'
’
8—14.
GAS-FILLED TRIODES '
177
the walls of the containing vessel, a uorescence occurs, greenish,
yellowish or bluish, according to the kind Of glass. This uores—
-
cence is'due to x—mys and begins with pressures of the order of
0.001 mm. of mercury;
Wheteas current passeseasily through
the gas at higher pressures, it now becomes diicult for it to get
through. Higher potentials are needed, since there is a scarcity of
-
particles to act
as carriers, unless a hot lament is used to supply
‘
‘
them. '
"
lf high potential discharges from a condenser are passed
tween metal electrodes placed less than a millimeter apart in 'a
vacuum around 10-“4 mm., a brilliant ash of light is obtained.*
'
This
“
hot spark
”
is a good source for use in the extreme ultraviolet (100 to 2000 angstroms). The radiations'are characteristic '
-
of the atoms making up the electrodes and the gases occluded
therein.
Using the hot spark, various stages in the removal of
the valence electrons of the atoms have been studied.
8—14.
Gas—lled Triodes.l3—“Thyratron”
tubes contain 'a cathode, a control grid, an anode and a gas whose
pressure ranges from a fewthousandths' to a few tenths of a milli-_
meter.
Their action is entirely different from that of the high
vacuum triodes, since“ the grid, Which might well be called a trigger
initia‘tefïain fd7”fù
the cathode and
theplate.» Qnœ ‘sta1'ted,.the plate‘- current
is no longeraffoted
‘
_
by the“gridvo‘ltärgeand can Onl'ÿ- be-‘s‘topÏ3‘èd by reducing the plate
,
zero
Themagn1tudeofth6plate current“
-
by
batteryvoltageandser1es
can have
any
apetp{ëthefullem1ssmnof the
In practice,
"
_
-…:
_
»
Ÿ tubesarecamparabletûlockmrelayswhereasmaamount0f -
PowerTheœmmerc1altradename’°thatmnmeansdoor :
_.
*
; : Letthegr1dofagasedtubebemadeaPPYeC1ablYeëatlVê
…
“
î
Whentheplatevoltagewrstapphedelectr0n5fmmthecathode
‘
pmducepsmvemnsandelectrnsnearthegduet@thed1f
»