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Il Nuovo Cimento (1955-1965)

, Volume 4, Issue 6, pp 1285–1306 | Cite as

New determination of the intensities of primary cosmic ray alpha particles and Li, Be, B Nuclei at λ= 41.5‡ using a čerenkov detector

  • W. E. Webber
Article

Summary

Measurements of the intensities of the α-particles and Li, Be, B nuclei in the primary cosmic radiation have been made at an average atmospheric depth of 18.5 g/cm2 in two « Skyhook » balloon flights at λ = 41.5‡. The measuring instrument consisted of a thin (3.0 g/cm2) čerenkov detector placed within the solid angle of a Geiger counter telescope. This detector yielded unusually good resolution of the α-particle and Li, Be, B components. This fact and the slow rate of rise of the two balloons made possible a detailed determination of the dependence of α-particle intensity on atmospheric depth. The quality of the data justified a new approach to the problem of extrapolating the α-particle intensity to the top of the atmosphere. This extrapolation was carried out by applying a « diffusion » equation of the type previoysly used for nuclei withZ > 2 to the observed pressure-altitude dependence of α-particle intensity. The resulting estimate of the α-particle intensity at the top of the atmosphere is significantly lower than previous estimates. At 18.5 g/cm2 the sum of the vertical intensities of the Li, Be, B components was found to be (3.11 ±0.31) (m2·sr·s)-1 and the intensitiesJLi/JBe/JB were found to be as 3/4/2. The (light nuclei/medium nuclei) intensity ratio at the top of the atmosphere as determined by this experiment was 0.35 ±0.09. The vertical intensities at the top of the atmosphere of the various components of the primary radiation as obtained in this experiment at gl = 41.5dg were:

Riassunto

Mediante due voli di palloni tipo « Skyhook » si sono eseguite ad un’altezza atmosferica media di 18.5 g/cm2 misure d’intensità delle particelle a e dei nuclei di Li, Be, e B presenti nella radiazione cosmica primaria a λ = 41.5‡. Lo strumento di misura era un sottile (3.0 g/cm2) detettore čerenkov posto nell’angolo solido di un telescopio di contatori Geiger. Questo detettore dette una risoluzione straordinariamente buona delle componenti a e Li, Be, B. Questa circostanza e la lentezza d’ascesa dei due palloni hanno reso possibile una determinazione dettagliata della dipendenza dell’intensità delle « dalla profondità atmosferica. La qualità dei dati raccolti giustifica un nuovo esame del problema dell’estrapolazione dell’intensità delle particelle α alla sommità dell’atmosfera. Tale estrapolazione fu eseguita applicando alla dipendenza dell’intensità delle a dalla relazione pressione-altitudine osservata un’equazione di « diffusione » del tipo precedentemente usato per nuclei conZ > 2. Il valore risultante per l’intensità delle particelle α alla sommità dell’atmosfera è in misura significativa più basso dei valori precedentemente ammessi. A 18.5 g/cm2 la somma delle intensità verticali delle componenti Li, Be, B fu trovata essere (3.11 ±0.31) (m2·sr·s)-1 ed il rapporto fra le intensitàJLI/JBe/JB risultÒ 3/4/2. Il rapporto d’intensità (nuclei leggeri/nuclei medi) alla sommità dell’atmosfera determinato con questa esperienza fu 0.35± 0.09. Le intensità verticali alla sommità dell’atmosfera delle varie componenti della radiazione primaria ottenute nella presente esperienza a λ- 41.5‡ sono:

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Copyright information

© Società Italiana di Fisica 1956

Authors and Affiliations

  • W. E. Webber
    • 1
  1. 1.Department of PhysicsState University of IowaIowa City

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