Micromachined tantalum collimators for space applications

We present the prototype-development of a tantalum X-ray collimator for AXTAR (Advanced X-ray Timing Array), a mission concept for an advanced X-ray timing experiment. The collimator is micro-fabricated in a two step process: (i) laser-machining of a hole array in Ta and (ii) chemical etching of the hole with the desired porosity (hole vs. bulk volume). The collimator design was studied by Monte Carlo simulation using GEANT4. The anticipated collimator performance shows 2 orders of magnitude rejection over 2 degrees. The angular response of the collimator was measured with an Americum-241 source and a commercial silicon detector. The prototype collimates over +/- 3 degrees.