For the PRV instrument using simultaneous calibration technique such as with sources like thorium lamps, Fabry Perot Etalons or laser comb, it is essential that the instrument stays stable between the wavelength calibration frame and the actual scientific measurement. These instruments are usually in pressure and temperature controlled environments for example under vacuum. However this is not sufficient to reach the instrumental stability required to get to precision level of the ms^-1 and below required to build the next generation PRV instruments. Another requirement is an as constant as possible illumination of the spectrograph to stabilize the line profile of the instrument. To achieve this, it is necessary to use a device that will scramble the light coming from the star to mitigate the effects of the atmosphere. In addition this device should not increase significantly the beam etendue, which is already a technological challenge for large telescopes. The common solution to this problem is to use optical fibers. Historically the solution has been to use circular fibers as they were the only one available. Recently for other purposes non-circular fibers have been developed and made available. They have been tested, and present an important improvement in the scrambling over the circular fibers. We will present in this paper the properties of the octagonal fibers used for the HARPS-N2 instrument and the achieved performance of its fiber train.

Date Published: 13 September 2012
PDF: 9 pages
Proc. SPIE 8450, Modern Technologies in Space- and Ground-based Telescopes and Instrumentation II, 845013 (13 September 2012); doi: 10.1117/12.926188

Published in SPIE Proceedings Vol. 8450:
Modern Technologies in Space- and Ground-based Telescopes and Instrumentation II
Ramón Navarro; Colin R. Cunningham; Eric Prieto, Editor(s)