Analysis of the Interaction between Electron Orbits and Gas in Fluorescent Lamps

What is plasma

Matter is commonly classified into solids, liquids, and gases, but heating a gas further can produce plasma.

Therefore, plasma is described as the ‘fourth state’ of matter.

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Plasma is created when particles—ions, electrons, and atoms—collide with each other.

Under what conditions does plasma form?

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Primarily, plasma occurs in extremely high-temperature regions such as the sun, or when high voltage is applied to a gas.

This time, we will analyze fluorescent lamps, an industrial product that utilizes plasma.

Fluorescent lamps consist of a glass tube, a small amount of mercury, an inert gas such as argon, electrodes at both ends, and phosphor coating the inner surface of the tube.
The phosphor absorbs ultraviolet light generated by the discharge and emits visible light.

Fluorescent lamps are utilized not only in ‘residential and living spaces’ but also in the following industrial applications.

Ultraviolet Fluorescent Lamps (UV Lamps)

• Sterilization and disinfection (medical facilities, food processing plants)

• Air purifiers

• Water Treatment Equipment

Blacklight

• Counterfeit Money & Document Verification

• Fluorescent Paint Inspection

• Crack Inspection

The luminescence process of fluorescent lamps is as follows.

The luminous efficiency of fluorescent lamps is primarily determined by the number of thermionic electrons emitted and the collision efficiency with mercury atoms.

We will calculate this process using PIC-PLASMA 3D (plasma analysis software).

Analysis of Electron-Gas Collisions in Fluorescent Lamps

Let's simulate the discharge inside a fluorescent lamp using PIC PLASMA3D.

The analysis model is as follows. (Created in FreeCAD)

Analytical model

We created a fluorescent lamp analysis model as described above and performed trajectory analysis of thermionic electrons emitted from the cathode (the particles that originate plasma generation).

The plasma generation mechanism is as follows:

Figure 2: Plasma Generation Process

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This time, we're simulating the electrons emitted from the cathode, which is the origin of plasma generation!

So, in the figure above, you mean the very first electron?

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That's right! Since PIC-PLASMA3D can also calculate ionized plasma (both ions and electrons), try it if you have time.

Got it!

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The analysis conditions are as follows.

Table 1: Analysis Conditions

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Note that these initial conditions can be set within the software (PIC-PLASMA3D).

Analysis results

The above materials are actual analysis results calculated using PIC-PLASMA3D.

This simulates the trajectory of free electrons emitted from the cathode, the origin of plasma generation.

Note that the “data” shown in the video represents the electron number density [particles/m³].

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You can see the electrons emitted from the cathode moving toward the anode.

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These electrons collide with the gas inside the fluorescent lamp, generating ultraviolet light. That ultraviolet light strikes the phosphor, causing it to emit light.

The CAD model used here was created simplistically, so the number of electrons and other conditions are simplified.

Additionally, PIC-PLASMA3D can output various data in addition to the above calculation results.

*The above is just one example.

We highly recommend using PIC-PLASMA 3D for plasma product development.ご活用ください。