Present status of heavy liquid counter (helicon)

Following the thallium formate solution and the thallium formate-malonate (Clerici) solution, we have tested several lead compound solutions and a tetrabromoethane heavy liquid as a Cherenkov radiator material for a total absorption counter (calorimeter). We report here the results of optical transmission measurements of a binary solution of lead acetate and lead propionate and of a tetrabromoethane heavy liquid. We present also a result of trials of mixing organic scintillators in these heavy liquids to increase the light output. At present, we have neither obtained an adequate scintillator for lead compound solutions, nor for a tetrabromoethane heavy liquid. However, we obtained a promising indication of getting scintillations from a mixture of thallium formate-malonate (Clerici) solution, water and a liquid scintillator added with a surfactant and a naphthalene in a colloidal state. We need to examine the data more carefully and quantitatively before making a definite affirmative conclusion.