Document Title:
Remote Tomo5 operation guide for eBIC microscopes
Author(s):
Kyle Morris
Julika Radecke
Andrew Howe
Version:
2.0.3
Date:
27 Jun 2022
If you have any questions at any point during set-up, please ask your Local Contact for assistance Page 12 of 29
3.1.5 Dose calculation
Set calculated exposure time in Preparation > Presets > Exposure
In this example, there are a few considerations to keep in mind:
-
The dose per tilted image is 3.20 e
-
/Å
2
, 3.0 to 3.5 is reasonable for sub-tomogram averaging
-
‘Fractions (Nr.)’ are set to 6 for a tilt movie with ~0.5 e
-
/Å
2
per fraction, sufficient for motion
correction
Your LC will have told you the
physical pixel dose rate
over vacuum. Follow the example calculation below to
calculate and enter your target exposure time based on your desired target dose per tilt or in total (e
-
/Å
2
). You may
Example
exposure time calculation with
parallel illumination
targeting optimal dose
per tilt
Example
exposure time calculation with
parallel illumination
targeting total dose
Physical pixel dose rate:
5.281 e
-
/px/sec
Pixel size (magnified):
1.63 Å/px
Pixel area (magnified):
2.66 Å
2
/px
𝒆
−
/𝒑𝒙/𝒔𝒆𝒄
Å
𝟐
/𝒑𝒙
=
𝒆
−
/Å
𝟐
/𝒔𝒆𝒄
Dose per tilt (target):
3.2
e
-
/Å
2
Dose rate:
1.988
e
-
/Å
2
/sec
𝒆
−
/Å
𝟐
𝒆
−
/Å
𝟐
/𝒔𝒆𝒄
=
𝒔𝒆𝒄
Exposure time per tilted image
(sec)
:
1.61
Physical pixel dose rate:
5.281 e
-
/px/sec
Pixel size (magnified):
1.63 Å/px
Pixel area (magnified):
2.66 Å
2
/px
𝒆
−
/𝒑𝒙/𝒔𝒆𝒄
Å
𝟐
/𝒑𝒙
=
𝑒
−
/Å
2
/𝑠𝑒𝑐
Dose rate:
1.988
e
-
/Å
2
/sec
Total dose (target):
131 e
-
/Å
2
Tilt range (°):
-60 to +60
Tilt step (°):
3
Tilt image number:
41
Dose per tilt
= 131 / 41
= 3.2
e
-
/Å
2
𝒆
−
/Å
𝟐
𝒆
−
/Å
𝟐
/𝒔𝒆𝒄
=
𝒔𝒆𝒄
Exposure time per tilted image
(sec)
:
1.61
From your calculation, will each tilt receive sufficient dose for the imaging and tracking to work? If you are unsure,
later during set up, you could move to an unused area to acquire data acquisition images at zero and increasing
tilts that reflect your collection.
