The target cell is either a 25 cm or 40 cm long aluminosilicate glass (GE180) high pressure (up to 15 atm) double chamber cell. Typical dimensions for a 40 cm cell are shown in Figure . A 25 cm cell is identical except the target chamber is 25 cm long instead of 40 cm. It is a closed system filled with a gas mixture which consists of He, rubidium and nitrogen.
The cell volumes range from 160 ml for a 25 cm cell to 200 ml for a 40 cm cell. The interior pressure of the cell at room temperature is between 8 and 10 times atmospheric pressure. The cells contain approximately 70 torr of nitrogen to help with the spin-exchange process. There is usually 0.1-0.3 g of Rb in the pumping chamber. The tritium contamination of the He gas used to fill the cell is less than 10 according to the specifications from the manufacturer, Spectra Gases.
The glass walls of the cell vary in thickness from cell to cell and from chamber to chamber. The end windows of the target chamber are 120-150 microns thick and are therefore the thinnest part of the cell. The walls of the target chamber and transfer tube are over a millimeter thick and the pumping chamber walls are up to 2 mm thick.
The cell is installed on a target ladder and then this ladder is mounted to the bottom of the oven. The cell is attached to the target ladder with a high-temperature elastomer, GE RTV106. The ladder is then bolted onto the oven.