An Underappreciated Radiation Hazard from High Voltage Electrodes in Vacuum

TL;DR

High voltage electrodes in vacuum can unintentionally produce hazardous X-ray radiation through electron emission, posing safety risks in laboratory settings that are often underrecognized.

Contribution

This paper highlights the overlooked radiation hazard from high voltage vacuum electrodes and provides a case study with mitigation strategies and safety guidelines.

Findings

X-ray radiation correlates with leakage current in HV vacuum devices.

Implementing safety measures reduces radiation exposure.

Laboratory awareness of this hazard is generally insufficient.

Abstract

The use of high voltage (HV) electrodes in vacuum is commonplace in physics laboratories. In such systems, it has long been known that electron emission from an HV cathode can lead to bremsstrahlung X-rays; indeed, this is the basic principle behind the operation of standard X-ray sources. However, in laboratory setups where X-ray production is not the goal and no electron source is deliberately introduced, field-emitted electrons accelerated by HV can produce X-rays as an unintended hazardous byproduct. Both the level of hazard and the safe operating regimes for HV vacuum electrode systems are not widely appreciated, at least in university laboratories. A reinforced awareness of the radiation hazards associated with vacuum HV setups would be beneficial. We present a case study of a HV vacuum electrode device operated in a university atomic physics laboratory. We describe the characterisation of the observed X-ray radiation, its relation to the observed leakage current in the device, the steps taken to contain and mitigate the radiation hazard, and suggest safety guidelines.