Apparatus for analysing a sample using x-ray, neutron ray, gamma ray or particle-beam radiation to analyze the sample , the apparatus comprising: a sample chamber having a surface into which a sample cavity is formed, said sample cavity forming a portion of a sample path through which the sample is moveable, an analysis engine having a radiation interface; a barrier , comprising a film transparent to the radiation, and separating the sample from the engine , the barrier moveable relative to the radiation interface and over the sample cavity ; a barrier movement system to effect movement of said barrier ; and a plate opposing the sample cavity having an aperture allowing passage of the radiation to and from the sample cavity , wherein the barrier is disposed between the surface of the sample chamber and the plate , and wherein the sample chamber is moveable relative to the plate to increase and decrease pressure on the barrier , the apparatus being configured to decrease the pressure on the film to allow movement of the barrier , wherein the sample path is pressurized and the barrier maintains the sample in said cavity , and wherein the sample is a liquid, the sample path comprises at least a portion of a pressurized pipeline through which the liquid is flowing, and the analysis engine performs a compositional analysis of the liquid while the liquid is flowing, characterized in that the analysis engine includes a focusing device which produces a focused beam of said radiation through the barrier , and toward said sample , and in that the apparatus further comprises an expandable ring disposed between the sample chamber and the plate , and around the sample cavity , to maintain an adequate pressure in the sample path. a sample chamber having a surface into which a sample cavity is formed, said sample cavity forming a portion of a sample path through which the sample is moveable, an analysis engine having a radiation interface; a barrier , comprising a film transparent to the radiation, and separating the sample from the engine , the barrier moveable relative to the radiation interface and over the sample cavity ; a barrier movement system to effect movement of said barrier ; and a plate opposing the sample cavity having an aperture allowing passage of the radiation to and from the sample cavity , wherein the barrier is disposed between the surface of the sample chamber and the plate , and wherein the sample chamber is moveable relative to the plate to increase and decrease pressure on the barrier , the apparatus being configured to decrease the pressure on the film to allow movement of the barrier , wherein the sample path is pressurized and the barrier maintains the sample in said cavity , and wherein the sample is a liquid, the sample path comprises at least a portion of a pressurized pipeline through which the liquid is flowing, and the analysis engine performs a compositional analysis of the liquid while the liquid is flowing, characterized in that the analysis engine includes a focusing device which produces a focused beam of said radiation through the barrier , and toward said sample , and in that the apparatus further comprises an expandable ring disposed between the sample chamber and the plate , and around the sample cavity , to maintain an adequate pressure in the sample path. <EOS>