Parabolic Reflector Research Articles

Spatiotemporal walk-off and improved focusing of plasma THz sources

High-field THz sources with peak field strengths exceeding MV/cm are essential for nonlinear THz spectroscopy and coherent control of matter on ultrafast time scales. Two-color femtosecond laser plasma sources employing long filamentation have been reported as providing single-cycle, >MV/cm fields, with multi-decade spanning bandwidth and polarization control, making them promising sources for such experiments. In this work, we report the observation of spatiotemporal spreading of the THz pulse when standard off-axis parabolic mirrors are used for collection and focusing of long filament plasma-based THz pulses. This produces a flying focus for THz light, with the axial focal region propagating at a velocity of 1/3 the speed of light. The THz emission is then subsequently spread over a temporal width of ∼10 ps, approximately 100 times the THz pulse duration detected by electro-optic sampling at any single point along the focus. The consequences of this non-ideal focusing are a potential and drastic overestimation of the peak THz electric field based on energy measurements, as well as significant phase noise arising from beam pointing fluctuations. We show that this spatiotemporal spreading can be minimized using a simple axicon lens that perfectly collimates the extended filament source, resulting in improved spatial and temporal focusing of the THz pulse.

Single-frame fringe pattern analysis with synchronous phase-shifting based on polarization interferometry phase measuring deflectometry (PIPMD)

In the domain of phase measuring deflectometry (or fringe projection profilometry), utilizing only a single-frame fringe pattern to achieve high-precision three-dimensional reconstruction has emerged as a focal point of ongoing research. To achieve four-step phase-shifting demodulation from a single-frame fringe pattern, this paper proposes a Polarization Interferometry Phase Measuring Deflectometry (PIPMD). This method primarily relies on a Michelson polarization interferometry structure to produce projected polarization interference fringes, which are then captured by a polarization camera as modulated single-frame deformed fringe patterns. These single-frame fringe patterns enable pixelated four-step phase shifting with adjacent 2 × 2 pixel units. To validate the proposed method, a series of experiments has been conducted, including surface shape detection of a concave spherical mirror and an off-axis parabolic mirror, as well as dynamic deformation measurements of a deformable mirror. All experimental results consistently indicate that the polarization interference-based fringe projection technique can achieve synchronized phase-shifting demodulation of single-frame fringe patterns, thereby facilitating high-precision reconstruction of the fringe patterns captured in a single frame. This synchronous phase-shifting technique can overcome the influence of air disturbances in traditional four-step phase-shifting methods, thereby enhancing the accuracy of phase demodulation. Additionally, this polarization interference-based Phase Measuring Deflectometry exhibits promising application prospects in dynamic measurements.

A mathematical model to generate a light reflector that produces a uniform irradiance distribution from a point light source

In this work, we present the development of a mathematical model profile for a light reflector that generates a uniform irradiance distribution from a point light source on a flat region at a fixed distance. The mathematical model is based on the theory of geometric optics, particularly the concepts of reflection, ray tracing, point light sources, spherical caps, and elliptical curvatures. Numerical simulations illustrate that the mathematical model is adequate because its geometry produces a uniform irradiance from a point source. This model allows manufacturers reflectors smaller than parabolic reflectors, which are currently used to generate this type of uniform light irradiance distribution, allowing these devices to be used in smaller optoelectronic systems.

Optimal design, construction and evaluation of symmetric compound parabolic concentrator integrated with photovoltaics system (CPC-PV)

To enhance the production and efficiency of photovoltaic systems, research has been conducted on various techniques including the use of compound parabolic reflectors (CPCs). A mathematical model is developed using the governing solar radiation and CPC geometry equations to optimize the geometrical parameters required for the experimental setup. The optimal values for the half acceptance angle and tilt angle were found to be 25° and 35°, respectively. Based on these optimal parameters, a laboratory setup was fabricated and evaluated. To compare the performance of our CPC-based system, three different panels constructed: a simple PV panel without a concentrator, a PV panel with a concentrator but without cooling (CPC-PV), and a PV panel with a concentrator and water cooling (CPC-PVT). Results showed that the use of a CPC with a concentration ratio of 1.7 in both modes, with and without cooling, led to a 10 % and 20 % increase in the output power, respectively, compared to the simple PV panel. In summary, this study demonstrates the effectiveness of using a CPC in enhancing the production and efficiency of photovoltaic systems. The mathematical model developed in this research can be utilized for optimizing the geometrical parameters required for the design of CPC-based systems. The experimental results obtained from this study indicate that the use of a CPC with water cooling can significantly improve the energy output of the photovoltaic system. These findings can aid in the design of cost-effective and efficient photovoltaic systems.

A comprehensive review on integration of receiver geometries, nanofluids, and efficient thermal energy storage for solar parabolic dish collectors

A comprehensive review on integration of receiver geometries, nanofluids, and efficient thermal energy storage for solar parabolic dish collectors

High precision wavefront correction method in interferometer testing

A wavefront correction method is proposed for high-precision optic surfacing, addressing the discrepancy between wavefront and real surface errors in Fizeau interferometer testing. We believe this to be a proposed novel method that encompasses optical surface function parameters fitting, lateral distortion correction, misalignment error removal, and sag surface error calculation. The method's error has been thoroughly analyzed, including aspects of function parameters fitting, ray tracing, and interpolation. The effectiveness of the method was demonstrated by correcting the wavefront of an off-axis parabolic mirror in null testing configurations, significantly reducing artificially created annular errors and improving off-axis direction errors from 0.23λ to 0.05λ (λ=632.8 nm), with the PV of aspheric departures exceeding 8.5 mm.

Inclusivity of thermal performance parameters for evaluation of solar cookers and the necessity of uniformity in the appraisal using generalized test procedure for different designs

Solar cookers play a vital role in decentralized energy solutions. Therefore, their appropriate rating is essential. The present work reviews and emphasizes the usefulness of thermal performance parameters (TPPs) for assessing solar cookers, such as box type, parabolic dish, panel type, Fresnel lens-based, and their hybrids. Although the TPPs are extensively used for testing solar cookers, several research studies depicted ambiguities, non-uniformities, and inconsistencies in their use. Interestingly, Cooker Opto-Thermal Ratio (COR) is one of the most generalized and, hence, useful TPP for the optical and thermal performance evaluation and rating/grading of multiple designs of solar cookers. In view of non-uniformities and inconsistencies found in determining TPPs, current work provides crucial insights into the existing TPPs, including COR, corresponding test standards/protocols, and quantification of test load(s) for solar cookers. Also, this work justifies the appropriate use of the different TPPs for solar cookers, and the usefulness and robustness of COR determined using linear regression fit of experimental data and derivate COR-dependent objective parameters. Finally, it includes insightful information for researchers, designers, and manufacturers on the future research pathways based on COR and corresponding test procedure and provide useful visions to avoid its deceptive, inconsistent, and inappropriate use.

Near 2π solid angle fluorescence collection for laser-induced breakdown spectroscopy.

Detecting heavy metal and radioactive elements distributed in the environment and human body is crucial for life and environmental safety. A lens with a high numerical aperture (NA) is used in laser-induced breakdown spectroscopy to collect the plasma fluorescence as much as possible and improve the limit of detection. However, even a lens with NA up to 0.6, only the fluorescence in a solid angle of 0.4π can be collected. In this work, a novel, to our knowledge, fluorescence collecting scheme composed of a parabolic mirror and a lens is proposed which can collect the plasma fluorescence in a solid angle of ∼1.4π for an opaque material and ∼1.9π for a transparent material. Simulation results show that for opaque samples, this method can improve the fluorescence collection ability by 3.8 times compared to a single lens (NA = 0.5) collection scheme, and for transparent samples 4.5 times may be achieved. In experiments, a 2.8-fold enhancement in the fluorescence collection ability is demonstrated, and the signal-to-noise ratio is increased by 2.5 times for opaque samples.

Distillation of treated dairy effluent using integrated solar dish collector and solar still: A case study of distillate output enhancement

A solar thermal distillation system was designed to be compatible with electrically powered conventional laboratory distillation assembly. Its efficacy was checked in converting the treated dairy effluent into distilled water. The experimental setup comprised of a solar parabolic dish collector (aperture area 4.15 m2) and a solar still (basin area 1 m2) and was designed such that both can be used separately or in the combination. The study was conducted during March – June 2023. The solar dish collector was tested with two receivers with different bottom materials viz., stainless-steel and brass, thereby an average daily yield of 6.5 litres and 6.9 litres were obtained for both receivers, respectively. Simultaneously, solar still produced 2.08 litres of water individually per day. Thus, the highest yield obtained for whole setup was 8.9 litres per day considering individual performances of both the systems. The daily average thermal efficiency of dish collector for was found 65.59 % with steel receiver and 63.33 % with brass receiver. Similarly, thermal efficiency of solar still was 35 %. The quality of distillate was analysed on 10 parameters viz., pH, TDS, TSS, COD, BOD, Oil & Grease, SPC, Coliform count, electrical conductivity, and chloride content which showed promising results.

Optimized Schlieren imaging for real-time visualization of high-intensity focused ultrasound waves.

This article presents an low-cost experimental setup for visualizing refraction anomalies caused by high-intensity focused ultrasound (HIFU). The technique is based on Schlieren imaging, commonly used to visualize temperature and pressure differences in a medium. With this setup, double images of the Schlieren or their shadows to be investigated occur, so that the experimental setup is modified to avoid these double image artifacts. The optical setup mainly consists of a point light source, a parabolic mirror, and a camera. Birefringence artifacts are avoided by placing the point light source at a certain vertical distance to the camera, so that the light beam passes through the medium only once. The soundfield is generated by a HIFU transducer in a water tank placed in the beam path of the optical setup. The experimental setup is capable of capturing Schlieren or shadow images. These images show the soundfield without disturbing double images and enable further analysis and qualitative assessment of the soundfield. The presented setup provides a reliable and efficient method for visualizing refraction anomalies caused by the sonic field of a HIFU transducer and allows for accurate depiction of the refraction anomalies. The double images that usually occur are avoided.

Energy optimization of parabolic dish solar concentrator coupled to organic Rankine cycle: Experimental and analytical investigation of cavity receiver design and covering effects

Concentrated solar power (CSP) systems offer a promising solution for sustainable energy, but achieving high and stable efficiency requires careful design optimization. This study evaluated the overall performance of a parabolic dish solar concentrator coupled to an Organic Rankine Cycle (ORC) system through experimental and analytical assessments. The research examined the impact of cavity receiver shape (cylindrical vs. spherical) and the use of a glass cover on thermal efficiency. Additionally, the effectiveness of a cone structure to reduce spillage losses and improve optical efficiency was explored. Testing showed a significant improvement in system performance, with an increase from 75 % for the open cavity to 90 % for the sealed cavity equipped with the cone structure (15 % increase). This highlights the importance of receiver design in reducing heat loss. To further optimize the system, a numerical model was developed and validated against experimental measurements. The simulation demonstrated that the overall system performance is significantly influenced by the water outlet temperature from the cavity receiver and the pressure drop within it. The model suggests that overall performance could be enhanced from 4.6 % to higher than 6 % by optimizing factors like water mass flow rate, cavity tube diameter, and the selection of a more suitable ORC working fluid (e.g., R245fa instead of R134a).

Influence of geometric design variables on the performance of a novel V-shaped cavity receiver

This study presents a novel cavity receiver for parabolic trough concentrators, incorporating a triangular envelope, a trapezoidal cavity, and a semi-circular flow channel. A total of 5120 designs were examined by tuning the rim angle of parabolic mirrors, the width and angle of the receiver's opening, and the depth of the absorber for different operating flow rates and temperatures. Batch simulations of these designs were automated by coupling newly developed and validated models of Monte Carlo ray tracing and semi-analytical 1-D energy balances in SOLTRACE® and MATLAB® to determine the heat fluxes and surface temperatures of the receiver, respectively. The results show that the rim angle must be reduced to maximize sun rays' interception, and the opening angle has the largest impact on performance. All dimensions must be decreased when operating at low flow rates and high temperatures to avoid excessive thermal losses. This results in maximum energy and exergy efficiencies of 74.7 % and 40.7 %, respectively. When operating at low temperatures and large flow rates, the largest energy and exergy efficiencies increase and decrease to 80.5 % and 27 %, corresponding to optimal rim angle, absorber depth, opening width, and opening angle of 60°, 85 mm, 200 mm, and 100°, respectively.

Solar-driven gasification for syngas production at low temperatures using a rotary hybrid porous media reactor

Solar-based technologies play a crucial role in the energy transition towards a green circular economy. This work investigates the solar-driven steam gasification of carbon char particles at low temperatures using an indirectly irradiated rotary hybrid porous media reactor. The solar concentration system consists of a heliostat and parabolic dish with a focus on the emitter plate located at the bottom of the reactor, allowing allothermal conditions for hydrogen (H2) and syngas production. The hybrid bed is composed of carbon and alumina particles randomly mixed in a 50/50 proportion in mass. Three sets were tested varying rotation speed of the unit, i.e., Set A (0 rpm), Set B (15 rpm), and Set C (20 rpm). Numerical simulations were performed using a one-dimensional model assessing mass, energy and chemical conservation equations, considering a semi-global kinetic scheme, including three homogeneous and four heterogeneous chemical reactions. The optical design configuration of the solar system, in addition to the high heat recirculation enhanced by the rotation of the reactor, allowed maximum temperatures of 662 K (outer surface) and 573 K (reaction chamber). At this low-temperature range, a good agreement between numerical simulations and experiments was achieved, observing a H2/CO ratio of 0.088 (Set B) and 0.163 (Set C), representing a 5.7% and 3.1% deviation, respectively. Numerical results show an increase in the temperature would lead to a higher H2/CO ratio production. Further studies are necessary to assess hydrogen and syngas production under these operating conditions at high temperatures.

Laser spectroscopy of highly charged ions at the storage ring CSRe: Schottky-based spectroscopic investigation and XUV fluorescence detector development

Laser spectroscopy stands out as a powerful tool to investigate atomic and nuclear properties and also test fundamental theories by precisely measuring the energy levels in highly charged ions. In this work, the fine-structure splitting 1s22s2S1/2−1s22p2P1/2 transition in lithium-like 16O5+ has been investigated in a laser spectroscopy experiment at the heavy-ion storage ring CSRe. The excitation resonance of the tunable narrowband UV laser and the ions was observed using a Schottky resonator with very high sensitivity. The experimental uncertainties including the ion beam velocity determination, the space charge effects, laser wavelength calibration, and angular misalignment between the laser and ion beam were analyzed, and the 2S1/2−2P1/2 transition wavelength was determined to be λ0= 103.45(38) nm. The primary source of experimental uncertainty arises from the inaccurate measurement of the high voltage applied on the electron cooler and therewith the ion beam velocity at the CSRe. In order to solve this problem, a high-precision divider to precisely measure the high-voltage of the electron cooler is under construction, which is expected to improve the present experimental accuracy by three orders of magnitude. In addition, an XUV optical detector equipped with an off-axis parabolic mirror has been developed and installed at the CSRe for the investigation of slow dipole-forbidden transitions in highly charged ions, such as hyperfine splitting and M1 transitions. The experimental studies presented here pave the way for future laser spectroscopy experiments at the CSRe as well as at the future larger-scale scientific facility HIAF in China.

A review: Performance of multibeam dual parabolic cylindrical reflector antennas in LEO satellites

The characteristics of multibeam dual parabolic cylindrical reflector antennas are summarized in this article. They can generate an arbitrary number of beams with arbitrary tilt angles for each beam. They can be remotely controlled to cover any arbitrary area, of any shape and size, even if the antenna was mounted on a quasi-stationary platform. Their performance in Low-Earth Orbit (LEO) satellites and ground stations (terminals) have been presented. A simple beam tracking technique was developed. For any specific satellite orbit, the orientation of the ground-station antenna could be adjusted such that its beams are parallel to the satellite's beams and directed toward them. The ground-station antenna can simultaneously communicate with multiple satellites in different orbits. A single antenna can cover the whole mm-band (17.8-30 GHz), which is one of the most widely used bands in LEO satellites. The overall size of a mm-wave antenna, generating 20-24 dB gain, is 14.8x10.4x3.7 cm3 and its weight is 0.37 kg.

Techno-economic assessment of concentrated solar power technologies integrated with thermal energy storage system for green hydrogen production

The present study investigates the viability of employing Solar parabolic trough collectors (PTC) and parabolic dish collectors (PDC) integrated with thermal energy storage (TES) as the primary heat source for a steam-powered Rankine cycle, aimed to produce 5500 kW power for green hydrogen generation. A techno-economic analysis finds the system's overall efficiency (solar input to generator output) as 15.06% with PTC and 18.80% with PDC. Besides, incorporating PTC with binary and ternary salts in the proposed system yields approximately 22.7 % lower capital costs and a 7.8 % shorter payback period than solar PDC. Likewise, the levelized hydrogen cost with these options is around 12.3 % lower than those of PDC across all zones. However, to sustain a maximum annual hydrogen production of 238.38 tonne, equivalent to an annual electricity generation of 11180.07 MWh in each zone, the required PTC area is approximately 24.85% larger than PDC area.

An ultrasonic transducer focusing ultrasound into a thin waveguide by two elliptical reflectors

A high-power ultrasonic transducer for minimally invasive treatments is proposed, capable of treating areas inaccessible by high-intensity focused ultrasound treatments. This transducer employs two elliptical reflectors that efficiently focus ultrasound waves into a thin waveguide by utilizing mode conversion. Additionally, a slit structure is introduced to suppress wave diffraction, further enhancing the focusing capabilities of the transducer. Finite element analysis demonstrates that the proposed transducer achieves an impressive energy density magnification factor of 325, with an energy efficiency of 24.2 %. This efficiency is 3.4 times higher than that of a conventional transducer, Double Parabolic refLector wave-guided Ultrasonic transducer.

Intensity patterns of a focused electromagnetic spherical wave with aberration

The laser pulse focused by a relativistic flying parabolic mirror can exceed the laser intensity focused by conventional physical focusing optics. Depending on the Lorentz γ-factor, the focal length of the relativistic flying mirror in the boosted frame of reference becomes much shorter than the incident beam size. The 4π-spherical focusing scheme is applied to describe such a focused field configuration. In this paper, a theoretical formalism has been developed to describe the field configuration focused by the 4π-spherical focusing scheme with an arbitrary phase error of an incident electromagnetic wave. The focused field configuration is described by the linear combination of the product of the spherical Bessel function and the spherical harmonics, resulting in the same expression as the multipole radiation. The mathematical expression showing the focused field for the femtosecond laser pulse, as well as the continuous wave, has been derived for the application to the femtosecond high-power laser. We show the three-dimensional intensity distribution near focus for the 4π-spherically focused electromagnetic field with phase error.

Experimental investigation of a sun tracking concentrated solar still with economic analysis

The current paper evaluated experimentally an innovative sun tracking concentrated solar still under Egyptian climatic conditions during the summer of 2022. The proposed system consists of a 120-cm-diameter parabolic reflector mirror that tracks the sun using a dual axis tracking system, a cylindrical solar still with a volume of 3.7 L positioned in its focal point, and a concentration ratio of 12.5. The performance of the concentrated solar still was investigated in the context of two critical parameters. First, three feed water salinity (17, 27, 37) ppt samples were evaluated, followed by four percentages of saline water filling ratio (26.5, 39.8, 53.1, 66.3)%. Increasing the salinity of the feed water had no effect on solar still productivity, but increasing the saline water filling ratio did. The daily cumulative productivity of the system was 6 kg/m2 with an optimal filling ratio of 53.1%, a daily efficiency of 42.88%, and an average cost of freshwater production of 0.0489 $/L. The proposed system also had the highest instantaneous efficiency of 61.77% and the highest distilled water productivity rate of 0.941 kg/h m2.

Design, Construction, and Performance Testing of a Collapsible Parabolic Dish Solar Cooker for Temperature Control

This paper proposes solar energy as a viable alternative to biomass fuels for cooking, introducing a collapsible parabolic solar cooker designed to regulate heat production. The collector is divided into three sectors, with a specific condition for effective convergence of reflected radiation. The total concentration ratio is 89.4, with the primary sector covering 42%, while sectors 2 and 3 occupy 29% each. In the analysis ASAE protocol was employed. The results obtained from the ASAE S580.1 test revealed a range of cooking power values, with a minimum of 215.5 W and a maximum of 280.9 W. The single measure of performance of the cooker was gauged at 234.17 W. Regarding the Standard Stagnation Temperature, it was observed that a reduction of the collector area by 0.343݉ଶ resulted in a temperature decrease of 59.5℃. The highest recorded SST for the entire solar cooker (when all three sectors were expanded) reached 279℃.