MATHEMATICAL-MODEL FOR PREDICTING THE MOLECULAR INTENSITY OF A SOLENOID-ACTUATED PULSED-BEAM SOURCE

A mathematical model for evaluating the molecular intensity produced b y a solenoid-actuated pulsed beam source is described. The particular source studied here is used to introduce reactant gas pulses at variou s user-specified intervals into a fixed-bed microreactor system for tr ansient catalysis studies where quantification of the inlet pulse inte nsity is required for data analysis. The model equations which describ e the beam source performance utilize relationships from one-dimension al isentropic gas expansion, gas effusion through a small hole, and ma croscopic mass balances around the valve orifice from which a closed-f orm algebraic expression for the pulse intensity is obtained. The para meters in this expression represent observables which include the idea l gas specific heat capacity ratio, the stagnation properties of the g as in the supply chamber of the beam source, and the beam valve driver settings. Comparisons between experimental and predicted values for t he pulse intensities, where the latter are of the order 10(17) molecul es per pulse, show excellent agreement.