referring now in specific detail to the drawings , and particularly the embodiments shown in fig1 and 2 thereof , fig1 illustrates a vessel 10 having an elongated cylindrical wall portion 12 and constituting a high - pressure container which possesses a hollow cylindrical interior or chamber 14 and a closed bottom 16 . the vessel 10 is preferably constructed from a high - strength metallic material which is able to resist extremely high internal operating pressures . the upper end 18 of the cylindrical wall portion 12 of the vessel 10 is provided with an external screwthread 20 so as to be able to engagingly receive a screwthreaded cover structure 22 which has a narrow orifice 24 drilled therethrough communicating with chamber 14 , and forms a connection to an infeed source ( not shown ) for a supercritical fluid . the entire vessel 10 and the cover structure 22 , when mounted thereon in a sealed relationship through the interposition of an annular gasket seal or o - ring 26 , may be attached to a support plate 28 of an apparatus ( not shown ) and fastened thereto by means of suitable screws or threaded bolts 30 . extending downwardly within the interior chamber 14 of the high - pressure vessel 10 in coaxial relationship with the longitudinal center axis of internal cylindrical chamber 14 is an elongated rod - like rib member 32 extending downwardly into a position which is somewhat centrally located within the cylindrical chamber 14 , and which includes a shaft element 34 rotatable about a transverse axis proximate the lower free end of member 32 . rotatably journaled on the shaft element 34 about a transverse axis in the direction of double - headed arrow a , as also shown in more extensive detail in fig2 is a workpiece mounting member 36 . this member 36 may be a plate like locator or chuck structure , having a clamping device 38 pivotably fastened to one end 40 thereof so as to be able to firmly clamp a workpiece w against a surface 42 thereof . the workpiece w is retained in position by the clamping device 38 which also clamps the workpiece positioning plate or locator structure 36 in position . as illustrated in fig1 and 2 of the drawings , the workpiece mounting member 36 , together with the workpiece w and the clamping device 38 by means of which they are fastened , may be rotated conjointly in either direction of arrow a until the surface 42 of the member 36 mounting the workpiece w , the surface of the latter of which may have a film for processing located thereon , is indexed into a suitable angular position for processing thereof to a desired exposure angle or orientation relative to the stream or flow of a supercritical fluid being introduced into the chamber 14 through the orifice 24 under a high superatmospheric pressure . after the rotatably indexable fixture which comprises the mounting member 36 , shaft element 34 and clamping device 38 , has been oriented in its desired angular alignment relative to the longitudinal axis of the chamber 14 of the high - pressure vessel 10 , suitable latching means ( not shown ) operatively associated with the shaft element 34 , may lock it to the mounting member 36 in a predetermined fixed angular position . thereafter , the vessel cover structure 22 may be sealingly secured to the vessel body , and a stream of supercritical fluid injected into chamber 14 through the inlet orifice 24 at the upper or head end of the pressure vessel 10 , in a manner well known in the technology . referring to fig3 of the drawings , illustrating a second embodiment of the invention , wherein there may be utilized a pressure vessel 50 analogous with or similar to that employed in connection with the embodiment of fig1 and 2 , and wherein components which are similar thereto or identical therewith are identified by the same reference numerals . in this instance , rather than having the rotatable workpiece the mounting fixture as shown in fig1 mounting member or the fixture 52 which is rotatably connected to free or the bottom end of the vertical rib member 32 extending downwardly within the chamber 14 of the pressure vessel 50 , is comprised of a cup - shaped holder 54 for receiving a workpiece w . the cup - shaped holder 54 may be provided with suitable apertures 56 selectively extending through , respectively , the bottom 58 and side walls 60 thereof , and in which the processing with the supercritical fluid is effected in , essentially the same mode as referred to hereinabove . however , in this instance wherein the workpiece holder 54 is cup - shaped , in contrast with the embodiment of fig1 and 2 , in which the workpiece w is typically immersed in a supercritical fluid and co - solvent mixtures in effecting process steps , it is desirable to utilize the transfer to the supercritical fluid processing by maintaining a limited amount of fluid coating . this basically enables the continuation of fluid coating through the intermediary of surface tension effects . the limiting control is provided by means of the apertures 56 or so - called weep holes which are formed in respectively , the bottom and side wall 58 , 60 of the cup - shaped workpiece holder 54 and enabling excess supercritical fluid to be stream out therethrough . in essence , once the workpiece w is loaded in the cup - shaped holder 54 and the fixture is inserted and retained in the pressure vessel 50 , in that the entire assembly including its mounting and being rotatably oriented on the vertical rib member 32 , with the vessel then being sealed and secured as described in connection with fig1 and 2 , the flow of the supercritical fluid under high pressure into the high pressure vessel 50 can them commence through the orifice 24 provided in the vessel cover structure 22 , as is known in the technology and the processing of the workpiece w can be initiated as required . from the foregoing it thus becomes readily apparent that the embodiments of present invention provide for unique and highly advantageous fixtures for processing workpieces under high pressure in a supercritical or pressurized fluid and possible co - solvent mixture flow or stream which will be protective of any film located on the workpiece w and resultingly inhibit any damage thereto during processing . while the invention has been particularly shown and described with respect to preferred embodiments thereof , it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention .