Analysis of x-ray film exposure parameters using the Crookes tube for educational applications

Abstract Although the Crookes tube is widely used in academic settings to demonstrate x-ray principles, standardized experimental conditions for its application have not been established. This study aims to investigate the optimal parameters for sensitizing x-ray films using weak x-rays emitted from the Crookes tube. A Crookes tube with a Maltese cross and a high-voltage induction coil capable of applying up to 30 kV was used with small dental x-ray films. A portion of the film was shielded from x-rays using a copper foil tape. The experiments were conducted at two applied voltages (15 kV and 30 kV) and five exposure durations (2–10 s). The developed films were analysed for pixel values and contrast using ImageJ software. The results demonstrate that at an applied voltage of 15 kV with a 2 s exposure, the difference in the pixel values of the exposed and shielded areas was visually detectable. However, extending the exposure time did not significantly alter the contrast. At 30 kV, the contrast increased with longer exposure times. However, when the voltage-application time exceeded 8 s, the pixel values increased more in the shielded areas than in the exposed areas, thereby reducing the contrast increment rate. To minimize radiation exposure, the induction coil must be carefully configured. An applied voltage of 15 kV with a 2 s exposure duration effectively demonstrates x-ray presence and image formation. For quantitative contrast evaluation, effective analysis can be achieved by applying 15 kV and 30 kV for 4 s, while minimizing radiation. At 30 kV, prolonged exposure times should be avoided because of increased radiation. This experimental setup provides an effective introduction to x-ray usage for beginners. This study provides guidelines for optimizing the applied voltage and exposure time in the Crookes tube to enhance the experimental outcomes while ensuring safety.