In 2017 Jaume Jaume Bestard started his PhD thesis at the IAC. His thesis advisors are Javier Trujillo Bueno and Jiri Stepan, and the topic of the thesis is three-dimensional modeling of the polarization of chromospheric lines. Jaume is applying the radiative transfer code PORTA of Stepan & Trujillo Bueno (2013). To this end, he is using the Mare Nostrum IV supercomputer of the Barcelona Supercomputing Center. Therefore, Jaume is contributing to the development of WP-4.