Four film boiling modes including the silent film boiling and the noisy film boiling were discriminated experimentally. Each mode was classified through visual observation and transient pressure and temperature measurements near the heater. It was found that in subcooled He II there were two film boiling modes, which are the strongly subcooled and weakly subcooled film boiling modes. The variation of boiling state between these two modes could be visually observed well by use of a transparent heater. All mode of film boiling is clearly mapped in diagrams as a function of pressure, temperature and heat flux. It is elucidated that the existence of He I layer influences the development of the vapor layer. (Translation of the article originally published in Cryogenics 49 (2009) 583-588

Synopsis: A very small displacement (∼ 10−20 m/ √ Hz at 100 Hz) needs to be measured to directly detect gravitational waves (GW), which have been predicted by Einstein's theory of general relativity. It is possible to detect such small displacement in the mirrors of the Large-scale Cryogenic Gravitational wave Telescope (LCGT) using interferometry. To reduce the noise level caused by thermal oscillation of the mirrors, LCGT mirrors will be cooled down to cryogenic temperature (∼20 K). For that purpose, the thermal radiation generated at room temperature has to be reduced, and this can be done using metal shields with low emissivity. To study the emissivity of some metals at low temperature, reflectivity at cryogenic temperatures has been measured at a wavelength of 10 m, where black body radiation of 300 K has the largest intensity. As a result, the three kinds of samples measured satisfied the requirements for the LCGT with a safety factor of more than 2. In addition, the incident heat through the duct shields of the LCGT was calculated using the results of these measurements, and it was concluded that 5 baffles in the duct shield can reduce the incident heat to a sufficient level.Keywords: gravitational wave, cryogenic, radiation, emissivity, reflectivity 1.Received

Synopsis:：A study on visualization of superheated He II -superheated He I interface in a narrow channel between parallel walls as a result of heating was investigated using a shadowgraph method. It was confirmed that a superheated state was readily created in the narrow channel that simulates cooling channels of superconducting magnets. Superheated He IIsuperheated He I interface transiently appeared above 2.0 K up to lambda temperature when applying small heat flux. The boiling accompanying with superheated He II-superheated He I interface that was repeatedly generated and collapsed was found to have a high heat transfer coefficient.

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