2 8 0 ▁is ▁composed ▁of ▁the ▁set ▁of ▁inner ▁sub - det ectors : ▁Pi - Zero ▁det ector ▁and ▁a ▁tra cker ▁with ▁ 2 ▁Fine - G rained ▁Det ectors ▁inter le aved ▁with ▁ 3 ▁Time ▁Pro jection ▁Ch amb ers , ▁placed ▁inside ▁of ▁a ▁metal ▁frame ▁called ▁a ▁basket . ▁The ▁basket ▁is ▁surrounded ▁by ▁the ▁elect romagnet ic ▁cal or imeter ▁and ▁a ▁magnet ▁rec yc led ▁from ▁the ▁U A 1 ▁experiment ▁producing ▁ 0 . 2 ▁T ▁uniform ▁horizontal ▁field ▁and ▁instrument ed ▁with ▁sc int ill ator ▁plan es ▁const itut ing ▁the ▁Side ▁Mu on ▁Range ▁Det ector . ▁ ▁Pi ▁Zero ▁det ector ▁ ▁The ▁Pi - Zero ▁() ▁Det ector ▁( P 0 D ) ▁contains ▁ 4 0 ▁pl astic ▁sc int ill ator ▁module ▁plan es , ▁which ▁in ▁the ▁central ▁part ▁are ▁inter le aved ▁with ▁ 2 . 8   cm ▁thick ▁b ags ▁fill able ▁of ▁water ▁and ▁thick ▁br ass ▁sheets , ▁and ▁in ▁two ▁peri pher al ▁regions ▁sc int ill ator ▁modules ▁are ▁sand wich ed ▁with ▁lead ▁sheets . ▁By ▁comparison ▁of ▁the ▁amount ▁of ▁interaction ▁between ▁modes ▁with ▁and ▁without ▁water ▁in ▁the ▁b ags , ▁it ▁is ▁possible ▁to ▁extract ▁the ▁number ▁of ▁neut r ino ▁interactions ▁occurr ing ▁on ▁the ▁water ▁- ▁the ▁target ▁material ▁inside ▁the ▁far ▁det ector ▁Super - K ami ok ande . ▁The ▁size ▁of ▁the ▁entire ▁active ▁P 0 D ▁volume ▁is