Vacuum leak check on the window line circuit of TM1 took place yesterday and again to confirm this morning. Both days the response to helium is in the area of a soldered reduction fitting at the top of the containment box above and to the shutter side of the extraction column (see attached picture). To verify this morning each joint in the system had a 1 second shot of helium and then timed for 1 minute to wait for a response. This area responded both times tested at about 40 seconds...no response at any of the other locations.