Lead System Research Articles

The upgrade of the ATLAS Luminosity detector (LUCID) for HL-LHC

Throughout LHC (Large Hadron Collider) Run 2, the LUCID detector, that is located 10 cm from the beampipe on both sides of the interaction point (17 m on the z axis), has been the reference luminosity detector for the ATLAS experiment, providing the on-line and off-line luminosity measurement with high stability and a preliminary uncertainty of about 1.7%. For the high-luminosity LHC, new beampipe equipment and more demanding luminosity precision requirements and LHC beam conditions are expected. The detector will therefore be completely redesigned, exploiting both new and tried-and-tested technologies. Prototype detectors for the new running conditions and technologies have been developed and installed and will be tested during the upcoming Run 3. These consist of a detector based on PhotoMultiplier Tubes (PMT), which uses the quartz window as a Cherenkov medium and is positioned 30 cm from the beampipe, a low-rate PMT detector, located in the shadow of one of the ATLAS shieldings, and the fiber detector, in which fiber bundles are used as Cherenkov-light emitters and transmitters and that are calibrated with an innovative hybrid LED and radioactive-source system. In these prototypes, the behavior of new Hamamatsu R1635 and R7459 PMTs will be evaluated. In this contribution, the motivations for the detector redesign and a description of the LUCID upgrade are illustrated, as well as a detailed account of the preliminary tests performed with the prototypes, including PMT characterization and a study of the fiber degradation under irradiation.

Adaptive blind receiving for deep VLC coverage innon-uniform LED systems.

Recently, visible light communication (VLC) has become a promising technology for reliable communication in the industrial Internet of Things. In VLC, light sources with non-uniform parameters make uncontrollable signal blind zones and aliases. The unknown parameters also lead to the problem of channel estimation. Hence, deep coverage of VLC is challenging. In this paper, we design a dual-sensor elongated receiver. The receiver expands the signal receiving area by increasing the distance between photon detectors and realizes aliased signal recovery without channel estimation. Cooperatively, an adaptive blind receiving scheme is proposed. The scheme separates aliased signals by parameter estimation of a Gaussian mixture model without knowing transmitter parameters. It unifies the aliased and blind receiving cases by an adaptive signal combining method. Finally, the simulation results demonstrate that our scheme achieves better reliability and deeper communication coverage in the given system.

A new system to prevent SARS-CoV-2 and microorganism air transmission through the air circulation system of endoscopes.

Background and study aims Evidence for the modes of transmission of SARS-CoV-2 remains controversial. Recently, the potential for airborne spread of SARS-CoV-2 has been stressed. Air circulation in gastrointestinal light source boxes and endoscopes could be implicated in airborne transmission of microorganisms. Methods The ENDOBOX SC is a 600 × 600 mm cube designed to contain any type of machine used during gastrointestinal endoscopy. It allows for a 100-mm space between a machine and the walls of the ENDOBOX SC. To use the ENDOBOX SC, it is connected to the medical air system and it provides positive flow from the box to the endoscopy room. The ENDOBOX SC uses medical air to inflate the digestive tract and to decrease the temperature induced by the microprocessors or by the lamp. ENDOBOX SC has been investigated in different environments. Results An endoscopic procedure performed without ventilation was interrupted after 40 minutes to prevent computer damage. During the first 30 minutes, the temperature increased from 18 °C to 31 °C with a LED system. The procedure with fans identified variations in temperature inside the ENDOBOX SC from 21 to 26 °C (± 5 °C) 1 hour after the start of the procedure. The temperature was stable for the next 3 hours. Conclusions ENDOBOX SC prevents the increase in temperature induced by lamps and processors, allows access to all necessary connections into the endoscopic columns, and creates a sterile and positive pressure volume, which prevents potential contamination from microorganisms.

Design Optimization of an Efficient Bicolor LED Driving System

There are some challenges involved in the design of a multicolor LED driver, such as the precise control of color consistency, i.e., maintaining the correlated color temperature (CCT) and luminous intensity. CCT deviation causes a color shift of composite light. This paper approaches the method of nonlinear optimization of the LED currents of two LED sources to achieve the desired CCT. A bicolor blended-shade white LED system is formed by using a warm color LED source of 1000 K CCT and a cool color LED source of 6500 K CCT. By using a nonlinear optimization methodology, the reduced deviation of the blended CCT and optimum LED currents are obtained. The optimized currents in the two LED strings are maintained by the control circuit of the single-ended primary inductor converter (SEPIC). The obtained reduced deviation of the CCT is 43 K, and the precision is 99.15%. Again, harmonics in the input current hamper power quality, i.e., reduce the power factor and increase power loss. This paper proposes the harmonic reduction technique to achieve the lowest value of total harmonic distortion (THD) through the nonlinear parametric optimization of the SEPIC. Measured THD = 4.37%; PF = 0.96; and efficiency = 92.8%. The system stability was determined and found to be satisfactory.

TiO2-C nanocomposite synthesized via facile surfactant-assisted method as a part of less energy-consuming LED-based photocatalytic system for environmental applications

A novel facile method was used to incorporate carbon into the titania structure. An alternative synthesis method of carbon-doped TiO2 has been proposed by using a widely used and cheap surfactant. During the process, cetyltrimethylammonium bromide plays a dual role, as a morphology modifier and as a carbon source. The presented approach allows obtained TiO2-C nanostructures to be anatase nanocrystals with carbon being deposited either on the surface or between the TiO2 nanoparticles. The innovative nature of the research subject is related to the design of cheap LED solutions and facile synthesis of TiO2-C for use in novel energy-saving photocatalytic systems. Photocatalytic studies showed promising activity in the oxidation of 4-chlorophenol. Furthermore, it was indicated that LED-based photocatalytic systems allow a significant reduction in energy consumption compared to conventional photocatalytic sets. In addition, the high thermal efficiency of LED systems was confirmed with a thermal imaging camera. Hence, the presented novel LED photocatalytic systems can be an important part of a broad strategy for the protection of the environment.

Experimental generation of adjustable partially coherent optical vortices from coherent and incoherent light sources.

Adjustable spatial coherence systems allow the possibility to make different intensity distributions using one source. Most common adjustable sources are based on the Collet-Wolf system. However, it is also possible to adjust the spatial coherence of the illumination field from white light sources by spatially filtering the source mutual intensity spectrum. We implement the Collet-Wolf source and the LED-based system to experimentally contrast a variety of partially coherent optical vortices that can be generated with spatial light modulation. We experimentally study the effects of changing the transverse coherence in partially coherent optical vortices, using a proposed metric of vortex contrast depth that quantifies the change of the vortex hollowness. To expand the analysis, we use a Michelson interferometer to reconstruct the spiral wavefronts using phase shifting. We found that the LED system at lower spatially correlated light produces truncated triangular distributions (a 50µm pinhole is used), and with higher correlated light, it produces partially coherent optical vortices (a 10µm pinhole is used). The Collet-Wolf system generates partially coherent optical vortices up to 0.5mm of focal shift in the diffuser. Our results provide an experimental understanding and instrumental methodology capable of steering the optical transverse coherence, producing adjustable partially coherent optical vortices that can be obtained using incoherent and coherent sources.

Influence of UV-A irradiation on the selected nutrient composition and volatile profiling of whole milk: Safety and quality evaluation

Aflatoxin (AF), a mycotoxin produced by several genera of fungi, is an important concern in milk-based products due to its toxicity and health consequences. The present study evaluates whether UV-A irradiation can preserve the composition of whole milk (WM) while degradaing these toxins. In addition, this study also investigates the expression of p53 proteins which can be correlated with carcinogenocity. UV-A irradiation experiments were conducted using a near collimated beam system operating at 365 nm. AFs at known concentrations were spiked in WM and irradiated at quantifiable UV doses based on the average volumetric intensity. The impact of ultraviolet light (UV-A) irradiation on volatile compounds, certain amino acids, and oxidative products were evaluated. No significant reduction in amino acids was observed except tryptophan (p < 0.05). Therefore, tryptophan particularly gets degraded under UV and generates OH− radical. At 838 mJ/cm2 no significant lipid peroxidation was observed, p < 0.05. The volatile profiling showed that alcohols, the key contributor of oxidized flavor was not significantly affected by the UV-A irradiation. As the overall volatile composition was comparable between the untreated and UV-A irradiated WM there may not be an adverse impact on the sensory attributes. Western blotting was used to assess the effect of UV-A irradiated WM on protein expression in HepG2 cells. Because the targeted gene p53 was not considerably altered, we can affirm that UV-A irradiated WM may be safe and not cytotoxic. Herein, the substantial breakdown of AF in WM by UV-A as well as no accumulation of toxic components from protein, lipid, and FAA degradation was observed. This study conclusively proves the performance of the UV-A LED system in degrading AF in WM below the levels recommended by Food and Drug Administration without compromising the product's quality or safety.

Enumeration reduction algorithm for the characterization of multi-primary LED systems

Multi-primary tunable LED lighting systems can generate a vast number of spectral outputs, with the exact number depending on the resolution of the control signal and number of LED primaries. Computing all combinations to identify optimal spectral power distributions (SPDs) with a specified chromaticity would require a tremendous amount of time and computational power. Here, an enumeration reduction (ER) algorithm is described to reduce the computation time by defining a bounding pyramid in the three-dimensional tristimulus space that maps to the circumscribed square of the target region in the chromaticity diagram. This method enables computing only the necessary amount of tristimulus values (and resulting chromaticity coordinates) for SPDs that fall into a user-defined target chromaticity area, reducing computation time by avoiding the need to generate each combination and calculate its chromaticity coordinates. The results show that the proposed ER algorithm can greatly reduce the time – up to 922 times in a series of tests – to determine a set of metamers compared to a full enumeration computation.

LED Lighting Agrosystem with Parallel Power Supply from Photovoltaic Modules and a Power Grid

The paper considers the operation of an LED lighting system with a parallel power supply from photovoltaic modules and a power grid. Such systems are supposed to be widely applicable in premises with limited natural lighting, particularly agrosystems where artificial light of a certain spectrum is specifically required to ensure efficient plant growth. The paper presents the scheme of the developed LED lighting system, as well as an assembled prototype containing a single 36-watt lamp. The data of the experimental study are provided on the developed LED lighting system using the developed monitoring system. The experimental study demonstrates an efficient power take-off and the reliability of the proposed scheme to competently select the characteristics and circuit solutions for the converter of voltage from the PV module. The proposed LED system allows simplification of the PV system by eliminating circuits with an inverter and storage devices, hence significantly reducing the cost of the photovoltaic systems. Likewise, such a simplicity has a positive effect on PV system reliability, which benefits the cost as well.

Flicker: A review of temporal light modulation stimulus, responses, and measures

Flicker has been an important lighting system consideration for over a century. More precise terms are temporal light modulation (TLM) as the stimulus, and responses to TLM as the unwanted visual, cognitive, or physiological consequences. As lighting technology evolved, different forms of TLM emerged, and so did responses to them. Today, some LED systems – encompassing the LED, driver, and control – can result in TLM causing severe unwanted effects, while other LED systems produce no unwanted effects at all. LED systems can deliver a much wider range of luminous waveforms than conventional lighting systems, some exhibiting very high modulation depths. More than any light source before, they can elicit perceptions of the phantom array. Direct flicker effects at modulation frequencies less than about 80 Hz and the stroboscopic effect at frequencies greater than 80 Hz are fairly well understood, but the phantom array effect needs more exploration and characterisation. This review focuses on the technology and research history that led to current metrics for quantifying TLM and human responses to TLM. Visually impaired individuals may exhibit alterations in their response to TLM, but such a discussion is beyond the intent of this review. Thus, the focus is on individuals with normal visual function.

Near-infrared LED system to recognize road surface conditions for autonomous vehicles

Abstract. The driving safety of autonomous vehicles will strongly depend on their ability to recognize road surface conditions such as dry, wet, snowy and icy road. Currently, the existing investigations to detect road surface conditions still have limitations in daytime and nighttime conditions. The objective of this paper is to propose and develop a new system with three near-infrared (NIR) LED sources. This choice is based on the advantages of LED sources over laser diodes. They are less sensitive to temperature and have lower costs. Considering these advantages, the feasibility of the LED system to recognize road surface conditions is investigated. For this, the appropriate wavelengths of the LED tri-wavelength source are first computed from experimental data taking into account the specific LED spectral shape. In addition, the effect of the spectral bandwidth of the LED sources on the system performance is theoretically studied. Finally, the NIR LED system with the LED sources at 970, 1450 and 1550 nm is experimentally tested and validated with an incident angle from 78.7 to 86.2∘. According to the results of the experiments, the accuracy of the classification of snow, wet and water can reach 97 %, while the accuracy of the dry and wet road surface conditions is respectively 73 % and 68 %.

Underwater wireless optical communication utilizing multiple input–multiple output (MIMO)-LED system for RF transmission with solar panel receiver

Abstract In this article, we designed an experimental system for underwater wireless optical communications. A function generation device sent frequencies (1–500 kHz) by amplitude shift key modulation technology, and these frequencies were loaded over light-emitting diode to propagate through a glass water tank with a length of 1 m, width of 40 cm, and height of 30 cm containing clean water of 80 L. These frequencies were received by a photodiode (BPX61), and the received signal was displayed through a digital storage oscilloscope device. Four techniques, single input–single output (SISO), single input–multiple output, multiple input–single output, and multiple input–multiple output (MIMO), were applied under the same optical conditions to know the quality of receiving the optical signal and the difference between them. Finally, the parameter values of signal-to-noise ratio, peak-to-peak voltage, and voltage gain were checked for each technique, and they were the lowest values for the SISO technique and the highest values for the MIMO technique.

Microscopy is better in color: development of a streamlined spectral light path for real-time multiplex fluorescence microscopy.

Spectroscopic image data has provided molecular discrimination for numerous fields including: remote sensing, food safety and biomedical imaging. Despite the various technologies for acquiring spectral data, there remains a trade-off when acquiring data. Typically, spectral imaging either requires long acquisition times to collect an image stack with high spectral specificity or acquisition times are shortened at the expense of fewer spectral bands or reduced spatial sampling. Hence, new spectral imaging microscope platforms are needed to help mitigate these limitations. Fluorescence excitation-scanning spectral imaging is one such new technology, which allows more of the emitted signal to be detected than comparable emission-scanning spectral imaging systems. Here, we have developed a new optical geometry that provides spectral illumination for use in excitation-scanning spectral imaging microscope systems. This was accomplished using a wavelength-specific LED array to acquire spectral image data. Feasibility of the LED-based spectral illuminator was evaluated through simulation and benchtop testing and assessment of imaging performance when integrated with a widefield fluorescence microscope. Ray tracing simulations (TracePro) were used to determine optimal optical component selection and geometry. Spectral imaging feasibility was evaluated using a series of 6-label fluorescent slides. The LED-based system response was compared to a previously tested thin-film tunable filter (TFTF)-based system. Spectral unmixing successfully discriminated all fluorescent components in spectral image data acquired from both the LED and TFTF systems. Therefore, the LED-based spectral illuminator provided spectral image data sets with comparable information content so as to allow identification of each fluorescent component. These results provide proof-of-principle demonstration of the ability to combine output from many discrete wavelength LED sources using a double-mirror (Cassegrain style) optical configuration that can be further modified to allow for high speed, video-rate spectral image acquisition. Real-time spectral fluorescence microscopy would allow monitoring of rapid cell signaling processes (i.e., Ca2+ and other second messenger signaling) and has potential to be translated to clinical imaging platforms.

Energy efficiency of a LED lighting system using a Peltier module thermal converter

With LED lighting systems, 70% of the energy consumed is lost in thermal form. It would be possible to increase the efficiency of the system by converting this wasted thermal energy into light. Some proposals using Peltier modules have been made. This article is interested in the limits of these solutions by evaluating the drop in the luminous efficiency of the LED system induced by the thermal effects generated by the addition of the Peltier module compared to the potential gain in terms of electrical power produced.

Data-driven modeling of the thermal dynamics of a dual-spectral ultraviolet sterilizer and control of the output irradiance

Multi-channel LED light sources possess complicated nonlinear photo-electro-thermal (PET) dynamics. Modeling such PET dynamics is challenging, but important to ensure the performance of these light sources. Traditional first-principle modeling methods that have been reported in the literature yield either single-channel LED dynamic models, or multi-channel static models. On the other hand, system identification (SID) methods have also been applied, and lead to both single-channel nonlinear dynamic models and multi-channel linear time invariant (LTI) models. However, there are still few attempts given to build multiple-input-multiple-output (MIMO) nonlinear dynamic models of multi-channel LED systems. In this work, we try to model the PET dynamics of a dual-spectral ultraviolet (UV) light source, with a structured nonlinear system identification technique, i.e., linear parameter varying (LPV) SID technique. The experimental prototype contains a 280 nm UVC channel and a 365 nm UVA channel, respectively driven by two separate constant current sources, and is hence a MIMO system. Its nonlinear electro-thermal model is first identified from experimental data by the LPV-SID method, which is then integrated with the estimated photo-electro model to form a complete PET dynamic model. The experimental results have verified that the model can accurately predict the temperature variations at two representative points on the LED board. Moreover, the identified model has been applied in designing a feedforward-feedback controller to precisely track the reference radiation levels of the two UV channels, despite the strong nonlinearity caused by both the electro-thermal dynamics and the temperature-dependent lumen efficacy.

Clinical evaluation of a mobile, low-cost system for fluorescence guided photodynamic therapy of early oral cancer in India

Background: Morbidity and mortality due to oral cancer in India are exacerbated by a lack of access to effective treatments amongst medically underserved populations. We developed a user-friendly low-cost, portable fibre-coupled LED system for photodynamic therapy (PDT) of early oral lesions, using a smartphone fluorescence imaging device for treatment guidance, and 3D printed fibreoptic attachments for ergonomic intraoral light delivery. Methods: 30 patients with T1N0M0 buccal mucosal cancer were recruited from the JN Medical College clinics, Aligarh, and rural screening camps. Tumour limits were defined by external ultrasound (US), white light photos and increased tumour fluorescence after oral administration of the photosensitising agent ALA (60 mg/kg, divided doses), monitored by a smartphone fluorescence imaging device. 100 J/cm2 LED light (635 nm peak) was delivered followed by repeat fluorescence to assess photobleaching. US and biopsy were repeated after 7–17 days. This trial is registered with ClinicalTrials.gov, NCT03638622, and the study has been completed. Findings: There were no significant complications or discomfort. No sedation was required. No residual disease was detected in 22 out of 30 patients who completed the study (26 of 34 lesions, 76% complete tumour response, 50 weeks median follow-up) with up to 7.2 mm depth of necrosis. Treatment failures were attributed to large tumour size and/or inadequate light delivery (documented by limited photobleaching). Moderately differentiated lesions were more responsive than well-differentiated cancers. Interpretation: This simple and low-cost adaptation of fluorescenceguided PDT is effective for treatment of early-stage malignant oral lesions and may have implications in global health.

An Investigation on CCT and Ra Optimization for Trichromatic White LEDs Using a Dual-Weight-Coefficient-Based Algorithm.

Spectral optimization is applied as an effective tool in designing solid-state lighting devices. Optimization speed, however, has been seldomly discussed in previous reports as regards designing an algorithm for white light-emitting diodes (WLEDs). In this study, we propose a method for trichromatic WLEDs to obtain the optimal Ra under target correlated color temperatures (CCTs). Blue-, yellow-, and red-color monochromatic spectra, produced by the GaN LED chip, YAG:Ce3+ phosphors, and CdSe/ZnSe quantum dots, respectively, are adopted to synthesize white light. To improve the effectiveness of our method, the concept of dual weight coefficients is proposed, to maintain a numerical gap between the proposed floating CCT and the target CCT. This gap can effectively guarantee that Ra and CCT ultimately move toward the targeting value simultaneously. Mechanisms of interaction between CCT, Ra, and dual-weight coefficients are investigated and discussed in detail. Particularly, a fitting curve is drawn to reveal the linear relationship between weight coefficients and target CCTs. This finding effectively maintains the accuracy and accelerates the optimization process in comparison with other methods with global searching ability. As an example, we only use 29 iterations to achieve the highest Ra of 96.1 under the target CCT of 4000 K. It is hoped that this study facilitates technology development in illumination-related areas such as residential intelligent lighting and smart planting LED systems.

Robot Communication Via Motion: A Study on Modalities for Robot-to-Human Communication in the Field

In this article, we propose, implement, and evaluate a motion-based communication system for field robots: robots that operate in dynamic, unstructured, outdoor environments. We perform two pilot studies to guide our development of the system, then evaluate it alongside an audio communication system, an LCD display, and a system of blinking LEDs. We compare the usage of these four systems with three different robots from up to five different viewpoints of interaction in a large study administered via Amazon Mechanical Turk. We contribute in two ways to the development of a more robust form of field human-robot interaction, wherein robots can select the most appropriate communication vector for a given situation and context. First, we contribute a motion-based communication system for field robots along with three baseline systems against which to test it. Second, we present results from our development of this motion system, showing that it is easier to learn than a baseline blinking LED system, viable for use underwater, aerial, and terrestrial field robots, and less negatively affected by adverse viewpoints than other communication methods.

Wide multicolor tunability of blue-to-green up-conversion emission and white light generation in Pr3+/Yb3+ co-doped yttrium tantalates

We achieved wide multicolor tunable up-conversion emission and white light generation in Pr3+/Yb3+ co-doped yttrium tantalates prepared by a soft sol–gel method designed to afford the cubic Y3TaO7 and monoclinic M′-YTaO4 crystalline phases. The annealing temperature influenced the crystallization kinetics and stabilized a preferential phase. To investigate how the crystalline phase affected the Pr3+ photoluminescence properties, we recorded up-conversion emission spectra for the samples annealed at 900 or 1100 °C. Excitation at 980 nm elicited emissions assigned to the Pr3+ transitions in the blue (3P0→3H4), green (3P1,0→3H5), and red (3P0→3H6,3F2; 3P1→3F3) regions. The Yb3+ content, crystalline phase, and laser power influenced such emissions. The most dominant mechanisms are proposed to elucidate the differences in the number of photons during the power dependence studies. Spectroscopic studies showed that the crystalline structure composition and Yb3+ concentration affected the population of the Pr3+:3P1,0 states and modified the relative intensity of bands particularly in the green and red regions. These changes provided extensive color gamut, so we evaluated emission color tunability from blue to green as a function of the Yb3+ concentration. The above-mentioned structural and photoluminescent properties make these Pr3+/Yb3+ co-doped yttrium tantalates potential candidates for applications in Photonics, mainly in the integration of white, blue, or green LED systems, multicolor displays, and other devices for security applications.

High Performance Adaptive Active Harmonic Filter Design for Non-Linear LED Loads

Today, illumination systems use approximately 1/3 of the electrical energy produced. For this reason, new technologies constantly increase energy efficacy in illumination technology. Consequently, the use of LED type light sources gets more widespread with low power electronics-based versions. The most important advantage of this type of systems has high luminous efficacy. However, since electronic systems have non-linear static loads, they cause unwanted harmonics in electrical distribution systems. Harmonics affect the operational safety as they cause unnecessary heating of the conductors in the electrical network. It also adversely affects the measuring and control systems of the buyers and so decreases the energy performance. In this study, an adaptive Butterworth low pass active harmonic filtermodel that can cut all current/voltage harmonics outside the operating frequency of different types of LED driver light sources is designed. In addition, harmonic analysis of different LED driver systems is performed experimentally by considering the total harmonic distortions (THD,%). In this way, harmonic components and (THD) values of different LED systems are obtained. These harmonic components obtained is filtered with the designed filter structure and the effects of the filter structure at each filtering degree on the harmonic components and THD were investigated. In this way, the designed filter is proved to be an adaptive model that can be adjusted automatically for different types of LED systems.