Terahertz spectroscopy with a Josephson oscillator and a SINIS bolometer

The voltage response of a thin-film normal-metal hot-electron bolometer based on a SINIS (superconductor-insulator-normal metal-insulator-superconductor) structure to the radiation of a high-temperature Josephson junction in the terahertz frequency region was measured. Bolometers were integrated with planar log-periodic and double-dipole antennas, and Josephson junctions were integrated with log-periodic antennas. Measurements showed that the Josephson junction at a temperature of 260 mK was overheated by the transport current, so that its electron temperature exceeded 3 K at a bias voltage of 1 mV. The maximum response of a bolometer with a double-dipole antenna was observed at a frequency of 300 GHz, which agreed well with the calculated value. The Josephson radiation was observed at frequencies up to 1.7 THz. The voltage response of a bolometer reached 4×10⁸ V/W, and the total noise-equivalent power reached 1.5×10^?17 W/Hz^1/2.     

Data acquisition system for the socal plane detector of the mass separator MASHA

The results of the development and the general information about the data acquisition system which was recently created at the MASHA setup (Flerov laboratory of nuclear reactions at Joint institute for nuclear research) are presented. The main difference from the previous system is that we use a new modern platform, National Instruments PXI with XIA multichannel high-speed digitizers (250 MHz 12 bit 16 channels). At this moment system has 448 spectrometric channels. The software and its features for the data acquisition and analysis are also described. The new DAQ system expands precision measuring capabilities of alpha decays and spontaneous fission at the focal plane position-sensitive silicon strip detector which, in turn, increases the capabilities of the setup in such a field as low-yield registration of elements.     

Radioactive-Ion Beams for the Fission Study of Heavy Neutron-Rich Nuclei

Physics of Atomic Nuclei - Quasi-elastic, multi-nucleon transfer reactions induced by the radioactive-ion beams with energy 4–6 MeV/u allow one to produce moderately excited neutron-rich...     

Superheavy hydrogen (5)H

Experimental search for (5)H using a secondary beam of (6)He has been performed. The transfer reaction (1)H((6)He,(2)He)(5)H was studied by detecting two protons emitted from the decay of (2)He. A peak consistent with a (5)H resonance at 1.7+/-0.3 MeV above the n+n+t threshold was observed, with a width of 1.9+/-0.4 MeV. The angular distribution of the (1)H((6)He,(2)He)(5)H reaction was measured as well as the energy correlation of the two protons.     

Temperature sensitivity and noise of an HTSC Josephson detector on a sapphire bicrystal substrate at 77 K

In YBa₂Cu₃O_{7 − x} films grown on sapphire bicrystal substrates, the Josephson junctions are prepared based on artificial grain boundaries formed by the turn of the crystal lattices about the [100] axis. The films are deposited by the laser ablation method on the buffer CeO₂ layer. The critical film temperature reaches 88.5 K with a transition width of 1.5 K. Junctions from 2 to 3-μ m wide are integrated into the planar log-periodic antennas and their characteristics are measured at 77 K. The characteristic voltage I _c R _n reaches 570 μV. With exposure to external radiation at a frequency of 113 GHz, the Shapiro steps were observed on the current-voltage characteristic. The temperature sensitivity of this detector placed in a quasi-optical receiving unit is measured. At the modulation of the input radiation temperature 77 K/300 K, a response of more than 200 nV is observed at the detector output. At the modulation frequency, intrinsic noise is about 1 nV/Hz^1/2, which corresponds to a temperature resolution of 1 K. Original Russian Text ? M. Tarasov, E. Stepantsov, A. Kalabukhov, M. Kupriyanov, D. Winkler, 2007, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 86, No. 11, pp. 828–831.     

Exposure of nuclear track emulsion to 8He nuclei at the ACCULINNA separator

Nuclear track emulsion is exposed to a beam of radioactive ⁸He nuclei with an energy of 60 MeV and enrichment of about 80% at the ACCULINNA separator. Measurements of 278 decays of the ⁸He nuclei stopped in the emulsion allow the potential of the α spectrometry to be estimated and the thermal drift of ⁸He atoms in matter to be observed for the first time.     

Submillimeter-wave Josephson spectroscopy

A Josephson high-temperature superconducting (HTSC) submillimeter-wave spectrometer is designed, built, and experimentally investigated. The integrated detection structure of the spectrometer includes a YBCO Josephson junction on a bicrystalline boundary, a double-slot or log-periodic antenna, and a low-inductance resistive shunt. The selective detector response and the response at an intermediate frequency of 1.4 GHz are measured under the action of a signal in the frequency range 350–1250 GHz. Three methods of spectroscopy are investigated using this setup: 1) a method of Hilbert spectroscopy with processing of the detector response is implemented; 2) it is found that for a wide Josephson line at intermediate frequency (IF) the response has the same form as the detector response, making it possible to obtain a spectrum and the width of the generation line from IF response measurements; 3) for a narrow Josephson line the IF response corresponds to the regime of conversion with self-pumping. A new method is proposed for calculating the emission spectrum. The method consists of simple shift, summation, and subtraction operations. The advantages of the method are simplicity, high sensitivity, and high resolution. Pis’ma Zh. éksp. Teor. Fiz. 70, No. 5, 338–343 (10 September 1999)     

Resonance states of hydrogen nuclei 4H and 5H obtained in transfer reactions with exotic beams

To investigate ⁵H resonance states with a better instrumental resolution, we utilized the two-neutron transfer reaction ³H(t, p)⁵H accomplished with the use of a cryogenic liquid-tritium target and 57.5-MeV triton beam. As a result of this study, a valuable fraction of protons detected at ? _lab=18°–32° in ptn coincidence events was attributed to the states of the ⁵H nucleus. Two resonance states situated at 1.8±0.1 and 2.7±0.1 MeV above the t + n + n decay threshold were obtained in the missing mass energy spectrum of the ⁵H nucleus. The peak located close to E5_H was clearly seen in the ⁵H spectrum obtained from the energy distributions of ³H nuclei emitted in the reaction ²H(⁶He, ⁵H)³He at ? _lab=17°–32°. The width (Γ_obs≤0.5 MeV) obtained for the two ⁵H resonance states is surprisingly small. A state of ⁴H with E _res=3.3 MeV and γ ²=2.3 MeV was obtained in the reaction ²H(t, p)⁴H from the spectra of protons leaving the target at ? _lab=18°–32° and detected in coincidence with neutrons emitted in the decay of ⁴H nuclei.     

Structure of Artificial Grain Boundaries in Sapphire Bicrystals with Intermediate Layers

The structure of the artificial grain boundaries in Al₂O₃ bicrystals withY₃Al₅O₁₂ and Y-stabilizedZrO₂ (Y-ZrO₂) intermediate layers was studiedwith high resolution electron microscopy, electron diffraction and energydispersive X-ray analysis. TheY₃Al₅O₁₂ intermediate layer wasfound to be polycrystalline with three different orientation relationshipsbetween the ₂O₃ and theY₃Al₅O₁₂. The structure of theY₃Al₅O₁₂/₂O₃ interfaces is described.Also₂O₃ bicrystals with an Y-ZrO₂/₂O₃/Y-ZrO₂/₂O₃/Y-ZrO₂intermediate layer, prepared at two different temperatures, werestudied.Recry stallization of the intermediate layers occurred during thesolid phase intergrowth of the ₂O₃ bicrystalsparts and only an Y-ZrO₂ layer was found as intermediatelayer. The misorientation between the consecutive Y-ZrO₂grains was less than 1.5°. Misfit dislocations and atomic height stepsdecorate the Y-ZrO₂/₂O₃interface.