Optimizing Image Resolution in Electron Microscopy with FYRA
Adding Precise Vacuum Control to Optimize Microscopy Image Resolution
Root of the problem
A customer approached DigiVac to assist with vacuum control in an electron microscope. A vacuum within the microscope deeper than 20 Pascals (approx. 150 millitorr) causes visible degradation in the final image. The customer needed the ability to measure inside the chamber and precisely control the vacuum between 20 and 30 pascals while the electron microscope captures the image. He was looking to optimize the image resolution of the final image. Resolution is the ability to separate (resolve) two closely spaced points (particles) as two separate entities.
How it Works
Most electron microscopes are high-vacuum instruments. A deep vacuum is needed to prevent arcing so that the electrons can travel unobstructed within the instrument. However, the specific electron microscope used by the customer did not have on-board vacuum control. The user chooses between Low Vacuum and High Vacuum settings depending on the makeup of the sample being observed. Different electron emission sources require different vacuum levels. There are 2 classes of emission sources for scanning electron microscopes, thermionic emitters and field emitters. Field emission systems require high-vacuum that is clean to avoid particulate/carbon deposits on the sample.
Solving the Issue
The hypothesis is that raising the pressure slightly will attract the negatively charged electrons causing imaging difficulty. Having a controllable chamber pressure allows the user to find the pressure that reduces the charging effect enough that analysis can be performed. We achieve this precise level of control with the FYRA’s controlled bleed valve that allows ambient air (or a connected inert gas supply) to be drawn into the chamber, “balancing” the vacuum level in the chamber. The bleed valve is controlled by the FYRA controller using a feedback control based on the measured chamber pressure.
How Can FYRA Improve the Imagery of Electron Microscopy ?
FYRA provides the perfect supplement to electron microscopy equipment, epitomizing versatility with a touchscreen or dial interface and the ability to measure vacuum from atmosphere down to 1 millitorr. The accuracy of this FYRA controller when paired with a thermocouple sensor is from 6 Torr down to .01 mTorr. The accompanying bleed valve is capable of precise vacuum control from 10 millitorr to 6 Torr. Our instrumentation is easily integrated with existing electron microscopy equipment and will assist in limiting degradation caused by vacuum levels that are too deep.
Our Fyra bleed bundle includes 1 VacStable valve , 1 Agilent 531 thermocouple sensor (and driver cards), and 1 controller. With our sensor attached to one side of the vacuum chamber and the Vacstable bleed valve on the other, we began to pump out the vessel and capture images. Below 20 pascals, the degradation was clear. We set the controller to bleed to 20 Pascals, scanning the image field every few seconds. The images were much clearer at this vacuum level. After some fine tuning with the built-in PID controller that is integrated into FYRA, we had a clearly defined SOP for alleviating the degradation issues when the vacuum level dipped below the required range. The FYRA with bleed control is thus an indispensable resource for any industry in need of precise vacuum control.
Interested on how you can optimize your process and efficiently use bleeding in your lab? Check out our FYRA bundle here!
FYRA Bleed bundle Set Up
How FYRA Bleed bundle works
Watch how FYRA works below!