A reproducible method for preparation and operation of microwave excited electrodeless discharge lamps: SIMPLEX optimization of experimental factors for a cadmium lamp

Abstract

By means of a SIMPLEX optimization procedure, cadmium electrodeless discharge lamps (EDLs) operated at microwave frequencies (2450 MHz) were prepared and optimized with respect to: weight of cadmium, W1 = 680-750 μg; time interval of the EDL blank under vacuum after water removal, t1 = 0-1000 s; pressure of argon gas (under microwave excitation) during preparation, A1 = 1-2.5 torr; microwave power for discharge during preparation, P1 = 90-10O W; time interval for microwave discharge during preparation, t2 = 20-28 s; time for EDL to cool before evacuation, t3 = 240 s; time under vacuum after cooling period, t4 = 0-500 s; pressure of argon to fill lamp, A2 = 6-9 torr; microwave power for operation of EDL, P2 = 55-65 W; and operating temperature of EDL, T = 290-330°C. Under the above conditions, EDLs were prepared reproducibly (atomic fluorescence detection limits were all within a factor of 3 or less). The resulting EDLs were consistently as good as or better than the best EDLs prepared in the past by the laboratory. Throughout the SIMPLEX optimization procedure, no EDL failed; all EDLs behaved as would be predicted by the preparation procedure. © 1977.