A sleeve holder assembly for a radiation source is disclosed. The sleeve holder assembly comprises: an elongate radiation transparent sleeve element； a sleeve holder receptacle portion coupled to the elongate radiation transparent sleeve element； a sleeve bolt assembly portion coupled to the sleeve holder receptacle portion； a first sealing element disposed between the sleeve holder receptacle portion and the sleeve bolt assembly portion； and a locking element configured to prevent decoupling of the sleeve bolt assembly portion and the sleeve holder receptacle portion. The first sealing element is configured to provide a substantially fluid impermeable seal between the elongate radiation transparent sleeve element and the sleeve holder receptacle portion.
