18—14.
MANUFACTURE OF COUNTER TUBES
observed in one minute (corrected for background), then Noa is
the inactive portion of that minute and (1 —— Noa) is the active time.
Now, during the time available, No counts were obtained, whereas,
if the full minute had been useful, the total number of particles
(îz) capable of initiating a discharge would have'beeri counted.
Therefore
-
No
1 —- Noa
_
E
7“?
—
1
(18—6)
from which it is seen that the efciency
* of a counter depends on
the counting rate (Ng) and on the inactive time (0).
Approximately seven per
cent
of the length of the usual
Geiger-Müller tube, near each end, is ineicient. _The effective
"
region of a Geiger (point) counter consists of the cone made
between the point and the window.
’
.
18—14.
The Manufactufè of Geiger—Müer Counter TubeS.— '
It is comparatively easy
to make a reasonably good gamma ray
counter tube of small dimensions.
There _is some disagreement
among the various experimenters as to the manufacturing details
but, if the following technique is used, most o£ the tubes Will have '
sufcient sensitivity and stability and low background
count
classroom work.
A copper
tube several centimeters long and
'.
about one centimeter in diameter, is ared at the
ends and has a
‘_
tungsten lead wire welded toit.
It is cleaned Withgrit-free soap
solution, thoroughly Washed and
dried.
A three mil, :thor1um
—
free, tungsten anode wire is cleaned_ by passing it slowly through
a
hot solution of potassium nitrite, then,
and
dried.
The copper
tube is slipped insidea' pyrex
lized with several glass dimples around thCj
The
wire is then mounted along theaxis
ately as can be JUdge.d_
’
by eye (see gure 18—5>ë‘ Th dfthtbwhd W@ï
cleaning solution
amd),
_
bÿ pumping for several hoursW1thafŒepumpIt18
thn}Îihe
'
,
.
.
,
tlonsh,betweentheobservedandtme —
__
MANUFACTURE OF COUNTER TUBES
observed in one minute (corrected for background), then Noa is
the inactive portion of that minute and (1 —— Noa) is the active time.
Now, during the time available, No counts were obtained, whereas,
if the full minute had been useful, the total number of particles
(îz) capable of initiating a discharge would have'beeri counted.
Therefore
-
No
1 —- Noa
_
E
7“?
—
1
(18—6)
from which it is seen that the efciency
* of a counter depends on
the counting rate (Ng) and on the inactive time (0).
Approximately seven per
cent
of the length of the usual
Geiger-Müller tube, near each end, is ineicient. _The effective
"
region of a Geiger (point) counter consists of the cone made
between the point and the window.
’
.
18—14.
The Manufactufè of Geiger—Müer Counter TubeS.— '
It is comparatively easy
to make a reasonably good gamma ray
counter tube of small dimensions.
There _is some disagreement
among the various experimenters as to the manufacturing details
but, if the following technique is used, most o£ the tubes Will have '
sufcient sensitivity and stability and low background
count
classroom work.
A copper
tube several centimeters long and
'.
about one centimeter in diameter, is ared at the
ends and has a
‘_
tungsten lead wire welded toit.
It is cleaned Withgrit-free soap
solution, thoroughly Washed and
dried.
A three mil, :thor1um
—
free, tungsten anode wire is cleaned_ by passing it slowly through
a
hot solution of potassium nitrite, then,
and
dried.
The copper
tube is slipped insidea' pyrex
lized with several glass dimples around thCj
The
wire is then mounted along theaxis
ately as can be JUdge.d_
’
by eye (see gure 18—5>ë‘ Th dfthtbwhd W@ï
cleaning solution
amd),
_
bÿ pumping for several hoursW1thafŒepumpIt18
thn}Îihe
'
,
.
.
,
tlonsh,betweentheobservedandtme —
__