The Evolution of Compact Binary Star Systems

We review the formation and evolution of compact binary stars consisting of white dwarfs (WDs), neutron stars (NSs), and black holes (BHs). Binary NSs and BHs are thought to be the primary astrophysical sources of gravitational waves (GWs) within the frequency band of ground-based detectors, while compact binaries of WDs are important sources of GWs at lower frequencies to be covered by space interferometers (LISA). Major uncertainties in the current understanding of properties of NSs and BHs most relevant to the GW studies are discussed, including the treatment of the natal kicks which compact stellar remnants acquire during the core collapse of massive stars and the common envelope phase of binary evolution. We discuss the coalescence rates of binary NSs and BHs and prospects for their detections, the formation and evolution of binary WDs and their observational manifestations. Special attention is given to AM CVn-stars -- compact binaries in which the Roche lobe is filled by another WD or a low-mass partially degenerate helium-star, as these stars are thought to be the best LISA verification binary GW sources.Comment: 105 pages, 18 figure

Design and fabrication of Cherenkov flux-flow oscillator

The Josephson Flux-Flow Oscillator (FFO) has been used as an on chip local oscillator at frequencies up to 650 GHz. The FFO linewidth of about 1 MHz was measured in the resonant regime at V <915 mu V for niobium - aluminum oxide - niobium tunnel junctions, while considerably larger values were reported at higher voltages. To overcome this fundamental linewidth broadening we propose a novel on chip Cherenkov radiation flux-flow oscillator (CRFFO). It consists of a long Josephson junction and a superconducting slow wave transmission line that modifies essentially the junction dispersion relation. Two SIS detectors are connected both to the long Josephson junction and the transmission line to evaluate available microwave power. The output power coming both from the long junction and the transmission line is estimated at different bias conditions

Forward and backward waves in Cherenkov flux-flow oscillators

Josephson flux-flow oscillators (FFOs) have been used as an on-chip local oscillator at frequencies up to 650 GHz. An autonomous FFO linewidth of about 1 MHz was measured in the resonant regime at V-b <950 mu V for niobium-aluminium oxide-niobium tunnel junctions, while considerably larger values were reported at higher voltages. To overcome this fundamental linewidth broadening we propose an on-chip Cherenkov radiation Aux-flow oscillator (CRFFO). It consists of a long Josephson junction and a superconducting slow-wave transmission line that modifies significantly the junction dispersion relation. Two superconductor-insulator-superconductor junction detectors are connected to both the long Josephson junction and the slow-wave line to determine the available microwave power. The power is measured at different CRFFO biasing conditions. Both a forward wave and a backward wave oscillation regime are observed. An FFO and a CRFFO with the same junction parameters are compared

First implementation of the fully superconducting 500 GHz receiver with integrated flux-flow oscillator

An integrated quasioptical receiver consisting of a planar double dipole antenna, SIS mixer and a superconducting local oscillator with matching circuits has been designed, fabricated and tested. A Flux-Flow Oscillator (FFO) based on unidirectional viscous flow of magnetic vortices in a long Josephson tunnel junction is employed as a local oscillator. All components of the receiver are integrated on a 4 mm x 4 mm x 0.2 mm crystalline quartz substrate on a base of the same Nb-AlOx-Nb trilayer in one technological run. The receiver has been studied in the frequency range 360 - 490 GHz. A lowest DSB noise temperature of 470 - 560 K has been achieved within the frequency range 425 - 455 GHz. Test circuits each comprising a FFO and a SIS detector have been experimentally investigated at frequencies up to 850 GHz. A new reliable technique for measuring the spectral linewidth of the integrated oscillators has been developed; the possibility of frequency locking of a FFO to an external microwave source has been demonstrated. The spectral linewidth of a FFO has been measured in the frequency range 250 - 580 GHz; a linewidth as low as 200 kHz is obtained at 450 GHz