Composite Bolometer Research Articles

Modelling Signal Oscillations Arising from Electro-Thermal Coupling and Stray Capacitance in Semiconducting Bolometer Impulse Response

Electro-thermal coupling in semiconductor bolometers is known to create nonlinearities in transient detector response, particularly when such detectors are biased outside of their ideal regions (i.e. past the turnover point in their IV curves). This effect is further compounded in the case where a stray capacitance in the bias circuit is present, for example in long cryogenic cabling. We present a physical model of the influence of such electro-thermal coupling and stray capacitance in a composite NTD germanium bolometer, in which previous experimental data at high $$V_\mathrm{bias}$$ resulted in oscillations of the impulse response of the detector to irradiation by alpha particles. The model reproduces the transient oscillations seen in the experimental data, depending both on electro-thermal coupling and stray capacitance. This is intended as an experimental and simulated example of such oscillations, demonstrated for the specific case of this bolometric detector.

Interferometric bunch length measurements of 3 MeV picocoulomb electron beams

We report picosecond bunch length measurements using an interferometric method for a 3 MeV electron beam having bunch charge ranging from 1 to 14 pC. The method senses the single-cycle sub-terahertz (THz) pulse emitted by each electron bunch as coherent transition radiation which, in turn, is analyzed using a Michelson-type interferometer, forming an interferogram that is then processed to yield the nominal electron bunch length. This sub-THz coherent radiation intensity was measured using a quasi-optical detector (QOD) operated at room temperature. This experiment was quite challenging since the divergence angle of the sub-THz pulse emitted by the low-energy electron bunch exceeds ±10°, and its pulse energy at the entrance to the detector was as low as 100 pJ. When compared to a conventional helium-cooled silicon composite bolometer designed for frequencies above 0.5 THz, the QOD provided much better signal-to-noise ratio in the ∼80 GHz frequency range, which was critical for the successful measurement of the bunch length.

Benefits of Bolometer Joule Stepping and Joule Pulsing

We introduce the `Joule stepping' technique, whereupon a constantly-biased bolometer has its bias voltage modified by a small additional step. We demonstrate this technique using a composite NTD semiconductor bolometer and a pulsing device which sends an extra step in voltage. We demonstrate the results of the technique over a range of bias voltages at 100, 200, and 300 mK. We find that Joule stepping allows us to directly measure long thermal tails with low amplitudes in the bolometer response, and could be a useful tool for quickly and easily understanding response functions of bolometric detectors. We also show that the derivative of the Joule step is equivalent to the bolometer response to a $\delta$-pulse (or Joule pulse), which allows for greater understanding of fast transient behaviour.

Towards a physical model for energy deposition via cosmic rays into sub-K bolometric detectors

Cosmology space missions have been known to be particularly sensitive to systematic effects arising from the interaction between cosmic rays and highly sensitive detectors below 200 mK. To remove this signal, one must first understand the deposition and dissipation of energy into these detectors. Using a well-known NTD germanium composite bolometer, we simulate the effect of cosmic rays using a radioactive source in the laboratory. Through analysis of experimental data, we find that the glitch signal shape is a function of incoming particle position, as well as the incoming particle energy. We report also on nonlinear effects in the fit, in order to lay the groundwork towards a new physical model for this energy propagation in the bolometer.

Interferometer measurements of terahertz waves from Bi2Sr2CaCu2O8+d mesas

We fabricated rectangular mesa structures of superconducting Bi2Sr2CaCu2O8+d (Bi2212) using e-beam lithography and Ar ion beam etching techniques for terahertz (THz) emission. c-axis resistance versus temperature (R–T), current–voltage (I–V) characteristics and bolometric THz power measurements were performed to characterize Bi2212 mesas. The emission frequency of mesas was determined using a Michelson interferometer setup which also demonstrates polarized emission. Interference patterns of THz radiation from Bi2212 mesas were detected by various detectors such as a liquid helium cooled silicon composite bolometer, a Golay cell and a pyroelectric detector. An emitted power as high as 0.06 mW was detected from Bi2212 mesas. For the first time, most of the pumped power was extracted as THz emission from a Bi2212 mesa. The radiation at 0.54 THz was detected using the Michelson interferometric setup.

A new technique for the identification of surface contamination in low temperature bolometric experiments

In the framework of the bolometric experiment CUORE, a new and promising technique has been developed in order to control the dangerous contamination coming from the surfaces close to the detector. In fact, by means of a composite bolometer, it is possible to partially overcome the loss of spatial resolution of the bolometer itself and to clearly identify events coming from outside.

BOLUX: A cryogenic electrical-substitution radiometer as high accuracy primary detector in the 150–11,000 eV range

We have measured the electrical and radiometric properties of a cryogenic absolute radiometer BOLUX (Bolomètre pour l’Utilisation dans le domaine de rayons X). BOLUX is intended for use as a primary detector standard for radiant power measurement of a synchrotron beam from EUV to X-ray spectral ranges. The absolute radiometer uses a composite bolometer with a built-in electrical heating element. The bolometer's absorber, optimized for beam diameter and for X-ray absorption, is coupled both to a Ge doped thermometer and to the electrical resistance calibrator with similar thermal paths so that electrical and radiant heating are equivalent. This device operates between 4 K the liquid helium temperature, and 1.25 K obtained by pumping helium. The main advantage of BOLUX over other radiometers is its portability (weight 12 kg) which means it can be used with any synchrotron beamline. The second advantage is its very small time constant (20 ms) compared with other apparatus (typically a few min). We can use it in DC mode or in AC mode and Alpha sources calibration experiments have already been realized. We have measured synchrotron radiant power at the laboratory of the Physikalisch- Technische Bundesanstalt (PTB) at the Berlin electron storage ring BESSY II. We reported experiments in DC mode and showed the possibility to study the drift and the temporal stability at the exit of a synchrotron beamline. For a helium bath temperature of 1.33 K and in the spectral range of 150 eV–11 keV, we have measured a high limit of detection (in 1 s integrated) to be 10 −10 W, with a DC responsivity of 1.3×10 5 V/W, spatial nonuniformity over 4 mm diameter below 1% and possibility to use over five decades between a few nW and 100 μW with a good linearity (<1%). Typically available radiant power of 50 nW can be measured with a standard uncertainty as low as 1%. BOLUX response has been directly compared with qualified photodiodes [1]; we have observed a standard deviation between the two detectors lower than the total uncertainty of the detectors.

Laboratory set-up for studying ices at the MIR and FIR region

H 2 O, CO and CO 2 ices are condensed on carbonaceous and silicate dust grains in dense interstellar clouds and circumstellar environments. The presence of these ices is inferred by analysing their infrared (IR) spectra. The upcoming Herschel space observatory (HERSCHEL) and ground-based astronomy project (ALMA) will provide new spectral data in the unexplored far infrared (FIR) and sub-millimetre range. In our laboratory we are developing instrumentation to study ices at IR region. One of the key components of our laboratory is a silicon composite bolometer in our IFS. This detector allows us to obtain spectra with a sensitivity much greater than that obtained with a standard deuterated triglycine sulphate (DTGS) detector working at room temperature and under vacuum conditions. We plan to collect mid infrared (MIR) and FIR spectra of simple ices and their mixtures and compare these with observational data. It is also planned to do a systematic laboratory study of the effects that ultraviolet (UV) photolysis and thermal annealing have on the ice band profiles and their structure.

Characterization of the composite bolometer with a high- Tc superconductor thermometer for an absolute radiometer of synchrotron radiation

The article describes the structure and calculation modeling of characteristics of the detector for an absolute synchrotron radiation radiometer in the soft X-ray range of 8–0.4 nm. The detector is a bolometer working on the principle of substitution of electrical power for radiation power, with a high-temperature superconductor film as an element, sensitive to heat. The noise-equivalent power is predicted to be down to 4×10 −11 W/Hz 1/2 at 10 Hz.

Modelled V-I Performance of A 3HE Composite Bolometer Detector

The V-I characteristics of a 3He-cooled, composite bolometer detector designed for submillimetre astronomy are modelled. The modelling yields detector parameters that cannot be measured directly. The system NEP predicted from theoretical V-I equations is found to agree with the measured noise values. The calculated dynamic thermal conductance and the electrical responsivity are found to deviate from the standard model at low temperatures.

New technique for linearity correction of bolometers

A low-temperature, composite silicon bolometer was tested for use as a highly sensitive infrared detector in spectrometric setups. The sensitivity of the detector was calculated as a function of the cryogenic temperature, the continuous background, and chopped-signal radiation. Based on this result, a new technique was used to characterize the linearity of bolometer sensitivity. The characteristic feature of this technique is that the bolometer is exposed to superimposed beams of chopped and continuous radiation. The intensity of both beams can be varied over a wide range, closely simulating the actual operation of the bolometer. Since the effect of the changing background radiation is not distinguishable from the effect of a shift in the reference temperature of the Dewar, or of other environmental factors, they can be modelled together by continuous radiation alone. The results are given. This technique can be used for any thermal detector if both the ac and dc electrical signals corresponding to the chopped and background radiation, respectively, are available together or separately. The correction factors refer only to the actual resistance of the bolometer. These factors determined by the new method for every combination of the two electrical signals can be applied even with unstable reference temperature or environmental factors. The same setup was used to determine the frequency response of the bolometer. The results show good agreement with the calculated value of sensitivity as a function of frequency.

Bolometer characterisation with a specially developed cryogenic source having more than five peaks in the 1–6 keV range

Abstract At very low temperature (10–50 mK), and at relatively low energy (typically 100 eV–10 keV), the linearity and resolution of bolometers need to be carefully tested. Commercially available sources below 6 keV are rare and difficult to cool down. We have developed a specially designed compact X-ray source where 55Fe is combined with an ion-exchanged membrane containing more than three fluorescent elements. More than five peaks can be identified form 1 keV to 6.5 keV. A spectrum obtained with a 0.5 mg composite diamond bolometer, allowing a good measurement of linearity and resolution as a function of energy is presented. It is compared with a spectrum of the same source measured with a classical germanium detector. Since bolometer detectors have neither window, nor dead layer effects, bolometer spectra obtained with these sources could be used to directly calibrate the efficiency response of classical detectors at very low energy.

Composite bolometer based on high temperature superconducting Bi2Sr2CaCu2O8+x crystals for application in the far infrared

We discuss the feasibility of a new type of high temperature superconducting bolometer operating in the sub-millimeter region (λ>300μm) of the spectrum in the temperature range 80K:100K. We use the sharp resistive transition of Bi 2 Sr 2 CaCu 2 O 8+x superconducting single crystals as sensitive thermometer. The sensor is thermally coupled to a thin diamond substrate covered on the back side with a bismuth film that performs the absorbtion of the radiation. Such a detector should have large sensitive area and short time response due to the low heat capacity of both crystal and substrate. We describe the results of the electrical bolometric characterization, noise measurements and optical calibration carried out on the first prototype and use them to predict the Noise Equivalent Power (NEP) of a well designed detector

Blackbody radiation from hot two-dimensional electrons in AlxGa1-xAs/GaAs heterojunctions.

We have studied the broad-band far-infrared (FIR) radiation from hot two-dimensional (2D) electrons in selectively doped ${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As/GaAs heterojunctions. The combination of a composite Si bolometer and a magnetic-field-tuned InSb cyclotron resonance filter allows a spectroscopic as well as an intensity analysis of the FIR emission from hot 2D electrons. It is found that the radiation spectra are well explained by the theory of blackbody radiation and the emissivity assuming a classical Drude conductivity. The behavior of the determined effective blackbody temperatures of hot 2D electrons is quantitatively explained by a theory of acoustic- and optical-phonon emissions.

Composite bolometer based on Bi 2Sr 2CaCu 2O 8+x single crystals

We describe the properties of a prototype bolometer operating at liquid nitrogen temperature based on a Bi 2Sr 2CaCu 2O 8+x single crystal 15 μm thick grown by the flux method. The use of thin single crystals having low thermal capacities was suggested by the request of decreasing the response time τ of the device. Preliminary results indicate that single-crystal-based far infrared bolometers can be competitive with the commercial detectors operating at room temperature.

Cooling of coupled solids by helium films.

Recently, Mester et al. have made measurements of the cooling effect of a superfluid He film on a composite bolometer. In interpreting their results they suggest that the main thermal resistance is caused by an insufficient generation of excitations, which can cause evaporation, in the He film. In this Letter we suggest an alternative explanation which accounts for their measurements in considerable detail. The main thermal resistance is found to be between the Ge and sapphire, and we conclude that the Kapitza conductance to a $^{4}\mathrm{He}$ film is the same as that to bulk liquid $^{4}\mathrm{He}$.

Far infrared photoelectric thresholds of extrinsic semiconductor photocathodes

Far infrared detection is demonstrated in forward biased Ge (out to 240 μm), Si (220 μm), and InGaAs (90 μm) p-i-n diodes with D up to 5×1010 cm Hz1/2/W at 4.2 K. For silicon detectors, this is the longest response wavelength ever reported. Estimates for the responsivity and the detectivity for unoptimized commercial samples are provided by comparison with a silicon composite bolometer. The variations observed in the long wavelength threshold (λt) suggest that if correlations with device processing parameters can be successfully established, this approach can be used to tailor detectors for different IR wavelength regions. Spectral response comparison with a single p-i structure strongly supports the detection mechanism and opens the possibility of detector optimization using multilayered structures.

A Novel Wavelength Tunable Silicon Detector for Infrared Detection

ABSTRACTA cryogenic extrinsic silicon detector which can detect IR photons of very low energy, i.e., down to about 5.5 meV ( 220 μm) is presented. The mechanism involves photoexcitation of carriers over low energy interfacial work function barriers at p-i or n-i interfaces in a process analogous to the classic photoelectric effect. Estimates for the responsivity and the detectivity for unoptimized commercial samples containing both p-i and n-i interfaces and a sample containing only a single p-i interface are provided by comparison with a silicon composite bolometer. The range of long wavelength thresholds (λt) observed suggests that this approach can be used to tailor detectors for different IR wavelength regions by changing the dopant impurity and the impurity concentration at levels near the metal-insulator transition. Single interface results confirm the possibility of detector optimization using multilayered structures. This should lead to a unique family of uniform monolithic IR focal plane structures with tailorable and tunable response characteristics within virtually all the IR spectral range of interest.

Detector system with cryogenic semiconductor and superconductor bolometers

The design and characteristics are reported of a two-channel receiving device based on a semiconductor (Ge:Ga) and a superconductor (Pb+Sn) bolometers operating at deep cooling. The device is intended to detect radiation in the spectral region 50 to 500 μm at the aperture ratio 1:6 and the input hole of the field system 7 mm in diameter. The semiconductor composite bolometer has a noise equivalent power (NEP) of 3·10 −13 WHz − 1 2 at the response time 2·10 −3 s and the helium-bath temperature 1.34 K, and the superconductor one 2.1·10 −12 WHz − 1 2 at 3·10 −6 s and 4.23 K, respectively.

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 O telescope equipped with He-cooled filters and a composite silicon bolometer with an NEP of 1.3 10−14 W/Hz1/2 for imaging, radiometry and spectroscopy of the Cygnus region at the wavelengths 80 μm, 130 μm and 310 μm. 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.