Simple filters enable x-ray polarizationmeasurements

A novel transmissive technology could add a polarimetry capability to future high-energy astronomical observatories with large effective areas. Measurements of the degree and angle of polarization of emis-sion from astronomical sources enable physical characterization of the objects and environmental conditions fromwhich the pho-tons originate. However, a lack of suitable instrumentation in the x-ray and gamma-ray regimes has been frustrating astronomers for over three decades. To date, only one unambiguous astro-physical x-ray polarization measurement has been obtained: the Crab Nebula was observed to exhibit 19 % linear polarization at 2.6keV.1 Conventional x-ray polarimetry relies on Bragg reflection or Thomson scattering, but instruments operating on the basis of either effect tend to suffer from low sensitivity. The next genera