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TY - CONF AU - Mitsuhashi, T.M. ED - Liu, Zhengzheng ED - Lidia, Steven ED - McCausey, Amy ED - Schaa, Volker RW TI - Analysis of Mie Scattering Noise of Objective Lens in Coronagraph for Halo Measurement J2 - Proc. of IBIC2017, Grand Rapids, MI, USA, 20-24 August 2017 C1 - Grand Rapids, MI, USA T2 - International Beam Instrumentation Conference T3 - 6 LA - english AB - In beam halo measurements by means of a coronagraph viewing visible SR light, the theoretical image contrast is dominated by leakage of the diffracted fringe pattern from the Lyot stop. On other hand, the noise background in an actual coronagraph also contains light scattered from imperfections in the first objective lens. Most of this light is due to Mie-scattering from dig imperfections on the surface of objective which can reduce the image contrast to the 10⁻³ range for a lens with 60/40 scratch and dig figures. By introducing a high-quality objective lens into the system the theoretical value of 10-5-10-6 image contrast can be recovered for the Lyot coronagraph. In this paper, Mie-scattering due to dig imperfections is analyzed theoretically and results from measurements of the Mie scattering are presented. PB - JACoW CP - Geneva, Switzerland SP - 369 EP - 372 KW - ion KW - scattering KW - background KW - simulation KW - synchrotron DA - 2018/03 PY - 2018 SN - 978-3-95450-192-2 DO - 10.18429/JACoW-IBIC2017-WEPCC10 UR - http://jacow.org/ibic2017/papers/wepcc10.pdf ER -