An insensitive gamma‐ray detector for measurement of fast rising, transient gamma‐ray fluxes has been developed. Linear signals ≥5×102A have been observed, corresponding to a 1.25 MeV dose rate of >1016R/h. The detector can also be used in the steady state mode where signals ≤10−12A can be measured. This current corresponds to a60Co dose rate of ∼20 R/h. Detector design criteria, sensitivity as a function of energy, linearity, and time response are also discussed.