Radio frequency and microwave spectroscopy of magnetized plasma

Crownfield, F. R., Jr.

English

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F I N A L  R E P O R T  
On Research Supported by NASA Grant NeG 106-61 
NASA CR71189 
RADIO FRE2lIENCY AND MICROWAVE SPECTRC.SCQPY CF MAGNEJ'IZED PLASMAS 
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N66-19653 
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F r e d e r i c  R .  C r o w n f i e l d ,  Jr. 
Plasma P h y s i c s  Laboratory 
Department of P h y s i c s  
C~Ilege nf W i l l i a m  and Mary 
Wllliam8bWg, Virginia 
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1 January 1066 
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ABSI’RACT 
This report summarizes the original propoaed reeearch, the 
reports prepared, tine expenditures, and the  results of research 
performed under NASA Research Grant NeG 106-61. 
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..- 
Gur o r i g i n a l  proposal was t o  i n v e s t i g a t e  Faraday E f f e c t  
and/or e l ec t ron  sp in  resonance (ESR) In  a gas discharge.  We 
intended t o  u s e  a Penning Ionizat ion Gauge t o  produce t h e  d i s -  
charge for t h e  ESR experiments, bu t  prel iminary inves t iga t ions  
led t o  t h e  discovery of  coherent o s c i l l a t i o n s  In t h e  very high 
frequency (VHF) range. T h e  largest e f f o r t  has  been devoted t o  
an inves t iga t ion  of t hese  o s c i l l a t i o n s  and related phenomena. 
The Faraday Effec t  was inves t iga ted  in a c y l i n d r i c a l  cav i ty ,  i n  
order  t o  avoid d i f f i c u l t i e s  with end e f f e c t s .  
t h i s  work severa l  FORTRAN programs were developed which may be 
of use i n  o the r  areas. The details of t h i s  work are covered i n  
s eve ra l  r e p o r t s  listed i n  the  next s ec t ion  of t h i s  r epor t ,  and 
w e  w i l l  only summarize t h e  work here. 
In t h e  process of 
TECHNICAL REPORTS SUBMITTED, AND MEETING PAPZRS PRESENTED 
The following t echn ica l  r e p o r t s  have been prepared: 
1: V I P  O s c i l l a t i o n s  i n  a Penninv Gauge, by R. N. Dennis, Jr. 
(M. A. Thes is ) ,  June 1962. 
@o. 2: Blmodal-Cavity Measurement of t h e  Microwave Faraday Effec t  
i n  a Gaseous Mametoplasma, by M. T. Raiford (M. A. Thes i s ) ,  
June 1963. 
No. 3: Nonlinear Response of an O s c i l l a t i n g  Discharge t o  Applied 
V e r y  High Frequency Signals, by D. B. Raiford (M.A. T h e s i s )  
J u l y  1965. 
No, 4: Aguaratus  f o r  Recording C s c i l l a t i o n  P rope r t i e s  of a Penning 
I cn iza t i cn  Cartge at  V e r y  High Frequencies,  by M. D. H o l t  & 
D. B. Raiford,  June 1965. 
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In  add i t ion ,  t h e  following mathematical r e p o r t s  have been 
prepared: 
No. 2 A Generalized Least-Squares Computer Program f o r  t h e  IBM 
- 1620, by M. D. Holt and D. B, Raiford,  June 1964. J 
#‘z: L i s t i n n  of FORTRAN Programs Developed i n  Connection with 
NASA Grant No .  NsC 106-61, by F. R, Crownfield, Jr., M. D. 
H o l t  and D. B, Raiford. 
The following meeting papers were presented; i n  t h e  case of 
t h e  two international meetings t h e  f u l l  papers have appeared or 
W i l l  appear i n  t h e  Proceedings. In t h e  o ther  cases  (American 
Physical Society and Virginia Academy of Science) t h e  r e fe rence  
i n  each case i s  to  t h e  published a b s t r a c t .  Copies of t h e s e  have 
been t ransmit ted t o  NASA except when t h e  t a l k  w a s  a presenta t ion  
of t h e  results included i n  a t echn ica l  of mathematical r epor t .  
VHF O s c i l l a t i o n s  i n  a Penning Gauge, by R .  N .  Dennis, Jr.,  Vi rg in i a  
Journal of Science 13, 226 (1962) 
of Science) 
(1962 meeting of Virginia Academy 
VHF O s c i l l a t i o n s  and AnomoLous Volt-Ampere C h a r a c t e r i s t i c  of a 
Penning Gauge, by F . R. Crownfield, Jr . and R. N. Dennis, Jr., 
B u l l .  Am, Php, SOC. 2,  641 (1982) (F i f t een th  Annual Gaseous 
Electronics Conference) 
Microwave Cavi ty  Measurement of t h e  Faraday Effect  i n  a Magneto- 
plasma, by F, R. Crownfield and M. T. Raiford,  Bul l .  Am. Phys. 
Soc. ti, 298 
Physical  Society). 
(1963), (1963 Washington Meeting of t h e  American 
Microwave Cavi ty  Measurements of t h e  Faraday Effect i n  a Mae;- 
net ized  Gaseous Plasma, by M. T. Raiford,  Va.  Journal of Science 
14, 192 (1963) (1963 V a .  Academy of Science Meeting). 
Plasma Osc i l l a t ions  and Conduction Phenomena i n  a Penning Gauge, 
by F. R.  Crownfield, Jr., V a ,  Journal of Science 3.4, 184 (1963) 
(1963 Va.  Academy of Science Meeting). 
-3- 
Microwave Cavity Nieasurement of t h e  Faraday Ef fec t  i n  a Mameto_- 
plasma, by M. T. Raiford and F. R .  Crownfield, Jr., Proc. V I  In t .  
Conf. on Ionizat ion Phenomena i n  Gases, Vol. 111, 167 (SERMA, P a r i s  
1964). 
I n t e r a c t i o n  of Plasma Osc i l l a t ions  with Conduction i n  a Penning 
Gauge, by F. R.  Crownfield, Jr., Proc. V I  I n t .  Conf. on Ionizat ion 
Phenomena i n  Gases, V o l .  11, 451 (SERMA, P a r i s  1964). 
AGeneral lzed Least-Squares Computer Program by M1 D. H o l t  and D. B. 
Ralford,  Va.  Journal of Science l5, 275 (1964) (1964 Meeting of t h e  
Virg in ia  Academy of Science) 
Applicat ion of a Generalized Least-Square Proerram t o  t h e  Analysis of 
Wave and O s c i l l a t i o n  Proper t ies  of a G a s  Discharge by D. B. Raiford 
and M. D. Holt, V a .  Journa l  of Science 15, 282 (1964) (1964 Meeting 
of t h e  V a .  Academy of Science) 
C s c l l l a t i o n  P rope r t i e s  of a Penning Ioniza t ion  Gauge a t  V e r y  High 
Frequencies by M. D. H o l t ,  D. B. Ra i ford ,  and F. R. Crownfield, Jr., 
B u l l .  Am. Phys. SOC. l0, 476 (1965) (1965 Washington Meeting of t h e  
American Physical  Society) .  
Per turba t ion  of t h e  DC Current Drawn by a Penning Ioniza t ion  GauKc 
by Applied V e r y  Hiah Freauencv S igna l s  by D. B. Raiford,  M. D. H o l t ,  
and F. R .  Crownfield, Jr. Bull. Am. Phys. SOC. l0, 477 (1965) (1965 
Washington Meeting of t h e  American Physical  Society) .  
Per turba t ion  of t h e  DC Current i n  a Penning Ioniza t ion  Gauge Discharge 
by Applied VHF S igna l s  by D. B. Raiford and M. D. Ilolt. ~ V a .  Journal  
of Science Y.6, 316 (1965) (1965 Meeting of t h e  Virg in ia  Academy of 
Science) . 
O s c i l l a t i o n  P rope r t i e s  of a Penning Gauge by M. D. H o l t  and D. F. 
Raiford,  V a .  Journa l  of Science l6, 317 (1965) (1965 Moeting of t h e  
V a .  Academy of Science).  
on-Llmear Response of a Penning Ioniza t ion  Gauge Discharce t o  Applied 
V e r y  High Frequency E i g n a s  by F rede r i c  R. Crownfield, Jr ,  , Dzciel  
Rai ford ,  and David H o l t .  Proc. V I 1  In t e rna t iona l  Conference on Phenomena 
i n  Ionized Gases, Gradevinska Knjiga, Beograd 1965 ( t o  be puPlished). 
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CCNCLUSILNS 
. .-- 
As a r e s u l t  of the  research performed under t h e  g ran t ,  four  
s t u d e n t s  (Dennis, Maurice Raiford,  Hol t ,  and Dan Raiford)  have 
received Master 's  degrees i n  Physics and t h r e e  papers have been 
published i n  the  proceedings of i n t e r n a t i o n a l  conferences. 
n i c a l  results are summarized below. 
Tech- 
V e r y  high frequency o s c i l l a t i o n s  have been discovered which 
i n t e r a c t  with conduction i n  t h e  Penning Ioniza t ion  Gauge. These 
o s c i l l a t i o n s  seem t o  be assoc ia ted  with t h e  i n t e r a c t i o n  between 
longi tudina l  e l ec t ron  motion and the  slow-wave modes of a plasma- 
f i l l e d  conducting cy l inder .  T h i s  suggests  t h a t  one might approach 
problems of t h e  s t a b i l i t y  of self -consis tent  s t a t iona ry  so lu t ions  
of t h e  non-linear Vlasov equation i n  a similar way: one should 
look f o r  cases where t h e  frequency of t h e  wave modes i n  a plasma 
correspond t o  t h e  o s c i l l a t i o n s  of e l e c t r o n s  i n  t h e  se l f -cons is ten t  
p o t e n t i a l  d i s t r i b u t i o n .  When these  f requencies  agree,  one may 
expect i n s t a b i l i t y  . 
The o s c i l l a t i o n s  in t h e  Penning Gauge also have been found t o  
i n t e r a c t  with e x t e r n a l  VHF s igna ia  appl ied  t o  the mzde, c a i i s l ~ , ~  
small changes i n  t h e  direct cur ren t  drawn by t h e  discharge.  
add i t ion ,  w e  observed that t h e  cur ren t  drawn by t h e  gauge was not  
a l i n e a r  func t ion  of gas  pressure when o s c i l l a t i o n s  occur. 
In 
In  connection with t h i s  research ,  a recording sys tem was devel- 
oped t o  allow rap id  ( r a the r  than point-by-point) recording of oscil-  
l a t i o n  frequencies ,  amplitudes,  and s p e c t r a  simultaneously ~ 5 t h  
cur ren t  and pressure.  
The Faraday Effec t  has been observed i n  a TE microaace c:wi ty  
with a coaxia l ly  loca ted  p lasma,  and a general ized least-squares  pro- 
111 
gram developed w h i c h  allowed ue to show t h a t  o u r  o r i g i n a l  s impl i f ied  
-6 - 
. 
4, 
theory was inadequate. This work was then suspehded, and was 
later resumed under grant N s G  567 D. 
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Radio frequency and microwave spectroscopy of magnetized plasmas Final report

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