17—6.
INSERTING A NEW LEAF—
393
_
The natural leak should be such that itis only a small percent
.
age
of the activity being measured. Usually this means that the
natural fall of the leaf can just be seen, amounting to, perhaps, one
small division per'minute in an electroscope ”of the type shown in
’
gure 17—1. It is due to leakage across the surface of the insulator,
local radioactive contaminations and cosmic rays.
'
.
To reduce the natural leak; (1) Clean the insulator With ether
or alcohol and wipe With a clean lint-free cloth. In
cases,
the surface of the insulator may be scraped with a razor blade or a
sharp knife. Only a thin layer need be removed. (Z) Sandpaperf
‘
the metal parts,wash With ether or alcohol and wipe with a
cloth.
(3) When rst used, the natural leak— will be large, as the
insulator “soaks up a charge.” It should decrease exponentially \
and be suiciently constant that measurements may be made after
one-half to one hour. (4) I t may be necessary to place a Small metal
_
cap over the top of the charging rod, where it projects above
instrument. The cap is removed to charge the leaf andmust always be replaced in exactly the same position. (5) With
humid conditions, it is useful to place a drying agent in
the electtoscope.
Calcium chloride, phosphorous pentoxide or sulplmric acid are
suitable.
(6) If the natural leak is still high move to another
_
location, as there is probably some cohtaminating material in the
room.
…
‘
.
’
17—6.
InSerting a New Leaf.——Aluminum leaf is easier to
‘
handle but gold leaf is steadier in operation.
;
.
'
Clean the supporting metal strip With ether or alcoholand
'
wipe With a clean, lint-free cloth. Spread
of
-
soft beeswax over the upper end of the support, dow‘n—
verse scratch iri the metal.Which
1111?)
for the
leaf.
Ï
Cut a piece of foil îto;thÇ
keepmglt
tWO_Of
the sheets of paper thati—t comesln
With“
_
ether or alcohol,
.used.}' DOHŒÏPT‘îSSdOWn
too hard on —_the_
guiding ruler or the foilW1HstmktOthepapercarefuuyfœmo,ve - ‘
the
papér- ahd
°Ëne
'
*
end of the
“
Ihv<æm
cfullyndprssthf1gnyntfhwnd…Ï . -
.
.
INSERTING A NEW LEAF—
393
_
The natural leak should be such that itis only a small percent
.
age
of the activity being measured. Usually this means that the
natural fall of the leaf can just be seen, amounting to, perhaps, one
small division per'minute in an electroscope ”of the type shown in
’
gure 17—1. It is due to leakage across the surface of the insulator,
local radioactive contaminations and cosmic rays.
'
.
To reduce the natural leak; (1) Clean the insulator With ether
or alcohol and wipe With a clean lint-free cloth. In
cases,
the surface of the insulator may be scraped with a razor blade or a
sharp knife. Only a thin layer need be removed. (Z) Sandpaperf
‘
the metal parts,wash With ether or alcohol and wipe with a
cloth.
(3) When rst used, the natural leak— will be large, as the
insulator “soaks up a charge.” It should decrease exponentially \
and be suiciently constant that measurements may be made after
one-half to one hour. (4) I t may be necessary to place a Small metal
_
cap over the top of the charging rod, where it projects above
instrument. The cap is removed to charge the leaf andmust always be replaced in exactly the same position. (5) With
humid conditions, it is useful to place a drying agent in
the electtoscope.
Calcium chloride, phosphorous pentoxide or sulplmric acid are
suitable.
(6) If the natural leak is still high move to another
_
location, as there is probably some cohtaminating material in the
room.
…
‘
.
’
17—6.
InSerting a New Leaf.——Aluminum leaf is easier to
‘
handle but gold leaf is steadier in operation.
;
.
'
Clean the supporting metal strip With ether or alcoholand
'
wipe With a clean, lint-free cloth. Spread
of
-
soft beeswax over the upper end of the support, dow‘n—
verse scratch iri the metal.Which
1111?)
for the
leaf.
Ï
Cut a piece of foil îto;thÇ
keepmglt
tWO_Of
the sheets of paper thati—t comesln
With“
_
ether or alcohol,
.used.}' DOHŒÏPT‘îSSdOWn
too hard on —_the_
guiding ruler or the foilW1HstmktOthepapercarefuuyfœmo,ve - ‘
the
papér- ahd
°Ëne
'
*
end of the
“
Ihv<æm
cfullyndprssthf1gnyntfhwnd…Ï . -
.
.