Winston Cone Research Articles

Enhanced Delivery and Detection of Terahertz Frequency Radiation from a Quantum Cascade Laser Within Dilution Refrigerator

We report on significant enhancements to the integration of terahertz (THz) quantum cascade lasers (QCL) and THz detection with a two-dimensional electron gas (2DEG) within a dilution refrigerator obtained by the inclusion of a multi-mesh 6 THz low-pass filter to block IR radiation, a Winston cone to focus light output, and gating the 2DEG for optimised sensitivity. We show that these improvements allow us to obtain a > 2.5 times reduced sample electron temperature (160 mK compared with 430 mK previously), during cyclotron resonance (CR) measurements of a 2DEG under QCL illumination. This opens up a route to performing sub-100 mK experiments using excitation by THz QCLs.

The throughput calibration of the VERITAS telescopes

Context. The response of imaging atmospheric Cherenkov telescopes to incident γ-ray-initiated showers in the atmosphere changes as the telescopes age due to exposure to light and weather. These aging processes affect the reconstructed energies of the events and γ-ray fluxes. Aims. This work discusses the implementation of signal calibration methods for the Very Energetic Radiation Imaging Telescope Array System (VERITAS) to account for changes in the optical throughput and detector performance over time. Methods. The total throughput of a Cherenkov telescope is the product of camera-dependent factors, such as the photomultiplier tube gains and their quantum efficiencies, and the mirror reflectivity and Winston cone response to incoming radiation. This document summarizes different methods to determine how the camera gains and mirror reflectivity have evolved over time and how we can calibrate this changing throughput in reconstruction pipelines for imaging atmospheric Cherenkov telescopes. The implementation is validated against seven years of observations with the VERITAS telescopes of the Crab Nebula, which is a reference object in very-high-energy astronomy. Results. Regular optical throughput monitoring and the corresponding signal calibrations are found to be critical for the reconstruction of extensive air shower images. The proposed implementation is applied as a correction to the signals of the photomultiplier tubes in the telescope simulation to produce fine-tuned instrument response functions. This method is shown to be effective for calibrating the acquired γ-ray data and for recovering the correct energy of the events and photon fluxes. At the same time, it keeps the computational effort of generating Monte Carlo simulations for instrument response functions affordably low.

Modeling of optical concentrators for the upgraded camera of the TAIGA-IACT Cherenkov gamma-ray telescope

A quantitative simulation of a system of optical concentrators based on Winston's hexagonal cones, intended for the registration camera of the TAIGA-IACT Cherenkov gamma-ray telescope, has been performed. The data on the transmission of the cones are obtained; the distributions of the photon flux intensity in the plane of the detector are given. On the basis of the results obtained, an optimal configuration of optical concentrators is proposed, taking into account the design features of the mount, mirror and TAIGA-IACT camera, as well as the features of its new detector units. Keywords: Cherenkov gamma-ray telescope, TAIGA-IACT, Winston cone, numerical simulation.

Correction for angular acceptance of the TAIGA-HiSCORE

TAIGA-HiSCORE is an array of wide-angle air-Cherenkov detectors distributed on the area of 1 km2. It is a part of a hybrid gamma-ray observatory TAIGA which combines imaging and timing techniques to detect Cherenkov emission from the extensive air showers. To collect Cherenkov light TAIGA-HiSCORE uses light guides —Winston cones—combined with PMTs. We present the results of measurements of angular acceptance of PMT+cone unit and entire TAIGA-HiSCORE installation. Orientation of the dynode system in the PMT makes the PMT+cone unit angular characteristic asymmetric. This asymmetry is combined with another one caused by the detector orientation with respect to the zenith. It determines the angular acceptance of the installation. Asymmetric angular characteristic distorts a signal of initial event flux—distribution of detected events. To obtain an original signal this distortion should be corrected using appropriate weight functions according to the certain energy range. With energy increase distribution of detected events becomes more uniform. Obtained results can be used for estimation of cosmic ray background, simulation of the TAIGA-HiSCORE detectors and for hybrid operation of the two installations.

Water-based Liquid Scintillator detector as a new technology testbed for neutrino studies in Turkey

This study investigates the deployment of a medium-scale neutrino detector near Turkey’s first nuclear power plant, the Akkuyu Nuclear Power Plant. The aim of this detector is to become a modular testbed for new technologies in the fields of new detection media and innovative photosensors. Such technologies include Water-based Liquid Scintillator (WbLS), Large Area Picosecond Photo-Detectors (LAPPDs), dichroic Winston cones, and large area silicon photomultiplier modules. The detector could be used for instantaneous monitoring of the Akkuyu Nuclear Power Plant via its antineutrino flux. In addition to its physics and technological goals, it would be an invaluable opportunity for the nuclear and particle physics community in Turkey to play a role in the development of next generation of particle detectors in the field of neutrino physics.

Modelling of SiPM Performance for Detection of Cherenkov Radiation from Extensive Air Showers in UV and Visible Ranges for Application at the TAIGA-IACT Telescope

Abstract A novel cluster of sensitive detectors based on silicon photomultipliers (SiPM) is being developed for the Cherenkov gamma-ray telescope TAIGA-IACT (Tunka valley, Republic of Buryatia, Russia). The cluster will be able to detect Cherenkov radiation from extensive air showers in two wide bands: 250–300 nm (UV) and 250–700 nm (visible and UV). Each pixel consists of a Winston cone, 4 SiPMs with the total sensitive area of 144 mm2, and readout electronics based on fast analogue memory. During operation in the UV band, a UV-bandpass filter is used to suppress cluster sensitivity in the visible range. In order to evaluate the detection efficiency of the selected SiPMs, a specific software simulator of SiPM output signal has been developed. This simulator takes into account such inherent parameters of SiPMs as total number of microcells, their recharge time, the dark count rate, the effective detection area, the quantum efficiency, the crosstalk between microcells, as well as conditions of SiPM operation, namely, the background noise and the Ohmic load in the readout (front-end) electronics. With this simulator it is possible to determine the expected trigger threshold under given conditions and parameters of selected detectors. Based on preliminary simulations, OnSemi MicroFJ-60035 SiPM chips have been chosen for the novel cluster of TAIGA-IACT. These SiPMs have sensible efficiency in the ultraviolet range (5–20% in the 250–300 nm band) and are distinguished by the presence of a fast output, which allows one to capture a low amplitude signal above a relatively high background noise.

Advanced Net Flux Radiometer for the Ice Giants

The design of an advanced Net Flux Radiometer (NFR), for inclusion as a payload on a future Ice Giants probe mission, is given. The Ice Giants NFR (IG-NFR) will measure the upward and downward radiation flux (hence net radiation flux), in seven spectral bands, spanning the range from solar to far infra-red wavelengths, each with a $5^{\circ}$ Field-Of-View (FOV) and in five sequential view angles ($\pm 80^{\circ}$, $\pm 45^{\circ}$, and $0^{\circ}$) as a function of altitude. IG-NFR measurements within either Uranus or Neptune’s atmospheres, using dedicated spectral filter bands will help derive radiative heating and cooling profiles, and will significantly contribute to our understanding of the planet’s atmospheric heat balance and structure, tropospheric 3-D flow, and compositions and opacities of the cloud layers. The IG-NFR uses an array of non-imaging Winston cones integrated to a matched thermopile detector Focal Plane Assembly (FPA), with individual bandpass filters, housed in a diamond windowed vacuum micro-vessel. The FPA thermopile detector signals are read out in parallel mode, amplified and processed by a multi-channel digitizer application specific integrated circuit (MCD ASIC) under field programmable gate array (FPGA) control. The vacuum micro-vessel rotates providing chopping between FOV’s of upward and downward radiation fluxes. This unique design allows for small net flux measurements in the presence of large ambient fluxes and rapidly changing ambient temperatures during the probe descent to ${\geq} 10$ bar pressure.

The CLAS12 Low Threshold Cherenkov detector

The CLAS Cherenkov threshold gas detector was instrumental for electron identification in the Hall B 6 GeV era at Jefferson Lab. The detector’s scope has been modified for the new CLAS12 spectrometer to identify π+ and π− for momenta greater than 3.5 GeV, thus becoming a Low Threshold Cherenkov Counter (LTCC). This was accomplished with a refurbishment of the gas container, its windows, mirrors, Winston light collecting cones, and photomultipliers. The design, construction, and performance of the refurbished LTCC are described. The lightweight mirrors and Winston cones have been re-surfaced with a highly reflective coating, the 5-in photomultiplier tube entrance windows have been treated with p-terphenyl to enhance the ultraviolet response, and the gas volume has been expanded to increase the thickness of the radiator gas and correspondingly the number of photoelectrons in the response signal. The LTCC response calibration has been performed on the single photoelectron signals, and the system efficiencies and response functions have been measured.

High-Resolution Muography Using a Prototype Portable Muon Telescope

We report on our continued development of a portable muon telescope with excellent angular resolution capable of imaging large archaeological structures in detail. The first prototype (Phase I) consists of four trays of scintillator bars, Winston cones, silicon photomultipliers (SiPMs), readout electronics, and a network of Arduinos to handle data acquisition. Finally, we developed a reconstruction algorithm to create the final image. The cosmic muons produce scintillation photons as they pass through the scintillator bars; these photons are transported by the Winston cones to the SiPMs where they are converted into electrical signals. The electrical signals are then digitized and transmitted to an offline computer for reconstruction. The entire system is mounted on a wheeled cart and can be pointed to target different objects of interest. With Phase I, we are able to reconstruct large objects in two-dimensional space with an angular resolution of 20 mrad with an operating efficiency of 89%.

A compact and light-weight refractive telescope for the observation of extensive air showers

A general purpose instrument for imaging of Cherenkov light or fluorescence light emitted by extensive air showers is presented. Its refractive optics allows for a compact and light-weight design with a wide field-of-view of 12°. The optical system features a 0.5 m diameter Fresnel lens and a camera with 61 pixels composed of Winston cones and large-sized 6x6 mm2 photo sensors. As photo sensors, semi conductor light sensors (SiPMs) are utilized. The camera provides a high photon detection efficiency together with robust operation. The enclosed optics permit operation in regions of harsh environmental conditions. The low price of the telescope allows the production of a large number of telescopes and the application of the instrument in various projects, such as FAMOUS for the Pierre Auger Observatory, HAWC's Eye for HAWC or IceAct for IceCube. In this paper the novel design of this telescope and first measurements are presented.

Occulting Light Concentrators in Liquid Scintillator Neutrino Detectors

The experimental efforts characterizing the era of precision neutrino physics revolve around collecting high-statistics neutrino samples and attaining an excellent energy and position resolution. Next generation liquid-based neutrino detectors, such as JUNO, HyperKamiokande, etc, share the use of a large target mass, and the need of pushing light collection to the edge for maximal calorimetric information. Achieving high light collection implies considerable costs, especially when considering detector masses of several kt. A traditional strategy to maximize the effective photo-coverage with the minimum number of PMTs relies on Light Concentrators (LC), such as Winston Cones. In this paper, the authors introduce a novel concept called Occulting Light Concentrators (OLC), whereby a traditional LC gets tailored to a conventional PMT, by taking into account its single-photoelectron collection efficiency profile and thus occulting the worst performing portion of the photocathode. Thus, the OLC shape optimization takes into account not only the optical interface of the PMT, but also the maximization of the PMT detection performances. The light collection uniformity across the detector is another advantage of the OLC system. By considering the case of JUNO, we will show OLC capabilities in terms of light collection and energy resolution.

Development of a composite large-size SiPM (assembled matrix) based modular detector cluster for MAGIC

The MAGIC collaboration operates two 17m diameter Imaging Atmospheric Cherenkov Telescopes (IACTs) on the Canary Island of La Palma. Each of the two telescopes is currently equipped with a photomultiplier tube (PMT) based imaging camera. Due to the advances in the development of Silicon Photomultipliers (SiPMs), they are becoming a widely used alternative to PMTs in many research fields including gamma-ray astronomy. Within the Otto-Hahn group at the Max Planck Institute for Physics, Munich, we are developing a SiPM based detector module for a possible upgrade of the MAGIC cameras and also for future experiments as, e.g., the Large Size Telescopes (LST) of the Cherenkov Telescope Array (CTA). Because of the small size of individual SiPM sensors (6mm×6mm) with respect to the 1-inch diameter PMTs currently used in MAGIC, we use a custom-made matrix of SiPMs to cover the same detection area. We developed an electronic circuit to actively sum up and amplify the SiPM signals. Existing non-imaging hexagonal light concentrators (Winston cones) used in MAGIC have been modified for the angular acceptance of the SiPMs by using C++ based ray tracing simulations. The first prototype based detector module includes seven channels and was installed into the MAGIC camera in May 2015. We present the results of the first prototype and its performance as well as the status of the project and discuss its challenges.

Using In-situ Cryogenic Radiometers to Measure the Performance of a Large Thermal Vacuum Chamber

The James Webb Space Telescope will operate in space at temperatures lower than 50 K. To test the major parts of the telescope and instruments on the ground requires a very large thermal vacuum chamber with a helium-cooled shroud operating below 20 K. This chamber and shroud are being subjected to a series of 4 preliminary tests to characterize the chamber and the ground support equipment before the telescope and instruments are tested. We have made measurements in the first of these preliminary tests using simple radiometers, which are located in the chamber and are pointed at various locations and items of interest within the chamber. The radiometers, which have been previously described[1], consist of a Cernox thermometer attached to an absorber suspended behind a Winston cone with an acceptance half-angle of 11 degrees. 9 of these radiometers were anchored to the chamber at temperatures between 17 and 25 K and were able to resolve 2 mW over an area of one m2. This level of sensitivity corresponds to a 60 K blackbody, which spans the radiometer field of view, changing in temperature by 0.04 K. The results of this test and plans for future tests will be described.

Condensing efficiency of the truncated cone condenser and its comparison with the Winston cone condenser in terahertz region

The angle-dependent condensing efficiency of a truncated cone condenser (TCC) in the terahertz (THz) region has been examined by 2D ray tracing and 3D electromagnetic simulation. The condensing efficiency in the THz region is transferred to that in the optical region by theoretical dispersive reflection from a rough surface, and it is confirmed that the latter is consistent with the measured condensing efficiency in the optical region. Although the TCC has a gradual field of view (FOV) compared with the Winston cone condenser (WCC), we improved the steepness of the FOV by adding a baffle before the input aperture of the TCC. We also proved that the TCC has a high condensing efficiency at around normal incidence in comparison with the WCC in the THz region.

Design, optimization and characterization of the light concentrators of the single-mirror small size telescopes of the Cherenkov Telescope Array

The focal-plane cameras of γ-ray telescopes frequently use light concentrators in front of the light sensors. The purpose of these concentrators is to increase the effective area of the camera as well as to reduce the stray light coming at large incident angles. These light concentrators are usually based on the Winston cone design. In this contribution we present the design of a hexagonal hollow light concentrator with a lateral profile optimized using a cubic Bézier function to achieve a higher collection efficiency in the angular region of interest. The design presented here is optimized for a Davies–Cotton telescope with a primary mirror of about 4m in diameter and a focal length of 5.6m. The described concentrators are part of an innovative camera made up of silicon-photomultiplier sensors, although a similar approach can be used for other sizes of single-mirror telescopes with different camera sensors, including photomultipliers. The challenge of our approach is to achieve a cost-effective design suitable for standard industrial production of both the plastic concentrator substrate and the reflective coating. At the same time we maximize the optical performance. In this paper we also describe the optical set-up to measure the absolute collection efficiency of the light concentrators and demonstrate our good understanding of the measured data using a professional ray-tracing simulation.

Non-Imaging Winston Cone Concentrators for Submillimeter-Wave, Overmoded Waveguide

We describe the design, simulation, and measured performance of concentrators designed to couple submillimeter wavelength radiation from free space into highly overmoded, rectangular, WR-10 waveguide. They consist of a combination of a Winston cone (also called a compound parabolic concentrator or CPC) with an adiabatic circular to rectangular transition. They are intended for use as adapters, between instruments using overmoded WR-10 waveguide as input or output and sources propagating through free space. Unlike conventional waveguide-coupled antennas, a geometric optics analysis is more appropriate than a mode-by-mode electromagnetic calculation of impedance and far-field pattern. Six separate designs were studied, with input diameters from 5 to 16 mm, and “throat” diameters (i.e., diameters at the circular interface between cone and transition sections) of 1 to 4 mm. Measurements at 394 μm wavelength (760 GHz) using a far-IR waveguide laser beam indicate efficiencies of 40%-55%. The angular response is primarily determined by the Winston cone, and is well predicted by geometric optics theory, i.e., approximately constant out to an angle determined by the ratio of input to throat diameters. The efficiencies are primarily determined by the transition section, and for all concentrators are consistent with an average reflectance of 94% from the gold-plated, electroformed, interior surfaces. For each individual concentrator, efficiency variations with polarization, angular orientation and beamsize are below the measurement uncertainty.

FAMOUS – A prototype silicon photomultiplier telescope for the fluorescence detection of ultra-high-energy cosmic rays

Due to their high photon detection efficiency, silicon photomultipliers (SiPMs) promise to increase the sensitivity of today's fluorescence telescopes which use photomultiplier tubes to detect light originating from extensive air showers. On the other hand, drawbacks like a small sensitive area, a strong temperature dependence, a high noise rate and a reduced dynamic range have to be managed.We present plans for FAMOUS, a prototype fluorescence telescope using SiPMs and a special light collecting optical system of Winston cones to increase the sensitive area. The prototype will make use of a Fresnel lens. For several different types of SiPMs we measured their characteristics. Moreover, we will present the R&D in compact modular electronics using photon counting techniques. An evaluation of the performance of the optical telescope design is performed by means of a full detector simulation.

Optimization of the collection efficiency of a hexagonal light collector using quadratic and cubic Bézier curves

Reflective light collectors with hexagonal entrance and exit apertures are frequently used in front of the focal-plane camera of a very-high-energy gamma-ray telescope to increase the collection efficiency of atmospheric Cherenkov photons and reduce the night-sky background entering at large incident angles. The shape of a hexagonal light collector is usually based on Winston’s design, which is optimized for only two-dimensional optical systems. However, it is not known whether a hexagonal Winston cone is optimal for the real three-dimensional optical systems of gamma-ray telescopes. For the first time we optimize the shape of a hexagonal light collector using quadratic and cubic Bézier curves. We demonstrate that our optimized designs simultaneously achieve a higher collection efficiency and background reduction rate than traditional designs.

Angle dependent condensing efficiency of Winston cone in terahertz region

The condensing performance of Winston cone has been examined in the optical and terahertz (THz) regions by geometrical and wave optics simulations and the measurement of visible light. We have confirmed that the Winston cone possesses a sharp cutoff of incidence angle in condensing efficiency as expected; however we have found the condensing efficiency decreases at around normal incident, which is due to many times of reflection losses inside the condenser.

Ultra Precision Machining of the Winston Cone Baffle for Space Observation Camera

The Winston cone baffle was developed for the space observation camera of the MIRIS (Multi-purpose Infrared Imaging System) which is the main payload of STSAT-3 (Science and Technology Satellite). The Winston cone baffle reduces the orbital heat load to the STSAT-3 and is thermally connected to the radiator to cool down. The jig and ultra precision machining jig was designed using a 3D modelling program and analyzed using a computer aided engineering program (ANSYS). The reasons for designing the jig for the baffle were to enhance the stability of the machining and improve the form accuracy of the baffle. The strength, weight and barycentre of the jig are investigated to find the optimized ultra precision machining conditions. To maintain the weight balance of the baffle at high speed rotation, there are lots of holes that can be inserted by heavier bolts. Vibration of the natural diamond bite tool is reduced by using thin copper pipe and urethane silicone. Using this bite tool, we could decrease patterns on the surface of the Winston cone baffle. The results of the simulation using ANSYS show that maximum deformation of the baffle is less than the tolerance limit. Surface roughness of the fabricated Winston cone baffle is machined with the jig and the machining tool is under 5 nm. The Winston cone baffle is plated with gold after being electroless plated with nickel. This baffle is applied to the flight model of the MIRIS.