Laboratory design for high-performance electron microscopy Page: 3 of 10
This article is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to Digital Library by the UNT Libraries Government Documents Department.
The following text was automatically extracted from the image on this page using optical character recognition software:
Designs and Implementations
Electron microscope laboratories at our four institutions [2-4] have taken similar approaches
designed to minimize adverse ambient conditions caused by the environmental effects described above
(Fig. 1). Acoustic noise, vibrations and heat from electron microscope ancillary equipment are minimized
by separating the equipment room (yellow) from the microscope room (green) with sound-and-vibration
attenuating internal walls. Low-frequency vibrations coming through the laboratory foundations are
minimized by mounting the microscope on a large heavy concrete pad (blue). Air-handling systems
(HVAC) are designed to deliver just enough cold air to balance the heat production of sources in the
microscope room (including the operator) so as not to cycle between temperature extremes. The four
laboratories were prepared for different circumstances. The NCEM's laboratory is a three-room extension
to an existing building (Fig. 1a). Sheffield University's is a one-room site in an existing building (Fig. 1b).
The TSRI (Fig. 1c) and ORNL labs (Fig. 1d) were built as new facilities, to house six and four micro-
scopes respectively, with the TSRI lab optimized for biological use and the ORNL for high-resolution
The National Center for Electron Microscopy's One-Angstrom Microscope (OAM) laboratory 
was built in 1996-97 to house three high-resolution electron microscopes (Fig. 1a). The general seismic
instability of the location in Northern California produces a constant background of small vibrations called
microseisms. Since low-frequency (< 5Hz) vibrations are best attenuated by large masses, we mounted
the microscope on a thick concrete slab. Pumps and ancillary equipment such as chillers were banished
to an adjacent equipment room behind a solid wall with acoustic damping on both sides. To de-couple the
instrument room slab from the rest of the world, we specified an air-gap on the sides. Cost, and the
discovery of shallow bedrock on the site, limited us to a 3ft-thick slab extended to occupy most of the
microscope room area (about 1 m by 3.3m by 4.2m) placed directly on a thin layer of tamped fill (Fig. 2).
Construction practicalities replaced the air-gap with a 1" layer of closed-cell foam, with the advantage of
preventing the accidental dropping of vibration-coupling objects (e.g. screwdrivers) into the gap.
Measurements of vibration spectra, carried out using a B&K type 2515 vibration analyzer with an
8318 sensor, show significant attenuation of vibration on the slab (Fig 3). Vertically, vibration attenuation
is close to a factor of three in the critical range from 1Hz to 5Hz (Fig.3 top); horizontal attenuation in this
range is even stronger (Fig.3 center and bottom). Our final layout moved the HT tank and computers to
the back room to join the ancillary equipment. To move the computer noise and heat out of the instrument
room we used solid-state amplifiers that allowed us to extend the keyboard, mouse, and monitor cables to
25ft. Because the ground sloped sharply up to a road at the rear of the building, we built a retaining wall to
create an air-gap between the back of the building and the hill. Offices, required for the second floor, all
have carpet over thick rubber. Walls between instrument rooms and back rooms extend up to the base of
the office floor to ensure acoustic separation.
All four walls in both the equipment room and the main microscope room were made acoustically
"dead" by application of a 50mm-thick cloth-covered fiberglass sound absorbent. In the microscope room,
air currents were minimized by arranging the air inlets along the side of the room farthest from the
microscope column, providing a laminar flow down the wall and across the floor. Individual air-handling
units were provided for each microscope room for temperature stability with variations of less than 0.5 C
per hour. To minimize electromagnetic interference, all power conduits were routed as far as possible
from the microscope column, giving a measured field of less than 0.1 milliGauss at 60Hz. Power and
signal cables, and all cooling-water hoses, were routed between the rooms in cable trenches (Fig.1a).
University Of Sheffield:
The electron microscope laboratory required a JEOL 2010F to be located in refitted accommo-
dation in an eighty-five year old building in Sheffield . To prepare the site for the microscope, we used a
microscope foundation consisting of a large (1m thick and 4m square) concrete base weighing around
30,000kg, poured onto the sandstone bedrock and isolated from the building foundation with a 2 cm air
gap. For comparison, the weight of the TEM is around 1,500kg. Precautionary measures were taken to
reduce the entrance of noise and to damp noise in the room. Principal among these was to remove noisy
microscope equipment (pumps, power racks, compressor) to a purpose-built back room (Fig. 1 b). A small
entrance lobby was included, and the microscope room is therefore separated from a noisy corridor by two
doors. A reduction of existing electro-magnetic fields at the Sheffield site occurred as a result of the
general overhaul of existing wiring while installing dedicated supplies for the microscope. The AC fields,
once an unacceptable 2.5 mGauss (rms), are now less than the required 1 mGauss.
Submitted to Microscopy Today
Here’s what’s next.
This article can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Article.
O'Keefe, Michael A.; Turner, John H.; Hetherington, Crispin J.D.; Cullis, A.G.; Carragher, Bridget; Jenkins, Ron et al. Laboratory design for high-performance electron microscopy, article, April 23, 2004; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc788453/m1/3/: accessed August 20, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.