1. System overview:

This document summarizes essential details for materials, setup, and operation. This is for transcription, archival, and research purposes only. It is based on an old patent and is not intended as a finished product. Operating conditions described require specialized handling and safety precautions, and the descriptions outlined here do not constitute a recommendation or endorsement to build or operate the device. Attempts to replicate or build upon these models are entirely at your own risk.

Source patent:

• Shoulders, Kenneth R. U.S. Patent No. 5,123,039. Issued June 16, 1992.
• Image: Figure 45
• Text: FROM Column 40 line 43 UNTIL Column 42 line 36

1.1. Purpose

Basic Function:
This multi-electrode source allows for a pre-charged cathode to fire an EV by applying a positive pulse to a third electrode.

Core Behavior:
There are constructions in which it would be more desirable to have a constant negative potential on the cathode with respect to ground instead of providing a single highly negative pulse. In these situations, a third electrode at a similarly constant intermediate low potential can be used at or around the location of the cathode tip where the negative field would be strongest. This negative electrode near the EV emitting electrode can suppress the emission of EVs, and can trigger the emission of EVs by receiving a positive potential pulse.

In this way, it acts similarly to early cathode designs where a counterelectrode at ground potential was included in the emitter design, where its proximity to the cathode helps form the field strength required to emit an EV once the cathode's pulse arrives. Except in this multielectrode source, where the cathode is constantly at a potential relative to ground fit to emit EVs with, the nearby electrode is also negative instead of at ground, reducing the field strength experienced at the tip of the emitter below the point required for the emission of EVs until a positive pulse is applied.

The power of the pulse required on the control electrode is relatively high owing to the capacitance formed between it and the anode. A tetrode configuration shown later in the patent can overcome this.

Scale & Format:
A later Tetrode device is described as having channel widths and depths of 20 micrometers, and this triode device has been edited to reflect those dimensions. This gives it a size of 160 by 120 micrometers.

1.2. Components

Diagram(s):

Parts list:

Notes:
In column 42 line 2, a broad array of options for material composition are given (ending with "In general, any stable dielectric material and stable metallic conductor material may be utilized"). Produced using (photo)lithographic techniques, etching of the channels/grooves, and deposition of evaporable/sputterable metal onto the electrode sites.

2. Device materials and environment

2.1. Materials

Suggested Materials:

• Referring to Column 42 line 2, Aluminum Oxide dielectrics and sputtered molybdenum would be typical.
• For the emitter specifically, an electrode that can tolerate high temperatures like molybdenum or tungsten is essential, although another metal may also work if mercury-wetting is used.
• Molybdenum needs to be treated before it can be effectively mercury-wetted, though for the emitter (or all electrodes) another metal may also be chosen.
• In the case mercury-wetting is employed, care needs to be taken to prevent stray mercury splatter from affecting the field structure in the channel. Instead, the tungsten or molybdenum electrode can be pointed to improve field structure. This is a tradeoff between reliablity and durability.

2.2. Operating Conditions

Electrical: Specific voltages are not mentioned, though from the dimensions voltages may be inferred.

• A steady cathode voltage in the order of -100 V with respect to the anode should be enough
• The "anode" will be at ground
• The control electrode should be somewhere between the cathode and anode voltage, enough to normally inhibit the cathode from emitting EVs. When pulsed in the positive direction, this generates enough of a field on the cathode to emit an EV. While the control electrode will have no net current transferred through it, the increase and decrease pulse will have to be large to overcome the capacitance felt between the control electrode and anode.

Environment: Pressure not directly mentioned, but inferred to be similar low-pressure (10^-3 torr) xenon as usual.

3. Additional information

3.1. Attachments

• Figure 45
• Multielectrode sideview
• Multielectrode1.FCStd
• Multielectrode1.stl
• Multielectrode1_annotated.FCStd