After screwing around in my copy of LR 6, it looks like WHERE Lightroom puts its cache and catalog files is not up to you. It puts them in the 'My Documents' and 'program data' folders whether we like it or not.
For what it's worth, I checked the registry with regedit and could not find any references to my LR folders in My Docs. So I checked various internal, hidden directories and files and the best I could find was it's buried in one or more of their unique format - unreadable without their internal software - 'preferences' files. In short, us 'mortals' can't change what they have forced us to do.
However... You can go to the 'edit' tab, then 'preferences', 'file handling' and then click the two 'purge cache' buttons to clear the cache, but I doubt it will free up any space on your SSD. If you wish, you could relocate your 'camera raw cache' on the same screen to a slower HD. But then you've successfully defeated one of the purposes of an SSD....speed. Do you REALLY want to wait and wait for LR to react to your next click.
For what it's worth, it's my opinion as a retired mainframe programmer/consultant that LR uses a sequential 'chain' file for each action you take, in the order you take them. In other words. The first action you take goes to record #1 of the chain file. The next action to record #2, and so on. When you make action #3, it first 'reads' record #1 and #2 to determine that spot #3 is where to put the new action. For #4, it reads #1, #2, and #3 to find the next available spot, and on and on. Averaging 20-30 clicks per slide, after 100 images, that's 2,000-3,000 'read' actions before it writes the next new 'action' to disk. That's how it safely keeps all the changes you made intact in the event of a power failure, computer lockup, etc. Unfortunately, I've discovered that when performing scanned slides and I'm manually removing larger dust and scratches with the 'heal' function, by the time I get to slide #100 or so, computer response is noticeably sluggish compared to when I started. And I'm running on an 8-processor computer overclocked to 4.8ghz with 32gb RAM with NOTHING else running on my computer other than Windows 7 background trash. So I'm happy that LR puts its cache on my SSD. I've also ensured all of Windows work/temporary files are on the SSD as well. So, I ask again...do you REALLY want to wait and wait for LR to react to your next click?