Every day Professor David Flannigan goes to his lab and marvels. The lab houses an ultrafast electron microscope (UEM) which is the first of its kind in the world, allowing Flannigan and his colleagues to study the dynamics of materials at the atomic and molecular scale over time spans measured in femtoseconds (one millionth of a billionth of a second.) But the UEM is not the only thing that Flannigan marvels.It’s also the perfection of the room itself.
“I tell everyone that comes into my lab that without the high-precision of the room, the microscope is worthless,” said Flannigan, an Assistant Professor at the University of Minnesota Department of Chemical Engineering and Materials Science.
“The new lab space in the Gore Annex is going to give us extremely sensitive environmental control. That, combined with this new ultrafast electron microscope is going to allow us to do experiments that literally have never been done before,” said Flannigan.
“For example, we are very interested in imaging energy propagation through materials at the atomic scale. Energy moves very fast at these small length scales, so we need to be able to take snapshots quickly enough to capture the motion. Equally important is the stability of the room; at the length scale of a single atom, it doesn’t take much room noise, temperature variation, or air flow to disrupt the experiment and blur the image. The UEM and a high-quality room must go hand-in-hand, and we now have that here in the Department of Chemical Engineering and Materials Science.”
The UEM Microscope lab is part of the newly-completed Gore Annex, which opened in July 2014 after 15 months of construction by Kraus-Anderson. KA Project Manager Paul Wilczynski talked about some of the details involved in creating a lab space built for extremely sensitive environmental control.
Q: What are some of the considerations that needed to be addressed to make the environment suitable for the sensitive UEM equipment housed there?
WILCZYNSKI: The space had to be built with controls for noise, light, vibration, dust, temperature, temperature fluctuations, airflow and electromagnetic interference. And we had some pretty substantial interference in the proximity of the light rail transit tracks, which run 125 feet from the building.
Q: What sort of specifications had to be followed to deliver those controls?
WILCZYNSKI: Seeing as this space was the first of its kind, there were no exact specifications to follow. Instead we engaged in a lengthy collaboration process including Professors Jeff Schott and David Flannigan of the Chemical Engineering and Materials Science Department; FEI (manufacturer of the UEM), AEI (Affiliated Engineers, Inc., the mechanical engineer), our subcontractors and ourselves. KA and our subs provided options to this consultant team on every aspect of the lab space and they gave us a yes or no. Together we worked incrementally to arrive at the specifications the team believed were necessary to allow the UEM to function at peak performance.
Q: How did these requirements affect various stages of construction?
WILCZYNSKI: Some examples:
- While excavation was taking place for the building, a big effort was put into how best to electrically ground the room and the equipment inside it from electromagnetic interference. It was determined that dual system would be the best. 1) Tying the room and equipment into the building’s grounding mat; and 2): Driving a ground rod into earth that would penetrate the slab-on-grade. These two options gave us future flexibility.
- During the concrete foundation pour, a free standing massive block of concrete was poured to create an isolation slab for the UEM to sit on.
- Wall assembly considerations: We wanted to stay away from using sand- filled CMU to fulfill the sound/vibration rating the wall was presumed to require, in order to allow for future modification to the space. Any future penetrations into sand- filled CMU would result in sand pouring out of the wall. Instead we opted for a UL- rated gypsum wall assembly.
- A huge effort was put into the type of diffusers and duct configuration that would be used in the space. It was believed that we had to meet an air flow of 5 m/min. Therefore the diffusers used and the duct configuration in the room would play a big part in accomplishing this requirement. Duct configuration also played a big part in sound transfer through the walls.
- Finding the right insulating materials for duct work, plumbing piping, and mechanical piping was another big consideration. Everything within the room is insulated with sound absorbing insulation in the effort to make everything as quiet as possible.
- Finding the right drop ceiling system. We ultimately used a clean room ceiling in which all the ceiling pads sit on rubber gaskets and all the suspension rods are mounted to the grid system with rubber grommets to reduce noise/vibration.
- LED fixtures with drives that produced little to no noise were chosen for the lighting of space; again, to reduce noise and/or vibration.
- Siemens created a control sequence with very tight tolerances to insure that the room’s temperature and air flow met anticipated performance requirements.
WILCZYNSKI: Because the requirements of the lab space were taken into consideration during every stage of construction, from excavation through finishes and commissioning, it essentially was under construction throughout the duration of the Gore Annex construction– 15 months.
Q: What have been the results of the team’s painstaking work?
WILCZYNSKI: When FEI came and installed the microscope they used very sensitive sensors to measure all of the above mentioned consideration and were thrilled with the readings they were getting. For example, the sensors were unable to detect any vibration whatsoever over a range of low frequencies, even when the light rail train went past. They had to recalibrate their air temperature fluctuation sensors to 1/10th of a degree to get a reading; it was thought that the room could only fluctuate +/- 1 degree over a 24 hour period for the microscope to work and we were able to get it to only fluctuate +/- 1/10th of a degree over a 24 hour period. The FEI tech said it can take months to calibrate electron microscopes to reach their peak performance, but with the UEM he was able to get to peak performance in 3 weeks. He said the main reason he was able to do this was because the room was move-in ready, very stable, and quiet. FEI has already sent some of their engineers out to observe the quality of the room and see the high performance first hand.