SIMULATION OF A HEMISPHERICAL DEFLECTOR ANALYZERS AND FRINGING FIELD OPTIMIZATION

THE ENERGY RESOLUTION OF A HEMISPHERICAL DEFLECTOR ANALYSER (HDA) CAN BE SUBSTANTIALLY IMPROVED BY USING ITS ENTRY FRINGING FIELDS ADVANTAGEOUSLY, RATHER THAN TRYING TO ELIMINATE THEM, THE TRADITIONAL APPROACH. THE INTRINSIC LENSING PROPERTIES OF THESE FRINGING FIELDS, AS SHOWN IN SIMULATIONS, ARE ABLETO NOT ONLY RESTORE, BUT EVEN IMPROVE FIRST-ORDER FOCUSING AT THE 180^O DEFLECTION PLANE IN A CONTROLLED WAY, WITHOUT THE USE OF ANY ADDITIONAL FIELDCORRECTION ELECTRODES. THIS IS ACCOMPLISHED BY CHANGING THE ENTRY RADIUS R0AND BIASV (R₀) FROM THEIR CONVENTIONAL VALUES OF R0=`R, THE MEAN RADIUS `R=(R1+R2) /2 AND V (R₀) =0 TO NEW VALUES R₀>`R WITH V (R0)<0 ORR<sub>0</sub><`R WITHV (R₀)>0.