Emulsion Detector Research Articles

Charge measurement with nuclear emulsions spectrometers for hadron therapy fragmentation cross section measurements with the FOOT experiment

Experimental data concerning projectile and target fragmentation is limited, increasing the uncertainty on the dose in the entrance channel in particle therapy treatments. The FOOT experiment measures nuclear fragmentation cross sections with two complementary detectors. The performance of the FOOT nuclear emulsion detectors in identifying the charge of nuclear fragments has recently been studied using 16O beams at 200 and 400MeV/n, directed at carbon and polyethylene targets. This work extends the previous analysis, comparing experimental data and FLUKA Monte Carlo predictions, focusing on the angular distribution and relative abundances of fragments with Z≤5 originating from the interactions of a 400MeV/n oxygen beam with a carbon target.

Nuclear emulsion film production system for experiments in full-area scanning and analysis era

Research utilizing the sub-micron three-dimensional spatial resolution of nuclear emulsion detectors has been expanding in various fields, triggered by the development of automated emulsion scanning technology. This paper describes a new production system capable of supplying several thousand square meters of nuclear emulsion film per year. The development and introduction of improved emulsion gel, knife coating, and drying equipment have enabled the mass production of double-side coated nuclear emulsion films with thick emulsion layers suitable for full-area scanning and analysis. This system has played an essential role in numerous nuclear emulsion experiments.

First Measurement of ν_{e} and ν_{μ} Interaction Cross Sections at the LHC with FASER's Emulsion Detector.

The first results of the study of high-energy electron neutrino (ν_{e}) and muon neutrino (ν_{μ}) charged-current interactions in the FASERν emulsion-tungsten detector of the FASER experiment at the LHC are presented. A 128.8kg subset of the FASERν volume was analyzed after exposure to 9.5 fb^{-1} of sqrt[s]=13.6 TeV pp data. Four (eight) ν_{e} (ν_{μ}) interaction candidate events are observed with a statistical significance of 5.2σ (5.7σ). This is the first direct observation of ν_{e} interactions at a particle collider and includes the highest-energy ν_{e} and ν_{μ} ever detected from an artificial source. The interaction cross section per nucleon σ/E_{ν} is measured over an energy range of 560-1740GeV (520-1760GeV) for ν_{e} (ν_{μ}) to be (1.2_{-0.7}^{+0.8})×10^{-38} cm^{2} GeV^{-1} [(0.5±0.2)×10^{-38} cm^{2} GeV^{-1}], consistent with standard model predictions. These are the first measurements of neutrino interaction cross sections in those energy ranges.

Is alpha spectroscopy possible with superheated emulsion detector?

In this work we develop a model where superheated emulsion detectors have the capacity to be used in α-spectroscopy of liquid source and we have found evidence that alpha-spectroscopy is theoretically possible under some circumstances to be explained. Experimental results for different refrigerant and radioactive source with α energies ranging from 4 to 6 MeV were analyzed to check the validity of the recently introduced α–droplet interaction model.

Hunting muonic forces at emulsion detectors

Hunting muonic forces at emulsion detectors

Fabrication of a superheated emulsion based on Freon-12 and LiCl suitable for thermal neutrons detection

This study develops superheated emulsion detectors that are both sensitive to fast neutrons, and thermal neutrons owing to the exergonic Li36(n,α)H13 capture reaction caused by the 6Li-containing compound dispersed throughout the gel-like medium. The experimental research was conducted on two SEDs. One detector was an ordinary Freon-12 detector and the other was a Freon-12 detector containing 3.4 % (by weight) LiCl. In order to investigate the sensitivity of lithium-containing SEDs to thermal neutrons, two types of SEDs were simultaneously exposed to various flux levels of thermal neutrons from 241Am–Be neutron source inside a cylindrical tank filled with water. A Boron-lined proportional counter was used to estimate the thermal neutron flux and the relevant MCNP code was developed for flux and dose calculations in the prepared set-up around 241Am–Be source. The results demonstrate that there is a proportional relationship between the variations of SED response and the change in thermal neutron flux and dose. Also, the sensitivity of SED was estimated.

Nuclear Emulsion Detectors for the Muography of Underground Structure of Holy Dormition Pskov-Caves Monastery

Nuclear Emulsion Detectors for the Muography of Underground Structure of Holy Dormition Pskov-Caves Monastery

Development of proton beam irradiation system for the NA65/DsTau experiment

Tau neutrino is the least studied lepton of the Standard Model (SM). The NA65/DsTau experiment targets to investigate Ds , the parent particle of the ντ , using the nuclear emulsion-based detector and to decrease the systematic uncertainty of ντ flux prediction from over 50 % to 10 % for future beam dump experiments. In the experiment, the emulsion detectors are exposed to the CERN SPS 400 GeV proton beam. To provide optimal conditions for the reconstruction of interactions, the protons are required to be uniformly distributed over the detector's surface with an average density of 105 cm-2 and the fluctuation of less than 10%. To address this issue, we developed a new proton irradiation system called the target mover. The new target mover provided irradiation with a proton density of 1.01 × 105 cm-2 and the density fluctuation of 1.9 ± 0.3% in the DsTau 2021 run.

Study of multiplicity fluctuations in terms of strongly intensive quantity in forward-backward zone

A completely new study of forward-backward multiplicity fluctuation of produced pions in nuclear emulsion detector has been carried out by the method of strongly intensive quantity ΣFB for 16O-AgBr, 28Si-AgBr and 32S-AgBr interactions at 4.5 AGeV/c. Experimental analysis has been compared using MC-RAND events and UrQMD simulated events. UrQMD model could not reproduce the experimental results. Outcome of this analysis supports the presence of dynamical fluctuations in multiparticle production at 4.5 AGeV/c. The results on strongly intensive fluctuation measures at a lower energy show much larger fluctuations in comparison to the higher energy data studied so far.

Environmental sub-MeV neutron measurement at the Gran Sasso surface laboratory with a super-fine-grained nuclear emulsion detector

The measurement of environmental neutrons is particularly important in the search for new physics, such as dark matter particles, because neutrons constitute an often irreducible background source. The measurement of the neutron energy spectra in the sub-MeV scale is technically difficult because it requires a very good energy resolution and a very high $\ensuremath{\gamma}$-ray rejection power. In this study, we used a super-fine-grained nuclear emulsion, called nano imaging tracker, as a neutron detector. The main target of neutrons is the hydrogen (proton) content of emulsion films. Through a topological analysis, proton recoils induced by neutron scattering can be detected as tracks with submicrometric accuracy. This method shows an extremely high $\ensuremath{\gamma}$-ray rejection power, at the level of $5\ifmmode\times\else\texttimes\fi{}{10}^{7}\phantom{\rule{0.16em}{0ex}}\ensuremath{\gamma}/{\mathrm{cm}}^{2}$, which is equivalent to five years accumulation of environmental $\ensuremath{\gamma}$ rays, and a very good energy and direction resolution even in the sub-MeV energy region. In order to carry out this measurement with sufficient statistics, we upgraded the automated scanning system to achieve a speed of 250 g/(year machine). We calibrated the detector performance of this system with 880 keV monochromatic neutrons: a very good agreement with the expectation was found for all the relevant kinematic variables. The application of the developed method to a sample exposed at the INFN Gran Sasso surface laboratory provided the first measurement of sub-MeV environmental neutrons with a flux of $(7.6\ifmmode\pm\else\textpm\fi{}1.7)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}\phantom{\rule{0.16em}{0ex}}n/({\mathrm{cm}}^{2}\phantom{\rule{0.16em}{0ex}}\mathrm{s})$ in the proton energy range between 0.25 and 1 MeV (corresponds to neutron energy range between 0.25 and 10 MeV), consistent with the prediction. The neutron energy and direction distributions also show a good agreement.

Ξ − atomic X-ray spectroscopy using a counter-emulsion hybrid method

Abstract Ξ− atomic X-ray spectroscopy is one of the most useful methods for investigation of the Ξ–nucleus strong interaction. Since the X-ray energy is shifted and/or broadened due to the Ξ–nucleus strong interaction compared to those calculated from electromagnetic interaction alone, the measurement of the energy shift, ΔE, and the width, Γ, give us information on the Ξ–nucleus potential. A serious problem in the measurement is the significant background derived from in-flight Ξ− decay. A novel method of identifying stopped Ξ− events using the nuclear emulsion was developed to realize the first Ξ− atomic X-ray spectroscopy experiment as the J-PARC E07 experiment, which also aimed at searching for ΛΛ and Ξ− hypernuclei in the emulsion. The X-rays emitted from Ξ− Br and Ξ− Ag atoms were measured using germanium detectors. No clear peaks were observed in the obtained spectra. However, we succeeded in reducing the background to 1/170 by this method employing coincidence measurements using nuclear emulsion and X-ray detectors.

Track and vertex reconstruction using moving emulsion blocks and a silicon pixel tracker for particles induced by 400 GeV/c protons on a thick target

The SHiP-charm experiment is designed to measure the charm production cross section, including cascade production, of 400 GeV/c protons hitting a thick, SHiP-like target. For the detection of production and decay of heavy charmed particles, emulsion films are employed in a multilayered moving target, forming an emulsion cloud chamber. While the emulsion films provide excellent spatial resolution they do not provide timing information, integrate all events, and quickly get saturated. For the charm measurement the emulsion target is thus moving at a constant speed during data-taking. A first optimization run at the CERN SPS has been performed in 2018, with the purpose to develop the required analysis tools and to fine-tune the detector layout. We report on the experiment design, track reconstruction in the pixel tracker and the track matching with the moving emulsion detector.

Momentum reconstruction of charged particles using multiple Coulomb scatterings in a nuclear emulsion detector

Abstract This paper describes a new method for momentum reconstruction of charged particles using multiple Coulomb scatterings in a nuclear emulsion detector with a layered structure of nuclear emulsion films and target materials. The method utilizes the scattering angles of particles precisely measured in the emulsion films. The method is based on the maximum likelihood to include the new information on the decrease of the energy as the particle travels through the detector. According to the Monte Carlo simulations, this method can measure momentum with a resolution of 10% for muons of ${500}\, {\rm MeV}/c$ passing through the detector perpendicularly. The momentum resolution is evaluated to be 10–20%, depending on the momentum and emission angle of the particle. By accounting for the effect of the energy decrease, the momentum can be reconstructed correctly with less bias, particularly in the low-momentum region. We apply this method to measure the momentum of muon tracks detected in the Neutrino Interaction research with Nuclear emulsion and J-PARC Accelerator (NINJA) experiment where the momentum is also measured independently by using the track range. The two measurements agree well within experimental uncertainties, verifying the method experimentally. This method will extend the measurable phase space of muons and hadrons in the NINJA experiment.

Three-dimensional density tomography determined from multi-directional muography of the Omuroyama scoria cone, Higashi–Izu monogenetic volcano field, Japan

Scoria cone is one of the basic forms of volcanoes, and clarifying its detailed internal structure and magma movement during its formation is important for understanding the nature of eruptions and also for volcanic disaster mitigation. We conducted a multi-directional muographic survey of the Omuroyama scoria cone, Japan, in order to determine the three-dimensional density structure of the scoria cone. We used a nuclear emulsion detector optimized for multi-directional muography that was installed at 11 sites around the volcano. Muon tracks recorded on emulsion films were read with a high-speed automated readout system. We obtained the three-dimensional density structure by applying a linear inversion to the muographic images, and evaluated the uncertainties. High-density zones were detected in scoria cone. Based on these observations and detailed topographic and geological constraints, we infer that high-density zones are the central, highly welded vent of the scoria cone, three-directional radial dikes extending from the central vent, respectively. We also infer that an E-W-trending dike fed a small lava flow, and that a SSE-NNW-trending dike caused a small flank eruption and produced a crater on the flank of the cone. Our results visualize the three-dimensional internal structure of volcanoes with novel resolution, and thereby demonstrate that the formation process of volcanoes can be discussed in detail. Since it has been difficult to directly detect such clear visualization of the internal structures and eruptive processes in the past, multi-directional muography has resulted in providing one hope for understanding volcanic activity.

Measurements of protons and charged pions emitted from νμ charged-current interactions on iron at a mean neutrino energy of 1.49 GeV using a nuclear emulsion detector

This study conducted an analysis of muons, protons, and charged pions emitted from $\nu_{\mu}$ charged-current interactions on iron using a nuclear emulsion detector. The emulsion detector with a 65$\,$kg iron target was exposed to a neutrino beam corresponding to 4.0$\times$10$^{19}$ protons on target with a mean neutrino energy of 1.49$\,$GeV. The measurements were performed at a momentum threshold of 200 (50)$\,$MeV/$c$ for protons (pions), which are the lowest momentum thresholds attempted up to now. The measured quantities are the multiplicities, emission angles, and momenta of the muons, protons, and charged pions. In addition to these inclusive measurements, exclusive measurements such as the muon-proton emission-angle correlations of specific channels and the opening angle between the protons of CC0$\pi$2$p$ events were performed. The data were compared to Monte Carlo (MC) predictions and some significant differences were observed. The results of the study demonstrate the capability of detailed measurements of neutrino-nucleus interactions using a nuclear emulsion detector to improve neutrino interaction models.

Emission feature of the singly-charged and doubly-charged projectile fragments emitted in the interaction of 84Kr36 + Em at 1GeV per nucleon

In this paper, the emission features of singly-charged and doubly-charged projectile fragments emitted in interactions of [Formula: see text] with emulsion at 1[Formula: see text]A[Formula: see text]GeV are studied. We have also observed the dependence of the singly-charged and doubly-charged projectile fragments on the interaction with different target groups of the emulsion detectors. The multi-source model can characterize the projectile fragments, and each source provides an exponential distribution, according to our calculations. The present observation shows that the emission features of the singly-charged and doubly-charged projectile fragments are independent on the interaction with different target groups of the emulsion.

A novel nuclear emulsion detector for measurement of quantum states of ultracold neutrons in the Earth's gravitational field

Hypothetical short-range interactions could be detected by measuring the wavefunctions of gravitationally bound ultracold neutrons (UCNs) on a mirror in the Earth's gravitational field.Searches for them with higher sensitivity require detectors with higher spatial resolution.We developed and have been improving an UCN detector with a high spatial resolution, which consists of a Si substrate, a thin converter layer including ^10B_4C, and a layer of fine-grained nuclear emulsion.Its resolution was estimated to be less than 100 nm by fitting tracks of either ^7Li nuclei or α-particles, which were created when neutrons interacted with the ^10B_4C layer.For actual measurements of the spatial distributions, the following two improvements were made.The first improvement was to establish a method to align microscopic images with high accuracy within a wide region of 65 mm × 0.2 mm.We created reference marks of 1 μm and 5 μm diameter with an interval of 50 μm and 500 μm, respectively, on the Si substrate by electron beam lithography and realized a position accuracy of less than 30 nm.The second improvement was to build a holder for the detector that could maintain the atmospheric pressure around the nuclear emulsion to utilize it under a vacuum during exposure to UCNs.The intrinsic resolution of the improved detector was estimated to be better than0.56(8) μm by evaluating the blur of a transmission image of a gadolinium grating taken by cold neutrons.The evaluation included the precision of the gadolinium grating.A test exposure was conducted to obtain the spatial distribution of UCNs in the quantized states on a mirror in the Earth's gravitational field.The distribution was obtained, fitted with the theoretical curve, and turned out to be reasonable for UCNs in quantized states when we considered a blurring of 6.9 μm.The blurring was well explained as a result of neutron refraction due to the large surface roughness on the upstream side of the Si substrate.By using a double-side-polished Si substrate, a resolution of less than 0.56 μm is expected to be achieved for UCNs.

Resonances in ν¯e−e− scattering below a TeV

We consider the resonant production and detection of charged mesons in existing and near-future neutrino scattering experiments with ${E}_{\ensuremath{\nu}}\ensuremath{\lesssim}1\text{ }\text{ }\mathrm{TeV}$, characteristic of high-energy atmospheric neutrinos or collider-sourced neutrino beams. The most promising candidate is the reaction ${\overline{\ensuremath{\nu}}}_{e}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}$. We discuss detection prospects at $\mathrm{FASER}\ensuremath{\nu}$, the LHC's forward physics facility with nuclear emulsion ($\mathrm{FASER}\ensuremath{\nu}2$) and liquid argon detectors (FLArE), and we estimate the number of expected resonance-mediated events in the existing data set of IceCube. We also outline possible detection strategies for the different experimental environments. We predict dozens of events at the forward physics facility and identify cuts with order-one signal efficiency that could potentially suppress backgrounds at $\mathrm{FASER}\ensuremath{\nu}$, yielding a signal-to-background ratio larger than 1. Antineutrino-induced $s$-channel meson resonances are yet unobserved Standard Model scattering processes which offer a realistic target for near-term experiments.

Design and performance of a scintillation tracker for track matching in nuclear-emulsion-based neutrino interaction measurement

Precise measurement of neutrino–nucleus interactions with an accelerator neutrino beam is highly important for current and future neutrino oscillation experiments. To measure muon-neutrino charged-current interactions with nuclear-emulsion-based hybrid detector, muon track matching among the detectors are essential. We describe the design and performance of a newly developed scintillation tracker for the muon track matching in the neutrino–nucleus interaction measurement with nuclear emulsion detectors. The muon tracks are reconstructed using the scintillation tracker and another detector called Baby MIND, then, they are matched with the tracks in nuclear emulsion detectors.The scintillation tracker consists of four layers of horizontally and vertically aligned scintillator bars, covering an area of 1m×1m. In the layer, 24mm-wide plastic scintillator bars are specially arranged with deliberate gaps between each other. By recognizing the hit pattern of the four layers, a precise positional resolution of 2.5mm is achieved while keeping the number of readout channels as small as 256. The efficiency of the track matching is evaluated to be more than 97% for forward-going muons, and the positional and angular resolutions of the scintillation tracker are 2.5mm and 20–40mrad respectively. The results demonstrate the usefulness of the design of the scintillation tracker for the muon track matching in the nuclear-emulsion-based neutrino–nucleus interaction measurements.

Emission characteristics of the target fragments at relativistic energy

In this recent work, we present the characteristic of the emission of the black particles ejected with [Formula: see text] [Formula: see text] [Formula: see text] and [Formula: see text] [Formula: see text][Formula: see text] i.e., in the forward and backward hemispheres, respectively. For the multiplicity variation study of black particles, we have considered the interaction of [Formula: see text]Kr beam with the CNO, AgBr target present in the nuclear emulsion detector. After doing the analysis of the data, we have found that the emission possibility of black particle is greater in the forward hemisphere (FHS) angle whereas in the backward hemisphere (BHS) angle, it is quite low. Along with this, we have also found that the emission probability of black particles does not posses any relation with projectile mass as well as with the incident energy. In this work, we have also studied the characteristics of shower and et al. particles using a new parameter Q (total charge [Formula: see text] of the outgoing projectile fragments emitted in forward cone [Formula: see text], here Z denotes charge, and PF denotes Projectile Fragment) instead of impact parameter to distinguish the different type of collision for two interacting nuclei. The observation from this study suggests that the emission probability of the shower particles as well as gray particles increase as the value of Q decreasing (i.e., as we move from peripheral to central colisions). The results of this work are also compared with the context of other experimental observations and it seems to be relevant.