High-precision CTE measurement of hybrid C/SiC composite for cryogenic space telescopes

Abstract

This paper presents highly precise measurements of thermal expansion of a "hybrid" carbon-fiber reinforced silicon carbide composite, HB-Cesic®a trademark of ECM, in the temperature region of ~310 10K. Whilst C/SiC composites have been considered to be promising for the mirrors and other structures of space-borne cryogenic telescopes, the anisotropic thermal expansion has been a potential disadvantage of this material. HB-Cesic® is a newly developed composite using a mixture of different types of chopped, short carbon-fiber, in which one of the important aims of the development was to reduce the anisotropy. The measurements indicate that the anisotropy was much reduced down to 4% as a result of hybridization. The thermal expansion data obtained are presented as functions of temperature using eighth-order polynomials separately for the horizontal (XY-) and vertical (Z-) directions of the fabrication process. The average CTEs and their dispersion in the range 293 10K derived from the data for the XY-and Z-directions were and , respectively. The absolute accuracy and the reproducibility of the present measurements are suggested to be better than and , respectively. The residual anisotropy of the thermal expansion was consistent with our previous speculation regarding carbon-fiber, in which the residual anisotropy tended to lie mainly in the horizontal plane.

CTE homogeneity, isotropy and reproducibility in large parts made of sintered SiC

“…All absolute CTE measurements are made with use of interferometric heads giving quite good accuracy but several laboratories claim some difficulties [5], [6], [7], [8], [9], [10]. For its Zerodur® material, Schott claims improved dilatometric measurements with an accuracy of +/-0.0062 .…”

Thermal expansion coefficient of single-crystal silicon from 7 K to 293 K

“…in semiconductor industry, precision optics or in aerospace applications 1,2 . To enable high accuracy operation many measurement systems use reference material samples as calibration standards.…”

“…Thermal expansion of ultra stable materials at cryogenic temperatures is of increasing scientific interest driven by technological applications [2][3][4][5][6][7] . High accuracy CTE values at cryogenic temperatures are essential e.g.…”

Wideband infrared spectrometer for characterization of transiting exoplanets with space telescopes

“…Though the tip-tilt mirror is a moving part, it is expected to enable more accurate EChO adopts a 1.5m class telescope with spectrometers, and covers the wavelength region of 0. [4][5][6][7][8][9][10][11][12][13][14][15][16] microns (e.g., Tinetti et al 2012). If SPICA will the wideband infrared spectrometer, it will be complementally with these dedicated missions because of difference of stability of the system (available stability/dedicated stability), telescope time (part time of multi-purpose mission/full time) , and the size of the telescope aperture.…”

“…Therefore, next generation space-borne infrared telescopes, for instance, the Space Infrared telescope for Cosmology and Astrophysics (SPICA; e.g., Nakagawa 2010 and its references) and the James Webb Space Telescope (JWST; e.g., Clampin 2008), will be important platforms for such observations because of their large aperture, wide infrared wavelength coverage, capability of observations free from air turbulence, and high stability of optics at cryogenic temperature (Enya et al 2007;2012). With taking these features into consideration, this paper presents a conceptual design for a wideband infrared spectrometer designed specifically for observing transiting exoplanets with space-borne infrared telescopes.…”