Target thickness uniformity gauge

A method to accurately and quickly measure target thickness and uniformity for large area targets is described. The technique takes advantage of the fact that typical transmission curves for continuous beta-ray spectra are exponential up to very small transmission (⪡1%) under suitable conditions. Depending upon the particular beta source used, the technique can be optimized for any region of target thickness between 0–800 mg/cm 2 . A system to measure target thicknesses between 1–30 mg/cm 2 using a 147 Pm beta source was constructed and its performance is evaluated.