Pros & Cons of two guns design
Second electron gun for SEM postiioned close to the sample with mechanical XY positioning
What additional time is added when using two guns?
Given Electricity is 2kwh per hour .5Euro/hr
Single gun manufacturing times of Part A was 2480 min 1.7 days part B 248 min 4 hrs
Two gun design with SEM electron Gun with XY mechanical movement manufacturing part A 2866 min 2.0 days B 287 min 4.8 hrs ( max speed of movement of 0.3m per second)
So 15 percent longer manufacturing time as well as 2 extra motors ( one vacuum tolerant / expensive ) and extra position sensors and extra computer processing putting the patches together as one image. But advantage of normal sized PIN diode sensors for SEM in back-scatter mode as sensors only 0.1m from sample like a traditional SEM rather than 1m distance from sample a new situation ( see further walk through for detailed calculation).