NOVELTY - An integrated roll-to-roll rapid thermal processing tool (100) for forming a solar cell absorber by reacting a precursor layer on a surface of a continuous flexible workpiece, comprises an elongated housing that includes a sealed common chamber including a heating chamber (101), a supply chamber (103), and a receiving chamber (104). The heating chamber defines a narrow process gap (111) that applies a predetermined temperature profile to that portion of the continuous flexible workpiece disposed in it. It has a heating chamber input opening and a heating chamber output opening.    USE - The tool is used for forming a solar cell absorber or for forming an absorber layer on a surface of a continuous flexible workpiece (claimed). It is useful for group IBIIIAVIA absorber layer; copper (Cu), indium (In), gallium (Ga), selenium (Se), and sulfur (S) type solar cell absorber; or Cu(In,Ga)(Se,S)2 absorber layer for use in radiation detector and photovoltaic applications.    ADVANTAGE - The tool increases throughput and minimizes substrate handling. It is suitable for large scale manufacturing.    DETAILED DESCRIPTION - An integrated roll-to-roll rapid thermal processing (RTP) tool for forming a solar cell absorber by reacting a precursor layer on a surface of a continuous flexible workpiece, comprises an elongated housing that includes a sealed common chamber including a heating chamber, a supply chamber, and a receiving chamber. The heating chamber defines a narrow process gap that applies a predetermined temperature profile to that portion of the continuous flexible workpiece disposed in it. It has a heating chamber input opening and a heating chamber output opening. The narrow process gap is defined by a top wall, a bottom wall, and side walls that form an opening in which a height is less than a width. The supply chamber holds a supply roll of the continuous flexible workpiece and has a supply chamber opening, which aligns with the heating chamber input opening, where the continuous flexible workpiece is advanced into the heating chamber from the supply chamber. The receiving chamber holds a receiving roll to collect the continuous flexible workpiece from the heating chamber and has a receiving chamber opening, which aligns with the heating chamber output opening, where continuous flexible workpiece is advanced into the supply chamber from the heating chamber. The tool comprises a moving mechanism (105A, 105B) to hold the continuous flexible workpiece within the common chamber and move the continuous flexible workpiece through the narrow process gap of the heating chamber, by feeding previously unrolled portions of the continuous flexible workpiece from the supply roll and taking up and wrapping processed portions of the continuous flexible workpiece on the receiving roll in the receiving chamber. The height of the narrow process gap is 0.5-10 mm. The width of the narrow process gap is 100-2000 nm. The temperature profile comprises a maximum temperature within 350-600degrees C. An INDEPENDENT CLAIM is included for a process of forming an absorber layer on a surface of a continuous flexible workpiece as the workpiece is advanced through a roll-to-roll RTP chamber.    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional view of integrated roll-to-roll RTP tool for reacting precursor layers in a reel-to-reel fashion to form a group of IBIIIAVIA layer on a flexible foil base.    Integrated roll-to-roll RTP tool (100)    Heating chamber (101)    Supply chamber (103)    Receiving chamber (104)    Moving mechanism (105A, 105B)    Narrow process gap (111)