Global luminescent lifetime measurements on a body in free fall

An experiment to investigate the feasibility of making global luminescent lifetime measurements in the laboratory is described. The measurements, on store models in free fall in still air, was motivated by the availability of a fast framing CCD (FF-CCD) camera under development. The store models were coated with a pressure sensitive paint (PSP) incorporating platinum meso-tetra (Pentafluorphenyl) Porphyrin (PtTFPP) dye having a luminescent lifetime of approximately 20 /spl mu/sec at atmospheric pressure. Changes in paint lifetime were induced by injecting inert gas in the vicinity of the falling store. The test region was illuminated with a standard, frequency-doubled Nd:YAG laser. The luminescence of the paint was acquired using the FF-CCD camera which employs a unique focal plane array having the facility to store images on the array itself. The camera system can acquire images at rates up to 1 MHz. The luminescent lifetimes were measured using rapid lifetime determination, a time domain technique which involves monitoring the luminescence of the paint following pulsed excitation. Lifetime measurements are presented for the store model in free fall. Measurement error sources are discussed. Characteristics of an improved measurement system are proposed.