ɡˈæmɚɹˈeɪz, ɪn pɚtˈɪkjʊlɚ, kʊd biː kˈɑːlᵻmˌeɪɾᵻd baɪ sɚɹˈaʊndɪŋ ðə dɪtˈɛktɚz wɪð hˈɛvi ʃˈiːldɪŋ mətˈɪɹiəlz mˌeɪd ʌv lˈiːd ɔːɹ ˈʌðɚ sˈʌtʃ ˈɛlɪmənts, bˌʌt ɪt wʌz kwˈɪkli dɪskˈʌvɚd ðætðə hˈaɪ flˈʌksᵻz ʌv vˈɛɹi pˈɛnɪtɹˌeɪɾɪŋ hˈaɪˈɛnɚdʒi ɹˌeɪdɪˈeɪʃən pɹˈɛzənt ɪnðə nˌɪɹspˈeɪs ɛnvˈaɪɹənmənt kɹiːˈeɪɾᵻd ʃˈaʊɚz ʌv sˈɛkəndɚɹi pˈɑːɹɾɪkəlz ðæt kʊd nˌɑːt biː stˈɑːpt baɪ ɹˈiːzənəbəl ʃˈiːldɪŋ mˈæsᵻz.
Gamma-rays, in particular, could be collimated by surrounding the detectors with heavy shielding materials made of lead or other such elements, but it was quickly discovered that the high fluxes of very penetrating high-energy radiation present in the near-space environment created showers of secondary particles that could not be stopped by reasonable shielding masses.