PolKa - Polarimeter fuer bolometer Kameras
PolKa - A new concept of polarimeter, named PolKa after the German "Polarimeter fur Bolometer-Kameras", was developed by the Bolometer Group at the MPIfR in Bonn and installed on APEX in October 2009. PolKa is not an instrument "per se", in the usual meaning of the term, but a sort of plug-in that gives polarization sensing capabilities to an existing bolometer camera. It was successfully experimented at the Heinrich-Hertz telescope in 2001 and 2002, and it is now installed, since the 27th of October 2009, in the C-cabin of APEX to work in combination with LABOCA.
The combination PolKa + LABOCA makes the most powerful polarimeter for continuum emission in the world. Additionally, it is the first ever in the southern hemisphere.
Applications for such an instrument are numerous, from the study of magnetic field in molecular clouds in our galaxy to the study of variability of the polarization in the synchrotron emission form the jets of AGNs, just to mention a few.
The design of PolKa, although based on the classical scheme of a rotating half-wave plate (RHWP), has some unique characteristics, like the use of a reflection-type half-wave plate and of the continuous spinning modulation. These particular design choices make PolKa different from any other existing polarimeter.