What is the general energy range of a portable XRF machine?

• A. 5-20 kV
• B. 15-50 kV
• C. 60-100 kV
• D. 1-5 kV

Answer: (B)

The tube voltage controls how energetic the X-rays produced by the handheld unit are. Portable XRF devices are designed to excite a wide range of elements, so they use a practical window of voltages that lets you target many elements without excessive dose or background noise. A range around 15–50 kV provides enough energy to excite characteristic X-rays from light to mid-heavy elements, making it suitable for most common analysis tasks with a handheld instrument.

If you use too low a voltage, heavier elements can’t be excited effectively; if you push the voltage too high, you increase radiation dose and background, and you may compromise detector performance. That’s why choices at the very low end (1–5 kV or 5–20 kV) or very high end (60–100 kV) aren’t as generally applicable to portable XRF as the 15–50 kV range.