tkarmil L I I C

-r *

' / r !

stance from the heater and cathode to the ^ " L T n d T x t ' ^ a r i e a d s i s as g r e a t a s . p o s s i b l e . ^ H o w e v e r .

S S ^ e S ^ S S K S i r l i f H l ^ i V J S V ^ J ^ l l between'these two i n c o m p a t i b l e requ i rements T i i amen u » — r P ^ l l l t S . . ^ a . . i n n a i r e a t t h e

S E L ^ S S is"transmitted by rad1 at1 on t h r o u g h t h e v a c u ^ ^ o ^ . n e nIatrThe'reialnder of the. h t * p r o * ^ ^ the plate 1s radiated into tne ture enve.uw* —

S ^ i ^ l ^ L S t ^ l n ^ c t r i n ^ i e s . other than transmiIttlng types.

^ p T ™ 350®C to"as"h1gh as 600'C. Most of

a'plate Is transmitted t h r o u g h the^vacuum o y - - ^ ' u ^ l h e ' c o n ^ l g u r a .

through or absorbed Dy w e 9i«» c,

'^,

;r'ii;

r

transmission characteristics,

tlons and relative temperatures. Due to its transmis in

frared .Urtrnn tube alass usually begins to be a.P°?

r

uH«p radiation at 2.5 microns. For example, most tube glass is essencia.^ ^

rAOr m.m*A nnl u sources near jou V, auu

Thus. 1t is semi-aDSorDent iaui<.<..«» - — nnamiA to radiation from

I ) CJJCMWIU ' • J ~ I 1 ' i .f

r r\Or rnilu w nf the enerav raoiatea Trum a sources near « u <. ohu r~ r throuoh the average glass this temperature may be transmitted d i r e c t l y througn^c »

3 5 ( ).

c

pnvelooe. The remaining 97* of,the heat "aiatea^rrom^^ can be absorbed by the glass, (see ^ ^ o n v e c t s reradiates part o r j n Y n v i "sSw heat from the plate

S to" 1 OS)S

i s'.'conducted" along "the pia

« ftgWc^intTf* versely, when plates operate between 400 and 500 C ^ larger inc ,

f

the radiated e n e r g y f ^ L ^ . ^ ^ ' ^ r ^ d ^ T f ^ B O to'856'C (cherry red).

lL^nt%r»nsmi ttinq tubesV a significant portion of the

" a d i a t r o n ^ ^ passes directly J ^ E & E shorter wave length of the.rad atlon spectra High w m u r e ^ ^

1u 1 r e d

.f 0

': «!e

^ ^ ^ ^ ^ " ^ H s T e l a t W ^ y - l o w . However, the the emissivity o»

u

' V ' ^ r VllI'H iacc than 1n a carbon plate tuoe. * M c tvDe of tube 1s heated l e s s tnan in c ua.uu ^

* whlch'wlll'be'transmitted through a given glass

envelope is"influenced by several variables Including:

Th. emissivity of the plate. Plates range from bright and blackened metal and their emis-

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