HAL Id: jpa-00219385
https://hal.archives-ouvertes.fr/jpa-00219385
Submitted on 1 Jan 1979
HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.
L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
THE USE OF GAS DISCHARGES AS ULTRAVIOLET RADIOMETRIC STANDARDS
W. Ott, J. Bridges, J. Klose
To cite this version:
W. Ott, J. Bridges, J. Klose. THE USE OF GAS DISCHARGES AS ULTRAVIOLET RA- DIOMETRIC STANDARDS. Journal de Physique Colloques, 1979, 40 (C7), pp.C7-803-C7-804.
�10.1051/jphyscol:19797387�. �jpa-00219385�
JOURNAL DE PHYSIQUE CoZZoque C7, suppldment au n07, Tome 40, JuiZZet 1979, page C7- 803
THE USE OF GAS DISCHARGES AS LLTRAVIOLET RADIOMETRIC STANDARDS
W.R. Ott, J.M. Bridges and J.Z. Klose.
NationaZ Bureau o f Standards, Atomic and Plasma Radiation Division, Washington, D.C. 20234.
This paper describes the various gas dis- charges used currently o r under development a t NBS as radiometric standards i n the spectral region 110-350
nm.
Some review material i s included in addition t o new measurements i n order t o provide a balanced overview of the NBS UV radiometry program. The application of such sources as a diagnostic will also be described f o r a few typical experiments, e.g. tokomak impurity concentration determinations, dense plasma temperature determinations, photochemical r a t e coefficient measureme,nts, and uv spectro- radiometer efficiency measurements aboard space shuttle.Six radiation sources have been investigated:
1 ) a hydrogen wall-stabilized arc; 2) a blackbody- 1 imi ted 1 ine thermal a r c plasma; 3) an argon
"mini-arc"; 4 ) an argon "maxi-arc"; 5 ) a deuterium lamp; 6 ) a krypton dimer r f discharge lamp.
Determinations of both the spectral radiance (W cm-2nm-1 sr-' ) and t h e spectral irradiance ( W have been undertaken.
The use of a hydrogen arc plasma as an absolute primary standard of uv spectral radiance has been described previously.1 The o p t i c a l l y thin Balmer continuum radiation between 360 nm and about 130 nm can be calculated t o within an uncertainty of l e s s than 3%. When operated a t electron temperatures such t h a t the radiance reaches the Larenz maximum (about T = 20 O O O K ) ,
the uncertainties in the calculation are minimized since the radiance i s not sensitive t o the
plasma diagnostics and any deviations from LTE are expected t o be minimized. The spectral irradiance of the hydrogen a r c has now been measured f o r the f i r s t time. I t s potential use a s a spectral irradiance standard will be d i s - cussed.
The blackbody 1 ine radiation source i s similar t o the one described by Boldt and 2
others. Contaminants of N2, C o p , and H2 are added t o a thermal argon a r c plasma and the NI and CI atomic resonance l i n e s become o p t i c a l l y thick and in f a c t blackbody limited. The spectral radiance a t the l i n e centers i s a function of temperature and i s given by the Planck radiation law. I t i s used as a primary standard of spectral radiance i n the spectral region 100-200 nm.
A t NBS the hydrogen arc and the blackbody l i n e arc a r e used as primary standards t o c a l i - brate the radiance of recently developed secondary standards such as the argon "mini-arc" and the
"maxi-arc" which a r e e a s i e r t o operate and a r e more portable. For example the mini-arc3 i s 10 cm long, needs no b a l l a s t r e s i s t o r , and can be operated w i t h a 1 kW, 10 kg dc power supply.
The spectral radiance and irradiance of both the mini-arc and the maxi-arc have been measured and a r e available from NBS as secondary standards in the wavelength region 110-330 nm with uncertain-
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19797387
t i e s within 5-20% depending on wavelength.
Their c h a r a c t e r i s t i c s as standards have been extensively studied and will be described.
Commercially available 1 ow pressure deuterium lamps have been used f o r a number of years as secondary standards of spectral radiance i n t h e region 165-350 nm. Measurements a r e now extended t o shorter wavelengths (115 nm) where the many- l i n e Lyman band dominates the spectrum. Our measurements show t h a t the blended l i n e s form a pseudo-continuum below 165 nm when a low re- solution spectroradiometer is used f o r detection.
The s e n s i t i v i t y of the spectral irradiance t o t h e bandpass has been determined. The lamps were enclosed in a vacuum system; no change was observed i n the spectral irradiance when the system was evacuated. This has special implications concerning space applications and f o r applications in which one desires t h a t the radiometric standard be placed inside a vacuum system.
A commercially available krypton dimer radiation source was also tested a s a potential standard of radiance and irradiance in the spectral region 125-170 nm. I t s reproducibility and aging c h a r a c t e r i s t i c s , both inside a vacuum system and a t atmospheric pressure, have been measured. Operation of the lamp with other noble gases which emit continuum radiation i n other wavelength bands i s being investigated.
In summary, t h i s Family of gas discharges provides convenient and r e l i a b l e laboratory source standards in the 110-350 nm spectral region. Calibrations of both spectral radiance and spectral irradiance are made with sources whose i n t e n s i t y levels cover a range of almost 6
orders of magnitude, thus allowing a variety of radiometric appl ications.
References
1. W . R. O t t , K. Behringer, and 6. Gieres,
Appl
.
Opt.14,
21 21 (1 975).2. G. Boldt, Space Sci. Rev.
11,
728 (1970).3. J . M. Bridges and W. R. O t t , Appl. Opt.
16, 367 (1977).
