fɹʌmðɪ ɪnsˈaɪd ˈaʊt, ðə fˈɜːst ɪz ɐ tɹˈækɚ, wˌɪtʃ mˈɛʒɚz ðə moʊmˈɛntəm ʌv tʃˈɑːɹdʒd pˈɑːɹɾɪkəlz æz ðeɪ kˈɜːv ɪn ɐ mæɡnˈɛɾɪk fˈiːld.
From the inside out, the first is a tracker, which measures the momentum of charged particles as they curve in a magnetic field.