Nuclear Emulsion Treatment for Study of $S=-2$ Nuclear Systems at AGS-E964

The purpose of the E964 experiment is to study $S=-2$ nuclear systems with 10$^4$ stopping events of $\Xi^-$ hyperons and also to know $\Xi^-$$N$ interaction by measuring atomic X-ray from $\Xi^-$ absorption, for the first time. In the experiment, nuclear emulsion is used for detecting sequential weak decay of double-$\Lambda$ hypernuclei and also pointing $\Xi^-$ hyperons stopping events in huge amount of X-ray data. We have developed a new type of nuclear emulsion for E964. Very thin film made of polyethyleneterephthalate (PET) is used for the first time as emulsion support so as to minimize a dead space. We use the emulsion with fine and uniform AgBr(I) crystal of the size of 0.18$\pm$0.015$\mu$m, which was improved from that used in the previous experiments (0.24$\pm$0.078$\mu$m) to get better position resolution. A method of its treatment is reported in detail on each process of plate making, beam exposure and development.