Development of an experimental setup for in situ visualization of lyophilization using neutron radiography and computed tomography.

This article shows a new conceptional design of an experimental setup for in situ visualization of the lyophilization process using neutron radiography and computed tomography and its validation. The setup is designed for the neutron imaging beam line ANTARES at FRM II, considering all the requirements for this method. Neutrons are ideally suited to detect water in a sample because of the high neutron attenuation of hydrogen, whereas other materials like aluminum have a low absorption of neutrons resulting in an image where the drying fronts in bulk materials are observable. Consisting of a freeze-drying cell and a sample-stick, the setup is basically inspired by a common freeze-drying unit. The cell is axial symmetrical to allow computed tomography measurements. The developed sample stick connects the vacuum cell with the measurement devices and the vacuum pump. Experiments were performed at FRM II, showing that the setup is functional. In addition, the experiments discovered some possibilities for improvements, which can be used in further measurements.