320
14.
ARTIFICIAL TRANSMUTATION
*"
'
of a lens System, through a hole in the pole piece or from the side
when a mirror M was used. A sheet of lead was placed in a horizontal plane inside the chamber. A large number of
were taken of the tracks due to cosmic rays coming down from
_
above, (chapter 15). Among these, there appeared a few tracks,
_
originating in the lead sheet, which were curved by the magnetic
.eld in the direction to be expected of negatively charged particles
and, simultaneously, tracks of identical appearance (thin and
dotted) with an opposite curvature. Calculation from the measured
curvature and the strength of the eld showed that both kinds were
due to particles of the same charge—to-mass ratio as that of elec—
‘
trous.
The particles which curved in the opposite direction were,
_
__
therefore, identied as positively charged electrons, now called
positrons (+6). Sometimes the negative electron (_e) is called &
negatron and the'term “electron” is used as a general word for
both positrons and negatrons.
The discovery by Anderson of the positron was very shortly
veried by Blackett and Occhialini”h Two Geiger-Müller counter tubes (chapter 18) were mounted, one above and the other be—
low the expansion chamber and connected in a coincidence circuit
whose output operated a mechanism for expanding the chamber
and taking photographs of drop
Thus, the chamber was
‘
operated only at a time when drop tracks were formed in it by
passage of a particle in a vertical direction through both counter
'
tubes.
Many photographs of the type shown in gure 14—9b were
obtained.
If the magnetic lines of force are, for example, directed
«
into
paper, the tracks curved to the left are due to negative
'
electrons and those to the right are due to positrons. StereoscopiC
photographs
that the tracks originate within a small area
P031tronscan also be produced by the action of gamma rays,16
asülustratedm gure 14—95.” .Here a lead sheet is placed man
larto thepaper)and is bombarded with gamma ravs. Nearlyequa1
numbersof+eand—e tracks
'
…
SmnœsasdlscussedmtheneXt section.” :
‘
-
14.
ARTIFICIAL TRANSMUTATION
*"
'
of a lens System, through a hole in the pole piece or from the side
when a mirror M was used. A sheet of lead was placed in a horizontal plane inside the chamber. A large number of
were taken of the tracks due to cosmic rays coming down from
_
above, (chapter 15). Among these, there appeared a few tracks,
_
originating in the lead sheet, which were curved by the magnetic
.eld in the direction to be expected of negatively charged particles
and, simultaneously, tracks of identical appearance (thin and
dotted) with an opposite curvature. Calculation from the measured
curvature and the strength of the eld showed that both kinds were
due to particles of the same charge—to-mass ratio as that of elec—
‘
trous.
The particles which curved in the opposite direction were,
_
__
therefore, identied as positively charged electrons, now called
positrons (+6). Sometimes the negative electron (_e) is called &
negatron and the'term “electron” is used as a general word for
both positrons and negatrons.
The discovery by Anderson of the positron was very shortly
veried by Blackett and Occhialini”h Two Geiger-Müller counter tubes (chapter 18) were mounted, one above and the other be—
low the expansion chamber and connected in a coincidence circuit
whose output operated a mechanism for expanding the chamber
and taking photographs of drop
Thus, the chamber was
‘
operated only at a time when drop tracks were formed in it by
passage of a particle in a vertical direction through both counter
'
tubes.
Many photographs of the type shown in gure 14—9b were
obtained.
If the magnetic lines of force are, for example, directed
«
into
paper, the tracks curved to the left are due to negative
'
electrons and those to the right are due to positrons. StereoscopiC
photographs
that the tracks originate within a small area
P031tronscan also be produced by the action of gamma rays,16
asülustratedm gure 14—95.” .Here a lead sheet is placed man
larto thepaper)and is bombarded with gamma ravs. Nearlyequa1
numbersof+eand—e tracks
'
…
SmnœsasdlscussedmtheneXt section.” :
‘
-