[en] We demonstrate neutron detection using a solid-state ³He-free superconducting current-biased kinetic inductance detector (CB-KID), which consists of a superconducting Nb meander line and ¹⁰B neutron absorption layer. The CB-KID is based on the transient process of kinetic inductance of Cooper pairs induced by the nuclear reaction between ¹⁰B and neutrons. Therefore, the CB-KID can be operated in a wide superconducting region in the bias current–temperature diagram, as demonstrated in this paper. The transient change of the kinetic inductance induces the electromagnetic wave pulse under a DC bias current. The signal propagates along the meander line toward both sides with opposite polarity, where the signal polarity is dominated by the bias current direction. The full width at half maximum of the signals remains on the order of a few tens of ns, which confirms the high-speed operation of our detectors. We determine the neutron incident position within 1.3 mm accuracy in one dimension using the multichannel CB-KIDs. (paper)

[en] In our preceding works, we demonstrated successful neutron detection using a superconducting current-biased kinetic inductance detector (CB-KID), which is composed of two Nb-based superconducting meanderlines and the ¹⁰B neutron absorption layer. The CB-KID with a ¹⁰B absorption layer outputs the voltage pulses when it is irradiated by pulsed neutrons. We expected that the voltage V is proportional to a product of the bias current I _b and a time derivative of the local kinetic inductance dΔL _k/dt, and a pair of signals propagate along the Nb stripline as an electromagnetic wave at a certain fraction of the light velocity c toward end electrodes. It still remains to be revealed why the signal voltage shows such a continuum in the histogram of the signal height even if the incident energy of the light ion is apparently monochromatic. In the present work, we investigated the distribution of the height and width of the signal. We found a clear correlation between height and width, which might be a key of understanding the operating principle of our detector. We consider that the origin of the signal distribution is due to the positional dependence of the light ion bombardment with respect to the meandering Nb nanowire. (paper)

[en] Our preceding works reported the development of a high spatial and temporal resolution imaging system by using a current biased kinetic inductance detector (CB-KID) with the use of a delay-line technique. We called this system as a delay-line CB-KID, and succeeded in imaging of neutron events caused by the nuclear reaction and hot spots produced by using the delay-line CB-KID system. It was essentially important for our proposal to use a superconducting stripline to guide the pulsed signal where the signal propagates at a constant fast velocity along the stripline. In the present study, we intend to measure a propagation velocity of the signal along the stripline precisely to compare with the theoretical prediction of the signal propagation, which was recently developed with a superconducting waveguide S-I-S model by Koyama and Ishida [11]. Our present measurements showed a good agreement between the theoretical predictions and the experimental results on the propagation velocity as a function of temperature. (paper)