16—24.
PROCESS
383
inum, which are diicult, as well as those which are easy to sputter.
Further, the body to be coated remains cool, and may even be a
wax, provided its vapor pressure is low, such as Apiezon wax W
.
A large electrical current is required instead of the highvoltage
used in sputtering. The disadvantage is
_
that the system must be highly evacuated
,
‘
(10—5 millimeter of mercury) and a fast
pump must be used to remove the gases
..
thrown out when the material is evaporating. The amount of material deposited
per square centimeter is inversely pro—
—‘
—
portional to the square of the distance
…
“
'.
between the source and the mirror and
, ]
_
to the cosine of the angle of incidence of
|_
'—
the particles upon the mirror, provided the
_
.
.
_'
distances are not excessively large.
……M ……
’
.
.
In a particular evaporati0n apparatus,
Fm.
Evaporàtion
_
the coil (C) was located 15 centimeters
-
apparatus, .,
_
below the plate (P) and consisted of 15
_
.
'
‘
7
_
closely wound turns of 30 mil tungsten wire wound on
a rod 5 l’Illlll'
meters in diameter. Aluminum pellets were boiled‘ in ni—tric_açid
approximately one—half of one minute,
j
1n
distilled water, dried and then placed inside_the coil (C).;(half
lling it). The clean glass plate ”was placed on:
cover added and sealed
The .SYSŒH_1
-
’
.
below the conducting stage (tesædWltha largfê
about 40 amperes (a.c.) Wei”ç used ”t? heat Chi“?
(1011 for 5 seconds,
For greater distances betWeen‘
material
must
be
If the
th?
deposit will be: discolofed orhmapowderY
=V_eïY.
J
.
*
,…
"
"
the vacuum“chehafdefan‘ï1”1f‘ghttheahnmnum°°atlbnlg
'
.
Ï
.
f f ' Some
ï