Stark-broadened emission lines in plasma radiatio

Greig, S. R.

Griem, H. R.

English

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"EZWElUMENTAL AND THEOBETIGAL INVESTIGATION OF 
PLASMA ZZBDLATION" 
CASE F ILE 
Covering ~ e * d  COPY 
March 1969 - August 1969 
Submitted to the 
National Aeronautics and Space Administration 
Washington, D. C. 
By the 
Department of Physics and Astronomy 
University of Wsryland 
College Park, Maryland 
and 
https://ntrs.nasa.gov/search.jsp?R=19700007683 2020-03-12T01:51:02+00:00Z
From a direct comparison of the profiles of the optically thick, 
Stark-broadened emission lines AIX1048 8 and AIX1067 a with those of 
Lyman -a and Lyman -8 ,  we have determined the product of the damping constant 
(for Stark ~roadening) and the oscillator strength for each of the argon 
I lines. Our values are 
and 
- 3 
where N is electron density in cm . 
e 
For our plasma conditions (N = 1.6 t 0.2 x 1017 = 
e 
1.2 + 0.03 eV) this method of measurement is very insensitive to both Ne 
r 
and Te, such that the error on the products (- f) is due almost entirely 
Ne 
to experimental uncertainty in the vacuum ultra-violet intensity measure- 
ments (relative only) and to uncertainty in the calculated values of the 
broadening constants for the hydrogen Lyman lines. 
The truncated profiles of the lines L and L were also used 
C1 B 
to measure temperature. From the half-widths of these lines we determined 
the hydrogen ground state density. Then, using the measured electron density 
(from the half-width of H ) and applying the Saha equation we deduced a B 
temperature 
As anticipated this temperature which relies only on relative intensity 
measurements, agrees very well with the temperatue determined from the 
visible argon lines A1 h 6965 2 and AII h 4806 2 ,  
kT (Argon visible) = 1 - 2  t 0.03 e V .  
e 
2 
I. 2 ,  
Visible and Ultra-Violet Lines 
A re-analysis of our measurements on the broadening of the 
neutral helium lines X 3889 8 and X 5016 2, has shown that there is very 
good agreement between measured and calculated values for both the width 
and shift of each of these lines,2 provided that for the line A 5016 8 
we allow for Debye shielding. In this re-analysis numerical fitting 
techniques were used and proper allowance was made for the interference. 
of the line He1 A 4922 with H ,which was used to measure electron density. B 
We have also observed emission in the forbidden line He1 X 5042 8 ( 2 ' s  - 3'D) 
in these measurements. 
Using a 2m grazing incidence monochromator we have recorded 
profiles of the ionized helium resonance line He11 X 304 a in the emission 
from our T-tube source. This line is very optically thick under our 
plasma conditions (N 1 3 x 1017 ~ m - ~ ,  kTe 2. 4eV) and shows the typical e 
truncated profile. The half-width of the profile (AX % 0.4 a appears to 1/ 2 
be in agreement with the calculated broadening caused by ions and electrons 
3 in the plasma and the significant blue shift (1 0.0 5 + 0.01 8) can be 
explained in terms of the polarization of the plasma in the vicinity of a 
positively charged emitter, 4 
Little progress has been possible on the measurement of the 
broadening of argon ion lines because of the unavailability of the graduate 
research assistant caused by the present Draft Regulations. 
1. 3. Collective ~remsstrah1i.n~' from Collision Free 
Shock Waves 
Using our new O-pinch apparatus with hydrogen as the filling 
gas we have found strong emission of far infra-red radiation (0.1 mm < X < 4mm). 
This emission begins a little before the time the gradient of B - the magnetic 
piston, is steepest and gets more intense as the initial filling pressure 
is decreased, These observations indicate that the emission occurs in the 
current layer and is probably not caused by collisions. The electron density 
I ?  -3 
of the preheater plasma was Q 3 x 1 0 - I  cm at the time the main bank is 
3 
fired and there was an anti-parallel bias field of about 400 gauss. 
Initial attempts to obtain the spectral distribution of this 
far infra-red radiation suggest that there may be a peak at X % 0.7 m, 
but this is very dependent on the relative sensitivity of the far infra- 
red system which unfortunately has a strong wavelength dependence. 
11. THEORETICAL PROGRAM 
The calculations of ionized helium lines in the Lyman, Balmer 
and Paschen series were continued and and are now almost completed. A 
journal paper on these lines is being written by Dr. Kepple, and the 
tables obtained will be made available as a technical report. 
In collaboration with Dr. Bely from Nice Observatory we 
carried through the very first fully quantum-mechanical calculation of 
any impact broadened line (the MgII resonance line). A paper reporting 
on the results will appear shortly in Physical Review. This paper discusses 
also the question which of the various classical-path approximations are 
reasonably good, which not. 
4 
References : 
1, "Measurement of the S t a r k  broadening for the Neutral Resonance lines 
A1 1048 8 and A 1  1067 at!, G .  A.  'Moo-Young, J. K. Greig and H. R, 
Griem. To b e  p r e s e n t e d  a t  A.P.S. - D.P.P. meet ing November 1969. 
2. "On t h e  S t a r k  Broadening of Two N e u t r a l  Helium L i n e s  i n  Plasmas",  
J .  R. Greig  and L. A. J o n e s ,  submi t t ed  t o  P h y s i c a l  Review (October 
1969) .  
3.  "Measurement of t h e  S t a r k  Broadening of He11 Lyman-Alpha", L. A.  
J o n e s ,  T. Oda and J. R. Greig .  To be  p r e s e n t e d  a t  A.P.S. - D.P.P. 
meet ing November 1969. 
4. " Observa t ion  of a Plasma P o l a r i z a t i o n  S h i f t  f o r  t h e  Resonance L ine  
O f  I o n i z e d  ~ e l i u m " ,  J .  R. G r e i g ,  H. R. G r i e m ,  L .  A. Jones  and T .  Oda. 
To B e  submi t t ed  t o  P h y s i c a l  Review L e t t e r s  (October 1969) .  


Experimental and theoretical investigation of plasma radiation Semi-annual status report, Mar. - Aug. 1969

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