Dear colleagues

Good day

I want to know how can find the instrumental beta or (standard beta) for Y3Al5O12:Ce phosphor (YAG)? And what is Beta sample which was used in the following equation:

Beta sample=SQR((beta exp.)^2-(beta ins)^2)

or

(Beta)^2=(beta sample)^2-(beta standard)^2

What is the difference between Beta and Beta sample?

I think instrumental and standard beta are the same, right?

Many thanks with best regards

Fayroz