Metallic bolometers with temperature dependent thermal impedance

The paper gives the solution of a bolometer with thermal impedance, which is a general function of the temperature. The general solution is applied to a bolometer cooled by radiation for which the appropriate expressions fo the resistance, sensitivity and dynamic resistance are derived and the expression for the maximum sensitivity of this type of bolometers from nickel, platinum and electrolytical platinum is given. The case of a bolometer cooled by conduction through the air and radiation is solved as the case of a bolometer with several ways of cooling. The paper also gives a graphico-numerical method for determining all the important parameters of the bolometer from the measured dependence of the resistance on the electric power RI²; an example of the application of this method is given for a conduction and radiation cooled bolometer. Deviations from the theoretical course are explained by convection of heat caused by the flow of air along the bolometer due to the increase in temperature of the bolometer over that of its surroundings. The paper also gives the maximum attainable sensitivity of this type of bolometer and metallic bolometers in general.     

Metallic bolometers in periodically interrupted radiation

A theory of metallic bolometers is given for the case that the measured radiation is periodically interrupted. The impedance of a bolometer through which a direct and an alternating current simultaneously flow, is derived generally. Separate solutions are given for bolometers cooled by heat conduction and bolometers with thermal impedance dependent on the temperature. Expressions are derived for the sensitivity and minimum measurable power and the conditions for the choice of a coupling transformer with optimum ratio. In conclusion the lowest value of the minimum power at all measurable by metallic bolometers working in interrupted radiation is determined.Delivered in an abbreviated form. at the congress of the Physics Society of the German Democratic Republic in Leipzig, April 11, 1957.     

The influence of background power on the performance of an ideal bolometer

The effects of radiant power loading on the performance of an ideal bolometer are analysed. The operation of the bolometer is characterized in terms of dimensionless parameters which correspond to the temperature sensitivity of the thermometric material, the electrical bias point and the amount of optical power loading. Expressions are derived for the zero frequency NEP and responsivity. Examples are given for the case of a bolometer cooled to 100 mK and used for ground-based astronomical photometry at submillimetre wavelengths.     

Design of quick-response bolometers

Design equations for a solid bolometer are derived. The expressions obtained take into account the temperature distribution in both the dielectric and heat removal layers. Criteria for selecting the proper materials in the design of quick-response bolometers and for computing the dielectric layer thickness are presented.The author is grateful to A. F. Mal'tsev and L. S. Kremenchugskii for their interest in the present study and to A. G. Momanchuk for his assistance in carrying out the numerical computations.     

High Precision Characterisation of Semiconductor Bolometers

We describe techniques for testing and characterising semiconductor bolometers, using the bolometer model presented in Sudiwala et. al. [1]. The procedures are illustrated with results from a prototype bolometer for the high frequency instrument (HFI) in the Planck Surveyor cosmic microwave background mission. This is a bolometer using spider-web geometry and a neutron transmutation doped (NTD) germanium thermistor, designed for operation at 100 mK. Details are given of the laboratory facility used to take data at temperatures from 70 mK to 350 mK. This employs an adiabatic demagnetisation refrigerator to cool the detector and optics. The spatial and spectral properties of the optical system are controlled using feedhorns and edge filters. To characterise the bolometer, blanked and optically loaded load curves were measured over a range of temperatures, and the response to modulated radiation was measured as a function of modulation frequency, temperature and bias current. Results for the prototype bolometer show that its behaviour is well represented by an ideal thermal detector down to a temperature of approximately 100 mK. Below this, non-thermal effects such as electron-phonon decoupling or electric field dependent resistance appear to lead to departure from ideal behaviour. The performance was in good agreement with the design goals for the bolometer.     

Low heat capacity He3-cooled bolometers of differentiated structure

The performance of far-infrared bolometers is analyzed in terms of two fundamental noise processes: radiation noise from thermal emission of the background, and detector noise from Johnson and temperature fluctuation thermodynamic contributions. In terms of the former process, generally imposed by the conditions of the experiment itself, an optimization scheme assuring quasi-BLIP performance is suggested. The importance of operation at low temperatures and low heat capacity is discussed and a summary of the heat capacities per unit volume of materials entering into the construction of bolometers is given. Techniques for the construction of an ultra-low heat capacity bolometer for operation at He³ temperatures are discussed.     

Carbon nanotube based bolometer

The contacts of single carbon nanotubes and bundles of carbon nanotubes with superconducting and metallic electrodes are investigated in order to create bolometers and electron coolers. Tunneling contacts of the carbon nanotubes with aluminum electrodes are obtained. The current-voltage characteristics of junctions are analyzed for temperatures from room temperature to 300 mK. The resistance of individual nanotubes is primarily determined by defects and is too large for applications. The use of the bundles of carbon nanotubes makes it possible to considerably reduce the resistance of the bolometer, which is determined by a small number of conducting tubes with good tunneling contacts with the electrodes. The energy gap is equal to hundreds and tens of millivolt in the former and latter cases, respectively. Structures containing bundles of carbon nanotubes can be described in a model with a Schottky barrier. The samples with bundles of carbon nanotubes exhibit the bolometric response to external high-frequency radiation at a frequency of 110 GHz with an amplitude up to 100 μV and a temperature voltage response to 0.4 mV/K.     

High TcYBa2Cu3O7−δ superconducting transition-edge microbolometers

High T_c superconducting thin film YBa₂Cu₃O_7−δ (YBCO) bolometers have been fabricated on various substrates such as MgO, LaAlO₃, YSZ and Si using laser ablation technique. Performance of these IR bolometers operating with a Joule-Thomson refrigerator has been investigated. Measurements of the responsivity and low frequency noise near T_c in the current biased YBCO bolometers show that reliable devices can be fabricated. Measured noise equivalent power (NEP), for YBCO/YSZ bolometer, reaches 6 × 10⁻¹⁰W/Hz^1/2 at 165 Hz and has a responsivity of 60 V/W with a blackbody source. This performance is comparable to that of the optimized pyroelectric detectors. The characteristics of YBCO films deposited on Si substrates reveal that superconducting thin film multi-elements or focal plane array with silicon integrated readout circuit are feasible. Such bolometers exhibit NEP of 7 × 10⁻⁹W/Hz^1/2, and significant improvement appears possible. Electrical measurements show no noticeable film degradation after the bolometer is exposed to atmosphere for three months.     

Electron cooling in a normal-metal hot-electron bolometer

Normal-metal hot-electron bolometers, each of which contains two superconductor-insulator-normal metal (SIN) junctions for electron cooling and two SIN junctions for temperature measurements, were fabricated and experimentally studied. The electron cooling by SIN junctions is an analog of the Peltier effect and allows one to reduce the effective electron temperature of a bolometer. The electron temperature was determined from the ratio of the differential resistance to normal one for several values of a constant bias. At a phonon temperature of 250 mK, the resistance ratio at zero bias reached 1000, which was close to the theoretical value for an ideal SIN junction. A decrease in the electron temperature from 250 to 90 mK was obtained.     

THz/sub-THz bolometer based on electron heating in a semiconductor waveguide

Direct detection THz/sub-THz bolometer is proposed. In it an electromagnetic wave propagates in the bipolar semiconductor waveguide, heats electrons and holes there, and therefore creates their bipolar thermodiffusion flow and, as well as, the electromotive force (emf). The flow causes the carrier excess concentration. Both this concentration and emf are used to get the bolometer response voltage. The bolometer theoretical model is developed. The possibility without cooling or moderate cooling (about 100 K for the Cd_0.2Hg_0.8Te bolometers) to get acceptable for applications values of the noise equivalent power is shown. Experimental results confirm the main model conclusions.     

Nickel bolometers

A modified method of the production of nickel bolometers and their properties are described. A typical example is a bolometer of dimensions 005×2 mm and resistance 14.9 , the NEP (noise equivalent power) of which is 6.23×10^–11 Wc^–1/2 in air and 1.9×10^–11 Wc^–1/2 in vacuo. The paper also describes the influence of cooling the surroundings with liquid nitrogen on the properties of the bolometer. The NEP of a bolometer that works in vacuo with cooled surroundings is 5 times lower. A method is given for correcting the characteristics of two similar bolometers for use in a d.c. bridge which makes the equilibrium of the bridge independent of bridge-current fluctuations in a large range of current.     

Comparative study of annealing and gold dopant effect on DC sputtered vanadium oxide films for bolometer applications

Vanadium oxide (VO_x) thin film has been widely used for IR detectors and it is one of the promising materials for THz detectors due to its high temperature coefficient of resistance (TCR) values. VO_x films with proper TCR values have also high resistance and it restricts bolometer performance especially for uncooled bolometers. To overcome this problem, deposition at elevated temperatures or annealing approach has been accepted and used but gold co-deposition approach has been proposed recently. In this study, vanadium oxide films were fabricated on high resistivity silicon substrates by reactive direct current magnetron sputtering in different O₂/Ar atmosphere at room temperature. We investigated influence of oxygen partial pressure during deposition process and fabricated VO_x thin films with sufficient TCR values for bolometer applications. In order to decrease resistivity of the deposited films, post annealing and gold doping approaches were performed separately. Effect of both post annealing process and gold doping process on structural and electrical properties of VO_x thin films deposited at room temperature were investigated and detailed comparison between these methods were presented. We obtained the best possible approach to obtain optimum conditions for the highly reproducible VO_x thin films which have the best resistivity and suitable TCR value for bolometer applications.     

Thermo-electric charge-to-voltage converter with superconductor–insulator–normal tunnel junction for bolometer applications

A novel type of the zero-biased thermo-electric bolometer (TEB) is proposed. The bolometer is based on a charge-to-voltage converter (CVC) with a superconductor–insulator–normal (SIN) tunnel junction and a superconducting absorber. The absorption of photons in the absorber leads to excitation of quasiparticles with some fraction of charge imbalance, tunneling through the SIN junction in zero-biased mode and generation of voltage. The thermoelectric voltage is determined by accumulation of tunneling charge in an external capacitance. Conversion efficiency is very high and voltage values comparable with a superconducting gap are easily achieved. The zero-biased CVC–TEB can be effectively used for creation of an array of bolometers and multi-pixel detection systems.     

超巨磁阻测辐射热仪

基于超巨磁阻(CMR)材料在金属-绝缘体(M-I)转变点附近的巨大电阻变化,设计并测试了一种新型超巨磁阻测辐射热仪(CMR bolometer).用外延法生长的La_0.67Ca_0.33MnO₃ 薄膜作为测辐射热仪的辐射敏感元件,测量了该器件对黑体和He-Ne激光器的光学响应.所测的信号、噪声都随调制频率的上升而下降,但对于He-Ne激光源,它的信噪比却没有明显的改变.测量了薄膜铁磁金属态和顺磁绝缘态的信号-温度关系,最强的信号出现在靠近M- 关键词： 超巨磁阻     

Seven matched bolometers for millimeter wave observations

We have fabricated a millimeter wave observation system using an array of bolometric detectors. The performance of the system depends largely on obtaining identical performance from each bolometer. We achieved a variance in the responsivity of less than 4% except for one of the seven elements. The bolometers had an electrical NEP of 1.3×10^–16 W/Hz under radiation background loading of 30pW. We used an AC bridge readout circuit to significantly improve the stability of the array and showed that observations can be done without a mechanical beam switch. The bolometer array is now in use on the Nobeyama 45-m telescope for 150GHz observations.H. Matsuo thanks those who helped him work on bolometers during his stay in Berkeley, especially to T. Wilbanks, M. Devlin and C. Inman. The authors are also grateful to S. Sato and T. Watabe at Nagoya University for their advice on the AC bridge circuit. This work is partly supported by the Shimazdu Science Foundation.     

Thermal Modelling and Characterisation of Semiconductor Bolometers

A revised version of the Griffin & Holland ideal semiconductor bolometer model is presented and its use in determining bolometer properties and parameters from experimental load curve measurements is discussed. We show that degeneracy between some bolometer parameters can only be broken by model fitting a family of load curves over a range of bath temperatures, and that measurements with the bolometer blanked (zero absorbed radiant power) are essential for unambiguous determination of the main parameters. The influence of measurement errors on parameter recovery is analysed using synthetic noisy data sets.     

Double Beta Decay Experiments with Thermal Detectors

Massive low temperature particle detectors and their possible impacts on searches for neutrinoless double beta decay (O-DBD) are presented and discussed. In particular, the experimental work of the Milano group is described. Special relevance is given to the present status of the search for O-DBD of ¹³⁰Te and to the possible expansion of this experiment in the near future. The most recent results obtained by the Milano-Gran Sasso collaboration with a 20 bolometer array are presented. On the basis of these results, the construction of a 42 kg array consisting of 56 TeO₂ bolometers (CUORICINO project), to extend the sensitivity of the present experiment, has been proposed. CUORICINO should represent also a feasibility test for a large array of 1000 bolometers (CUORE project) aiming at the search for neutrinoless Double Beta Decay, Cold Dark Matter and Solar Axions with extremely high sensitivity.     

Bolometers operated at 0.1 K and 0.2 K cooled by adiabatic demagnetization

We have constructed bolometers operating at temperatures of 0.1 K and 0.2 K cooled by adiabatic demagnetization. The electrical noise equivalent power (NEP) of the bolometers was found to be 1.8×10^–16 W/Hz^1/2 and 6.6×10^–16 W/Hz^1/2 respectively. These values are within a factor of two of the expected performance based upon bolometer theory. The thermistor material used was gallium doped single crystal germanium, for which we find a resistivity temperature dependence of the form = ^o exp (AT^–1/2).     

Noise Equivalent Power of Background Limited Thermal Detectors at Submillimeter Wavelengths

With the advent of large submillimeter telescopes at high, dry sites, the atmospheric background noise in a moderate bandwidth can be low enough to challenge the ability of instrument designers to produce sufficiently low noise bolometers to be background limited. We compare the predictions for the noise power of a bolometer observing through an emissive atmosphere, considering the effect of atmospheric absorption, telescope optical efficiency, and detector optical efficiency, with measurements through the atmosphere over Mauna Kea.     

Multiplexed Readout of Superconducting Bolometers

Studies of emission in the far-infrared and submillimeter from astrophysical sources require large arrays of detectors containing hundreds to thousands of elements. A multiplexed readout is necessary for practical implementation of such arrays, and can be developed using SQUIDS, such that, e.g., a 32 × 32 array of bolometers can be read out using 100 wires rather than the >2000 needed with a brute force expansion of existing arrays. These bolometer arrays are made by micromachining techniques, using superconducting transition edge sensors as the thermistors. We describe the development of this multiplexed superconducting bolometer array architecture as a step toward bringing about the first astronomically useful arrays of this design. This technology will be used in the SAFIRE instrument on SOFIA, and is a candidate for a wide variety of other spectroscopic and photometric instruments.