12—6.
ION IZATION BY ALPHA PARTICLES
273
The specic
ionizaz‘ion is dened as the number of ionspro.
duced by a particle per unit path. The specic ionization of
alpha particles 13 greatest Just before the end of their paths;
’
-
1.e., they are most eic1ent a‘s ionizers just» before *they stop,
because they are travelling slower. This phenomenon may
“___—lc ……
‘
‘. '. : -' I
__
'
il = :‘ :'
'
"
.
‘.‘.Ë;.‘
'
-
‘-_':::f
"
"
"""
l
-.35::
.
_
FIG. 12—10.
To study the iohizatioh produced by an alpha particle at yarious‘ \
_
points along its path.
.
?
—
studied With a shallow ionization
such as
C
guré
-
_
12—10.
Here, the alpha particles from the source X, in a lead
‘
shield, traverse the distance D_tothe
a
wire
.
gauze for its lower plate) where,they produce
are.»
_' -
,
>c,:
,
,
_,X
,
,,
Q_
__
,
.
“'
_,
.,
_
.
'
‘
"
123456!“
a
msasured
,;Ï
…
Ÿ
_
thatofalpharaysfr@mradmmC’wh@S€fange(ï)‘
.