Means for suppressing helix current during mechanical focusing of traveling wave tube

Claim 2

A beam focusing means for a traveling wave tube of the type including a helix and a beam focusing means positionable with respect to said helix by means of which helix current may be minimized to attain beam focusing; means for reducing beam current to a safe average value during focusing whereby helix current is limited to a predetermined magnitude under worst defocused conditions; comprising, power supply means supplying normal operating voltages of predetermined magnitudes and potentials to the beam defining and controlling electrodes of said traveling wave tube, means for controlling the application of the supply voltage to at least one of said beam defining tube electrodes between the normal operating potential and a second predetermined potential the application of which is instrumental in effecting a predetermined suppression of beam current in said traveling wave tube, whereby the average beam current is reduced to a value such that average monitored helix current may not exceed a predetermined magnitude.

Claim 3

Means as defined in claim 1 wherein said traveling wave tube anode supply voltage is periodically applied to the anode of said tube at a rate corresponding to a predetermined duty cycle to effect said beam current suppression.

Claim 4

Means as defined in claim 2 wherein the anode voltage supply is selectively connected to said anode electrode of said traveling wave tube through switching means the energization of which is controlled by a source of energizing pulses.

Claim 5

Means as defined in claim 3 wherein said source of pulses comprises the output from a pulse generator, said pulses being of a predetermined duty cycle.

Claim 6

Means as defined in claim 4 wherein said duty cycle is between the limits of 20 and 30 percent based on normal operating anode voltage application.

Claim 7

Means as defined in claim 1 wherein said traveling wave tube includes a Wehnelt suppressor electrode, said power supply including a source of voltage negative with respect to said cathode normal operating voltage for application to said Wehnelt suppressor electrode, and control means for selectively applying said Wehnelt suppressor power supply potential to said Wehnelt electrode alternately with application of a further negative potential substantially more negative than said cathode supply voltage, whereby said average beam current is suppressed to an average value such that average helix current under worst defocused conditiOns of said traveling wave tube is beneath said predetermined magnitude.

Claim 8

Means as defined in the claim 6 wherein said control means comprises a relay a first fix contact of which is connected to the normal Wehnelt electrode operating voltage and a second fixed contact of which is connected to said further negative potential, and means for selectively operating said relay between respective positions thereof.

Claim 9

Means as defined in claim 7 wherein said relay comprises an energizing winding selectively connectable to the output of a pulse generator means, said pulse generator means developing a train of pulses the duty cycle of which effects said predetermined beam current suppression.

Claim 10

Means as defined in claim 8 including switching means, a first position of said switching means effecting a connection between said relay energizing winding and a source of energizing voltage, a second position of said switching means connecting said relay energizing winding to the output of said pulse generator.

Claim 11

Means as defined in claim 8 wherein the periodic switching of said normal and further supply voltages to said Wehnelt electrode establishes a duty cycle in the range of 15 percent based on the application of normal operating voltage to said electrode.

Claim 12

In conjunction with a power supply for a traveling wave tube, control means for varying the duty cycle of the application of normal operating voltage to at least one beam current determining electrode at a predetermined rate to reduce average beam current to a value in response to which average helix current under worst tuned conditions is held beneath a predetermined magnitude, whereby damage to said traveling wave tube is prevented during focusing arrangements, said control means comprising switching means, a first position of said switching means effecting continuous application of normal supply voltages to said traveling wave tube and a second position of said switching means effecting alternate application of the normal operating value of a predetermined one of said supply voltages to its associated tube electrode with application of a second potential, the application of said second potential being effective in suppressing beam current to a value substantially below that experienced under normal supply voltage application.

Claim 13

In conjunction with a power supply for a traveling wave tube, control means for varying the duty cycle of the application of normal operating voltage to at least one beam current determining electrode at a predetermined rate to reduce average beam current to a value in response to which average helix current under worst tuned conditions is held beneath a predetermined magnitude, whereby damage to said traveling wave tube is prevented during focusing arrangements, said control means comprising switching means, a first position of said switching means effecting continuous application of normal supply voltages to said traveling wave tube and a second position of said switching means effecting alternate application of the normal operating value of a predetermined one of said supply voltages to its associated tube electrode with application of a second potential, the application of said second potential being effective in suppressing beam current to a value substantially below that experienced under normal supply voltage application.