arXiv subjects

X. Y. Yang

Publications and source records attributed to X. Y. Yang.

3 recordsLinked to original sources

arXiv2021

Research on proton beam spot imaging based on pixelated gamma detector

The primary secondary particles from the spallation target of the China Spallation Neutron Source are mainly gammas and neutrons, which are related to the distribution of the incident proton. The reconstruction of proton beam spot could be implemented based on the distribution of secondary particles. The methods of pinhole imaging and Compton imaging are developed by measuring the gamma distribution based on the pixelated detector. The secondary gammas could be detected by the pixelated gamma detector directly. The neutron can be identified by detecting the characteristic (478 keV) $γ$-rays from the $^{10}B$(n, $α$) reactions. In order to detect secondary neutrons, a layer of $^{10}B$ converter is added before the pixelated gamma detector. The pixelated gamma detector is sensitive to the characteristic (478 keV) $γ$-rays and then the neutron imaging could be achieved based on measuring the distribution of the characteristic gamma.

physics.ins-det↗

arXiv2015

Parametric Excitation and Squeezing in a Many-Body Spin System

We demonstrate a new method to coherently excite and control the quantum spin states of an atomic Bose gas using parametric excitation of the collective spin by time varying the relative strength of the Zeeman and spin-dependent collisional interaction energies at multiples of the natural frequency of the system. Compared to the usual single-particle quantum control techniques used to excite atomic spins (e.g. Rabi oscillations using rf or microwave fields), the method demonstrated here is intrinsically many-body, requiring inter-particle interactions. While parametric excitation of a classical system is ineffective from the ground state, we show that in our quantum system, parametric excitation from the quantum ground state leads to the generation of quantum squeezed states.

cond-mat.quant-gas↗

arXiv2015

Superconducting nanowire single-photon detectors at a wavelength of 940 nm

We develop single-photon detectors comprising single-mode fiber-coupled superconducting nanowires, with high system detection efficiencies at a wavelength of 940 nm. The detector comprises a 6.5-nm-thick, 110-nm-wide NbN nanowire meander fabricated onto a Si substrate with a distributed Bragg reflector for enhancing the optical absorptance. We demonstrate that, via the design of a low filling factor (1/3) and active area (Φ = 10 μm), the system reaches a detection efficiency of ~60% with a dark count rate of 10 Hz, a recovery time <12 ns, and a timing jitter of ~50 ps.

cond-mat.supr-con↗