Experimental X-Ray Source

Introduction

This historical experiment used a DY87 high-voltage vacuum diode from a black-and-white television as a weak source of X-rays. A newer project using a proper X-ray tube is documented separately in the Radioactivity section.

Operating Principle

When several kilovolts are applied between the cathode and anode, electrons are emitted and accelerated toward the opposite electrode. Their sudden deceleration on impact produces heat and bremsstrahlung X-rays. I later learned that reversing the polarity can reduce severe heating of the small anode plate, depending on the exact tube construction.

Shielding and Measurement

X-radiation penetrates many materials and cannot be stopped by thin plastic or foil. The tube must be enclosed in an appropriate lead shield, historically about 1 cm thick for this kind of demonstration, with only a carefully controlled aperture. Any imaging medium should be backed by additional shielding so that radiation does not continue through the setup.

A calibrated radiation survey meter is essential. Never rely on visual appearance, distance alone or an uncalibrated detector. Exposure must be minimised and the experiment should not be operated in an occupied area.

Historical Test

The original test was performed with a DY87 tube and a high-voltage supply. The project was experimental and produced only a weak output, quoted at approximately 10 mR/h in the original notes. Even a weak source must be treated as dangerous because ionising-radiation dose is cumulative and invisible.

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