Wednesday, Nov. 18, 2015
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From symmetry

Cleanroom is a verb

It's not easy being clean. Photo: SNOLAB

Although they might be invisible to the naked eye, contaminants less than a micron in size can ruin very sensitive experiments in particle physics.

Flakes of skin, insect parts and other air-surfing particles — collectively known as dust — force scientists to construct or conduct certain experiments in cleanrooms, special places with regulated contaminant levels. There, scientists use a variety of tactics to keep their experiments dust-free.

The enemy within

Cleanrooms are classified by how many particles are found in a cubic foot of space. The fewer the particles, the cleaner the cleanroom.

To prevent contaminating particles from getting in, everything that enters cleanrooms must be covered or cleaned, including the people. Scratch that: especially the people.

"People are the dirtiest things in a cleanroom," says Lisa Kaufman, assistant professor of nuclear physics at Indiana University. "We have to protect experiment detectors from ourselves."

Humans are walking landfills as far as a cleanroom is concerned. We shed hair and skin incessantly, both of which form dust. Our body and clothes also carry dust and dirt. Even our fingerprints can be adversaries.

"Your fingers are terrible. They're oily and filled with contaminants," says Aaron Roodman, professor of particle physics and astrophysics at SLAC National Accelerator Laboratory.

In an experiment detector susceptible to radioactivity, the potassium in one fingerprint can create a flurry of false signals, which could cloud the real signals the experiment seeks.

As a cleanroom's greatest enemy, humans must cover up completely to go inside: A zip-up coverall, known as a bunny suit, sequesters shed skin. (Although its name alludes otherwise, the bunny suit lacks floppy ears and a fluffy tail.) Shower-cap-like headgear holds in hair. Booties cover soiled shoes. Gloves are a must-have. In particularly clean cleanrooms, or for scientists sporting burly beards, facemasks may be necessary as well.

These items keep the number of particles brought into a cleanroom at a minimum.

"In a normal place, if you have some surface that's unattended, that you don't dust, after a few days you'll see lots and lots of stuff," Roodman says. "In a cleanroom, you don't see anything."

Getting to nothing, however, can take a lot more work than just covering up.

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Chris Patrick

Photos of the Day

Prairie fire

nature, prairie, prairie burn, fire, ecology
Roads and Grounds conducts a controlled burn at the Interpretive Prairie Trail last week. Photo: Marty Murphy, AD
nature, prairie, prairie burn, fire, ecology
Controlled burns help restore the natural prairie habitat. Photo: Marty Murphy, AD
nature, prairie, prairie burn, fire, ecology
This shows a 15th-floor view of the area during ... Photo: Valery Stanley, WDRS
nature, prairie, prairie burn, fire, ecology
... and after the burn. Photo: Valery Stanley, WDRS

In memoriam: Dorothee B. Swanson

Fermilab retiree Dorothee B. (Cahall) Swanson, age 69, passed away Nov. 16. Known by coworkers and friends as Dotti, she worked for Fermilab for more than 20 years as an administrative assistant in several departments.

There will be no public memorial service for Swanson.

In the News

Homegrown particle accelerators

From KQuest, Nov. 12, 2015

More is more — nowhere is that truer than at the world's most powerful atom smasher, the Large Hadron Collider in Switzerland, where scientists last week concluded a six-month series of experiments where they forced infinitesimally tiny particles to smash against each other at double the energy level ever recorded.

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