We introduce a high pressure high temperature chamber for in situ synchrotron X-ray studies. The chamber design allows for in situ studies of thin film growth from solution at deeply buried interfaces in harsh environments. The temperature can be controlled between room temperature and 1073 K while the pressure can be set as high as 50 bar using a variety of gases including N-2 and NH3. The formation of GaN on the surface of a Ga13Na7 melt at 1073 K and 50 bar of N-2 is presented as a performance test. (C) 2015 Elsevier B.V. All rights reserved.