Submillimeter Range Research Articles

65 Cybele in the thermal infrared: Multiple observations and thermophysical analysis

We investigated the physical and thermal properties of 65 Cybele, one of the largest main-belt asteroids. Based on published and recently obtained thermal infrared observations, including ISO measurements, we derived through thermophys- ical modelling (TPM) a size of 302 × 290 × 232 km (±4%) and an geometric visible albedo of 0.050 ± 0.005. Our model of a regolith covered surface with low thermal inertia and default roughness describes the wavelengths and phase angle dependent thermal effects very well. Before/after opposition effect and beaming behaviour can be explained in that way. We found a con- stant emissivity of 0.9 at wavelengths up to about 100 µm and lower values towards the submillimetre range, indicating a grain size distribution dominated by 200 µm particle sizes. The spectroscopic analysis revealed an emissivity increase between 8.0 and 9.5 µm. We compared this emissivity behaviour with the Christiansen features of carbonaceous chondrite meteorites, but a conclusive identification was not possible. A comparison between the Standard Thermal Model (STM) and the applied TPM clearly demonstrates the limitations and problems of the STM for the analysis of multi-epoch and -wavelengths observations. While the TPM produced a unique diameter/albedo solution, the calculated STM values varied by ±30% and showed clear trends with wavelength and phase angle. 65 Cybele can be considered as a nice textbook case for the thermophysical analysis of combined optical and thermal infrared observations.

65 Cybele in the thermal infrared: Multiple observations and thermophysical analysis

We investigated the physical and thermal properties of 65 Cybele}, one of the largest main-belt asteroids. Based on published and recently obtained thermal infrared observations, including ISO measurements, we derived through thermophysical modelling (TPM) a size of 302x290x232 km (+/- 4 %) and an geometric visible albedo of 0.050+/-0.005. Our model of a regolith covered surface with low thermal inertia and default roughness describes the wavelengths and phase angle dependent thermal aspects very well. Before/after opposition effect and beaming behaviour can be explained in that way. We found a constant emissivity of 0.9 at wavelengths up to about 100 micron and lower values towards the submillimetre range, indicating a grain size distribution dominated by 200 micron particle sizes. The spectroscopic analysis revealed an emissivity increase between 8.0 and 9.5 micron. We compared this emissivity behaviour with the Christiansen features of carbonaceous chondrite meteorites, but a conclusive identification was not possible. A comparison between the Standard Thermal Model (STM) and the applied TPM clearly demonstrates the limitations and problems of the STM for the analysis of multi-epoch and -wavelengths observations. While the TPM produced a unique diameter/albedo solution, the calculated STM values varied by +/-30 % and showed clear trends with wavelength and phase angle. Cybele can be considered as a nice textbook case for the thermophysical analysis of combined optical and thermal infrared observations.

Fully Micromachined Finite-Ground Coplanar Line-to-Waveguide Transitions for<tex>$W$</tex>-Band Applications

A fully micromachined finite-ground coplanar (FGC) line-to-waveguide transition for W-band applications has been designed, fabricated, and tested. The transition utilizes a printed E-plane probe, inserted into the broad sidewall of a micromachined waveguide. This type of transition plays an important role in many applications where coupling between the popular FGC line and a waveguide is required. Excellent performance across the entire W-band of such a transition is presented in this paper. The investigated waveguide, micromachined in silicon using the deep reactive ion etching technique, demonstrates its potential as an alternative to costly conventional waveguides at high frequencies. A similar transition with a micromachined waveguide formed via bulk micromachining using a wet etchant is also demonstrated. The free-standing probe utilized in this second transition proves the potential of such transitions to be applicable well into the submillimeter and terahertz range.

Crystal undulator as a new compact source of radiation

Crystalline undulators with periodically deformed crystallographic planes offer coherent electromagnetic fields on the order of 1000 T and provide undulator period $L$ in submillimeter range. We present an idea for creation of a crystalline undulator and report its realization. One face of a silicon crystal was given periodic microscratches (grooves) by means of a diamond blade, with a period ranging from 0.1 to 0.5 mm in different samples. The x-ray tests of the crystal deformation have shown that a sinusoidal-like shape of crystalline planes goes through the bulk of the crystals. This opens up the possibility for experiments with high-energy particles channeled in the crystalline undulator, a new compact source of radiation. The first experiments on photon emission in the crystal undulator are in preparation at IHEP (Protvino) with 2--15 GeV positrons and at LNF (Frascati) with 500--800 MeV positrons, aiming to produce undulator photons in the range of 50--500 keV. The results of Monte Carlo simulations for the planned experiments are presented as well.

First observation of a solar X-class flare in the submillimeter range with KOSMA

We present the first solar flare observations with the KOSMA submillimeter telescope at 230 and 345 GHz. The GOES X2.0 flare on April 12, 2001 was also observed at millimeter and centimeter wavelengths, as well as in soft and hard X-rays. It exhibits both an impulsive phase of nonthermal gyrosynchrotron radiation and an extended phase of strong thermal free-free emission in the millimeter and submillimeter range. As in previous observations, a mismatch between the electron energy spectral indices, inferred from the millimeter and hard X-ray data, exists and is interpreted as a flattening of the energy spectrum above a break energy of several hundred keV. The observed thermal emission closely follows the shape of the mm/submm flux density time profile predicted from soft X-ray observations. As the observed absolute flux densities exceed the predicted ones by a factor of ~1.5–3.4, both the mm/submm emission and the soft X-rays must be thermal bremsstrahlung with a common energy source, but from locations with different plasma parameters. KOSMA observations allowed an estimate of source locations and sizes for the nonthermal and thermal sources. All of them coincide within 0.2 arcmin and with those seen in soft and hard X-rays. Surprisingly, the thermal submillimeter source diameters at 230 and 345 GHz (42 and 70 arcsec respectively) increase with frequency.

Low Noise Quasi-Optic Receiving in Millimeter and Submillimeter Range for Geophysical and Radio Telescope Measurements

This paper is focused on the choice of the module for low noise receiver in millimeter (mm) and sub millimeter (submm) wave ranges used in geophysical remote sensing systems for measurement of geophysical parameters by means of radiobrightness temperatures (radiometer systems obtaining data by means of radiobrightness temperatures). The observed data analysis, used in order to obtain recommendations and forecasts based on the radio telescope measurements and geophysical phenomena in the events of earthquakes, volcano explosions and typhoons, are realized by means of specialized computer codes.

Physics with large extra dimensions

The recent understanding of string theory opens the possibility that the string scale can be as low as a few TeV. The apparent weakness of gravitational interactions can then be accounted by the existence of large internal dimensions, in the submillimeter region. Furthermore, our world must be confined to live on a brane transverse to these large dimensions, with which it interacts only gravitationally. In my lecture, I describe briefly this scenario which gives a new theoretical framework for solving the gauge hierarchy problem and the unification of all interactions. I also discuss its main properties and implications for observations at both future particle colliders, and in non-accelerator gravity experiments. Such effects are for instance the production of Kaluza-Klein resonances, graviton emission in the bulk of extra dimensions, and a radical change of gravitational forces in the submillimeter range.

Investigation and optimization of a pulsed ultraviolet image amplifier within a micro-marking system

We present an all optical image amplifier in the pulsed ultraviolet (355 nm) based on photorefractive two wave mixing and its implementation in an optical micro-lithographic system. Due to the high possible amplification factor it is possible to use masks with low damage threshold such as polymeric slides or an amplitude modulator based on liquid crystals. This leads to a versatile system which is independent of expensively prepared masks. The amplified image is de-magnified to the sub-millimetre range and projected onto the target. The main application for our system is the authentication of artifacts by imprinting an individual code onto the item surface.

Experimental study of hydrocarbon hydrogenation and dehydrogenation reactions in silicon microfabricated reactors of two different geometries

Miniaturization is fast gaining importance and relevance in chemical processes that are conventionally carried out on a lab-scale or larger. Miniaturized chemical-reaction systems, or microreactors, are devices that behave as continuous flow systems and whose dimensions are in sub-millimeter range. Microreactors were successfully fabricated using wet silicon bulk micromachining and deep reactive ion etching (DRIE) techniques, were used to characterize reactions involving heterogeneous catalysis, and demonstrated their feasibility as efficient tools in catalyst and process development. In this study, the relatively simple reactions of cyclohexene hydrogenation and de-hydrogenation over a platinum catalyst were studied, reactions which are models for important classes of reactions of significance in petroleum industry. The conversion, selectivity and yield for products cyclohexane and benzene, were measured as a function of temperature and reactant flow rates. The experiments were done in microreactors of characteristic dimensions of 100 and 5 μm. The results are shown which compare the performance of these two types of reactors.

Microfabrication of ceramics by rapid prototyping process chains

Most shaping processes for ceramics are based on a powder technological moulding process using a negative mould and subsequent thermal compaction. Especially for prototypes and small-lot series of microcomponents, the outlay for moulds is the major costing factor. Therefore the use of rapid prototyping (RP) processes can decisively reduce the costs and time in product development of ceramic microcomponents. By combining the high resolution of, for example, stereolithography as an inexpensive and fast supply for master models with the high flexibility of low-pressure injection moulding, a rapid prototyping process chain (RPPC) has been established for the fabrication of micropatterned ceramic components as functional models or pre-production lots. This RPPC proved to have a very high moulding precision and accuracy in the submillimetre range, but also enables the fabrication of components with outer dimensions of several centimetres. Different RP techniques were investigated with regard to their suitability to be used as master models in the replication chain. The quality of the master models turned out to be of decisive significance for the quality and reproducibility of the ceramic mouldings.

Rotational Spectrum of Hydrazine in the Submillimeter Range

In the submillimeter range, from 345 to 410 GHz, 472 new rotational transitions in the vibrational ground state of hydrazine have been measured. The majority of recorded lines form eight K=2←1 Q-branches with J≤30, each branch being split due to internal rotation in hydrazine. New rotational transitions together with 443 known earlier have been fitted to an effective group-theoretical Hamiltonian originally developed by Hougen (J. T. Hougen, J. Mol. Spectrosc. 89, 296–327 (1981)). A reasonable fit was obtained using several Δ K=0, ±1, ±2, and ±4 matrix elements. For all 915 rotational transitions an overall standard deviation of the fit of 0.59 MHz was obtained using 32 parameters. These were 14 asymmetric rotor constants, 16 NH 2 inversion parameters, and 2 internal rotation parameters.

High beta and electron dose from 192Ir: implications for “gamma” intravascular brachytherapy

Purpose : Trains of multiple 192Ir seeds are used in many clinical trials for intravascular brachytherapy. 192Ir source is commonly considered as a gamma emitter, despite the understanding that this radionuclide also emits a wide range of electron and beta energies, with a similar range of energy. The high dose from betas and electrons in the submillimeter range due to unsealed ends of seed sources should be precisely quantified to fully understand the backdrop for complications associated with 192Ir coronary artery brachytherapy. Methods and Materials : Monte Carlo simulations (MCNP4C code) were performed for a model 5-seed 192Ir train used in SCRIPPS, GAMMA, and the Washington Radiation for In-Stent Restenosis (WRIST) randomized clinical trials. A stack of radiochromic films was also used to measure the dose distributions for an actual 6-seed train. Results : In the submillimeter range very close to the source, Monte Carlo results show that betas and electrons deposit a higher dose than 192Ir photons (gamma and X-rays) over the interseed gap. A high luminal dose from the combined effects of betas, electrons, and photons emitted from 192Ir can be deposited, particularly between seeds. When prescribing 15 Gy at 2 mm, the combined dose can be as high as 160 Gy at 0.5 mm. Different peak doses near the interseed gaps were noted, which may be due to variability of seed-end surfaces and nonuniformity of seed activity within a real multiseed train. Dose-volume histograms (DVH) of lumen surfaces were evaluated for an eccentric seed train. The DVH parameters indicating the extent of hot spots in the lumen wall, DV 10, DV 5, DV 2, and DV 1 (dose received by 10, 5, 2, 1% respectively of the total lumen surface), can be as high as 55, 76, 81, and 155 Gy for a lumen with 3-mm diameter, and 75, 80, 110, and 158 Gy for a narrow 2-mm lumen. Conclusion : 192Ir multiple seed trains used in the SCRIPPS, GAMMA, and WRIST trials can deposit a very high dose to the luminal wall. A particularly high electron and beta dose can be delivered near the interseed gap if the source is not centered in the catheter and lumen. The dose from 192Ir betas and electrons may partially explain adverse outcomes reported from 192Ir multiseed clinical trials. Improvement of the encapsulation design to filter out the betas and electrons should be seriously considered.

Evaluating Geometric Accuracy of Multi-Platform Stereotactic Neuroimaging in Radiosurgery

We used a spherical phantom to evaluate geometric accuracy in multi-platform stereotactic neuroimaging for radiosurgery. The phantom consisted of two plastic 16-cm-diameter hemispheres in which an exchangeable 8-cm plastic functional cube was incorporated. The functional cube contained cylinder and point targets. The targets were filled with a mixed aqueous solution of 2-mM copper sulfate and 300-mg/ml iodinated contrast medium and were visible on both MR and X-ray images. Two MR scanners and a biplane X-ray angio-suite were used to scan the phantom stereotactically in two sessions of the experiment. The angio-suite was equipped with digital subtraction and distortion-correction software. The resulting stereotactic images were transferred to a dose-planning computer for length measurement and coordinate determination of the targets. The mean errors of the measured cylinder length on distortion non-corrected X-ray stereotactic images were 0.24 ± 0.14 and 0.73 ± 0.10 mm, respectively, in the experiments; on distortion-corrected images 0.22 ± 0.10 and 0.35 ± 0.39 mm. They were 0.50 ± 0.24, 0.25 ± 0.19 and 0.49 ± 0.34, 0.23 ± 0.25 mm, respectively, of the two MR scanners. The mean errors of coordinate determination of point targets between the stereotactic MR and the distortion-corrected X-ray images were 0.70 ± 0.18, 0.52 ± 0.22 and 0.76 ± 0.25, 0.40 ± 0.10 mm, respectively, in the experiments. We found that the overall geometric errors of target delineation between stereotactic MR and X-ray images were in the submillimeter range. The current study validates the multi-platform and multi-facility stereotactic neuroimaging practice and ensures imaging accuracy in radiosurgery.

Asteroid detection at millimetric wavelengths with the PLANCK survey

The PLANCK mission, originally devised for cosmological studies, offers the opportunity to observe Solar System objects at millimetric and submillimetric wavelengths. In this paper we concentrate on the asteroids of the Main Belt, a large class of minor bodies in the Solar System. At present, more that 40 000 of these asteroids have been discovered and their detection rate is rapidly increasing. We intend to estimate the number of asteroids that can be detected during the mission and to evaluate the strength of their signal. We have rescaled the instrument sensitivities, calculated by the LFI and HFI teams for sources fixed in the sky, introducing some degradation factors to properly account for moving objects. In this way a detection threshold is derived for asteroidal detection that is related to the diameter of the asteroid and its geocentric distance. We have developed a numerical code that models the detection of asteroids in the LFI and HFI channels during the mission. This code performs a detailed integration of the orbits of the asteroids in the timespan of the mission and identifies those bodies that fall in the beams of PLANCK and their signal strength. According to our simulations, a total of 397 objects will be observed by PLANCK and an asteroidal body will be detected in some beam in 30% of the total sky scan-circles. A significant fraction (in the range from ∼50 to 100 objects) of the 397 asteroids will be observed with a high S/ N ratio. Flux measurements of a large sample of asteroids in the submillimeter and millimeter range are relevant since they allow to analyze the thermal emission and its relation to the surface and regolith properties. Furthermore, it will be possible to check on a wider base, the two standard thermal models, based on a nonrotating or rapidly rotating sphere. Our method can also be used to separate Solar System sources from cosmological sources in the survey. This work is based on PLANCK LFI activities.

Modelling infrared galaxy evolution using a phenomenological approach

To characterise the cosmological evolution of the sources contributing to the infrared extragalactic background, we have developped a phenomenological model that constrains in a simple way the galaxy luminosity function evolution with the redshift, and fits all the existing source counts and redshift distributions, Cosmic Infrared Background intensity and fluctuations observations, from the mid-infrared to the submillimetre range. The model is based on template spectra of starburst and normal galaxies, and on the local infrared luminosity function. Although the Cosmic Infrared Background can be modeled with very different luminosity functions as long as the radiation production with redshift is the right one, the number counts, and the anisotropies of the unresolved background, imply that the luminosity function must change dramatically with redshift, with a rapid evolution of the high-luminosity sources (L>3 10^{11} L_{\odot}) from z=0 to z=1 which then stay rather constant up to redshift 5. The derived evolution of the IR luminosity function may be linked to a bimodal star formation process, one associated with the quiescent and passive phase of the galaxy evolution and one associated with the starburst phase, trigerred by merging and interactions. The latter dominates the infrared and submillimetre ouput energy of the Universe. The model is intended as a convenient tool to plan further observations, as illustrated through predictions for Herschel, Planck and ALMA observations. Our model predictions for given wavelengths, together with some usefull routines, are available for general use.

Solar Submillimeter and Gamma‐Ray Burst Emission

Solar are emission was measured at 212 GHz in the submillimeter range by the Submillimeter Solar Telescope in the 1.2-18 GHz microwave range by the Owens Valley Solar Array and in the gamma-ray energy range (continuum) by experiments on board the Yohkoh ( > 1. 2 MeV) and Shenzhou 2 ( > 0.2 MeV) satellites. At the burst onset, the submillimeter and microwave time profiles were well correlated with gamma rays to the limit of the temporal resolution (less than or equal to10 s). At 212 GHz, fast pulses ( 1. 2 MeV), attaining nearly 50 pulses per minute at the maximum. These results suggest that gamma rays might be the response to multiple rapid pulses at 212 GHz and might be produced at different sites within the flaring region.

Beam profile determination by tomography of solar scans

Beam patterns of radio telescopes with moderate (arcmin) angular resolution in the millimeter and sub-millimeter range are difficult to measure as only weak sources are available in that spectral range. This limitation can be overcome with the deconvolution of radial scans over the knife edge of the solar limb which provides beam profiles down to secondary lobe levels. Numerous applications, such as quick adjustments and checkups of telescope optics, efficiency estimates and the reconstruction of partially unresolved structures such as active regions, become possible. We investigate here the inverse problem of the beam profile reconstruction from the beam convolution with the solar limb. With simple derivatives of solar radial scans we obtained line integrals of the beam profile under different scanning angles. Reconstruction methods used in tomography of filtered reverse projection allowed us then to obtain beam profiles down to the level of secondary lobes. Tests of the algorithm were carried out with simulated data and solar scans that are verified by planet observations and terrestrial beam pattern measurements.

Feedstock development for micro powder injection molding

Powder injection molding of microstructured parts with high aspect ratios requires feedstocks, which have a high mechanical stability for demolding. The binders of the feedstocks have to allow pressure free and complete debinding and sintering without deformation in the submillimeter range. For complete molding of especially small and complex detailed microstructures, powders with a small particle size have to be used. Additionally the microstructured mold inserts themselves must have an appropriate design, which allows complete filling of the cavity and an easy removal of the molded microstructures. By the development of new binder compositions, adapted micro mold inserts and optimized processing parameters it was possible to manufacture specimens for micromechanical investigations without substrate plates. Thus many machining and finishing worksteps, which have great influence on the mechanical properties of the microstructures, can be omitted.

Spin-polarized transport and submillimetric microwave spectroscopy of solids

The problem of spin transport (spin transfer and localization in space by charge carriers) is considered from the standpoint of implementing this phenomenon in microelectronic devices based on novel physical principles. Experimental data are presented to confirm the possibility of creating extremely-high-frequency solid state microelectronic devices, operating in the millimetric and submillimetric wavelength range, which can be used as the main elements for spin informatics. These devices can be based on ferromagnetic semiconductor-nonmagnetic semiconductor junctions, the output parameters of which are controlled both by the transport current and by an external magnetic field.

Submillimeter-wave Fourier transform spectroscopy of biological macromolecules

In this article we report experimental results on Fourier-transform infrared spectroscopy of deoxyribonucleic acid (DNA) macromolecules and related biological materials in the submillimeter range (i.e., ∼10–500 cm−1). Film samples made from commercial DNA fibers, polyadenylic acid potassium salt, and cellular agents such as the spore form of Bacillus subtillis have been prepared and measured. A broad series of measurements carried out in the low frequency region (10–50 cm−1) with a higher resolution of 0.2 cm−1 revealed fine features—multiple dielectric resonances in the submillimeter-wave spectra obtained from DNA samples. These long-wave absorption features are shown to be intrinsic properties of biological materials determined by phonon modes. The emphasis is on reproducibility of experimental spectra and on receiving reliable results. The effects of differences in sample preparation, including sample geometry, orientation, and aging are studied and separated from the phonon effects that determine the fine structure of transmission spectra. A direct comparison of spectra between different DNA samples reveals a large number of modes and a reasonable level of sequence-specific uniqueness. A theoretical study of two double helical DNA fragments has applied a normal mode analysis to predict spectra in the far infrared. Most of the modes determined by long-distance interactions are at frequencies below 220 cm−1, with the density higher than one mode per cm−1, which is approximately what was observed experimentally.