Experimental load map of two stage 1.5 W at 4.2 K (SRDK - 415D) GM cryocooler

Two stage GM cryocooler is one of the major components for development of any conduction cooled superconducting magnet system. Recently, IUAC New Delhi has developed a 6T conduction cooled NbTi magnet system using a two stage GM cryocooler (Sumitomo SRDK - 415D) of refrigeration capacity of 1.5W at 4.2K and 40W at 50K. The commercially available typical load map of the SRDK-415D cryocooler shows few ‘discrete’ points. The commercial load map most of the time is not sufficient to analyse the thermal characteristics of the NbTi magnet system. This paper briefly discusses the full scaled practical load map for the SRDK - 415D cryocooler generated using a test rig. This paper also gives the detail of the continuous load curves for both the stages of the cryocooler. Details of the test setup, measurement methodology to generate the practical load curves, parameters responsible for temperature fluctuation, have been described.