Systems are provided that include one or more retractable deposition source assemblies that eliminate the need for a bellows, but do not require breaking the ultra-high vacuum of a growth module for source replacement or recharging with deposition material. Systems of the present invention may include source heads that allow for a differential pumping option that provides marked improvement in base pressure around the source head (and material) that provides longer lifetimes for sources in corrosive, reactive or oxidizing environments. In addition, systems of the invention do not require an entire growth module to be vented to refill or repair an effusion source. Instead, for maintenance events that are tied to a specific source, a retractable source assembly of the present invention allows the sources to be withdrawn from the system, isolated from the growth environment, and removed without venting the entire chamber of the growth module.