2 August 2012
The inspiration behind NASA scientist Maxim Markevitch’s quest to build a highly specialized X-ray mirror using a never-before-tried technique comes from an unusual source: a roll of Scotch® tape.
Markevitch and a team of X-ray optics experts at NASA’s Goddard Space Flight Center in Greenbelt, Md., have begun investigating the feasibility of fashioning a low-cost mirror from plastic tape and tightly rolling it like the sticky adhesive commonly found in most homes and offices.
With funding from NASA’s Center Innovation Fund, the team now is pursuing Markevitch’s “early-stage” idea and has already begun testing candidate materials that could be fashioned into a rolled mirror capable of collecting X-rays — in itself a challenging proposition. To capture these ever-elusive photons, the mirrors must be curved and nested inside a cylindrical optical assembly. The rounded geometry allows the high-energy light to graze their surfaces, much like a stone skimming the surface of a pond.
Motivating Markevitch is the fact that these highly specialized mirrors are time-consuming and expensive to build and assemble, despite efforts to dramatically reduce production costs. Making matters more demanding is the fact that X-ray observatories in the future likely will require much larger collecting areas, therefore requiring an even greater number of individual mirror segments that all must be nested, coated with layers of highly reflective materials, and perfectly coaligned inside their optical assemblies. “It’s a lot of work fabricating these rigid shells and making sure they’re properly aligned,” he said.
One class of objects waiting to be better understood is cosmic rays — highly energetic subatomic particles generated in deep space — that reside in galaxy clusters and other large-scale structure in the universe. Scientists believe that cosmic rays and the magnetic fields between galaxy clusters can alter the physics within galaxy clusters. A better understanding of these physics could reveal more about the birth and evolution of the cosmos, Markevitch said.
The only solution then is developing a new technology that would dramatically reduce the cost of building X-ray optics and increase the size of the light-collecting area. “If we can build a mirror that’s big enough, this might be the way to go,” he said.