K. Yamamura | Searcharxiv

arXiv2014

Observation of the Spatial Distribution of Gravitationally Bound Quantum States of Ultracold Neutrons and Its Derivation Using the Wigner Function

Ultracold neutrons (UCNs) can be bound by the potential of terrestrial gravity and a reflecting mirror. The wave function of the bound state has characteristic modulations. We carried out an experiment to observe the vertical distribution of the UCNs above such a mirror at Institut Laue-Langevin in 2011. The observed modulation is in good agreement with that prediction by quantum mechanics using the Wigner function. The spatial resolution of the detector system is estimated to be 0.7 micro meter. This is the first observation of gravitationally bound states of UCNs with submicron spatial resolution.

hep-ex↗

arXiv2008

Study of the internal mechanisms of Pixelized Photon Detectors operated in Geiger-mode

In the 1990s, a novel semiconductor photon-sensor operated in Geiger-mode was invented in Russia (Silicon PhotoMultiplier), which consists of many tiny pixels and has a single photon level sensitivity. Since then, various types of the sensor with this scheme, Pixelized Photon Detectors (PPD), have been developed in many places in the world. For instance, Hamamatsu Photonics K.K. in Japan produces the PPD as a Multi-Pixel Photon Counter. While the internal mechanisms of the PPD have been intensively studied in recent years, the existing models do not succeeded to fully reproduce the output characteristic, such as waveforms at low temperature. We have developed a new model with the transient multiplication and quenching of the realistic avalanche process and have succeeded in reproducing the output waveform of the PPD at various temperature. In this paper, we discuss our improved model.

physics.ins-det↗