Your application should include
You may submit an application for enrolment at any time to igsm(at)tu-braunschweig.de
Before enrolment you should have a PhD position at PTB or TU Braunschweig in physics, chemistry, biotechnology, electrical or mechanical engineering, mathematics, information science or other related fields.
You don't have a PhD position either at TU Braunschweig or PTB yet?
You can find their offers here
...and here