V—2 ROCKETS—KRAUSE 
through two successive lead plates each 
only 2 cm. thick. It was then found 
that about 35 percent of the high- 
altitude rays were stopped in either 
the first plate or penetrated it and 
stopped in the second. This indicated 
that at least this component was not 
primary (if the improbable case is ex- 
cluded that it consisted of nuclei of 
high atomic number). It has been 
suggested (19) that these are electrons 
which arise from the atmosphere 
below and are due to meson decay. 
The ones observed presumably orig- 
inated above South America and 
spiraled around the earth’s magnetic 
field lines to reach the point of obser- 
vation. The remainder of the radia- 
tion (i. e., 65 percent) was observed 
to penetrate the 4 cm. of lead, some 
of it producing showers in either the 
first plate, the second plate, or both. 
An upper limit to the relative number 
of primary electrons is obtainable from 
these data. First, it cannot be greater 
than 65 percent minus 40 percent or 
25 percent of the total radiation (in- 
cluding the nonprimary electrons). 
Second, it must be less than the rela- 
tive number of events in which showers 
were produced below 2 and 4 cm., 
since some of these are ascribed to 
particles of high penetrating power. 
This reduces the possible number of 
primary electrons to 9 percent of the 
total or 18 percent of the primary 
radiation. 
The fourth experiment (20) con- 
sisted of a counter tube telescope 
arranged so that the percentage of 
particles penetrating 2 cm., 6 cm., 
and 12 cm. of lead could be deter- 
mined. The number of threefold 
showers under these same thicknesses 
was also measured. The telescope 
was mounted vertically in a specially 
designed warhead so that it looked 
directly through the warhead nose as 
shown in figure 3, and in plate 3, 
figure 1, and plate 4, figure 2. The 
heavy lead shielding around the lower 
half of the telescope was introduced in 
an attempt to reduce the number of 
195 
rocket showers found in previous ex- 
periments. This shielding, in con- 
junction with the absorbing lead plates, 
was sufficient to eliminate most of the 
registered rocket showers of primary 
or nonprimary electronic origin. It 
was found that the number of rocket 
showers actually doubled over that of 
previous unshielded experiments. ‘This 
would indicate that these showers must 
be of nonelectronic origin. It was 
found that, above the atmosphere, 25 
percent of the total radiation present 
was absorbed in 6 cm. of lead. Al- 
though this is somewhat less than 
that found in the first experiment, it 
is assumed to be the same type of non- 
primary electron component discussed 
above. The different percentages in 
the two experiments are attributed to 
the variation of this component with 
zenith angle. A total of 59 percent of 
the particles penetrated 12 cm. of lead. 
The remaining 16 percent was ab- 
sorbed in 12 cm. In all cases the 
large portion did not produce showers 
under the lead. Thus, primary elec- 
trons would be ruled out since these 
would produce large showers under 
2and4cm. Asa matter of fact it is 
difficult to understand how any of this 
component could be due to primary 
particles since the large energies 
associated with the primaries should 
produce some type of reaction below 
12) cmp ots lead) “unless; of ‘course, 
neutral particles are involved. If we 
assume that all the radiation except 
that absorbed in 6 cm. is primary, 
then we find that the electron com- 
ponent determined on the basis of 
shower production could not be more 
that a maximum of 14 percent of the 
primary; the nonelectronic component 
absorbed in 12 cm. is 18 percent of the 
primary and the nonelectronic com- 
ponent penetrating 12 cm. is 68 per- 
cent of the primary. The ratio of the 
total radiation in free space to that at 
sea level was 11.5. The ratio of the 
hard component (that which pene- 
trated 6 cm. of lead) in free space to 
that at sea level was 9.0. 
