18—6.
NOTES CONCERNING LINEAR AMPLIFIER 421
end of its range) in chamber (2), the grid will go negative. It
is thus possible to separate particles whose ranges are nearly
equal to each other. In one construction,3 the chambers are each
.
0.25 centimeter deep and the windows are of thin gold foil with
a stopping power of 0.4 millimeter.
'
'
18—5,
Notes Concenng the Linear AmplierÊ—This is of
_
the resistance—capacitance coupled type; Unusually cany”ul shieldz'ng is necessary all through the amplier and excellent ltering is
essential.
The rst tube is by far the most critical.- This tube'
must be non-microphonic, must have a fairly high input resistance
and a low effective or input capacity. It is usually operated with
sub-normal voltages in order to reduce the noise level. Inasmuch
as
the charge on the grid of the rst tube leaks to the ground
through the grid resistance or natural leakage of the tube itself,
the time constant (RC) for this stage is comparatively large.
The
“
sharpening
”
of the impulses is best
by making the
'
time constant of the second stage suiciently small. The product
RC for the remaining stages is made large to prevent oscillations,
but not so large as to cause
“
blocking
”
or‘
“
motor boating.”_
_
The voltage supply may be stabilized
4 by passing its current
through a tube whose grid voltage issuppliecl, in part, by an zr
drop produced in a resistance bytheycurrent itself: 'l‘hen, an
increase in the supply voltagegives more current, Which
increases
the bias on the stabilizer tube,
plate resistance_and
lowers the output
current
‘
f
_
”
_
,
18—6.
Scale—of—Two Counter
most df5h'
cately constructed
count€Y8œnn0t
-
œs_P9nîï
to
,
impulses above a denite
Clfcu1t Of
Hull has been modied
manner that
the counter (M of gure 18.4)lsoperatedbyeveryother _1mp
the in ut rate…
?»:«ï (:=
’
—
(seesectmn8—14)Th€ Plate
.
“al
.
ab-S?Y° Fh€
_
strikmgpmnt *;':;‘ç:s1 1 .