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Uniform Electron Beam Current Density Flood Gun

IP.com Disclosure Number: IPCOM000085275D
Original Publication Date: 1976-Mar-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 22K

Publishing Venue

IBM

Related People

Sansom, A: AUTHOR

Abstract

Storage tubes commonly use a flood gun to erase the charge on an electrostatic target. Desirably, the electron flood beam should be uniform across its pattern and should have an angle of dispersion which is relatively independent of the drive applied to the beam.

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Uniform Electron Beam Current Density Flood Gun

Storage tubes commonly use a flood gun to erase the charge on an electrostatic target. Desirably, the electron flood beam should be uniform across its pattern and should have an angle of dispersion which is relatively independent of the drive applied to the beam.

An electron gun having a cathode 10 with a part-spherical thermionic emitter 12 and a concentric part-spherical electrode 14 having a substantial transmission of low-energy electrons serve this purpose. The geometry is such that the electrons leave the cathode surface 12 of cathode 10 radially and are accelerated toward electrode 14. The operative part of electrode 14 consists of an electroformed mesh 16, typically 500 lines per inch and of about 50% to 60% transmission. Mesh 16 has a suitable curvature and is spaced to have the same center 18 of curvature as emitter 12.

After passing through mesh 16, the electrons are accelerated over a short distance up to the final energy at which they will strike the target, and proceed in a field-free region until arrival at the target. The field providing this acceleration is established by cylindrical electrode 20 which is at the voltage of the target, not shown.

Correct choice of the diameter of electrode 20 (which may be the graphite conductive coating on the inside of the tube envelope) will provide equipotentials near the mesh 16 on the side remote from emitter 12 which are substantially hemispherical over the be...