| 摘要 |
An electrode includes an electron or irradiation transmissive conducting layer and an electron-emissive layer of insulating material in spongy form. This layer may be of BaF2, LiF2, MgF2, MgO, Al2O2, CsI, KCl or NaCl and preferably has a density of only about 1% of the same material in bulk form, e.g. 0.01 to 0.1 gms. per cc. with a thickness of 10 to 100 m . The layer may be formed by deposition in a gaseous atmosphere, e.g. argon at 1 to 2 mm. of Hg pressure, with a spacing of about 3 inches between the evaporator and the receiver, which may be rotating. Alternatively magnesium may be burnt in air at atmospheric pressure about 14 inches from the receiver. The receiver may be an aluminium film supported by a metal ring and formed by vacuum deposition of aluminium on to a film of thermally removable cellulose nitrate to a thickness of 140 to 1000 . Specifications 792,507, 862,211 and 898,433 are referred to. |
