanism further comprises a screw 58 having a head portion 60 and a shaft portion, said shaft portion comprising a threaded portion 64 for screwing into the elongate holding element 14. The mounting mechanism further comprises a bushing 66 comprising a sleeve portion 68 receiving at least a part of the screw shaft and separating the one or more disc spring members 46 from said screw shaft portion. The screw head portion 60 is configured to receive the axial biasing force generated by the one or more disc spring members 46.