9 July 2008 Multi-stage apodized pupil Lyot coronagraph experimental results
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Prolate (Pupil) Apodized Lyot Coronagraphs (PPALC) are known to offer optimal performances for a Lyot-type Coronagraph configuration, i.e. with an opaque occulting focal mask. One additional benefit of PPALC is its possible use in a multi-stage configuration. In theory, the coronagraphic performance can be QN, where Q is the energy rejection factor of one stage (the first one), and N the number of stages. Several ground-based telescopes are considering PPALC as an option for their high-contrast instrumentation (e.g. Gemini/GPI, EELT/EPICS, Subaru HiCIAO). Although the PPALC suffers from several limitations, several works are currently focused on fabricating entrance pupil apodizers and trying to find ways to overcome chromatism issues. In this work, we present the first experimental results from Multi-Stage PPALC (MS-PPALC) that was done in the context of the Japanese space telescope SPICA coronagraph project. Our entrance pupil apodizers use small diameter High Energy Beam Sensitive glass (HEBS-glass) from Canyon Materials Inc. The current results show modest coronagraphic performance due to uncompensated phase aberrations inherent to HEBS-glass material. In addition, and due to these uncompensated phase aberrations, the present optical configuration is an altered version of the originally planned set-up. However, we can demonstrate the validity the MS-PPALC concept and compare it to numerical simulations.
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L. Abe, L. Abe, M. Venet, M. Venet, K. Enya, K. Enya, H. Kataza, H. Kataza, T. Nakagawa, T. Nakagawa, M. Tamura, M. Tamura, "Multi-stage apodized pupil Lyot coronagraph experimental results", Proc. SPIE 7014, Ground-based and Airborne Instrumentation for Astronomy II, 701467 (9 July 2008); doi: 10.1117/12.787305; https://doi.org/10.1117/12.787305

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