K2 Summit and K2 Base Direct Detection Camera User's Guide
23
Clicking the question mark button provides some guidance. Linear mode is not very sensitive
to dose rate, you could increase this from 5000 to 20000 if you like. If you decrease it from
the default, it’s best to scale the exposure factor accordingly (for instance if you halve the
dose rate, double the exposure factor).
figure 1-18. Gain reference exposure factor recommendations
Otherwise you can use the default values which work well under most circumstances, and
click
OK
to continue. (Note if you select a lower than default exposure factor which could
result in low image quality you see the warning message pop up again and have to reconfirm
your choice.)
You are now asked to adjust the beam to the selected dose rate. Because short exposures are
used, the requested dose (500 counts below) is a fraction of the desired dose rate (5000
counts/second above). Note the default Linear mode gain reference beam level is more than
10 times brighter than the typical Counted and Super-Resolution beam level, if you have been
operating in those modes you have to brighten the beam considerably.
figure 1-19. Beam intensity recommendation
When you adjust the beam and select
Done
, the script calculates input values for
DigitalMicrograph’s gain reference collection routine and fill them in. Do not change these
values, and click
OK
.
