High spatial resolution of ultracold neutron (UCN) measurement is of growing interest to UCN experiments such as UCN spectrometers, UCN polarimeters, quantum physics of UCNs, and quantum gravity. Here we utilize physics-informed deep learning to enhance the experimental position resolution and to demonstrate sub-micron spatial resolutions for UCN position measurements obtained using a room-temperature CMOS sensor, extending our previous work [1, 2] that demonstrated a position uncertainty of 1.5 microns. We explore the use of the open-source software Allpix Squared to generate experiment-like synthetic hit images with ground-truth position labels. We use physics-informed deep learning by training a fully-connected neural network (FCNN) to learn a mapping from input hit images to output hit position. The automated analysis for sub-micron position resolution in UCN detection combined with the fast data rates of current and next generation UCN sources will enable improved precision for future UCN research and applications.

A good electrode design not only produces the goal electric fields, but also eliminates harmful high-field spots that can cause electrical breakdown. In this paper, we present the equipotential method to generate electrode profiles. It is a physical method. The desired field is constructed first by a set of virtual electrodes, and then the equipotential contours naturally become the electrode profiles. We will demonstrate the simple procedures to design uniform field electrodes and recessed electrodes to accommodate dielectric structures. It shows versatility and flexibility in designing electrodes of low symmetry or irregular shapes as well as in complex boundary conditions.

The puzzle remains in the large discrepancy between neutron lifetime measured by the two distinct experimental approaches -- counts of beta decays in a neutron beam and storage of ultracold neutrons in a potential trap, namely, the beam method versus the bottle method. In this paper, we propose a new experiment to measure the neutron lifetime in a cold neutron beam with a goal sensitivity of 0.1% or sub-1 second. The neutron beta decays will be counted in a liquid helium scintillation detector at 0.5 K, and the neutron flux will be simultaneously monitored by the helium-3 captures in the same volume. The cold neutron beam must be of wavelength λ>16.5 A to eliminate scattering with liquid helium.

In this paper, we describe a new method for measuring surviving neutrons in neutron lifetime measurements using bottled ultracold neutrons (UCN), which provides better characterization of systematic uncertainties and enables higher precision than previous measurement techniques. An active detector that can be lowered into the trap has been used to measure the neutron distribution as a function of height and measure the influence of marginally trapped UCN on the neutron lifetime measurement. In addition, measurements have demonstrated phase-space evolution and its effect on the lifetime measurement.

Position-sensitive detection of ultracold neutrons (UCNs) is demonstrated using an imaging charge coupled device (CCD) camera. A spatial resolution less than 15 pm has been achieved, which is equivalent to a UCN energy resolution below 2 pico-electron-volts through the relation delta E = m(0)g delta x. Here, the symbols delta E, delta x, m(0) and g are the energy resolution, the spatial resolution, the neutron rest mass and the gravitational acceleration, respectively. A multilayer surface convertor described previously is used to capture UCNs and then emits visible light for CCD imaging. Particle identification and noise rejection are discussed through the use of light intensity profile analysis. This method allows different types of UCN spectroscopy and other applications. (C) 2016 Elsevier B.V. All rights reserved.

Little cross-cultural research exists on parental socialization of children's learning beliefs. The current study compared 218 conversations between European American and Taiwanese mothers and children (6-10 years) about good and poor learning. The findings support well-documented cultural differences in learning beliefs. European Americans mentioned mental activities and positive affect more, whereas Taiwanese mentioned learning virtues and negative affect more. Mothers, especially European American, reciprocated their children's talk about mental activities, learning virtues, and negative affect. Children, especially Taiwanese, reciprocated their mother's talk about positive affect. Mothers invoked more mental activities and positive affect when discussing good learning, but more learning virtues and negative affect when discussing poor learning. These findings reveal a source of cultural differences in beliefs and potential enculturation.

It has been shown that a bubble in liquid helium containing two electrons is unstable against fission. In this paper, we consider the stability of electron bubbles containing 4, 6, or 12 electrons. We find that a bubble with four electrons is unstable at zero pressure and presumably breaks up into single electron bubbles. Our calculation is not accurate enough to determine whether a bubble with six electrons is stable at zero pressure. We find that in liquid He-4 a bubble with 12 electrons is stable over a pressure range from -0.32 to 0.5 bar.

We have performed calculations of the properties of bubbles in liquid helium containing small numbers of electrons. We use an iterative approach to estimate the energy of the electrons inside a bubble of given shape, and then vary the shape of the bubble to find the minimum energy. For helium-3 we show that at zero applied pressure bubbles containing 4 electrons are unstable against breakup into single electron bubbles, but are stable at pressures between -0.23 and -0.15 bars. Bubbles with 6 electrons are stable between -0.17 and -0.05 bars and bubbles with 12 electrons are stable over the pressure range -0.1 to 0.08 bars.

The normal negative ion in liquid helium consists of an electron confined in a bubble of radius approximately 19 angstrom. These bubbles have been studied in many experiments. Time-of-flight mobility measurements have revealed that there are other types of negative ion of higher mobility and unknown structure. In this note we report on a study of the fastest of these and discuss the conditions under which it can be observed.

Lead magnesium niobate-lead titanate (PMN-xPT) single crystal plates were prepared close to the morphotropic phase boundary with PT compositions 27%−31%. The piezoelectric and dielectric properties of these plates at liquid-helium temperature (4.2 K) were obtained by fitting measured impedance curves. In particular, the piezoelectric strain constant e33 is found to be in the range of 5.1−5.7 C m−2 at 4.2 K, which indicates an extraordinarily large piezoelectric effect compared with other materials even at such a low temperature. This result shows that PMN-xPT single crystals are promising candidates for ultrasonic transducers at low temperatures.