Numerical modeling of a multi-frequency receiving system based on an array of dipole antennas for LSPE-SWIPE

Here we present the results of a numerical modeling of mode composition in the constriction of the Large Scale Polarization Explorer-Short-Wavelength Instrument for the Polarization Explorer (LSPE-SWIPE) back-to-back horn. These results are used for calculating the frequency response of arrays of planar dipole antennas with cold-electron bolometers for 145, 210, and 240 GHz frequencies. For the main frequency channel (i.e., 145 GHz) we have a 45 GHz bandwidth. For the auxiliary frequency channels (i.e., 210 and 240 GHz) placed on the same substrate, we have bandwidths of 26 and 38 GHz, respectively. We performed some op-timizations for cold-electron bolometers to achieve a photon noise-equivalent power of 1.1 x 10-16 W/Hz1/2. This was achieved by replacing one of two superconductor-insulator-normal tunnel junctions with a superconductor-normal metal contact

Efficiency of electron cooling in cold-electron bolometers with traps

Electron on-chip cooling from the base temperature of 300 mK is very important for highly sensitive detectors operating in space due to problems of dilution fridges at low gravity. Electron cooling is also important for ground-based telescopes equipped with 3He cryostats being able to function at any operating angle. This work is aimed at the investigation of electron cooling in the low -temperature range. New samples of cold-electron bolometers with traps and hybrid superconducting/ferromagnetic absorbers have shown a temperature reduction of the electrons in the refrigerator junctions from 300 to 82 mK, from 200 to 33 mK, and from 100 to 25 mK in the idle regime without optical power load. The electron temperature was determined by solving heat balance equa-tions with account of the leakage current, sixth power of temperature in the whole temperature range, and the Andreev current using numerical methods and an automatic fit algorithm

Record electron self-cooling in cold-electron bolometers with a hybrid superconductor-ferromagnetic nanoabsorber and traps

The Cosmic Microwave Background (CMB) radiation is the only observable that allows studying the earliest stage of the Universe. Radioastronomy instruments for CMB investigation require low working temperatures around 100 mK to get the necessary sensitivity. On-chip electron cooling of receivers is a pathway for future space missions due to problems of dilution fridges at low gravity. Here, we demonstrate experimentally that in a Cold-Electron Bolometer (CEB) a theoretical limit of electron cooling down to 65 mK from phonon temperature of 300 mK can be reached. It is possible due to effective withdrawing of hot electrons from the tunnel barrier by double stock, special traps and suppression of Andreev Joule heating in hybrid Al/Fe normal nanoabsorber

Spectral characteristics of the double-folded slot antennas with cold-electron bolometers for the 220/240 GHz channels of the LSPE instrument

We present the results of the experimental and theoretical study of the resonant properties and noise of a single cell of a receiving system based on cold-electron bolometers (CEB) with a double-folded slot antenna and coplanar lines. The system was designed to receive signals at 220/240 GHz frequencies with a 5% bandwidth. In measurements, we used the samples of the double-folded slot antennas with slot lengths of 162 um and coplanar line lengths from 185 to 360 um. Measurements of the resonance properties of CEB located at 0.3 K cryostat plate were carried out using a generator based on a high-temperature YBCO Josephson junction located inside the same cryostat at 4 K plate. This arrangement made it possible to obtain smooth amplitude-frequency characteristics with a clearly defined peak of a 15–21 GHz bandwidth at different frequencies. Based on these results, 2-D array of double-folded slot antennas with CEBs as 220/240 GHz LSPE channel prototype was calculated.The absorption efficiency of the array has reached 81% and 77% for 220 and 240 GHz channels, respectively

Multifrequency seashell antenna based on resonant cold-electron bolometers with kinetic Inductance Nanofilters for CMB measurements

A novel type of the seashell slot antenna with internal filters by the capacitance of resonant cold-electron bolometers (RCEB) and kinetic inductance of the NbN superconducting nanostrip has been realized for multifrequency pixels. Seashell antenna gives the opportunity to connect opposite slots by coplanar waveguides (CPW) instead of microstrip lines (MSL). A conventional multifrequency pixel combines a wideband antenna and narrowband filters with long microstrip lines with unavoidable losses and overlaps. Another problem is the frequency dependent beam width due to a fixed pixel diameter for multiple frequencies. The main advantage of the seashell antenna with nano-filters is independent tuning of the separate pairs of slots for each frequency avoiding frequency dependence of the beam width. We used λ/2 slots for 75 and 105 GHz, feeding by CPW near the end of slots for RF matching. Each RCEB includes two SIN (Superconductor-Insulator-Normal) tunnel junctions with a nano-absorber and NbN kinetic inductance of 450 or 310 pH. SIN junctions had capacitances of 9.3 and 7.2 fF and absorber matched to a wave impedance of the antenna near 50 Ohm. Kinetic inductance value was estimated at the level of 35 pH/sq. RF testing was done at 300 mK irradiating this chip by sweep generator from 60 to 120 GHz. The response curves showed clear resonances at 75 and 105 GHz with a quality factor of 10 and 7. These experiments confirm that the seashell antenna with the internal RCEB filters can be used for frequency selection in compact multiband pixels

Multichroic seashell antenna with internal filters by resonant slots and cold-electron bolometers

We have developed and realized a novel multichroic seashell antenna with internal bandpass filters by resonant slots and cold-electron bolometers (CEB). Slots and CEBs are connected by coplanar waveguides (CPW) instead of microstrip lines to realize the most reliable single-layer technology. The internal resonance is organized by a series resonance of slots with CPW and capacitances of superconductor/insulator/normal (SIN) tunnel junctions. In contrast, a conventional multichroic pixel consists of a wideband sinuous antenna coupled to TES detectors by long microstrip lines with overlap and external on-chip filters for different frequency bands. A common problem with a conventional multichroic pixel is that the beam width is frequency dependent for different frequency bands. Besides that, this system with external filters is quite large and includes long microstrip lines with unavoidable overlap and rater high losses. The multichroic seashell antenna with internal resonances avoids all these problems. The main advantage of this antenna is an opportunity to tune separate pairs of phased slots for each frequency band independently. We used pairs of lambda/2 slots for 75 and 105 GHz, connected by CPW to CEBs. The connection of CPW to slots was shifted closer to the end of slots for proper RF matching. Each CEB included two SIN junctions and an absorber. SIN junctions had capacitances of 77 and 67 fF. Wave impedance of the antenna was near 50 Ohm and resistance of the absorber was matched to this value. RF testing was done at 314 mK irradiating this chip by frequency sweep of a generator from 78-118 GHz. The response curves have shown clear resonances around 75 and 105 GHz with a quality factor around 5. These experiments confirmed that the seashell antenna with the internal filters by resonant slots and CEBs could effectively be used for creating multiband elements

Multichroic seashell antenna with internal filters by resonant slots and cold-electron bolometers

We have developed and realized a novel multichroic seashell antenna with internal bandpass filters by resonant slots and cold-electron bolometers (CEB). Slots and CEBs are connected by coplanar waveguides (CPW) instead of microstrip lines to realize the most reliable single-layer technology. The internal resonance is organized by a series resonance of slots with CPW and capacitances of superconductor/insulator/normal (SIN) tunnel junctions. In contrast, a conventional multichroic pixel consists of a wideband sinuous antenna coupled to TES detectors by long microstrip lines with overlap and external on-chip filters for different frequency bands. A common problem with a conventional multichroic pixel is that the beam width is frequency dependent for different frequency bands. Besides that, this system with external filters is quite large and includes long microstrip lines with unavoidable overlap and rater high losses. The multichroic seashell antenna with internal resonances avoids all these problems. The main advantage of this antenna is an opportunity to tune separate pairs of phased slots for each frequency band independently. We used pairs of lambda/2 slots for 75 and 105 GHz, connected by CPW to CEBs. The connection of CPW to slots was shifted closer to the end of slots for proper RF matching. Each CEB included two SIN junctions and an absorber. SIN junctions had capacitances of 77 and 67 fF. Wave impedance of the antenna was near 50 Ohm and resistance of the absorber was matched to this value. RF testing was done at 314 mK irradiating this chip by frequency sweep of a generator from 78-118 GHz. The response curves have shown clear resonances around 75 and 105 GHz with a quality factor around 5. These experiments confirmed that the seashell antenna with the internal filters by resonant slots and CEBs could effectively be used for creating multiband elements

Photon-noise-limited cold-electron bolometer based on strong electron self-cooling for high-performance cosmology missions

Bolometri per missioni da pallone e spaziali hanno subito un sviluppo notevole, grazie alla loro capacità di misurare le condizioni primordiali dell'universo. I maggiori miglioramenti riguardano l'operazione a temperature sempre più basse, per raggiungere maggiori sensibilità. Qui dimostriamo che un mosaico di 192 bolometri a elettroni freddi (CEB) mostra prestazioni limitate dal rumore fotonico ad una temperatura del criostato di 310 mK, grazie ad un efficace autoraffreddamento dell'assorbitore. Il raffreddamento elettronico diretto del nanoassorbitore localizzato le giunzioni metallo - isolante - semiconduttore ha efficienza significativamente maggiore del raffreddamento indiretto attraverso una piattaforma massiva sospesa, che richiede il superamento di una debole conduttanza elettrone-fonone. La temperatura elettronica ha raggiunto 120 mK senza carico e 225 mK con un carico di 60 pW, con rumore intrinseco di ciascun bolometro inferiore a 3E-18 W/sqrt(Hz) per carico radiativo di 0.01 pW. Questo bolometro lavora con una temperatura elettronica inferiore alla temperatura fononica, ed è quindi un buon cndidato per future missioni spaziali, non richiedendo l'uso di un refrigeratore a diluizione.Bolometers for balloon and space missions have seen extensive development because of their capacity to test primordial conditions of the Universe. The major improvements consist in lowering the operating temperature to reach higher sensitivities. Here we show that an array of 192 cold-electron bolometers (CEB) demonstrates photon-noise-limited operation at the cryostat temperature of 310 mK due to effective self-cooling of the absorber. The direct electron cooling of nanoabsorber placed between normal metal - insulator - superconductor junctions has considerably higher efficiency than indirect cooling through massive suspended platform, that requires overcoming a weak electron-phonon conductance. The electron temperature reached 120 mK without a power load, and 225 mK with a 60 pW power load with self-noise of a single bolometer below 3.10(-18) W Hz(-1/2) at a 0.01 pW power load. This bolometer works at electron temperature less than phonon temperature, thus being a good candidate for future space missions without the use of dilution refrigerators

YBaCuO Josephson generators as THz sources for bolometer characterization

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