ame 2 welts), and the feed-back resistor is 100 esgobes, tha maximum value of the «ow current Ly 3 giver bys = . = ix a § & 107 amperes (0.05 pa) Thus, In « typical clrouit the photomiultipiler-tubsa anodes. current cannot excoad 0.05 pa, and at this value of current toare fs no dangar of photocatiods fatigue. Sines this vas a 100-parcent feed-back clroult, it vas virtually inticpendont of control-tube cLaractaristics end dsponded only on tha photoxultiplier-tube charactertstta and the value of ths feed-back resistor. The response curve cf the fngbrusiat elosoly followed the photomultiplier tube's gain chacactaristic for vary~ ing dyueds voltage. Tra tube cosplezsnt tncluded-a U4 as control, @ LP2l photcsultiplier In the lossensitivity (bighvintensity soasurements) eystea, and a S819 protocultiplior for fallout svasuresmnta (bight supaitivdty syotea). Although tha rated plate-to-fLleswut voltsge of the lU4 ves excasded by @ fector of tun, no difficultied wera exporisneed if Pilasonty were allovad to warm up before appiying tia plate voltsca. A GS-volt tsttery applied a constant voltage tetwoen anode and ninth épisca of the paotoculiipiisr, eince the latter is most stable whan cperated with a constant Voltasa betjea thoes points, Ro varlatioa in insiaveont oheracteristtes could be dotacted when tho control tubes sere replaced. Tila was treo e.ua eben tittes tore trisd with cifferent chavastariatics (cush as the 124) bat alviter pin comnettena, This euistentiates tha thoory that in this l0O-percent feed* tack efreult, tha plotemltipliaretuos chucecteristis dy indapanient of ths controletube paraw etsrs. The dynazta ran.s of tha isstniant ds atoconimately 107. When the extrem velus of Synesie renge is not reqaitad, tha rmesxar cay bo adjusted to opsrate over & portion of thes ranja, thes providing an expasted scale over tha ragion of interest. For sxanple, in poms locac tions where a dynante revia of 1? ves auficlent, the reco.sr was adjusted to omrate over this Patan of ths instrument's culout. A morevaccurate recording wae provided by making thsas edustasnte. 31 em eeeee ee ee ee ae ne em ee oe Verne tate 4 SECRET en eee