Space-borne optical frequency references based on spectroscopy of atomic vapors may serve as an integral part of compact optical atomic clocks, which can advance global navigation systems or can be utilized for earth observation missions as part of laser systems for cold atom gradiometers. Nanosatellites offer low launch costs, multiple deployment opportunities, and short payload development cycles, enabling rapid maturation of optical frequency references and underlying key technologies in space. Toward an in-orbit demonstration on such a platform, we have developed a CubeSat-compatible prototype of an optical frequency reference based on the D2 transition in rubidium. A frequency instability of
1.7
×
10
−
12
at 1 s averaging time is achieved. The optical module occupies a volume of
35
c
m
3
, weighs 73 g, and consumes 780 mW of power.
We present a user-friendly and versatile tool for laser frequency stabilization. Its main focus is spectroscopy locking, but the software is suitable for lock-in techniques in general as well as bare proportional–integral–derivative (PID) operation. Besides allowing for sinusoidal modulation (up to 50 MHz), triangular ramp scanning, in-phase and quadrature demodulation (1–5 f), infinite impulse response, and PID filtering, Linien features two different algorithms for automatic lock point selection; one of them performs time-critical tasks completely on field-programmable gate arrays. Linien is capable of autonomously optimizing spectroscopy parameters by means of machine learning and can measure the error signal’s power spectral density. The software is built in a modular way, providing both a graphical user interface as well as a Python scripting interface. It is based on the RedPitaya STEMLab platform but may be ported to different systems.
Compactness, robustness and autonomy of optical frequency references are prerequisites for reliable operation in mobile systems, on ground as well as in space. We present a standalone plug and play optical frequency reference device based on frequency modulation spectroscopy of the D2-transition in rubidium at 780 nm. After a single button press the hand-sized laser module, based on the micro-integrated laser-optical bench described in [J. Opt. Soc. Am. B 38, 1885 (2021)10.1364/JOSAB.420875], works fully autonomous and generates 6 mW of frequency stabilized light with a relative frequency instability of 1.4×10−12 at 1 s and below 10−11 at 105 s averaging time. We describe the design of the device, investigate the thermal characteristics affecting the output frequency and demonstrate short-term frequency stability improvement by a Bayesian optimizer varying the modulation parameters.
High temperatures within the primary vane of a gas turbine system have been known to cause turbine blade failure due to high temperatures and stark, unexpected non-uniformities in the expelled gaseous product. Thus, to aid in the prevention of these costly and potentially dangerous failures, this study aimed to find ways to experimentally decrease temperature spontaneity at the nozzle by employing a blunt object and guide vanes to the common dilution hole approach to cool the primary air in a gas turbine simulator. Previous computational studies outlining these scenarios were experimentally produced, and verified the initial hypothesis that adding a blunt body and guide vanes, separately, to the simulator would provide more uniform exit temperature conditions. However, it was also found that, while similar in mixture capability, the guide vane approach appears to be the more feasible option due to a smaller resulting pressure drop and ease of implementation.
Nomenclature
A= cross sectional area W = tangential velocity ds = differential surface area ρ = density f = mixture fraction ζ = uncertainty ṁ = mass flow rate σ = standard deviation T adb = adiabatic temperature T ann = annular temperature T jet = jet temperature T pri = primary temperature R = swirler radius U = axial velocity 1 Professor,
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