A muographic study of a scoria cone from 11 directions using nuclear emulsion cloud chambers

One of the key challenges for muographic studies is to reveal the detailed 3D density structure of a volcano by increasing the number of observation directions. 3D density imaging by multi-directional muography requires that the individual differences in the performance of the installed muon detectors are small and that the results from each detector can be derived without any bias in the data analysis. Here we describe a pilot muographic study of the Izu–Omuroyama scoria cone in Shizuoka Prefecture, Japan, from 11 directions, using a new nuclear emulsion detector design optimized for quick installation in the field. We describe the details of the data analysis and present a validation of the results. The Izu–Omuroyama scoria cone is an ideal target for the first multi-directional muographic study, given its expected internal density structure and the topography around the cone. We optimized the design of the nuclear emulsion detector for rapid installation at multiple observation sites in the field, and installed these at 11 sites around the volcano. The images in the developed emulsion films were digitized into segmented tracks with a high-speed automated readout system. The muon tracks in each emulsion detector were then reconstructed. After the track selection, including straightness filtering, the detection efficiency of the muons was estimated. Finally, the density distributions in 2D angular space were derived for each observation site by using a muon flux and attenuation models. The observed muon flux was compared with the expected value in the free sky, and is 88 % ± 4 % in the forward direction and 92 % ± 2 % in the backward direction. The density values were validated by comparison with the values obtained from gravity measurements, and are broadly consistent, except for one site. The excess density at this one site may indicate that the density inside the cone is non-axisymmetric, which is consistent with a previous geological study.

Study of Angular Distribution and KNO Scaling in the Collisions of 28Si with Emulsion Nuclei at 14.6A GeV

An attempt has been made to study the angular characteristics of heavy ion collision at high energy in the interactions of 28Si nuclei using with nuclear emulsion. The KNO scaling behavior in terms of the multiplicity distribution has been studied. A simplest universal function has been used to represent the present experimental data.

Achieving Submicrometer Spatial Resolution for Neutron Imaging With Nuclear Emulsion

Neutron imaging is a non-destructive inspection technique with a wide range of potential applications. One of the key technical interests concerning neutron imaging is to achieve micrometer-scale spatial resolution. However, developing a neutron detector with a high spatial resolution is a challenging task. Recent efforts are focused on achieving this milestone or even submicrometer spatial resolution. Herein, we introduce our technique for neutron imaging using a fine-grained nuclear emulsion and evaluate the spatial resolution. We used the fine-grained nuclear emulsion with a gadolinium-based Siemens star test pattern and a grating with a periodic structure of 9 μm. The deduced value of the spatial resolution is less than 1 μm using the developed technique. To the best of our knowledge, the submicrometer spatial resolution that we achieved using our method is the best among all reported neutron imaging devices.

The major achievements of the OPERA experiment and its legacy

The OPERA experiment was designed to discover the [Formula: see text] appearance in a pure [Formula: see text] beam, resulting from neutrino oscillations. The detector, located in the underground Gran Sasso Laboratory, consisted of an emulsion/lead target complemented by electronic detectors and was exposed, from 2008 to 2012, to the (CERN Neutrinos to Gran Sasso (CNGS)) beam, an almost pure [Formula: see text] beam with a baseline of 730 km, collecting a total of [Formula: see text] protons on target. OPERA was unique in its capability of detecting all three neutrino flavors. OPERA discovered [Formula: see text] oscillations in appearance mode with a significance of [Formula: see text]. In this review, we report the major achievements of the OPERA experiment and its legacy in the nuclear emulsion technology.

Neutron Imaging Using a Fine-Grained Nuclear Emulsion

A neutron detector using a fine-grained nuclear emulsion has a sub-micron spatial resolution and thus has potential to be applied as high-resolution neutron imaging. In this paper, we present two approaches to applying the emulsion detectors for neutron imaging. One is using a track analysis to derive the reaction points for high resolution. From an image obtained with a 9 μm pitch Gd grating with cold neutrons, periodic peak with a standard deviation of 1.3 μm was observed. The other is an approach without a track analysis for high-density irradiation. An internal structure of a crystal oscillator chip, with a scale of approximately 30 μm, was able to be observed after an image analysis.