Cosmic-Ray Nuclear Interactions in Gases

Abstract

The natural rates of occurrences in the gases He, N, Ne, and A, of nuclear interactions of the cosmic --ay N-ccmponent in which more than 8 Mev are given to charged secondary particles, have been measured* The rates per gram atom of the four gases are in about the same ratio as their geometric nuclear cross sections. An integrated flux of N-rays of 6.0 x JO" 3 cm* 2 sec' 1 would produce the observed rates of occurrence of nuclear interactions if the cross section were geometric. The rates in argon, measured at sea level and 10,600 ft. elevation, correspond to an absorption mean free path in air of 132 £ 4 g cm* 2 for the total flux of N-rays. The interactions, 2783 in total, were observed in the gas of a cloud chamber filled to 5 atmospheres pressure. Inside the cloud chamber was placed a system of wires forming an ionixation chamber. An expansion was initiated whenever a pulse from the ionixation chamber corresponding to an energy release of more than 8 Mev (1.5 Po alpha) occurred. Fast reduction of the high voltage after electron collection was over permitted track formation on the positive ions. Of the nuclear interactions produced in argon about 20% are produced by charged particles at the higher elevation, and about 15% at sea level.

Scaling factors for production rates of in situ produced cosmogenic nuclides: a critical reevaluation

“…The lower value of 130 g/ cm 2 is used here because it describes the altitude dependence in the depth range relevant for most studies utilizing in situ produced cosmogenic nuclides. Moreover, this value for 1 agrees well with photographic emulsion [18] and cloud chamber data [19] that were obtained at altitudes between sea level and 3500 m (mean of 130 þ 4 g/cm 2 ). Thus the value of 130 g/cm 2 appears a good linear approximation for values of 1 for nuclear disintegrations induced by cosmic rays between sea level and 7000 m at high latitudes.…”

“…Hence the value of 132 þ 4 g/cm 2 obtained by Brown [19] (Table 1) is equally valid to describe the altitude dependence of in situ production of cosmogenic nuclides at the air^surface interface as the values of 1 obtained by [18]. Therefore, throughout this paper values of 130 þ 4 g/cm 2 (mean of [18] and [19]) and 149 þ 2 g/cm 2 [22,23] for high and low latitudes, respectively, will be used as guidelines for preferred values of 1 for cosmic ray-induced nuclear disintegrations at the Earth's surface. Note that the value for 1 obtained with the data collected with a BF 3 proportional counter at high latitudes and low altitudes (i.e.…”

“…Analogous to the photographic emulsion data the cloud chamber data were also obtained close to the air^surface interface [19] and record events of similar energy ( s 8 MeV [19]) as photographic emulsions ( s 35 MeV [27]). Hence the value of 132 þ 4 g/cm 2 obtained by Brown [19] (Table 1) is equally valid to describe the altitude dependence of in situ production of cosmogenic nuclides at the air^surface interface as the values of 1 obtained by [18].…”

“…The range in high latitude values for 1 is partially a result of the di¡erent detector designs. All data, except those of [18,19,22,23], were collected with BF 3 proportional counters embedded in para¤n using a lead core or cover; para¤n to shield the detectors from locally produced neutrons [13,24], lead as a target to produce secondary neutrons, from interactions with high-energy neutrons (200^1000 MeV [24]), that are recorded. A discussion of the in£uence of de-sign parameters on values for 1 is given in [13,25].…”

On the Influence of Cosmic Radiation on the Isotopic Composition of the Elements

“…The present production rate of Lie is calculated in the following way. The interaction of the cosmic radiation with nitrogen has been studied by BROWN (1954). He used a cloud chamber fded with nitrogen and observed the stars produced in the gas.…”