Inside the world’s quietest room

In a hole, on some bedrock a few miles outside central Zurich, there lived a spin-polarised scanning electron microscope. Not a nasty, dirty, wet hole: it was a nanotech hole, and that means quiet. And electromagnetically shielded. And vibration-free. And cool.

When you want to carry out experiments at the atomic scale—when you want to pick up a single atom and move it to the other end of a molecule—it requires incredibly exacting equipment. That equipment, though, is worthless without an equally exacting laboratory to put it in. If you're peering down the (figurative) barrel of a microscope at a single atom, you need to make sure there are absolutely no physical vibrations at all, or you'll just get a blurry image. Similarly, atoms really don't like to sit still: you don't want to spend a few hours setting up a transmission electron microscope (TEM), only to have a temperature fluctuation or EM field imbue the atoms with enough energy to start jumping around on their own accord.

One solution, as you have probably gathered from the introduction to this story, is to build a bunker deep underground, completely from scratch, with every facet of the project simulated, designed, and built with a singular purpose in mind: to block out the outside world entirely. That's exactly what IBM Research did back in 2011, when it opened the Binnig and Rohrer Nanotechnology Center.

The Center, which is located just outside Zurich in Rüschlikon, cost about €80 million (£60 million, $90 million) to build, which includes equipment costs of around €27 million (£20 million, $30 million). IBM constructed and owns the building, but IBM Research and ETH Zurich have shared use of the building and equipment. ETH and IBM collaborate on a lot of research, especially on nanoscale stuff.

Deep below the Center there are six quiet rooms—or, to put it another way, rooms that are almost completely devoid of any kind of noise, from acoustic waves to physical vibrations to electromagnetic radiation. Each room is dedicated to a different nanometre-scale experiment: in one room, I was shown a Raman microscope, which is used for "fingerprinting" molecules; in another, a giant TEM, which is like an optical microscope, but it uses a beam of electrons instead of light to resolve details as small as 0.09nm. Every room is eerily deadened and quiet, which is juxtapositionally belied by the hulking silhouette of a multi-million-pound apparatus sitting in the middle of it. After investigating a few rooms, I notice that my phone is uncharacteristically lifeless. "That's the nickel-iron box that encases every room," my guide informs me.

It's impossible to go into every design feature of the noise-free rooms, but I'll run through the most important and the most interesting. For a start, the rooms are built directly on the bedrock, significantly reducing vibrations from a nearby road and an underground train. Then, the walls of each room are clad with the aforementioned nickel-iron alloy, screening against most external electromagnetic fields, including those produced by experiments in nearby rooms. There are dozens of external sources of EM radiation, but the strongest are generated by mobile phone masts, overhead power lines, and the (electric) underground train, all of which would play havoc with IBM's nanoscale experiments.

Internally, most rooms are divided in two: there's a small ante chamber, which is where the human controller sits, and then the main space with the actual experiment/equipment. Humans generate around 100 watts of heat, and not inconsiderable amounts of noise and vibration, so it's best to keep them away from experiments while they're running.

To provide even more isolation, there are two separate floors in each room: one suspended floor for the scientists to walk on, and another separate floor that only the equipment sits on. The latter isn't actually a floor: it's a giant (up-to-68-ton) concrete block that rests on active air suspension. Any vibrations that make it through the bedrock, or that come from large trucks rumbling by, are damped in real time by the air suspension.

We're not done yet! To minimise acoustic noise (i.e. sound), the rooms are lined with acoustically absorbent material. Furthermore, if an experiment has noisy ancillary components (a vacuum pump, electrical transformer, etc.), they are placed in another room away from the main apparatus, so that they're physically and audibly isolated.

And finally, there's some very clever air conditioning that's quiet, generates minimal air flux, and is capable of keeping the temperature in the rooms very stable. In every room, the suspended floor (the human-designated bit) is perforated with holes. Cold air slowly ekes out of these holes, rises to the ceiling, and is then sucked out. The air flow was hardly noticeable, except for on my ankles: in a moment of unwarranted hipness earlier that morning, I had decided to wear boat shoes without socks.

That's about it for the major, physical features of IBM Research's quiet rooms, but there are two other bits that are pretty neat. First, the whole place is lit with LEDs, driven by a DC power supply that is far enough away that its EM emissions don't interfere. Second, each room is equipped with three pairs of Helmholtz coils, oriented so that they cover the X, Y, and Z axes. These coils are tuned to cancel out any residual magnetic fields that haven't already been damped by various other shields, such as the Earth's magnetic field.

Just how quiet are the rooms?

So, after all that effort—each of the six rooms cost about €1.4 million to build, before equipment—just how quiet are the rooms below the Binnig and Rohrer Nanotechnology Center? Let's break it down by the type of noise.

The temperature at waist height in the rooms is set to 21 degrees Celsius, with a stability of 0.01°C per hour (i.e. it would take an hour for the temperature to rise to 21.01°C). The max variation over 24 hours is just 0.03°C.

Electromagnetic fields produced by AC sources are damped to less than 3 nT (nanotesla)—or about 1,500 times weaker than the magnetic field produced by a fridge magnet. The variation of the damped DC field is 20 nT. There is approximately 43 µT from the Earth's magnetic field, too.

The vibration damping is probably the most impressive: for the equipment on the concrete pedestals, movement is reduced to less than 300nm/s at 1Hz, and less than 10nm/s above 100Hz. These are well below the specs of NIST's Advanced Measurement Laboratory in Maryland, USA.

Somewhat ironically for the world's quietest rooms, the weakest link is acoustic noise. Even though the rooms themselves are shielded from outside noises, and the acoustically absorbent material does a good job of stopping internal sound waves dead, there's no avoiding the quiet hum of some of the machines or the slight susurration of the ventilation system.

The acoustic noise level in the rooms is always below 30 dB, dipping down as low as 21 dB if there isn't a noisy experiment running. In human terms, the rooms were definitely quiet, but not so quiet that I could feel my sanity slipping away, or anything crazy like that. I was a little bit disappointed that I couldn't hear my various internal organs shifting around, truth be told.

Why did IBM build six of these rooms?

"You're only as good as your tools." It's a trite, overused statement, but in this case it perfectly describes why IBM and ETH Zurich spent so many millions of euros on the quiet rooms.

Big machines like the TEM or spin-SEM need to be kept very still, with as little outside interference as possible: if you can't stay within the machine's nominal operational parameters, you're not going to get much scientifically useful data out of it.

On the flip side, however, if you surpass the machine's optimal parameters—if you reduce the amount of vibration, noise, etc. beyond the "recommended specs"—then you can produce images and graphs with more resolution than even the manufacturer thought possible.

IBM Research's spin-SEM, for example, used to be located in the basement of the main building, on a normal concrete floor. After being relocated to the quiet rooms, the lead scientist who uses the spin-SEM said its resolution is 2-3 times better (an utterly huge gain, in case you were wondering).

For much the same reason, my guide said that "several tooling manufacturers" have contacted IBM Research to ask if they can test their equipment in the noise-free labs: they want to see just how well it will perform under near-perfect conditions.

The best story, though, I saved for last. Back in the '80s and '90s, before the Center was built, the IBM researchers didn't have a specialised nanotechnology facility: they just worked in their labs, which were usually located down in the basement. When Gerd Binnig and Heinrich Rohrer invented the scanning tunnelling microscope (STM)—an achievement that would later net them a Nobel prize—they worked in the dead of night to minimise vibrations from the nearby road and other outside interference.

After the new building was finished—which, incidentally, is named after Binnig and Rohrer—my guide spoke to some IBM retirees who had just finished inspecting the noise-free rooms. "We wish we'd had these rooms back in the '80s and 90s, so that we didn't have to work at 3am," they said.

Nanoscale, 2013. DOI: 10.1039/c3nr03373b (About DOIs)

Listing image by Sebastian Anthony