17—19. IONIZATION CHAMBERS FOR COSMIC RAYS 413
tion occurs at 0.374A.
It is a liquid at room temperatures and
atmospheric pressure. Connect the bottle containing the liquid,
through a PzO5 tube (the gas must not contain water vapor) to-an
evacuated ionization chamber, and allow the pressure to rise to
approximately 30 centimeters of mercury. At higher pressures
_
some of the gas will liquefy and ruin the insulation. With this
gas, it is necessary to take the chamber apart
cleanthe
insulation every three months or so.
Ethyl èromide (C2H5Br) is' most useful between“ 0.4'and 0.9A.
The same technique is used as with methyl iodide,
it'must be
dry, the chamber must‘be cleaned occasionally, and the pressure
must be below the point where the vapor condenses.
Ethy/ iadide (C2H5I) and methyl humide (CH3Br) have also
'
been used but are not common.
Helium is useless as it is too
light. It is desirable to have heavy molecules at high pressures,
no liquids and freedom from chemical reactions with the
itself.
'
—
‘
'
’
X-ray beams of the same wave-length may be compared
directly with a given chamber. With different wave-lengths,
certain corrections must be made.
The measurement
of the
absolute intensity of an X-ray (photonsper square centimeter per
second) is a still more elaborate process.
'
'
”
“
_
'
17—18.
Ionization
Use With Gamma RêŸSÎÏ—“ .
.
The construction is similar to théËtùSed WithX-rays except that
,:
the size of the chamber is of greater
ThiSis due
the fact that the
“€jeCfÇd bŸ "the “gamma r ?ŸS
have higher
many;10ns and CJ
-
ticles from the walls,
Use_highk,plç3çÿïê'
kind of gas used is not as important asw1thx—rays
-
Ÿ
=
‘
’
_
17—19.
Ionization ChâbfS f0steW1thC05mm ïRayŸ”-‘_”'
.
Chambers usedWlthœsmlcraŸsaredlscussed
-
in chapter 15 and as1mpl€für…1351escrlbêdm‘5Xp‘îrlment
15—1
.
Because of the smà_mœn31tyOfcosm1crays,therrchambers
.
and shield's to cutoutthelessenetratlngl@calradlatlons
tion occurs at 0.374A.
It is a liquid at room temperatures and
atmospheric pressure. Connect the bottle containing the liquid,
through a PzO5 tube (the gas must not contain water vapor) to-an
evacuated ionization chamber, and allow the pressure to rise to
approximately 30 centimeters of mercury. At higher pressures
_
some of the gas will liquefy and ruin the insulation. With this
gas, it is necessary to take the chamber apart
cleanthe
insulation every three months or so.
Ethyl èromide (C2H5Br) is' most useful between“ 0.4'and 0.9A.
The same technique is used as with methyl iodide,
it'must be
dry, the chamber must‘be cleaned occasionally, and the pressure
must be below the point where the vapor condenses.
Ethy/ iadide (C2H5I) and methyl humide (CH3Br) have also
'
been used but are not common.
Helium is useless as it is too
light. It is desirable to have heavy molecules at high pressures,
no liquids and freedom from chemical reactions with the
itself.
'
—
‘
'
’
X-ray beams of the same wave-length may be compared
directly with a given chamber. With different wave-lengths,
certain corrections must be made.
The measurement
of the
absolute intensity of an X-ray (photonsper square centimeter per
second) is a still more elaborate process.
'
'
”
“
_
'
17—18.
Ionization
Use With Gamma RêŸSÎÏ—“ .
.
The construction is similar to théËtùSed WithX-rays except that
,:
the size of the chamber is of greater
ThiSis due
the fact that the
“€jeCfÇd bŸ "the “gamma r ?ŸS
have higher
many;10ns and CJ
-
ticles from the walls,
Use_highk,plç3çÿïê'
kind of gas used is not as important asw1thx—rays
-
Ÿ
=
‘
’
_
17—19.
Ionization ChâbfS f0steW1thC05mm ïRayŸ”-‘_”'
.
Chambers usedWlthœsmlcraŸsaredlscussed
-
in chapter 15 and as1mpl€für…1351escrlbêdm‘5Xp‘îrlment
15—1
.
Because of the smà_mœn31tyOfcosm1crays,therrchambers
.
and shield's to cutoutthelessenetratlngl@calradlatlons