http://arxiv.org/abs/1611.07244
The key to photoelectric X-ray polarimetry is the determination of the emission direction of photoelectrons. Due to the low mass of an electron, the ionization trajectory is not straight and the useful information needed for polarization is stored only in the initial part of the track where less energy is deposited. We present a new algorithm, based on the shortest path problem in graph theory, to reconstruct the 2D electron track from the measured image that is blurred due to transversal diffusion along drift and multiplication in the gas chamber. Compared with previous methods based on moment analysis, this algorithm allows us to identify the photoelectric interaction point more accurately and precisely than previous, especially for complicated tracks resulted from high energy photons or low pressure chambers. This leads to a higher degree of modulation and consequently a better sensitivity toward high energy X-rays. The new algorithm is justified using simulations and measurements with the gas pixel detector but it should also work for other polarimetric techniques such as the time projection chamber.
T. Li, M. Zeng, H. Feng, et. al.
Wed, 23 Nov 16
16/68
Comments: 10 pages, 8 figures, submitted to NIM A
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