July 27, 2012
Future X-ray Telescopes Derived From Scotch Tape?
Lee Rannals for redOrbit.com - Your Universe Online
While some find it as the source of inspiration for wrapping gifts, Scotch tape inspired one scientist at NASA to build a special X-ray mirror.
NASA scientist Maxim Markevitch and a team of X-ray optics experts at the space agency's Goddard Space Flight Center are looking into the feasibility of creating a low-cost mirror out of plastic tape.
"I remember looking at a roll of Scotch tape and thinking, 'was it possible to use the same design for capturing hard X-rays,'" Markevitch recalled. "I talked with a few people, and to my surprise, they didn't see any principal reasons why it couldn't be done."
The team is pursuing his idea now with the added help of funding, provided by NASA's Center Innovation Fund.
They have already begun testing candidate materials that could be fashioned into a rolled mirror capable of collecting X-rays.
In order to capture photons, the scientists must curve the mirrors and place them inside a cylindrical optical assembly. These geometric shapes allows the high-energy light to graze their surfaces.
NASA said the motivation behind Markevitch is that these mirrors are typically both time-consuming and expensive to build and assemble. Future X-ray observatories will require a larger collecting area, which would require a larger number of individual mirror segments that must all be coated with highly reflective materials.
"It's a lot of work fabricating these rigid shells and making sure they're properly aligned," he said.
One class of objects Markevitch's vision for an X-ray mirror could capture is cosmic rays that reside in galaxy clusters and other large-scale structure in the universe. He said that a better understanding of this type of physics could help reveal more about the birth and evolution of the universe.
In order for scientists to study cosmic rays, X-ray observatories have to be tuned to hard X-rays, which are observatories that are less common. NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) and Japan's New X-ray Telescope (Astro-H) are both sensitive to hard X-rays, but Markevitch said they just "graze the surface" of studying cosmic rays.
An imaging X-ray telescope with a collecting area 30 times larger than NuSTAR, along with current and future radio telescopes, would be able to do the job, according to Markevitch.
"However, to our knowledge, nothing of the kind is planned or even proposed in the U.S. or elsewhere because of the cost something like this presents," he said.
He says the only solution is to develop a new technology that would help reduce the cost of building X-ray optics, while also increasing the size of the light-collecting area.
Markevitch's team is currently acquiring and testing tape that could be coated on one side with a multilayer of reflective material, and then could roll to form a large number of densely packed nested shells.
"The collecting surface is automatic, it's rolled, self-supporting, and already aligned," Markevitch said.
Multiple rolls could then be placed in the optical assembly, helping to provide a larger collecting area.
"Maxim's Scotch tape idea is in an early stage," Will Zhang, one of the team members, said. "In the next year, we will know whether it has a chance of working."
If the Scotch tape idea works, it could be a game-changer when building hard X-ray observatories, according to Markevitch.
"It could significantly reduce the cost of building large mirrors, bringing within reach the possibility of building a mirror with 10 to 30 times greater effective area than current X-ray telescopes," he said in the release.
Image 2 (below): Principal Investigator Maxim Markevitch is using R&D funding to pursue the feasibility of fashioning a low-cost X-ray mirror from plastic tape and tightly rolling it like the sticky adhesive ubiquitous in most homes and offices. The whiteboard drawing shows the shape of the X-ray mirror roll. Credit: NASA/D. McCallum