X-ray telescope borrows lobster-eye technique

X-ray telescope borrows lobster-eye technique

JOHN MAYER

At the University of Melbourne (Melbourne, Australia) researchers are developing a prototype imaging x-ray telescope based on the biological construction of a lobster retina. In collaboration with NASA, Los Alamos National Laboratory (Los Alamos, NM), and Leicester University (Leicester, England), the developers hope to prove the feasibility of a lobster-eye x-ray telescope that, from a small satellite, could exploit novel wide-field x-ray optics to deliver an order-of-magnitude improvement in sensitivity of distant astronomical object and events.

To reflect light to its retina, the lobster-eye telescope uses a lens composed of approximately square microchannels arranged in a spherical array. Light reflecting down the channels forms a cross-shaped image. This geometry allows x-ray reflections to occur at very small angles, boosting reflectivity and minimizing incident flux loss. Using this design, the intensity in the central region of the cross can be thousands of times greater than that of the incident x-ray flux, a key attribute when recording the image of a Type II Supernova.

Square channels

Researchers at the University of Melbourne are attempting to replicate this function with an array of spherically curved square channels or microchannel plates (MCPs) as small as 10 µm. To test the performance of the MCPs, developers focus an intense laser pulse on a target. The resulting plasma provides a source of x-rays that are then focused through the MCPs onto film. Early tests have demonstrated a focused intensity of about one-third the theoretical prediction of a perfect MCP. The goal is to reach two-thirds of the theoretical maximum.

Eventually, researchers envision launching a small satellite that would incorporate the lobster-eye telescope. Potential subjects of study include fast transient events such as gamma-ray bursts and Type II Supernovae and Coronal sources. Initial plans call for the University of Melbourne and Leicester University to work on x-ray optics and coatings and lens assembly, alignment and calibration, while researchers at Los Alamos develop detector readout electronics and handle spacecraft, ground stations, and flight-operation management. The Goddard Space Flight Center (Greenbelt, MD) will work on detectors and front-end electronics and contribute to the development of image-analysis software. For information, contact Andrew Peele at [email protected].

Possible lobster satellite design incorporates three modules of lobster-eye telescopes (a). Half side of each module is a portion of a spherical lobster-eye telescope. Researchers have simulated results from the telescope that include regions with a number of extremely bright sources (b) and more typical regions of the sky (c).