Abstract: Laser apparatus includes hydrogen or deuterium buffer gas and dispenser reservoirs which contain a hydride or deuteride as appropriate. As gas molecules from the buffer gas are lost within the discharge tube due to trapping and sputtering processes, hydrogen or deuterium is given off from the surfaces of the reservoirs at a greater rate to maintain the vapor pressure within the discharge tube at a substantially constant level. Thus the laser apparatus may operate in a "sealed-off" mode, that is without requiring that buffer gas be flowed through it.

Abstract: A co-axial magnetron is provided with a cavity whose resonant frequency can be very rapidly altered in a cyclic manner so that the microwave output frequency of the magnetron can be chosen to lie within the available frequency band of the cavity. The cylindrical walls of the co-axial resonant cavity are constituted by or coupled to the inner surfaces of one or more tuning forks which are maintained in vibration by externally mounted electro-magnetic transducers. As the tines of the tuning forks vibrate, the effect is to cyclically increase and decrease the effective diameter of the cavity, thereby changing its resonant frequency. An adjustable end plate can be provided for the cavity so that fine tuning or slow rate tuning can be provided in addition to the frequency agility provided by the tuning fork.

Abstract: The magnetic field produced by the periodic permanent magnets of a travelling wave tube is shaped to improve the transmission ratio of the electron beam. The first zero magnetic field occurs within the magnet region, and the first peak magnetic field occurs at the first minima of the diameter of the electron beam.

Abstract: A travelling wave tube having a periodic permanent magnetic focusing structure is provided with ferromagnetic plates having copper inserts which conduct heat away from the electron beam path and reduce the formation of hot spots.