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).     

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.     

Large area bolometers for millimeter-wave power calibration

An accurate monolithic power meter has been developed for millimeter-wave applications. The detector is a large-area Bismuth bolometer, integrated on a fused-Quartz substrate. It simply measures the temperature change caused by the absorption of millimeter-wave radiation. The power meter is simple to fabricate, inexpensive, and can be easily calibrated using a low-frequency network. The measured responsivity for a 50 bolometer, with an area of 1×1cm, at a bias of 1V. and a video modulation of 100Hz, is 1mV/W. The noise spectrum exhibits a 1/f rolloff till 1KHz, and is limited by the Johnson noise for higher frequencies. The NEP of the detector is 3WHz^–1/2 at a video modulation of 1KHz. It is possible to decrease the current NEP by fabricating bolometers with higher responsivities. Possible application areas are absolute power calibration and localized power density measurements at millimeter and submillimeter wavelengths.     

Development and operation of a balloon-borne telescope for fir imaging, radiometry and spectrometry of the galactic cygnus region

We have designed and built a balloon-borne far-infrared 60 cm telescope equipped with He-cooled filters and a composite silicon bolometer with an NEP of 1.3·10^–14 W/Hz^1/2 for imaging, radiometry and spectroscopy of the Cygnus region at wavelengths up to 330 m. A test flight took place at the CNES balloon station at Aire/Adour, F, on May 8, 1989. The balloon stayed 4_1/2 h at the observation height of 39 km. Tests and results are discussed.     

Radiant-energy detection by?Ba?Cu?O thin films

High T_c superconducting films offer promise as fast sensitive detectors of microwave and infrared. A high T_c superconducting transition-edge bolometer was fabricated from Y–Ba–Cu–O thin film on a (100) SrTiO₃ substrate, and tested at about the T_c midpoint using a 500 K blackbody source. In this initial work only NEP=5×10^–8W/Hz^1/2 was achieved with a large time constant caused by rather thick substrate. The sensitive element was put in the vacuum chamber of a liquid nitrogen metal cryostat for three weeks and through ten cold-hot cycles (80 K-300 K), the sensitivity of the bolometor kept repeatable. Some future work is also discussed.     

High resolution fourier transform spectroscopy using infrared synchrotron radiation: I. Instrumentation

A compact high resolution (.002 cm^–1) vacuum Fourier transform spectrometer for use with far infrared synchrotron radiation was constructed at the National Synchrotron Light Source at Brookhaven National Laboratory. The spectrometer may be operated using a gas cell of path length of 2 m and a He cooled bolometer with NEP of 10^–13. The pure rotational spectrum of Ammonia was used to test the spectrometer.     

Characterization of high purity GaAs far-infrared photoconductors

In this paper we report the results of an extensive study on the far-infrared photoconductivity of high purityn-type GaAs. The crystal, which was grown at Max-Plank-Institute for Solid State Physics using liquid-phase epitaxy, exhibited the fine structures of the excited state transitions of the residual shallow level impurities. The major peak in the spectral response belongs to the 1s-2p transition, with its responsivity about thirty five times higher than the continuum. At 3.4K detector temperature, 625 mV bias, and 100 Hz chopping frequency the detector responsivity at 35.4 cm^–1 (279 µm) was measured to be 0.017 A/W. Under these same conditions, the NEP was 5.9×10^–14 W/Hz. The (DC) dark current at 25 mV bias was 5.6×10^–14 A.     

Far-infrared observations of the galactic Cygnus region and Mars with a 60 cm diameter balloon-borne telescope

We have introduced secondary-mirror chopping in our balloon-borne far-infrared 60 cm Ø telescope equipped with He-cooled filters and a composite silicon bolometer with an NEP of 1.3 10^–14 W/Hz^1/2 for imaging, radiometry and spectroscopy of the Cygnus region at the wavelengths 80 m, 130 m and 310 m. The modified system was flown on September 26/27, 1990 with a 380'000m³ hydrogen balloon at the CNES station at Aire/Adour, France. Observations were performed at a platform height of 39 km during 5 hrs. We made successful measurements on the complexes DR21 and S106 of the Cygnus region as well as on Mars at the wavelengths mentioned.     

Micromachined Uncooled IR Bolometer Linear Array Using VO2 Thin Films

Mixed vanadium oxide thin films, as VO₂ for the main composition are materials for uncooled microbolometer due to their high temperature coefficient of resistance (TCR) at room temperature. This paper describes the design and fabrication of 8-element linear array IR uncooled microbolometers using the films and micromachining technology. The characteristics of the array is investigated in the spectral region of 8–12 m. The fabricated detectors exhibit responsivity of up to 10 KV/W, typical detectivity of 1.89×10⁸ cmHz^1/2/W, and thermal time constant of 11 ms, at 296 K and at a frequency of 30 Hz. Furthermore, The uncorrected response uniformity of the linear array bolometers is less than 20%.     

Quasioptical superconducting hot electron bolometer for submillmeter waves

We report on a superconducting hot electron bolometer coupled to radiation via a broadband antenna. The bolometer, a structured NbN film, was patterned on a thin dielectric membrane between terminals of a gold slotline antenna. We investigated the response to submillimeter radiation (wave-lengths 0.1 mm to 0.7 mm) in the fundamental Gaussian mode. We found that the directivity of the antenna was constant within a factor of 2.5 through the whole experimental range. The noise equivalent power of the bolometer at 119 µm was 3 · 10^–13 W/Hz^1/2; a time constant of 160 ps was estimated.     

A high-sensitivity near-millimeter-wave photoconductive detector using [Hg, Cd]Te

In an earlier paper [1], we reported the observation of photoconductivity from free-carrier absorption in [Hg, Cd]Te. By using samples of [Hg, Cd]Te with different electrical and alloy properties, we have improved the near-millimeter-wave (NMMW) responsivity by over two orders of magnitude. At 1.6 K a best sample responsivity of about 185 V/W and a bandwidth of over 5 MHz have been measured. This responsivity corresponds to a Johnson-noise-limited noise-equivalent-power (NEP) of 1.6 × 10^–12 . Another sample of similar compposition yielded an NEP of 1.8 × 10^–12 and a 25 MHz bandwidth. These results coupled with a wide spectral sensitivity [1] indicate that [Hg, Cd]Te NMMW detectors compare very favorably with similar InSb detectors [2].     

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.     

Experimental determination of the rates of the excited muonic hydrogen charge exchange on helium

The data of the experiment with the H₂+⁴He mixture are analyzed in order to estimate muon transfer rates from the excited states of p atoms to helium. Experimental data turned out to be insensible to the transfer rates from the metastable 2s state. The rates forn=3, 4, 5 were found to be: ⁽³⁾=(2±7)×10¹⁰ s^–1, ⁽⁴⁾=(16±13)×10¹¹ s^–1, ⁽⁵⁾=(75±60) ×10¹¹ s^–1, respectively.     

A resonant bridge for measuring ɛ and tan δ for highly conducting substances

This bridge covers the range 5–200 kHz for substances of conductivity up to 10^–2 ohm^–1 cm^–1. The relative error in for tan =100 is ± 3%, while tan is measured to ± 2%. Results are given for solutions of high conductivity.     

A pulsed laser employing Ar+ ions at high currents and low pressures

There are several papers [1–5] on pulsed Ar⁺ lasers, but all the tests have been done at low current densities (100 A/cm²). We have used densities up to 15–20 kA/cm², the best pressure range being 8×10^–3 to 2×10^–2 mm Hg. The generation under these conditions has some features not seen under ordinary conditions.     

Linear High-Tc YBa2Cu3O7?δ Superconducting Thin Film Infrared Detectors Coupled with a Cylindrical Microlens Array in Quartz Glass Substrate

Monolithic linear cylindrical microlens array in a quartz glass substrate is fabricated using photolithography and ion beam etching technique, the high-Tc YBa₂Cu₃O_7– superconducting thin films are deposited through excimer laser scanning ablation, the superconducting thin films are patterned by photolithographic method and ion beam etching technique, and the hybrid structure of the microlens array component and the superconducting IR detectors has been obtained using an IR glue to cement the microlens component onto the superconducting device. We also investigate the optical response characteristics of the hybrid device in the optical spectral region of 1 ~ 5 m, as follows. The average optical responsivity of the hybrid device is 1.6×10⁴ V/W, average noise equivalent power is 2.3×10^–12 WHz^–1/2, average detectvity is 3.2×10⁹ cmHz^1/2W^–1, and the non-uniformity of detectvity (D*) is not more than 14%. The experimental results show that the performance of the superconducting device is improved notably using a quartz glass refractive microlens array as the incident IR radiation concentrators.     

Redox reaction of μ−O in water determined by the chemical shift

The chemical shift of ^–O in water, ice and in aqueous hydrogen peroxide (H₂O₂) was examined using ^–O resonance. Two distinct signals are obtained in water and ice. Using ⁺ resonance signal as a standard, the observed shiftsg are –7.0×10^–4 (signal A) and –12.1×10^–4 (signal B) respectively. The intensity of the two fractions are almost equivalent in water; however, in ice, the intensity of signal B decreases with increase of signal A. After the addition of hydrogen peroxide to the water signal B disappears, A increases, and the total amplitude is increased.     

Optical constants of thin CoSi2 films on silicon

The optical transmission of CoSi₂ films of thickness 2.6–15 nm is measured in the wavelength range 1–20 m. The optical constants are evaluated by taking into account multiple reflections in the film and by fitting a Drude model. The plasma frequency _p=5.4–7.6 eV is equivalent to a carrier density n _eff=3×10²² cm^–3 and one carrier per unit cell. The relaxation frequency of the plasma resonance assumes high values =2 eV near the interface to silicon and decreases into the bulk film over several nanometers. Films grown off-axis from the (111) Si orientation exhibit an enhanced relaxation frequency.