Test of Phototube Responses

The UV glass could increase the number of detected photoelectrons. We tested the performance of UV-transparent R5155-PMT(2 in.), of which sensitive region lies between 185 nm and 650 nm, with UV-cut filter. (cf. 300 nm and 650 nm for R6233.) This measurements were also made by using Belle type. The filter cut the light with shorter wavelength than threshold value of 280 nm. The filter was set between the PMT window and the aerogel. Data from Matsushita and Novosibirsk aerogels are plotted in Fig. 37 The UV-transparent tube provided 30-40 % larger light yield than with the UV-cut filter for Matsushita aerogel, but 20-25 % for Novosibirsk aerogel. Accordingly, UV windows of PMT is effective to increase $N_{pe}$ detected.