Solid state chemical source for ammonia beam maser

Robinson, M.

English

NASA Technical Reports Server

REPLY TO 
ATTN OF: 
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 
WASIIINGTON, Cl C .  20540 
October 15, 1970 
TO : USI/Scien t i f ic  & Technical Information Div is ion  
FROM : GP/Office of A s s i s t a n t  General 
At ten t ion :  M i s s  Winnie M e  Morgan 
Counsel f o r  Pa ten t  Mat te rs  
SUBJECT: Announcement of NASA-Owned 
U.S .  Pa t en t s  i n  STAR 
I n  accordance wi th  the  procedures contained i n  t h e  Code GP 
t o  Code U S 1  memorandum on t h i s  s u b j e c t ,  dated June 8, 1970, 
the  a t t ached  NASA-owned U.S .  p a t e n t  i s  being forwarded f o r  
a b s t r a c t i n g  and announcement i n  NASA STAR. 
The fol lowing information i s  provided: 
U.S.  Pa t en t  No, 3,287,660 
Corporate Source Huqhes A i r c r a f t  Company 
Supplementary 
Corporate Source 
NASA Pa ten t  C a s e  No. :  XGS-01504 
Please note  t h a t  t h i s  p a t e n t  covers  an invent ion  made by an 
employee of a NASA c o n t r a c t o r .  Pursuant t o  Sec t ion  305(a) of 
t he  Nat ional  Aeronautics and Space A c t ,  t h e  name of t h e  
Adminis t ra tor  of NASA appears  on t h e  f i r s t  page of t h e  p a t e n t ;  
however, t h e  name of t h e  a c t u a l  i nven to r  (au thor )  appears  a t  
t h e  heading of Column N o .  1 of t h e  S p e c i f i c a t i o n ,  following t h e  
words 'I. e . w i t h  respect t o  an  inven t ion  of .  . . I '  
N 
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Enclosure 2 c 
copy of P a t e n t  3 
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https://ntrs.nasa.gov/search.jsp?R=19700032262 2020-03-17T02:10:10+00:00Z
Nov. 22, 1966 JAMES E. WEBB 3,287,660 ADMINISTRATOR OF THE N A T I O N A L  A E R O N A U T I C S  
AND S P A C E  ADMINISTRATION 
SOLID STATE CHEMICAL SOURCE FOR AMMONIA BEAM MASER 
Filed Jan. 24, 1364 
Patented N 
3 287,660 
SOLID STATE C ~ E M I C A L  SOURCE FOR 
AMMONIA BEAM MASER 
dames E. Webb, Admlnlstrator af tbe Ndoaal Aero= 
nautics and Space Adlrlinhttation, wlt& reepeet to ~tl 
lnventkm of Martaa RoMnson 
FMCd ha 24, I964 Set, NO, 340,113 
6 Claims. (Cl 331-94) 
This invention relates to apparatus for generating Base= 
ous ammonia and more particularly to a solid-state source 
of gaseous anhydrous ammonia for use in ammonia-beam 
masers or similar apparatus. 
Many experiments and technical operations connected 
with space flights require ultraprecise frequency standards 
and/or time measuring means. An example of such ex- 
periments is the investigation of relativistic phenomena in 
space flight which requires time measurement of the order 
of accuracy provided by ammonia-beam masers. 
A maser is a device for coherent amplification or gen- 
eration of electromagnetic waves by use of excitation en- 
ergy in resonant atomic or molecular systems. The de- 
vice uses an unstable ensemble of atomic or molecular 
particles which may be stimulated by an electromagnetic 
wave to radiate excess energy at the same frequency and 
phase as the stimulating wave, thus providing coherent 
amplification. Molecular beam masers are well known in 
the art, A discussion of the principles of operation can 
be found in the pnpers appearing in the Physical Review, 
volume 99, pages 1264-1274 (Aug. IS, 1955) and the 
Proceedings of I.R.E., volume 45, pages 291 to 316 
(March 1957). 
The gas beam-type maser was the first type of maser 
developed. Its operation requires that a known and con- 
trollable quantity of gas be supplied. Heretofore, liquid 
ammonia sources have been used in ammonia beam 
masers, but due to their high vapor pressure (typically, 
nine atmospheres at room temperature) they had to be 
contained in heavy stainless steel cylinders equipped with 
elaborate pressure reducing valves. Although there are 
many mechanical devices which can provide this func- 
tion, all suffer from the fact that they are heavy and 
subject 20 malfunction. In a typical construction am- 
monia gas obtained from the pressurized tank via pressure 
reducing regulators issues from a small orifice into a 
vacuum system to form a molecular beam. Molecules 
in the lower of the two states are deflected away from the 
axis of the state sorter or focuser by inhomogeneous elec- 
tric fields which act on their dipole moments. Those 
molecules in the upper state are deflected towards the 
axis and sent into the microwave-resonant cavity. If 
losses in the cavity walls and coupling holes are sum- 
ciently small, or if the number of molecules is sufficiently 
large, amplification or oscillation will occur. The am- 
monia-beam maser is particularly useful as a frequency or 
time standard because of the relative sharpness and in- 
variance of resonances of the ammonia beam. It is also 
particularly useful as a frequency standard for satellite 
and missile tracking systems where weight is a prime con- 
sideration in deciding the type of maser to be used. . An ammonia beam maser is also shown and described 
in Patent No, 3,013,218 entitled Molecular Beam Maser: 
The present hvention provide,La novel and improved 
solid-state source for gasms. anhydrous ammonia which 
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enhances the advantage.? of a maser as a frequency stand- 65 
ard in a iatellite or the' ike. In the present invention {* 
I 
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ammonia is stored in a form from which it can be clowly 
released at a controllable rate. The meanc by which thia 
is done is its conversion to a complex with the salt, silver 
chloridb. Since the latter is a pure compound with a &fi= 
nit6 equilibrium temperature and pressure, the refease of 
the ammonia is then a predictable and conwllabb 
phenomenon. This characteristic is precisely what is re- 
quired for optimum maser operation. 
As mentioned previously, in conventional ammonia- 
beam mawrs the amount of ammonia in the apparatus is 
regulated by an external source of ammonia which typi- 
cally comprises a tank of liquified ammonia under pres- 
sure, the associated valves, gages, pumps, and fittings or 
similar apparatus as known in the art. In a satellite or 
missile tracking system, where the vehicle may be con- 
tinuously tumbling and spinning, a liquid ammonia source 
must be ruled out, since the gas cannot be physically sep- 
arated from the liquid; to insure constancy of flow the 
gas phase must at all times be in contact with the flow 
regulating mechanism. However, the solid ammoniate of 
the present invention overcomes this difficulty since it can 
be separated from its vapor by simply covering it with a 
screen whose openings are smaller than the particle size  
of the solid. 
Since the decomposition mechanism of the complex 
salt, silver chloride-monoammoniate can be accurately 
predicted, it may be used in accordance with the invention 
to overcome the objection of prior devices. The novel 
technique of the present invention is automatic in the 
sense that it is based upon a chemical reaction rate which 
is fixed. 
It is therefore a principal object of the invention to 
provide novel means and apparatus whereby ammonia is 
stored in a form from which it can be readily nleaaed at 
a controllable rate. 
Another object of the invention is to provide a novel 
method and means for conversion of ammonia to a silver 
chloride complex salt and the subsequent liberation of 
gaseous ammonia therefrom. 
Another object of the invention is to pmvidc a novel 
and improved source of gaseous ammonia for ammonia- 
beam masers or the like. 
Still another object of the invention is to provide a 
source of ammonia for masers which is lighter in weight, 
more reliable, and less complex than sources used here- 
tofore. 
Still another object of the invention is to prbvide a 
novel source of gaseous ammonia for ammonia-beam 
masers or the like which may be operated in any position 
and which will operate within a moving vehicle. 
A general object of the invention is to provide a novel 
and improved solid-state chemical source for gaseous 
ammonia which overcomes disadvantages of previous 
means and methods heretofore intended to accomplish 
generally similar purposes. 
The features of this invention which are believed to 
be novel are set forth with particularlii k tho appended 
claims. The present invention itself, both 8 ~ 1  to its or- 
ganization and manner of operation, together with further 
objects anti advantages thereof may beit be understood 
by reference to the following description taken in con- 
junction with the drawing which shows a typical con- 
struction of a solid-state chemical 8 0 1 1 ~ ~  aa may be used 
in an ammonia-beam maser. 
The complex salt, silver chloride-monoammoniau, is 
prepared in a glass-lined copper spbre and is tadiesobd 
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at 1 in the drawing. The sphere, comprising glass lining 
2 and copper jacket 3, will be. referred to hereinafter as 
the reservoir. An insulating outer jacket 10 of suitable 
composition may be provided, as will k apparent to those 
versed in the art. The reservoir is provided with rn 
opening 4 by means of which the salt 1 m y  be intro- 
duced and through which the gaseous ammonia may 
escape. Opening 4 #may be provided with a screen 5 hav- 
ing a finer mesh than the particle size of salt 1 thereby 
preventing salt particles from entering conduit 6 and 
other parts of the system. The reservoir is wrapped with 
an electric heating element 7 .and a thermostat sensing 
wire 8 of any suitable and well-known construction. The 
.sensing wire 8 constitutes one arm of a Wheatstone bridge. 
The bridge circuit controls the power input to the Beat- 
ing element, in a well-known manner, whereby the tem- 
perature can 'be kept constant to - c O . Q 4 O  C. Interconnect- 
ing cable 9 couples element 7 and sensing wire 8 to the 
external temperature control apparatus 11 containing the 
bridge circuit and input power source. 
Conduit 6 is coupled to manifold 12 via stopcock 13. 
Capillary 14 and capillary bypass stopcock 15 are con- 
nected to manifolds 12 and 16. Leak-tight fitting 17 
permits the aboveddescribed apparatus to ,be attached to, 
or removed from, the ,ancillary apparatus. During 
preparation of the salt 1, the apparatus may be connected 
to a source of gaseous ammonia whereby ammonia is 
added to the silver chloride to form $the complex salt 
AgCI-NHs. As is known to those versed in the art, if 
anhydrous ammonia is added to many salts at low tem- 
peratures, compounds containing several molecules of 
ammonia are formed. When warmed, these complex salts 
lose ammonia at a rate which is dependent on tempera- 
ture. In the present invention, the salt dlver-chloride is 
used and molecules of *ammonia added thereto. Silver 
chloride-monoammoniate (AgClSNHa) is a solid com- 
pound formed by the chemical combination of the an- 
hydrous diver chloride (AgCI) with the gaseous an- 
hydrous ammonia (NHa) : 
ARCItNFII=ARCl*NII: 
(8nlltl) ((Ins) (Bolld) 
When the silver chloride is nearly 100% ammoniated, 
stopcock 13 is cloaed to isolate the source from the 
atmosphere. 
The apparatus is fitted with capillary 14 which is dc- 
signed to give a flow of 10" molecules per second at a 
given ammonia back pressure. The apparatus is now at- 
tached to the maser beam chamber 18 by means of a 
leak-tight fitting 17 which mates with conduit 19. After 
attachment the apparatus is evacuated, keeping the isola- 
ing stopcock 13 closed and stopcock 15 open. Bypass 
stopcock 15, which is opened during preparation of the 
source, is closed prior to operation of the apparatus. 
The reservoir is allowed to come to a predetermined tem- 
perature corresponding to the temperature calculated to 
give the proper beam flux for maximum power output, 
the isolating stopcock 13 is opened and immedi4ately a 
maser signal may be obtained. Gas Aow into chamber 
18 is via conduit 19 and nozzle 20. The high resistance 
of capillary passage 19 prevents any substantial change 
in the flow of gaseous ammonia to nozzle 20 due to 
changes in ambient temperature with the result that a 
highly stable ammonia beam is formed and is maintained 
until all of the ammonia in the reservoir is expended. 
One mole of AgC1.NH3 weighing 161 grams can re- 
lease enough ammonia at a constant beam flux of 10" 
molecule seconds -1 to operate an ammonia lbeam maser 
for 713 days, and because of its low vapor pressure it can 
be kept in .a simple, light-weight container such as the 
abovedescribed reservoir. This low molecular weight- 
low vapor pressure system when provided with tempera- 
ture controls 'and coupled to a simple capillary exhibits 
all of the characteristics of an excellent solid state source 
for ammonia beam masers. 
In the above description silva chloridwnonoauununiate 
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has 'bsen described as .the preferred ammoniate. How- 
ever, other solid state ammoniates may be used. Fbr 
example, ammonium salts of acids in the solid state dis- 
sociate readily into ammonia and the fm acid. If the 
6 solid state ammoniate is heated in a closed vessel, a 
definite pressure of ammonia is established in the presence 
of the solid salt. This pressure is determined solely by 
the temperature and, if the acid or metal salt is nonvala- 
tile, is called the dissociation pressure at that tempsrature. 
From the foregoing it can be wen that massive, pr.es- 
lo surized, sources of liqtrified ammonia are obviated dunng 
inAlght operation of ammonia beam masers in satellites 
and space vehicles. The pressure of the ammoniate sys- 
tem in the present invention is approximately qua l  to 
atmosphere at room temperature and remains constant 
at a given temperature as long as two phases are present. 
Therefore, the beam flow into the master chamber re- 
mains constant until all of the ammonia is expended. 
While there have been shown and described and pointed 
20 out the fundamental novel features of the invention as 
applied to a preferred embodiment, it will 'be understood 
that various omissions, substitutions, and changes in the 
form and details of the device illustrated and in its opera- 
tion may be made by those skilled in the art, without d e  
parting from the spirit of the invention; therefore, it 
is intended that the invention be limited only as indicated 
by .the scope of the following claims. 
What is claimed is: 
1. A solid state chemical aource for an ammonia beam 
maser comprising: 
a reservoir containing an ammonia salt; 
passage means connecting said reservoir to said maser; 
and 
m a n s  for regulating the temperature of slrid reservoir 
at a predetermined level thereby causing said salt to 
dissociate and liberate gaseous ammonia through said 
passage means at a predetermined. pressure propor- 
tional to the temperature of said reservoir. 
2. A solid state chemical source as defined in claim 1 
solid particks of silver chloride-monoammoniate. 
3. A solid state source as defined in claim 2 having 
screen means interposed in said passage means for re- 
tahbg said silver chloride=monoammoniate in said 
reservoir while allowing escape of said gaseous am- 
monia. 
4. A solid state source as defined in claim 2 having 
capillary means connected between said reservoir and 
said passage means for maintaining a given flow rate 
of said gaseous ammonia into said maser at a given 
ammonia dissociation pressure. 
5. A solid state chemical source as defined in claim 2 
an electric heating element substantially surroundiing 
said reservoir; and 
temperature sensing means disposed on said reservoir 
and responsive to changes in 'temperature thereof to 
control the supply of electric power to said heating 
element. 
6. A solid state chemical source for an ammonla 
a reservoir containing a solid ammoniate; 
8 conduit connected to said reservoir through which 
gasews ammonia may flow; 
an inlet passage having a leak-tight fitting attached 
thereto whereby said source may be connected first 
to a supply of ammonia and thereafter to said maser; 
isolating valve means interposed between said inlet pas- 
sage and said conduit whereby ammonia may be 
introduced from said supply during ammoniation of 
said ammoniate and whereby ammonia may be dis- 
charged to said maser during dissociation of said 
ammoniate; sand 
means for elevating the temperature of said reservoir 
to a temptsatwe sufficient r~ cause dissociation of 
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wherein said salt comprises: 
wherein said temperature regulating means comprises: 
beam maser comprising: 
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OTHER REFERENCES 
Mellor, A Comprehensive Treatise on Inorgaaic and 
Theoreticat Chemistry, vol.lIl, Longmans, Green and Ca., 
N.Y., 1946, page 400. 
5 
said ammoniate when said so~rce is connected to said 
maser. 
References Cited by tbe Examlner 
UNITED STATES PATENTS 0 
2,260,840 io/i94i  owe _ _ _ _ _ _ _ _ _ _ _  219--514 x ROY Primary E-iner- 
3,117,837 1/1964 Hasse -_-- ---____ 23-193 X S. W. GRIMM, Acting Exomiatr. 
3,214,630 10/1965 Helmer et al. _ _ _ _ _ _ _ _  33Q-4 X 


Solid state chemical source for ammonia beam maser Patent

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