Commonly used in travelling wave tubes (TWTs), radio frequency (RF) power amplifiers, and medical devices such as electron guns, control grids amplify RF signals and control the flow of electrons through devices.

A control grid (or gun grid) is indispensable in high-power systems used in the medical, defence and aerospace industries. It is used in amplifying thermionic valves (vacuum tubes) such as the triode, tetrode and pentode, controlling the flow of electrons from the cathode to the anode (plate) electrode. Usually, it is made up of a cylindrical screen or helix of fine wire surrounding the cathode and is surrounded in turn by the anode.

the role of control grids

Control grid play a crucial role in managing the flow of electrons through a device. It directs the electrons toward a specified area or point with high precision. In fact, it can control, shape and focus the electron beam inside electron guns.

The electron beam can be controlled precisely by varying the voltage to the gun grid. Efficient amplification or focusing of electron beams inside a device is crucial for it to function optimally.

customisation

By customising the dimensions of the grid structure and the patterns or apertures etched on it, we help our customers optimise the performance of the device. This customisation is pivotal as it ensures that the gun grid fulfils the intended functionality and performance requirements of the electron gun.

High-power RF amplification is a critical function in defence and aerospace applications. Similarly, precise and efficient electron beam delivery is vital for medical devices to deliver proper treatment protocols.

how we help

High precision in design and manufacturing is essential for producing control grids. Control grid etching processes must be designed and tested for high accuracy and repeatability. This level of precision is essential for high-performance devices to meet stringent quality control standards and reduce variations between devices. That’s why we apply tight process control and use highly skilled technicians.

Our experts use chemical etching to create intricate patterns and apertures on the control grid with tight tolerances. It allows us to create complex patterns or structures, such as slots or meshes on the grid, which ultimately determine the functionality and performance of the device. Parts made using chemical etching have a burr-free, stress-free finish, unlike other methods like stamping or laser etching and it creates crisp surfaces and walls -crucial for grid structure integrity, allowing for a consistent flow of electrons for efficient amplification of RF waves.

considerations

There are several considerations to keep in mind when creating control grids. These factors help ensure that the custom control grid will perform as intended and meet the rigorous demands of critical applications.

  1. Precise design specifications: These need to define the dimensions of the piece to be produced, the pattern of slots, meshes, or apertures, and the tolerances required.
  2. Choosing the right material: This is essential. Usually a refractory metal, it should have the strength to maintain the grid’s structural integrity and the appropriate electrical conductivity required for efficient electron flow and heat resistance to function properly – even if the device gets overheated during operation.
  3. Quality assurance: Control grid etching is a repeatable and consistent process and must conform to the highest of quality standards and industry-mandated compliances.

applications

Control grids play a crucial role an many critical applications

RF power amplifiers

As the name suggests, RF Power Amplifiers amplify a low-power radio frequency signal. Critically, they ensure that the signal is boosted to a level suitable for efficient and reliable signals over long distances.

This is particularly important in military communications. One of the key uses of RF power amplifiers is detecting objects, such as in avionics and radar applications. Avionics transponders generate an amplified electrical response when “interrogated” by a ground station or another aircraft.

travelling wave tubes (TWTs)

A Travelling Wave Tube amplifies a modulated electromagnetic wave to transmit data. The electromagnetic wave interacts with an electron beam inside a vacuum. Because both travel at almost the same speed, electrons transmit their kinetic energy to the wave (the Cherenkov effect).

TWTs are widely used as the power amplifiers and oscillators in radar systems, communication satellite and spacecraft transmitters, and electronic warfare systems:

TWTs in defence technology

satellite applications

In satellites, the microwave signal is amplified and converted at the antenna’s output. The output power of the transmitter at these frequencies must be high, as the satellites only receive a tiny portion of the power transmitted in their direction.

By transmitting high-frequency signals over vast distances, TWTs allow for crucial data transmission between the Earth and orbiting satellites, facilitating deep space exploration as well as for civil and defence purposes. They also enhance the sensitivity and accuracy of satellite-based detection systems, a vital aspect in tasks such as weather forecasting, earth observation, and surveillance.

electron guns

In an electron gun, often used for radiation therapy, a heated cathode emits electrons. When positive voltage is applied across the cathode and anode, it drives the electrons toward the far end of the gun tube where the electrons are focused into a beam.

A cathode ray tube is made up of a vacuum tube containing one or more electron guns, which emit electron beams that are manipulated to display images on a phosphorescent screen.

Oscilloscopes In an oscilloscope tube, the control grid adjusts the beam current and so the brightness.

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