A system (10) for delivery of reagent from a solid source thereof, comprising a structure (16, 22, 24) arranged to retain a solid source material (30) in confinement by at least a portion of the structure, for heating and generation of vapor from the solid source material by volatilization thereof, a heat source (82) arranged to heat the solid source material for such volatilization, and a vapor dispensing assembly (52, 54) arranged to discharge the vapor from the system. A high conductance valve (1510) is also described, suitable for use as a dispensing control valve for a reagent storage and dispensing vessel, e.g., a vessel containing a semiconductor manufacturing reagent that is dispensed at low pressure. The high conductance valve includes a valve body (1512) in which inlet and outlet passages are substantially perpendicular to one another, with their interior extremities communicating with a valve chamber (1536) containing a selectively positionable valve element movable between a fully open and fully closed position. Valve flow coefficient (CV) values on the order of 2.7 to 2.9 are achievable by such high conductance valve, enabling the valve to achieve superior dispensing operation even in extremely low pressure regimes, e.g., below 20 torr.Cette invention concerne un système (10) de distribution de réactifs à partir dune sources de réactifs solides, comprenant: une structure (16, 22, 24) conçue pour maintenir un matériau source solide (30) confiné dans au moins une partie de la structure pour le chauffage et la production de vapeur par volatilisation dudit matériau (30) une source de chaleur (82) servant à chauffer le matériau de la source solide en vue de ladite volatilisation et un ensemble distributeur de vapeur (52, 54) assurant la décharge de la vapeur à partir du système. Est également décrite une valve à haute conductance (1510) convenant comme soupape de commande de distribution pour un récipient de stockage et de distribution, cest-à-dire un récipi
