A measure of the strength of this effect, the "generalized perveance," is defined by
The difficulty of the problem can be gauged using the benchmark of generalized perveance, given in (2), to compare space-charge effects to existing machines.
Recently, theoretical results predicted a very promising new nonlinear regime for dramatically enhanced fusion reaction rates in a relatively large current (perveance) region.
The operating conditions were chosen as: He pressure of 20-3 0 mTorr, cathode voltage of 7-11 kV, cathode current of 30-40 mA (regulated) to enhance the beam perveance.
The second class of klystron modifications consists of devices aimed at increasing the optimal perveance
of the electron beams that allows for efficient, high-power operation.
The voltage-current relationship in a TWT electron gun is defined by the perveance, as follows:
Gun Perveance = Cathode Current / [(Cathode-to-Anode Voltage).sup.
Typical values of gun perveance range from 0.01 x [10.sup.-6] to [1.5 x 10.sup.6] pervs.
Selecting low voltage, high current operation means that the gun perveance must be high, and this presents several practical limitations.
Cathode current density and gun perveance considerations can be removed by designing the TWT for high voltage, low current (low perveance) operation.
An electron gun for a practical TWT will operate at an intermediate perveance, based on a tradeout study in which the factors shown in Table 2 are considered.
The electron gun is attached to the body (interaction space) via a metallic "flex-disk" which allows for adjustments in gun perveance
(current) and mechanical alignment during "hot" test of the device.