Use of high power Microwave and Radio frequency power supplies

Activity being assessed

Use of high power Microwave (MW) and Radio Frequency (RF) power supplies, for plasma generation, heating, etc.

Hazards

• Biological heating and cooking(!) effects of MW and RF radiation, especially to eyes (e.g. cataract formation), and other soft tissues.
• Electric shock and burns (these may be different from, and far more serious, than the types of burns caused by conventional electrical supplies).
• High temperatures associated with high power equipment.

Precautions

Ensure equipment is properly:

• screened and shielded. Use an emission monitor to check that emitted MW power is <5mW cm2 @ 5 cm. For RF emission, a good rule of thumb is if any LED or LCD displays in the lab start flickering they are being affected by excessive RF output, and the power supply or leads need more shielding. Note that at this level of interference, other sensitive electronic equipment may be adversely affected – with corresponding safety implications. For example, mass flow controllers that are monitoring (toxic, explosive…) gases are particularly susceptible to RFI, and can give incorrect readings or be fully open/off without the user being aware of this.
• cooled. If water cooling is used, ensure water connections are fitted correctly with no chance of leakage onto the power supply.
• earthed. The casing of all power supplies MUST be earthed, and all electrical leads must be shielded with coaxial cable

Training Requirements

Training by an experienced person is essential.

Risk Remaining

The handling of MW and RF power supplies will always have some degree of risk and constant vigilance is required in their use.

Emergency Procedures

Shut off power supply, seek First Aid help if necessary

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Adapted with permission from School of Chemistry, University of Bristol