METHOD FOR EVALUATION OF FIELD-EMISSION CATHODE QUALITY Russian patent published in 1999 - IPC

FIELD: quantum electronics, in particular, gas-discharge equipment. SUBSTANCE: method involves pulse stimulation of cathode surface, measuring of time dependency of after-emission and comparing measured dependency to reference one. Stimulation and measuring of time dependency of after- emission are done in condition s when density of discharge current, voltage amplitude and pulse duration are greater than density of normal glow discharge, statistical potential of discharge ignition and time of statistical discharge delay by 25 percents. Method involves at least 30 measurements of samples of discharge delay time, discarding maximal and minimal values. Cathodes which are judged durable for R conform to conditions , where I_ae is mean after-emission current, which is calculated using equation (in A), where t_di is discharge delay time in i-th sample (in seconds), δ_iae is mean square deviation of after-emission current from mean after-emission current, A is coefficient which is equal to tangent of inclination of dependency of after-emission current from given service life. Field-emission cathodes from pure materials with impurity concentration below 0.01% with oxide film on surface provide A = 3.5 10e20 A/h. EFFECT: increased reliability and fidelity of evaluation. 2 cl, 1 dwg