坂本 勇樹

At the European Spallation Source (ESS) ERIC, the liquid hydrogen moderator development is undertaken for its predominantly high parahydrogen fraction, which helps to attain a higher neutron intensity at a very high brightness. The Cryogenic Moderator System (CMS) is equipped with a catalyst to convert hydrogen from the ortho to the parastate to keep desirably high parahydrogen fractions of more than 99.5% in the cold moderators, which is required to deliver high brightness cold neutron beams to the neutron instruments. An in-situ measurement system for the ortho and para fractions of liquid hydrogen (OPMS) has been developed using a Raman spectroscopy to detect any undesirable shift towards a high orthohydrogen fraction caused by neutron scattering driven para-to-ortho back conversion. A Raman optics system was installed into a mock-up OPMS vacuum chamber and its performance evaluation tests have been conducted by flowing liquid hydrogen. It was verified that the developed Raman optics system succeeded in measuring the parahydrogen fraction with an accuracy of 0.1%, which met the requirement.

The Japan Aerospace Exploration Agency, in partnership with academia and industry, are developing the Air Turbo Rocket for Innovative Unmanned Mission (ATRIUM) engine: an air turboramjet + rocket combine cycle propulsion system intended to replace conventional liquid rocket engines in Vertical Takeoff Vertical Landing applications, such as reusable sounding rockets. A subscale Flight Test Bed (FTB) vehicle is also being developed to demonstrate the ATRIUM engine in a flight environment. In this paper, the ATRIUM engine and FTB vehicle are introduced, and current progress in their development is summarized. Future test plans and practical applications are also discussed.