Electron beams studied for use in lunar soil spectrometric analysi

Ivanova, V. E.

Pudov, A. N.

English

NASA Technical Reports Server

h '3- 
National Aeronautics and Space Administration 
Goddard Space Flight Center 
Contract No.NAS-5-12487 
ST-ACH-LS-10755 
ESTIMATE OF THE POSSIBILITY OF CONDUCTING MASS-SPECTROMETRIC 
MEASUREMENTS OF THE MATTER OF LUNAR SURFACE 
V. E. Ivanova 
& A. N. Pudov 
(USSR) 
I 
0 (THRU) 
3 
9 
E 
..I 
, 9 (b4ASA CR OR ThU OR AD NUMBER) (CATEGORY) 
10 SEPTEMBER 1968 
https://ntrs.nasa.gov/search.jsp?R=19680024721 2020-03-12T06:20:26+00:00Z
ST-ACH-LS-10755 
ESTIMATE OF THE POSSIBILITY OF CONDUCTING MASS-SPECTROMETRIC 
ANALYSIS OF THE MATTER OF LUNAR SURFACE 
Rosmicheskiye Issledovaniya 
Tom 6 ,  vyp. 4 ,  624 - 630 
Izda te 1 ' s tvo "NAUKA" , 1968. 
SUMMARY 
by V. F. Ivanova 
& A. N. Pudov 
A method is proposed for the determination of the chemical composition 
of the lunar surface with the utilization of a radio-frequency mass-spectro- 
meter. 
by vaporization of lunar rock at electron-beam heating. 
The intake of matter in the analyzer chamber may be materialized 
The processes of energyaonsumptionare computed for the case of electron 
beam interaction with the lunar rock. The efficiency of the vaporization 
process is determined. The total power is evaluated, which is required for 
the vaporization of the necessary amount of matter for the mass-spectrometric 
analysis. 
The technical requirements, imposed on a radio-frequency mass-spectro- 
meter, are represented for the possibility of its utilization in the analysis 
of formations of cosmic objects. 
* 
* *  
Mass-spectrometric analysis of lunar matter from a spacecraft soft-landed 
on the Moon may constitute one of the methods to obtain information on the 
composition of lunar rocks. 
The conducting of such an analysis requires the erection of a complex 
equipment, consisting of a mass-spectrometer and a vaporized assuring the in- 
take of matter in the analyzer chamber. 
The authors consider the possibility of using to that effect of a radio- 
frequency mass-spectrometer [l] with a vaporizer consisting of electron-beam 
gun. The block-diagram of the experiment is represented in Fig.1. 
(*) OTSENKA VOZMOZHNOSTI PROVEDENIYA MASS SPEKTRAL'NOGO ANALIZA VESH- 
CHESTVA L W O Y  POVERKHNOSTI. 
2 
For the solution of the problem introduced, radiofrequency mass-spectro- 
meters are sufficiently accurate with enough resolution, while still respond- 
ing to requirements set forth to devices installed aboard spacecrafts [ 2  - 41. 
Fig. 1 Block-diagram of the 
experiment 
The choice of electron gun for the vaporizer is dictated by its pecu- 
electric current maneuverability and applicability in conditions of 
liarities, advantageously featuring this source of energy: high energy den- 
sity, 
high vacuum. Moreover, electron-gun heating assures the total absence of 
contamination of matter vaporized. 
The processes of matter vaporization under the action of an electron 
beam are at present insufficiently described from the theoretical viewpoint. 
This makes their computations somewhat difficult. 
Presented in the current work are the results of some preliminary calcu- 
lations allowing, in the first place, to evaluate the possibilities of the 
method, and, secondly, to create laboratory and airborne variants of the 
device. 
1. VAPORIZATION OF MATTER BY ELECTRON BEAM 
The power consumption W of the electron beam at its passage through the 
matter takes place as a result of the following processes: heating, melting 
and vaporization of matter, propagation of heat from the place of ray inci- 
dence as a result of heat conductivity, temperature emission, ionization and 
excitation of vaporized atoms found to be in the path of the electron beam. 
The calculation of power distribution by the indicated processes and the 
total power of electron beam required for the vaporization of the mass of 
matter from the rock's surface, ensuring mass-spectrogram recording by the 
device, are determined for the fundamental types of rocks- granites, basalts, 
dunites and chondrites. 
3 
Loss of Power to Temperature Radiation 
The power consumption W1 to temperature radiation was estimated from 
the Stefan-Boltzmann law, assuming that the radiation takes place from the 
vaporizing surface S of 1 mm2 area at temperature T % 4000°K. 
where E is the coefficient taking into account the thermal emissivity 
(0 < E <  l), (T is the Stefan-Boltzmann constant. 
the quantity of 1 w. 
Calculation for W, yields 
Loss of Power to the Ionization and Excitation 
The loss of power to ionization and excitation as the electron beam tra- 
verses the cloud of vaporized matter is estimated from the expression 
where p is the density of matter in the vaporized flow. For our case 
m 
1 .  2kT ’ ( 3 )  
where m is the rate of matter vaporization from the surfece, in g/sec; 
the mass of one molecule, in g; is the loss of power 
over the electron path unit [ 5 ] ;  (I is the incidence angle of the electron beam 
to the surface; ro is the radius of the spot from which vaporization takes 
place; rm, is the distance from the electron gun to the vaporization sur- 
face; p,is the density of matter near the vaporization point. 
M is 
dE/dR = 30 kw cm2/mg 
The required rate of vaporization m was estimated from the condition 
that a gas cloud must be forming at theplace of location of the mass-spectro- 
meter; this gas cloud must have a density assuring the normal operation of the 
device ‘(the range of operation pressures of the mass-analyzer is mm 
Hg) 
Taking into account the Lambert cosine law from the distribution in space 
of particles vaporizing from an ideal surface, the number N, of particles 
entering the mass-spectrometer per unit of time is 
where n is the number of vaporized particles per sec; 
of mass-spectrometer‘s slot; 
porization takes place. 
AS is the useful area 
S is the surface of the hemisphere, where va- 
4 
On the other hand, from the correlation for the number of particles 
of ideal gas permeating an irea of diameter d, at pressure 2 and tempera- 
ture T, we may write for the number N, of particles entering the mass-spec- 
trometer per unit of volume 
where no is the number of particles in 1 cm3; c = d m  
bable velocity of molecules. 
is the most pro- 
Equating N, ( 4 )  and N, (5), we find 2, that is, the number of particles 
vaporizing in 1 sec. 
for R = 30 cm, @ = 4 5 " ,  n = 0.8 - lo1') particles/sec. 
Passing to the vaporized mass for various rocks, we obtain: 
for granite m = 0.75.(10-5 - g/sec, 
for basalt m = 0.75-(10-* - g/sec, 
for dunite m = 0.6 - g/sec 
for chondrite m = 0.6 - g/sec 
(7) 
Utilizing the found values of my from (3) and (2), we obtain the value 
of power loss W, of the electron beam to excitation and ionization. 
stitutes % lo', percent of energy fed. 
It con- 
Loss of Power to Heat Conductivity 
The loss of electron beam power as a consequence of heat conductivity 
of matter was estimated from the general solution of heat conductivity equa- 
tion for the case of heat propagation from a point source in an unbounded 
space [61 
f 
Ti - a2AT = - , T(r ,O)=  0, 
CP. . 
where T(r,t) is the temperature of the point M(x,y,z) at time t; a' = k/cp is 
the thermal conductivity coefficient (for rocks 
specific heat capacity; p is the density of matter; f is the dGnsity of ther- 
mal sources. In our case f = Wob(r - r,), where 6 is a delta-function; W, is 
the power of the electron beam reaching the surface. 
a2 = 0.006) ; c is the 
The solution of the given problem is represented in the form 
x f ( E t r l ,  5,z)dEdrl @dz, 
where G is a func t ion  of p o i n t  sou rce ' s  thermal in f luence  
\z - +(Y - r1I2 + ( 2  - G=( )3esp[ - 
2 T/na2 ( t  - z) 4a2 ( t  - z) 
I n t e g r a t i o n  of (9)  l e a d s  t o  t h e  express ion  
Af te r  s u b s t i t u t i o n  of v a r i a b l e s  
bu t ion  of temperature  t h e  express ion  
4 a 2 ( t  - T), w e  o b t a i n  f o r  t h e  d i s t r i -  
2a if 
1 rz 1 - exP[.- -1 du. WO T ( r ,  t )  = -
nl%.k uz U2 
The temperature  d i s t r i b u t i o n  (12) a l lows us  t o  eva lua te  t h e  energy W 3  
of t h e  e l e c t r o n  beam consumed t o  h e a t  t h e  matter as a consequence of t h e  
h e a t  conduction process:  
The q u a n t i t y  of energy consumed on t h e  vapor i za t ion  and i r r a d i a t i o n  is  - 
rl u 
where 
o r  
2 (f )= -= exp[ - $ I d (  $) is  t h e  i n t e g r a l  of e r r o r s ,  
vn 0 
For t h e  estimate of t h e  q u a n t i t y  (WO - W 3 ) / W o  , w e  s h a l l  s u b s t i t u t e  i n  
p l a c e  of t h e  i n t e g r a l  i n  express ion  (15) 
6 
Bearing 
u n i t  of t i m e  
would have a 
i n  mind t h a t  a volume of matter of r a d i u s  ro evaporates  in a 
, and t h a t  dur ing  t h e  t i m e  t t h e  volume of evapora t ing  matter 
r a d i u s  
- 
r = r,,k 
and t ak ing  t h e  va lue  t = 25 sec (cons ider ing  t h a t  a f t e r  25 seconds t h e  d i s -  
t r i b u t i o n  of temperature  over  t h e  s u r f a c e  fol lows t h e  s a m e  l a w  as does t h e  
d i s t r i b u t i o n  of temperature  from a po in t  sou rce ) ,  w e  o b t a i n  
Crawford brought  up i n  [8] t h e  va lue  of t h e  e f f i c i e n c y  of e l ec t ron -  
thermal process ing  of i r o n ,  say  0.083%, f o r  a power of e l e c t r o n  beam of 90 w. 
Taking i n t o  account t h a t  t h e  h e a t  c o n d u c t i v i t i e s  of m e t a l s  are by two o rde r s  
h ighe r  than  those  rock matter, t h e  eva lua t ion  of t h e  e f f i c i e n c y  of e l ec t ron -  
thermal  vapor i za t ion  of rocks obta ined  by u s ,  i s  no t  i n  con t r ad ic t ion  wi th  
Crawford d a t a .  
Power Consumption t o  Vaporize 
Matter 
To vapor i ze  a s p e c i f i c  q u a n t i t y  m of matter,  determined by u s  i n  (7) 
as t h a t  s p e c i f i c a l l y  r equ i r ed  
is taken)  : 
t h e  necessary  energy W, ( t h e  maximum value  
f o r  g r a n i t e  1200*0.75~10-3  c a l  rz 4.0 w 
b a s a l t  1300*0.7540-3  ca l  GS 4.2  w 
d u n i t e  120000.6 c a l  z 3,O w 
chondr i t e  1100.0.6 c a l  3.0 w. 
(18) 
(1200, 1300, 1200, 1100 c a l / g  being r e s p e c t i v e l y  t h e  s p e c i f i c  h e a t  f o r  t h e  
vapor i za t ion  of g r a n i t e ,  b a s a l t ,  d u n i t e  and chondr i te  [ 7 ] .  
T o t a l  Power of E lec t ron  B e a m  Required 
t o  o b t a i n  a mass-spectrum 
The t o t a l  power of t h e  e l e c t r o n  beam i s  obta ined  by summing up t h e  con- 
sumptions of power on a l l  t h e  above descr ibed  i n t e r a c t i o n  processes  of t h e  
e l e c t r o n  beam wi th  t h e  matter 
(19)  w = WI + w2 + w3 3. w4. 
L e t  u s  estimate i t s  va lue .  From ( 1 7 ) s  (WO - W3>/wO = (MI -!- W,>/wO = 0.08,  
assuming t h a t  W4 = 3.5 w, W, = 1.0 w, w e  o b t a i n  WO = 56 w. 
7 
Since W 
of t h e  energy 
t i o n  is 
- power consumption on t h e  i o n i z a t i o n  - c o n s t i t u t e s  % 
supp l i ed ,  w e  may neg lec t  it and thus  t h e  t o t a l  power consump- 
W = W, 56 w. 
2.  TECHNICAL REQUIREMENTS SET FORTH TO THE 
MASS SPECTROMETER 
The b a s i c  c h a r a c t e r i s t i c s  of t h e  radiofrequency mass-spectrometer 
(MX6407M) manufactured by our  i n d u s t r y ,  are presented i n  t h e  work [ 4 ] .  
I n  o r d e r  t o  e v a l u a t e  t h e  s u i t a b i l i t y  of t h e  device  f o r  t h e  a n a l y s i s  of 
rocks ,  one should examine F igures  2 and 3 .  
l i n e s  i n  t h e  b a s a l t  mass-spectrum i n  t h e  assumption of presence i n  t h e  analy- 
zed beam of atomic and molecular  i o n s  and a l l  p o s s i b l e  d i s s o c i a t i o n  d e b r i s .  
Reference s p e c t r a  of t h e  MX6407 device  are shown i n  Fig.3.  
Fig.2 r e p r e s e n t s  t h e  expected 
Fig.2.  Presumed mass-spectrum of b a s a l t  
It may be  seen  from t h e  f i g u r e s  type-MX6407 r-f  m a s s  spectrometer  can 
be used f o r  a n a l y s i s  of rocks  on t h e  cond i t ion  of widening t h e  r e g i s t e r e d  
band of m a s s  numbers t o  160 amu wi th  r e s o l u t i o n  i n c r e a s e  i n  t h e  r eg ion  of 
average atomic weights  ( 5 0  - 7 5  amu, where t h e r e  is  dens i ty  maximum of spec- 
t r a l  l i n e s )  t o  40 - 60 amu. 
The minimum r e g i s t r a b l e  element conten t  i n  rocks  is  es t imated  from t h e  
p a r t i a l  t h re sho ld  response of t h e  mass-spectrometer ( 3  
It  c o n s t i t u t e s  0.1 - 0.001 % of matter by weight (depending upon t h e  probabi- 
l i t y  of i o n i z a t i o n  of vaporized p a r t i c l e s ) .  
mm Hg by hydrogen) e 
8 
The dynamic range of the device being lo3 - lo4 , it was possible, by 
response cutover, to register not only the elements with small content, but 
also those constituting the bulk of rock mass. 
Fig a 2 
Reference spectrum of gas mixture filling the analyzer 
of MW6407 
C O N C L U S I O N S  
1. The mass-Spectralanalysis of lunar surface matter may be carried 
out with the use of a radiofrequency mass-spectrometer of the type MX6407M 
with extension of the range of registered mass numbers to 190 amu, and in- 
Srease of response in the average atom weight region to 40 - 60. 
of matter in the analyzer chamber may be realized by vaporization of rock’s 
surface material by an electron beam of 60 w. power. The same device may ser- 
ve for measuring the atmosphere of t he  Moon (without inclusion of electron gun? 
The intake 
2.  The fundamental process of energy consumption at electron beam inter 
The useful 
action with the rock is the heat conduction; about 90 to 92 percent of ray 
energy is lost to heating the matter outside thevaTxizedvolume. 
energy consumption to vaporization constitutes 6 to 8 percent. The loss of 
power toJfnization and excitation of molecules of the vaporized matter consti- 
tutes 10 xof energy supplied. The loss of power to ionization and excitation 
of moleculesofvaporized matter (at T = 4000°K) is “1 w. The total power, ne- 
cessary to vaporize the quantity of rock required for mass-spectral analysis 
constitutes 85 to 100 w. 
References follow../.. 
9 
ST -ACH -LS -10755 
R E F E R E N C E S  
[l]. W. H. BENNETT. J. Appl. Phys., 21, 2, 1950. 
[2]. V. G. ISTOMIN. Sb."ISZf' (AES), v. 3, p.98, 1959. 
-
[3]. V. A. PAVLENKO, A. E. RAFAL SON, M. D. SHUTOV. Kosm.Iss1. 1, 2, 287, 1963. 
[ 4 ) .  V. A. PAVLENKO, B. I. ZARKHIN, A. E. RAP& SON, M. E. SLUTSKIY. Ib. 4. 3 ,  
[5]. J. R. YOUNG. Phys. Rev. - 103, No.2, 1956. 
[ 6 ] .  A. N. TIKHONOV, A. A .  SAMARSKIY, Uravneniya matematicheskoy fiziki 
Math.Physics Equations). Izd"NAUKA'', 1966. 
457, 1966. 
171.  L. V. GUREVICH, G. A .  KHACHKURUZOV, ET AL. Termodinamicheskiye svoystna 
individual'nykh vesh(Therm0dynamic Properties of 
individual matters) 1zd.AN SSSR, 1962. 
[8]. WEDENIYE V TEKHNOLOGIYU ELEKTRONNO LUCHEWKH PROTSESSOV, Red.Ol'shansk. 
IIntroduction to Electron Beam Processes' Technology). 
Izd. "Metallurgiya", 1965. 
Manuscript received on 
1 March 1968. 
Contract No.NAS-5-12487 Translated by ANDRE L. BRICHANT 
VOLT INFORMATION SCIENCES, INC. 
1145- 19th St.NW on 10 September 1968 


Estimate of the possibility of conducting mass spectrometric measurements of the matter of lunar surface

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