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A possible way to increase measurement accuracy, the design principle, research methods, the characteristics of a precision calorimetric system calibrated electrically by the substitution method, and verification equipment for b~struments for measurement of high energy levels and the average power of laser rcutiation are e.rambled.Analysis of the errors of precision working and standard instruments for measurement of high ene~o-y levels and the average power of laser radiation, such as the IPI~-1-70, I PI~-1-70D, IPI~-1 -150, IPI~-1 -150D. IPI~-1-120M, OS II~-1-70, OSII5-1 -150, . shows that the main contribution to their error is introduced by the component that is determined by the error of the standard instrument used to verify them. Consequently, this measurement technique could provide a further substantial improvement in measurement accuracy if the acctiracy of the reference or standard instruments used to verify them were increased. To find rational ways to solve this problem, an experimental precision calorimetric system was created for measuring high energy levels of pulsed and quasicontinuous laser radiation that could be calibrated by the substitution method using electrical energ2r A diagram of the system is shown in Fig. 1.The system has a massive compound cavity receiving element 25, which includes main 19 and auxiliary 14 absorbing cavities. The diameter of the main cavity 19, all surfaces of which have an absorbing coating 26, is 45 mm, which exceeds the diameter of the working radiation beam. The cavity depth is 100 mm. All surfaces of the bottom part of the large auxiliary cavity 14 of the receiving element and a part of the cylindrical surface (164 mm in diameter) adjacent to it also have an absorbing coating 16.The remaining surfaces 27 of the auxiliary cavity are mirror-reflecting. Parts 20, 21, 24, and 25 of the receiving element are held together with good thermal contact. The main cavity 19 contains a sectional electric heater; three sections 23 are in the rear part of its bottom and the fourth section 18 located about the lateral cylindrical surface. The main cavity with electric-heater sections is covered by two heat shields 20 and 21. The receiving element 25 is held by seven supports 11 inside a massive cylindrical copper passive thermostat 17. The supports are long thin-walled stainless-steel tubes. Each support is equipped with an electric heater 13 and a differential thermopile 12 and is a gradient meter of the thermal flux passing through it. The supports are thermally and electrically insulated from the receiving element 25 and the passive thermostat and are parts of the electrical circuits of the leads to the electric-heater sections.The calorimeter has a differential thermopile 8, whose hot 9 and cold 7junctions are held tightly against the receiving element 25 and heater 13, respectively. A strip of heat-insulating material is placed between the hot junctions 9 and the receiving element of 17. Radiation enters the calorimeter through a tubular light ~maide 2, which has a vacuum...

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