Imaging slitless spectrometer, a combination of an X ray transmission /or reflection/ grating and image-forming X ray telescope, is capable of obtaining simultaneous spatial and spectral information about celestial X ray sources

Gursky, H.

Zehnpfennig, T.

English

NASA Technical Reports Server

December 1968	 Brief 68-10546 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Imaging Slitless Spectrometer for X-ray Astronomy 
Detector
— 
Grazing- Incidence 
Image-Forming Reft 	 Id 
lu 
Dispersive Comøonent	 Id 
(Transmission Mode) 
Dispersive Component 
(Reflection Mode) 
S	 Incident Radiation 
The problem: 
To obtain simultaneous spatial and spectral data 
from celestial soft x-ray sources. Spectrographic 
instrumentation was needed, which would be well-
suited for work with electromagnetic radiation in the 
wavelength ranges where optical systems with stand-
ard refracting or reflecting components do not func-
tion. For example, in the I to 100 angstrom range, 
slitless refracting spectrometers cannot be used be-
cause of very high absorption in their lenses, and 
because the index of refraction for all materials at 
these wavelengths is very nearly equal to 1.000. Stand-
ard reflecting optics also cannot be used since the 
reflection coefficients at the reflecting angles typical 
of such systems are very small. 
The solution: 
An imaging slitless spectrometer, designed for use 
in x-ray astronomy, which is a combination of an 
x-ray transmission (or reflection) grating and an 
image-forming x-ray telescope. It is capable of obtain-
ing simultaneous spatial and spectral information
about celestial x-ray sources, at relatively high reso-
lution (I minute of arc). The instrument could be 
adapted for use at any wavelength range in the soft 
x-ray spectrum, but is especially suited for the 2A to 
ISA range. 
The instrument has a large collecting-area to 
detector-area ratio, furnishing high-quality spectral 
data.on weak x-ray sources. It is capable of examining 
a source at high angular resolution at all wavelengths 
in a given range simultaneously. Further, it can be 
used in a spectral region where the application of a 
Bragg crystal spectrometer is difficult, because of the 
size of available crystal lattice constants. A Bragg 
spectrometer also cannot easily measure continuous 
spectra. 
How it's done: 
The instrument incorporates a dispersive compo-
nent, a grazing-incidence image-forming reflector, and 
a detector. The dispersive component can be a dif-
fracting crystal or an array of crystals, or a grating 
or array of gratings constructed for optimal optical 
(continued uver(eai) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
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effect in the desired spectral range. The dispersive 
component can be used in the transmission or reflec-
tion mode of operation as indicated in the schematic. 
The grazing-incidence image-forming reflector is a 
metallic system composed of a paraboloid and a con-
focal hyperboloid reflector. The detector can be a pho-
tographic plate with x-ray emulsion, or other suitable 
detecting or recording sensors such as fluorescent 
screens, scintillation crystals, or counters. 
Part of the incident radiation passes through the 
dispersive component undeviated and is imaged at 
lu on the detector surface by the grazing-incidence 
reflector. Another part of the radiation is deviated 
by the dispersive component to areas on the detector 
indicated by Id. The deviation is a function of the 
wavelength; thus, the intensity distribution of the 
deviated rays on the focal surface represents a spec-
trum of the source.
Notes: 
I. Possible applications of the spectrometer include 
the determination of the temperatures, densities, 
and compositions of hot plasmas (above tO °K) 
from the spectral distribution of the x-rays emit-
ted. The instrument may also be used for x-ray 
microanalysis of surfaces and small samples. 
2. Documentation is available from: 
Clearinghouse for Federal Scientific 
and Technical Information 
Springfield, Virginia 22151 
Price S3.00 
Reference: B68-10546 
Patent status: 
No patent action is contemplated by NASA. 
Source: H. Gursky and T. Zehnpfennig 
of American Science and Engineering 
under contract to 
Marshall Space Flight Center 
(M FS- 14309) 
Brief 68-10546	 .	
.	 Category 02


Imaging slitless spectrometer for X-ray astronomy

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