Abstract: An ion source employs a self-contained sample containment valve which serves to store, transport and dispense a gas sample from which a negative ion beam is generated. The valve is loaded with a sample of carbon dioxide gas by cryo-pumping carbon dioxide gas into a finger which is refrigerated with liquid nitrogen and which is connected to the stored volume of the valve. A sample contained in the gas containment valve is combined with a total of forty sample containment valves on a carousel which is mounted adjacent to the cathode of a negative ion source of a tandem accelerator facility within a vacuum chamber. When a particular sample containment valve is aligned with the cathode an actuator causes the sample containment valve to move forward a short distance positioning the valve to dispense gas to generate a negative carbon ion beam. When changing the samples contained on the carousel, the ion source must be shut off from the vacuum chamber. This is accomplished by interposing a gate valve.