What is the most desirable center wavelength for the light source used in fluorescent penetrant processes?

The most desirable center wavelength for the light source used in fluorescent penetrant processes is 365 nm. This wavelength falls within the ultraviolet (UV) spectrum, specifically in the UVA range. During fluorescent penetrant testing, the penetrant absorbs UV light at this wavelength and emits visible light, typically in the blue to green spectrum, which makes leaks or defects more apparent against the surface.

Using light at 365 nm is particularly effective because it provides optimal excitation of the fluorescent materials while minimizing background interference from ambient light. This results in clearer and more easily identifiable indications of defects in the materials being inspected.

In contrast, other wavelengths such as 254 nm tend to produce more ozone and can be harmful, while 420 nm and 500 nm fall into the visible light range and do not provide the same level of fluorescence excitation as 365 nm. Hence, 365 nm is chosen for its effectiveness in enhancing the visibility of defects through fluorescent processes.