My XRF Setup - Part 3 - Exciter

The exciter is the second main component of an XRF setup - this is the source of the primary X-Rays.

Two type of Exciters are generally used - X-Ray tube or Radioactive Isotope.

X-Ray tubes 

Pros:

- provide high-intensity beam

- low limit of element detection

- easy on/off capabilities 

- fast integration times

- fairly clean and uniform spectrum

- very small spot of irradiation / sampling 

Cons:

 - big, heavy, very delicate

- require additional cooling

- large, hazardous HV power supplies

- need for safety interlock system

- heavy beam collimators

- substantial shielding is required

- consideration must be made about beam scattering and reflection

- Not as portable

Radioactive Isotope source 

Pros: 

- smaller, lighter and simple to use

- 100% reliable

- very portable for field use

Cons:

- low intensity beam requires long acquisition times

- shielding is required as well a shutter-type on/off system

- highly regulated

- danger of contamination if source is damaged

- spectrum is not as clean and can contain various peaks

 The holder of the exciter was designed with TinkerCAD and 3D printed

While this method works and it is a convenient way to use a number of small individual sources, the main problem is that they need to be placed at some distance from the Object Under Test which decreases the flux and irradiates a larger area of the specimen. One can not easily select the area being sampled.

I made a small, single, directed source with a  Lead collimator / shield which works very well and I can place it much closer to the specimen without the detector picking up the primary X-ray.

Update: X-Ray tube is added as yet another option to do XRF excitation and I built a custom controller for it. See THIS post.