Fermilab Today Monday, June 2, 2008

Fermilab built parts to help GLAST search for dark matter

Artist rendering of the GLAST satellite. Credit: NASA/Sonoma State University/Aurore Simonnet
Members of the GLAST Team:(left to right) Ron Ray, Eileen Hahn, Lowell Klaisner, Phyllis Deering, Tom Johnson, John Korienek, Carl Lindenmeyer, Jim Schellpfeffer, Ron Miksa, Todd Nebel, Jack Upton, Steve Huey (Click on image for larger version.)

To look for keys to the mysteries of the universe, NASA will launch its Gamma-ray Large Area Space Telescope later this week. GLAST will survey the entire sky daily with the highest sensitivity yet. It will work more like a particle detector than a telescope, detecting the signals of high-energy gamma rays and tracking their cosmic origins.

Although not a GLAST collaborator, a Fermilab team manufactured a key component of GLAST's main instrument, the Large Area Telescope. Fermilab's CNC routing group within the Particle Physics Division's Technical Centers manufactured and finished sheets of plastic scintillator tiles that surround the heart of the GLAST detector.

Fermilab was chosen for this project because of its experience with manufacturing similar components for the Tevatron detectors, the MINOS neutrino detector and the LHC's CMS detector.

"The devil is in the details," said PPD Technical Centers Department Head Hogan Nguyen. "The handling of plastics is highly specialized in these groups. The teams are highly sought after for their ability to work with plastics."

Phyllis Deering, who retired two years ago, led a Fermilab team of specialized technicians who worked on parts for the GLAST mission between 2002 and 2004. Three subgroups were led by Deering, head of the CNC routing group; John Korienek, head of machine development; and Eileen Hahn, head of the Vacuum Thin Films group.

Korienek said the group often gets calls to create these very specialized parts. "Most of the time we're on the ground floor of experiments," he said.

The scintillator tiles make up the cosmic veto shield, or Anti Coincidence Detector, which identifies charged particles that are unimportant background. The machine development group manufactured and assembled the scintillator tiles to have an almost mirror-like finish, making them highly efficient to charged particles. The tiles generate light from the faint flashes of passing charged particles. That light then gets picked up by optical fibers, which were diamond cut and processed by Fermilab's thin films group. The fibers funnel the light to photo-multiplier tubes. These signals tell the telescope if the event was a charged particle, which on-board electronics should weed out as noise.

"All processes we do have tight quality controls and experience. You don't get the same high-quality mirroring in industry," Hahn said.

"NASA's GLAST was a chance to do something special. It's going up in the air. We're excited, because it is part of the American identity. NASA represents exploration. The U.S. identifies with NASA. To an ordinary citizen, who doesn't understand a lot of experiments, it's difficult to try to explain what you do. But when you say, 'Oh yeah, you see that NASA experiment going up? We're a part of that,' they understand," she added.

Todd Nebel, lead technician for Fermilab's role in the GLAST mission, will attend the launch this week. "That was the highlight project for me, there were unique challenges for me to figure out," Nebel said.

The teams had to work with an assortment of shape and space constraints. Korienek's machine development group had to bend plastic tiles. They also had to cut grooves within the tiles that would allow the optical fibers to lie within them, flush with the tile surface. Hahn's group diamond-cut the fibers and gave them a mirror edge.

Nguyen called the tile manufacturing and the processing of the optical fibers works of art.

The GLAST mission will bring together both the particle physics and astrophysics communities to study subatomic particles at energies far greater than those seen in ground-based particle accelerators, and gain valuable information about the birth and early evolution of the universe.

NASA joined with DOE and institutions across the globe for the mission. Stanford Linear Accelerator Center managed the development of GLAST's Large Area Telescope. The launch is currently scheduled for Thursday, June 5. Check NASA's GLAST Web site for more information.

-- Rhianna Wisniewski

Fermi National Accelerator - Office of Science / U.S. Department of Energy | Managed by Fermi Research Alliance, LLC.