Inordertoidentifyheavierelements,wehavedevelopedanewlongitudinalfieldgasionizationchamber(IC)withanangleof30°ofplate(asshowninFig.1).TheICisoperatedinflowingiso-butanegasatapressureof10kPa.Aftertestingbyusinga3-componentαparticlesourceandcomparingwiththeoldlongitudinalfield