Investigation of polarizing mirrors at 121.6 nm

1. Parameters Spécifications Justification Incidence angle 30° à 70° Limited dimensions of the instrument Angle of acceptance 2.6° (-/+ 1.3°) Field of view of the instrument Polarizing mirror in the LYOT optical design Rp/Rs 4. 10-3 Good rejection of the perpendicular polarisation Rs min 25% Photometry condition Ongoing development Present development Ongoing development 2 Present development 1 With optimized thicknesses (calculation) MgF2/float glass Multilayer PTB is working to install the set-up on a new dedicated VUV beam line: the MLS (Metrology Light Source). The precision of measurements should be increased. (First measurements are expected in the middle of 2008). Measurement: i = 67°, Rs = 0.45, Rp = 0.023, Rp/Rs = 0.05 Fit : i = 67°, Rs =0.45, Rp= 1. 10-4, Rp/Rs = 2.2 10-4 i = 69° Rs = 0.71 Rp = 0.06 Rp/Rs = 0.085 i = 62° Rs = 0.75 Rp = 1.6 10-3 Rp/Rs = 2.1 10-3 The precision of measurements at PTB is presently not sufficient to give the value of the actual minimum of Rp MgF2 Al Al2O3 (<1 nm) MgF2 Al MgF2 Al 1st SMESE Workshop, IAS Paris, 10-12 mars 2008 Investigation of polarizing mirrors at 121.6 nm F. Bridou, M. Cuniot-Ponsard, J-M. Desvignes Laboratoire Charles Fabry de l’Institut d’Optique Palaiseau, France Required specifications Summary From IAS team: A. Millard, F. Auchère, F. Rouesnel, J-C. Vial The goal of this study is to demonstrate the feasibility of polarizing mirrors at l = 121.6 nm designed within the framework of the Lymana Lyot Coronograph Imager project. Optical constants of the materials involved in the multilayers are determined experimentally. Reflectivity measurements in the VUV wavelength domain have been performed at PTB (Synchrotron at BESSY II, Berlin). Simulations, deposits, measurements and characterizations were made and first experimental results are in good agreement with calculated predictions. Fabrication and test of polarizing mirrors In collaboration with PTB where Polarized reflectivity measurements were performed [5,6] CONCLUSION A preliminary determination of indices in the wavelength range 80-140 nm was performed in order to select the materials and design of polarizing mirrors. Two different designs of polarizing mirrors at l = 121.6 nm have been prepared and tested at PTB. The first results show that each of these two designs allows to meet the requirements of the Lyman  Lyot Coronograph Imager project