scholarly journals Fracture of Be and Its Alloys - Webb Space Telescope Revisited

2021 ◽  
Author(s):  
Muhammad Musaddique Ali Rafique
Keyword(s):  
Near Infrared ◽  
Joint Venture ◽  
Coefficient Of Thermal Expansion ◽  
Infrared Range ◽  
Linear Coefficient ◽  
Space Telescope ◽  
Hexagonal Close Packed ◽  
James Webb Space Telescope ◽  
Layer Deposition ◽  
Slip Planes

NASA/ESA/CSA joint venture James Webb Space Telescope is about to be launched. It is hypothesized to operate in near-infrared range. It is also hypothesized to unveil early star formation, galaxies, and universe due to its orbit, point in orbit and orbital motion. It has been under manufacturing for over 20 years at a staggering cost of 10 billion US dollars (most expensive scientific experiment in history). Beryllium (Be) is chosen to be element for construction of its main mirrors due to its high stiffness, low density, low linear coefficient of thermal expansion (α) in cryogenics and high thermal conductivity. It is followed by gold (Au) layer deposition on its (Be) surface to enhance its sensitivity towards infrared radiation as later is hypothesized to bear superior properties. However, serious mistakes have been made in selecting this material for this application. Owing to its crystal structure (hexagonal close packed (hcp)), slip planes (basal, prismatic and pyramidal) and mechanisms of their activation, Be necessitates easy fracture at cryogenic temperature. It has anisotropic properties and prone to transverse fracture under tensile loading. Furthermore, its ductile to brittle transition temperature is very low making it entirely unsuitable for such an application. It is one of most expensive metals on planet. This study constitutes revisiting these fundamental properties and mechanisms which were entirely ignored during materials selection thus rendering whole project useless.

scholarly journals High Sensitivity Continuous Monitoring of Chloroform Gas by Using Wavelength Modulation Photoacoustic Spectroscopy in the Near-Infrared Range

2021 ◽  
Vol 11 (15) ◽  
pp. 6992
Author(s):  
Tie Zhang ◽  
Yuxin Xing ◽  
Gaoxuan Wang ◽  
Sailing He
Keyword(s):  
Photoacoustic Spectroscopy ◽  
Continuous Monitoring ◽  
Near Infrared ◽  
Resonant Cavity ◽  
High Sensitivity ◽  
Industrial Applications ◽  
Detection Sensitivity ◽  
Infrared Range ◽  
Wavelength Modulation ◽  
Linear Coefficient

An optical system for gaseous chloroform (CHCl3) detection based on wavelength modulation photoacoustic spectroscopy (WMPAS) is proposed for the first time by using a distributed feedback (DFB) laser with a center wavelength of 1683 nm where chloroform has strong and complex absorption peaks. The WMPAS sensor developed possesses the advantages of having a simple structure, high-sensitivity, and direct measurement. A resonant cavity made of stainless steel with a resonant frequency of 6390 Hz was utilized, and eight microphones were located at the middle of the resonator at uniform intervals to collect the sound signal. All of the devices were integrated into an instrument box for practical applications. The performance of the WMPAS sensor was experimentally demonstrated with the measurement of different concentrations of chloroform from 63 to 625 ppm. A linear coefficient R2 of 0.999 and a detection sensitivity of 0.28 ppm with a time period of 20 s were achieved at room temperature (around 20 °C) and atmosphere pressure. Long-time continuous monitoring for a fixed concentration of chloroform gas was carried out to demonstrate the excellent stability of the system. The performance of the system shows great practical value for the detection of chloroform gas in industrial applications.

Detectors for the James Webb Space Telescope near infrared spectrograph (NIRSpec)

2006 ◽  
Author(s):  
Bernard J. Rauscher ◽  
Torsten Böker ◽  
Craig Cabelli ◽  
Guido De Marchi ◽  
Pierre Ferruit ◽  
...  
Keyword(s):  
Near Infrared ◽  
Space Telescope ◽  
James Webb Space Telescope

scholarly journals Maximizing the power of deep extragalactic imaging surveys with the James Webb Space Telescope

2019 ◽  
Vol 486 (3) ◽  
pp. 3087-3104 ◽  
Author(s):  
T W Kemp ◽  
J S Dunlop ◽  
R J McLure ◽  
C Schreiber ◽  
A C Carnall ◽  
...  
Keyword(s):  
Galaxy Evolution ◽  
Parallel Imaging ◽  
Near Infrared ◽  
Infrared Imaging ◽  
Current Knowledge ◽  
Signal To Noise Ratio ◽  
Added Value ◽  
Space Telescope ◽  
James Webb Space Telescope ◽  
The Impact

Abstract We present a new analysis of the potential power of deep, near-infrared, imaging surveys with the James Webb Space Telescope (JWST) to improve our knowledge of galaxy evolution. In this work we properly simulate what can be achieved with realistic survey strategies, and utilize rigorous signal-to-noise ratio calculations to calculate the resulting posterior constraints on the physical properties of galaxies. We explore a broad range of assumed input galaxy types (>20 000 models, including extremely dusty objects) across a wide redshift range (out to z ≃ 12), while at the same time considering a realistic mix of galaxy properties based on our current knowledge of the evolving population (as quantified through the Empirical Galaxy Generator). While our main focus is on imaging surveys with NIRCam, spanning $\lambda _{\mathrm{ obs}} = 0.8\!-\!5.0\, \mu$m, an important goal of this work is to quantify the impact/added-value of: (i) parallel imaging observations with MIRI at longer wavelengths, and (ii) deeper supporting optical/UV imaging with HST (potentially prior to JWST launch) in maximizing the power and robustness of a major extragalactic NIRCam survey. We show that MIRI parallel 7.7-$\mu$m imaging is of most value for better constraining the redshifts and stellar masses of the dustiest (AV > 3) galaxies, while deep B-band imaging (reaching ≃ 28.5 AB mag) with ACS on HST is vital for determining the redshifts of the large numbers of faint/low-mass, z < 5 galaxies that will be detected in a deep JWST NIRCam survey.

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