Application Of Radiometry Research Articles

Toward the Realization of Single-Photon Sources for Radiometry Applications at Room Temperature

Toward the Realization of Single-Photon Sources for Radiometry Applications at Room Temperature

Photoluminescence of the integrating sphere walls, its influence on the absolute quantum yield measurements and correction methods

Determination of the absolute quantum yield (QY) of photoluminescence (PL) or electroluminescence is commonly performed using an integrating sphere (IS) – versatile device for radiometry applications. The key feature of IS is very high diffused reflectance of its internal surface. Two materials are commonly used: (a) the sintered high-density polytetrafluoroethylene (Spectralon) and (b) materials based on barium sulphate (Spectraflect). Using PL-micro-spectroscopy we show that both materials reveal PL from localized centers excitable by UV, blue and green light emitting broad PL spectrum extending up to the red spectral region. The main effect of PL from IS-walls is introduction of non-constant parasitic background which is mixed with PL from a tested sample during the QY measurements. We develop theoretical description of QY determination which includes effects of PL from IS walls. This allows us to propose and test a reliable and universal correction for the IS-related PL background. Finally, a method of “black sample” is proposed and applied to estimate PL QY of Spectraflect which is shown to decrease from 0.09 to 0.015% for excitation shift from 320 to 440 nm.

Characterization of a room temperature predictable quantum efficient detector for applications in radiometry and photometry

This paper presents the experimental characterization of predictable quantum efficient detectors, which have been designed for use at room temperature. The aim of the characterization was to validate modelled properties experimentally and, thus, the feasibility of such room temperature predictable quantum efficient detectors to be used as primary radiometric standards for applications in the fields of photometry and radiometry with an aimed uncertainty level of 0.01. The characterizations were focused on linearity, thermal, angular, spectral and polarization dependencies of the detector that need to be known and considered in the respective applications. The results of the characterization measurements confirm the predictability of the detector, within the aimed 0.01 uncertainty level and, thus, the high potential for using that kind of devices as primary standards for applications in radiometry and photometry.

Development and Realization of Iron–Carbon Eutectic Fixed Point at NPLI

The concept of metal–carbon eutectic temperature fixed point has been introduced in 1999 and is extensively being investigated by thermometry researchers to cover the high-temperature range above copper fixed point. Metal–carbon eutectic fixed points also helped to provide direct traceability with reduced associated uncertainty in the high temperature range for thermometry and radiometry applications. In view of this, CSIR-National Physical Laboratory, India (NPLI) has developed iron–carbon (Fe–C, 1153 °C) eutectic fixed point cell in the graphite crucible and realized by using the noble metal thermocouples. The preparation parameters such as design and fabrication of a graphite crucible, Fe:C eutectic composition and filling procedure, furnace profile, melting and freezing plateau measurements, heat flux immersion, inhomogeneity, etc. have been optimized and presented in this paper. The measurement uncertainty of the Fe–C eutectic cell realized with Type-S thermocouple was estimated to be 3.04 μV (0.25 °C) at coverage factor k = 2.

Ultraviolet Characteristics of a Silicon Inversion Layer for Applications in Radiometry

Ultraviolet Characteristics of a Silicon Inversion Layer for Applications in Radiometry

A Low-Power 136-GHz SiGe Total Power Radiometer With NETD of 0.25 K

This paper presents a low-noise SiGe radiometer at 136 GHz developed in an IBM 90-nm SiGe BiCMOS technology. The radiometer consists of a three-stage cascode low-noise amplifier with a gain of 36 dB, and a differential output square-law detector, all on a single chip. The detector results in responsivity of 11 kV/W and a noise equivalent power (NEP) of ${\hbox{0.6 pW/Hz}}^{1/2}$ at D-band frequencies. The radiometer chip consumes 45 mW and results in a minimum NEP of ${\hbox{1.4 fW/Hz}}^{1/2}$ with a peak responsivity of 52 MV/W at 136 GHz. The single-chip radiometer is suitable for high-resolution imaging systems having a noise bandwidth $>{\hbox{10 GHz}}$ and a low $1/f$ corner frequency $( . For an integration time of 3.125 mS $(\tau=3.125~{\hbox{mS}})$ , the temperature resolution [noise equivalent temperature difference (NETD)] is determined to be 0.25 K using several different independent methods, and is the lowest NETD demonstrated in silicon technologies at D-band frequencies. This state-of-the-art performance is comparable to the best III–V imaging systems and proves that the advanced SiGe technology is a reliable option for imaging and radiometry applications.

Design of an inexpensive integrating sphere student laboratory setup for the optical characterization of light sources

In this paper, the design of an inexpensive integrating sphere setup is presented, enabling students to perform optical characterization of light sources with reasonable accuracy, in a student laboratory context. Instead of using an expensive sphere with magnesium oxide or barium sulfate coating, a cheap polystyrene sphere is employed. In combination with a low-cost USB spectroradiometer, the system enables the direct measurement of the spectral radiant power of a light source. In addition to the radiant power, the luminous flux, luminous efficacy, and distinctive colorimetric quantities (colour coordinates, colour temperature, and colour rendering index) can be determined. Besides a description of the equipment used, the experimental measurement procedure and some typical measurement results are presented. A comparison between the data and the results obtained with scientific metrology instrumentation indicates reasonable accuracy. As a result, it can be concluded that the purpose of the presented experiments, being that students become acquainted with applications of radiometry and photometry, and with data collection and data analysis as in a professional context, is fully achieved with the described test setup.

A low power Ku phase locked oscillator in low cost 130 nm CMOS technology

This paper reports on a Ku low-power integer-N phase locked oscillator designed to investigate the potentialities of a low-cost 130nm CMOS technology for video broadcasting and radiometry applications. The design and the characterization of the prototype are described and the main performances are reported and compared to literature. The PLO generates an output tone in the 14.2GHz–15.1GHz frequency range. The phase noise is −68.9dBc/Hz for an offset frequency of 100kHz from a 15GHz carrier, and can be enhanced of about 20dB. The circuit core sinks 23.7mA from 1.2V supply.

A $W$-Band Monolithic Integrated Active Hot and Cold Noise Source

For application in radiometry or noise measurement systems, an integrated active hot-cold load (AHCL) operating in the W-band (75-110 GHz) is presented and realized as monolithic millimeter-wave integrated circuit (MMIC). It makes use of a novel circuit topology that employs only a single active noise source and monolithic integrated switches to provide a cold and a hot noise reference temperature. The AHCL provides a measured cold temperature of only 230 K and a hot temperature of 860 K around 94 GHz, thus enabling two-point radiometric calibration and absolute power measurements. The noise source of the AHCL has been fabricated as a two-port test structure too. In that configuration, it has been measured as a low-noise amplifier with a noise figure of 2.5 dB at 94 GHz proving its good noise performance. As a standalone active cold load (ACL), an excellent noise power of only 190 K at 93 GHz is achieved. The AHCL and ACL MMICs have been fabricated in 100-nm gate-length metamorphic high electron-mobility transistor technology.

An Active 60-90 GHz Single Pole Double Throw Switch MMIC

This paper introduces an active millimeter-wave switch in a GaAs metamorphic high electron mobility transistor (mHEMT) technology. The active switch exhibits broadband performance (60 to 90 GHz, 40%), a gain of 10 dB with flat frequency response and average noise figure of 2.8 dB. The unilateral receiver topology is dedicated to radiometry applications. The design combines two input-matched low noise amplifiers with an output capacitance compensation network. The switch consumes 28 mW.

Evolution equation for radiance and coherence

If the field of applications of radiometry is restricted to energy calculations of optical systems then the theorem about invariant of the phase radiance (or the reduced radiance) along the light ray takes the form of Liouville's equation. This differential equation is a good basis for the traditional radiometry of Lambertian sources, as well as radiometry of the quasi-homogeneous sources. It is known that the wave analogue of phase radiance is the Wigner definition function. This wave analogy helps to clarify the limits of applicability of the concepts and approximations, e.g. properties of optical media in which the radiation transfer can be described by Liouville's equation.

AgI-coated silver-clad stainless steel hollow waveguides for infrared lightwave transmission and their applications

We fabricated silver iodide (AgI)-coated silver hollow waveguides to transmit a wide range of infrared (IR) light. Silver-clad stainless steel pipes were used as a supporting pipe. Since this type of metallic hollow waveguide has high mechanical strength and heat resistance, it is suitable as a rigid lightwave probe for various applications such as dental or medical laser treatment, IR spectroscopy, thermal radiometry, and laser processing. Considering these applications, we estimated the hollow waveguides with different thicknesses of the AgI layer. By optimizing the AgI layer thickness according to the wavelength of propagating light, we succeeded in efficiently transmitting Er-YAG and CO(2) laser light. We also studied the optical characteristics of a wide range of incoherent light for IR spectroscopy and radiometry applications using these metallic hollow waveguides as lightwave probes.

Low Sidelobe Corrugated Horn Antennas for Radio Telescopes to Maximize ${\rm G/T}_{\rm s}$

Improving the G/Ts of radio telescopes and radiometers and their associated receive subsystems translates into increasing the ground received signal-to-noise ratios. Therefore, low noise amplification with cooling operation is required. However, the system designer must select an appropriate feedhorn antenna with low sidelobes and an adapted illumination at the edge of the reflector since the noise originated from the surroundings will be collected by the horn and added directly to the overall system temperature. Lower sidelobes help also to improve the spillover efficiency of the radio telescope which will lead at the same time to an increase of the gain. Three new corrugated horn antenna designs with Gaussian-shaped patterns in the main beam are presented in this paper. These designs were made for specific radio astronomy and radiometry applications. These designs are shorter than their similar performance conical corrugated counterparts. Two of the designs present sidelobe levels below -40 dB and as a consequence they improve the G/Ts relationship. Measured performance results are also presented. All of the designs have been included in latest generation radio telescope and radiometer systems.

DESIGN OF MEDICAL RADIOMETER FRONT-END FOR IMPROVED PERFORMANCE

We have investigated the possibility of building a singleband Dicke radiometer that is inexpensive, small-sized, stable, highly sensitive, and which consists of readily available microwave components. The selected frequency band is at 3.25-3.75 GHz which provides a reasonable compromise between spatial resolution (antenna size) and sensing depth for radiometry applications in lossy tissue. Foreseen applications of the instrument are non-invasive temperature monitoring for breast cancer detection and temperature monitoring during heating. We have found off-the-shelf microwave components that are sufficiently small (< 5 mm × 5 mm) and which offer satisfactory overall sensitivity. Two different Dicke radiometers have been realized: one is a conventional design with the Dicke switch at the front-end to select either the antenna or noise reference channels for amplification. The second design places a matched pair of low noise amplifiers in front of the Dicke switch to reduce system noise figure.Numerical simulations were performed to test the design concepts before building prototype PCB front-end layouts of the radiometer. Both designs provide an overall power gain of approximately 50 dB over a 500 MHz bandwidth centered at 3.5 GHz. No stability problems were observed despite using triple-cascaded amplifier configurations to boost the thermal signals. The prototypes were tested for sensitivity after calibration in two different water baths. Experiments showed superior sensitivity (36% higher) when implementing the low noise amplifier before the Dicke switch (close to the antenna) compared to the other design with the Dicke switch in front. Radiometer performance was also tested in a multilayered phantom during alternating heating and radiometric reading. Empirical tests showed that for the configuration with Dicke switch first, the switch had to be locked in the reference position during application of microwave heating to avoid damage to the active components (amplifiers and power meter). For the configuration with a low noise amplifier up front, damage would occur to the active components of the radiometer if used in presence of the microwave heating antenna. Nevertheless, this design showed significantly improved sensitivity of measured temperatures and merits further investigation to determine methods of protecting the radiometer for amplifier first front ends.

High-grade uniform light source for radiometric and photometric applications

Versatile applications in radiometry and photometry require uniform light source systems with a highly Lambertian radiance/luminance output. Examples for this kind of requirements include different applications such as calibration of photometers and radiometers, testing of electronic imaging devices like CCDs or similar array detectors or the use as a homogenous light source in, for instance, gonioreflectometric measurements. At the Physikalisch-Technische Bundesanstalt (PTB) a homogenous sphere radiator consisting of a medium sized integrating sphere (ϕ = 150 mm) with an internal reflector in the equatorial plane was developed. In its first stage of development it was equipped with an internal 250 W quartz tungsten halogen lamp. This sphere radiator had a radiance homogeneity of 99.8% of the emitted radiation measured in the plane of the limiting aperture (ϕ = 40 mm) at the output of the device. In the latest design of the system the radiative output power could be increased by a factor of about 3 by the use of an internal 400 W quartz tungsten halogen lamp while nearly maintaining homogeneity.

Cryogenic radiometry in the hard x-ray range

For many applications in radiometry, spectroscopy or astrophysics, absolute measurement of radiant power with low uncertainty is essential. Cryogenic electrical substitution radiometers (ESRs) are regarded as the highest-accuracy primary standard detector in radiometry, from the infrared to the ultraviolet region; in combination with tuneable monochromatized synchrotron radiation from electron storage rings, their range of operation has been extended to the soft x-ray region. ESRs are absolute thermal detectors, based on the equivalence of electrical power and radiant power that can be traced back to electrical SI units and be measured with low uncertainties. Their core piece is a cavity absorber, which is typically made of copper to achieve a short response time suitable for use with synchrotron radiation. At higher photon energies, the use of copper prevents the operation of ESRs due to increasing transmittance. A new absorber design for hard x-rays has been developed at the laboratory of the Physikalisch-Technische Bundesanstalt (PTB) at the electron storage ring BESSY II. The Monte Carlo simulation code Geant4 was applied to optimize its absorptance for photon energies of up to 60 keV, resulting in a cavity absorber with a gold base and a cylindrical shell made of copper, in combination with a thermal sensitivity of around 150 mK µW−1 and a time constant of less than 3 min, which is short compared with the lifetime of many hours for the storage ring current. The measurement of the radiant power of monochromatized synchrotron radiation was achieved with relative standard uncertainties of less than 0.2%, covering the entire photon energy range of three beamlines from 50 eV to 60 keV. Monochromatized synchrotron radiation of high spectral purity was used to calibrate silicon photodiodes against the ESR for photon energies up to 60 keV with relative standard uncertainties below 0.3%.

Bias Corrected PSD Estimation for an Adaptive Array With Moving Interference

We address the issue of computing power spectral density (PSD) estimates at the output of a beamforming sensor array in the presence of strong moving interference. It is shown that the time-varying spatial response of an adaptive beamformer (ldquopattern rumblerdquo) causes estimation bias in the PSD of both the signal of interest (SOI) and noise. In applications such as radio astronomy with stringent sensitivity requirements, even small pattern variations can be problematic because the resulting higher variance noise spectrum estimates make it impossible to detect signals of interest which are many decibels below the noise floor. Distortion in beam mainlobe shape also introduces errors in SOI direction estimates. To overcome this problem, an extension of the method described in Leshem , 2000, is developed which eliminates pattern-distortion-induced PSD bias and spatial response errors over the long-term PSD averaging window. Both simulated and real data experiments demonstrate algorithm effectiveness in realizing an undistorted effective (average) beam spatial response while maintaining a low noise floor level. This algorithm will enable PSD estimation using multi-antenna sensors and adaptive interference cancellation for radio astronomy, remote sensing, and other sensitive radiometry applications where cancellation has not been feasible.

Radiometry before World War II: measuring infrared and millimeter-wave radiation 1800-1925

I sketch some of the highlights of the neglected early history of radiometry. The only unifying theme is the measurement of infrared and millimeter-wave radiation, with an emphasis on the personalities involved. Although there were virtually no strictly commercial applications of radiometry during the period (unless one counts the making of scientific instruments), many of the investigators also tried their hands at applied research and inventions, with mixed results. However, the first researcher we consider was a good example of the eighteenth-century "gentleman scientist:" William Herschel

Fast multichannel plasma radiation losses measuring system

Abstract Fast Multichannel Radiation Losses Measuring System (MRLMS) has been developed for T-11M (Troitsk, Russia) and HL-1M (Chengdu, China) tokamak plasma diagnostics applications. Its main advantages are improved signal-to-noise ratio and fast response time achieved by utilization of silicon photodiode linear array manufactured by International Radiation Detectors Inc. (IRD, Torrance, CA, USA) for absolute radiometry applications in the vacuum ultraviolet, extreme ultraviolet and soft X-ray spectral regions.

Radiometric sensing

Hyperthermia, based on fever therapy as a cancer treatment has basically been abandoned in favor of ionizing radiation. In recent years, however, a renewed interest and effort in hyperthermia has taken place. Microwave radiometry can be used for measuring a patient's temperature. Microwave radiometry applications to breast cancer detection and fluid and blood warming are described.