Investigation of the Clustering Condition for Various Gasses Ejected from a Fast Solenoid Valve for Supersonic Cluster Beam Injection

概要

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The supersonic cluster beam (SSCB) injection method is being developed as a new fueling method for the Large Helical Devise (LHD) experiment. As a first step, cluster formation at a room temperature has been investigated for various gasses using a fast solenoid valve for SSCB. Rayleigh scattering of laser light by the cluster is measured by a fast charge coupled device camera. In the case of methane, nitrogen, and argon, clear scattering signals are observed at high valve backing pressure of more than 3-4 MPa. In the case of hydrogen, helium, and neon, on the other hand, no scattering signal is detected at < 8 MPa. The result that the expansion half angle is 22.5° suggests gas flow is supersonic. The scattering signals from argon and nitrogen clusters show approximately cubic dependence on the backing pressure as expected from a model. Meanwhile, stronger pressure dependence than this has been found in the case of methane, where the scattering signal increases with the fifth power of the backing pressure at 3.2 MPa-7 MPa, and it is further enhanced at > 7 MPa.