Abstract: The invention relates to systems and methods for delivering controlled doses of a liquid cryogen. Controlling a restriction in a return conduit and other system geometry maintains proper circulation through a delivery and return conduit, enabling reliable control over the temperature and pressure of the liquid cryogen at the site of dosing.

Abstract: A system for delivering a controlled stream of purified liquid cryogen from an outlet. The system includes a cryogen delivery flow path that is made up of a delivery conduit connecting a source of liquid cryogen to the outlet. A cryogen purifier positioned in a section of the conduit, is capable of purifying (sterilizing) liquid cryogen flowing therethrough, and a section of the delivery conduit downstream of the cryogen purifier is clean (sterile). The system also includes a cleansing flow path for cleansing (sterilizing) the cryogen purifier and the clean delivery conduit section. The cleansing flow path includes a cleansing conduit connecting a source of cleansing (sterilizing) medium to the delivery conduit and the cryogen purifier. The cryogen purifier and clean delivery conduit section are isolated from the cryogen source during conduit cleansing, and cleansing is accomplished without subjecting the cryogen source to the cleansing medium.