Okay, what I would do with brainstorms is first of all write down everything you want/need for this prison or even just the general rules of this world, then I'd start researching. Begin with looking at prison stories or just general rules or even horror stories that take place in a prison or with the inmates, if you find anything cool or that you think could work. Write this on a document so its more organized when you brainstorm.
Do the same thing for asylums, stories, rules, experiments, horror stories etc; write it down too. One more thing to remember is that if you find another branch of information or a topic you like just go look it up more, you know whats best for your story and you know what will work and what won't and I'm just giving you a starting point.
I did this when I had to research wiccan paths, just go one site at a time and branch off from then on. When you're done reread the information and edit or chang things up to be as intense as you want within you're world.
Basically just start with a basic search and then expand from then on, this helps me brainstorm or when I need to evolve and idea so try this if you have the time.