Which instrument is used to detect if all removable contamination has been removed?

The well counter is specifically designed for the measurement of low-level radioactive contamination and is particularly effective at detecting removable contamination on surfaces. It utilizes a scintillation crystal to detect gamma and beta radiation emitted from contaminated samples placed in the well-type geometry. This allows for a precise measurement of the radioactive material present.

In the context of contamination monitoring, the well counter's ability to measure small amounts of contamination makes it the preferred choice for ensuring that all removable contamination has been adequately addressed. It can provide accurate and sensitive readings, helping operators determine that a surface is clean and free of hazardous radioactive materials.

Other instruments like the Geiger-Muller counter and scintillation counter are also valuable for detecting radiation but may not offer the same level of sensitivity for removable contamination specifically. An ionization chamber is typically used for measuring high levels of radiation and might not be as effective in evaluating low-level contamination on surfaces.