Neutron spin filter made of special glass

A special glass (GE-180) is used to manufacture the ³He cells. It is particularly permeable to neutrons and can enclose the noble gas helium particularly tightly.

A major challenge, even for specialists

The glass has a high thermal expansion and must be processed at high temperatures. This results in high stresses during processing. This can lead to spontaneous cracking of the component. Only tubes with a diameter of 25 mm are available to the glass apparatus manufacturer as starting material. In order to produce cells with a diameter of up to 215 mm, up to 4.5 meters of the tube must be compressed by melting at an open flame and inflated without tools. Thanks to special work techniques, the inside of the cell never comes into direct contact with the flame from the metal burner. There must be no metal particles there that would influence the measurement results. At the end of production, the strength of each individual cell is tested at a pressure of 3.5 bar.

Unique in its kind

The cells manufactured at ZEA-1 are unique in the world due to their outstanding properties, size and geometry and are used at several neutron sources such as FRM2.