Emulsion Detector Research Articles

Pion emission in α-particle interactions with various targets of nuclear emulsion detector

The behavior of relativistic hadron multiplicity for 4He-nucleus interactions is investigated. The experiment is carried out at 2.1 A and 3.7 A GeV (Dubna energy) to search for the incident energy effect on the interactions inside different emulsion target nuclei. Data are presented in terms of the number of emitted relativistic hadrons in both forward and backward angular zones. The dependence on the target size is presented. For this purpose the statistical events are discriminated into groups according to the interactions with H, CNO, Em, and AgBr target nuclei. The separation of events, into the mentioned groups, is executed based on Glauber's multiple scattering theory approach. Features suggestive of a decay mechanism seem to be a characteristic of the backward emission of relativistic hadrons. The results strongly support the assumption that the relativistic hadrons may already be emitted during the de-excitation of the excited target nucleus, in a behavior like that of compound-nucleus disintegration. Regarding the limiting fragmentation hypothesis beyond 1 A GeV, the target size is the main parameter affecting the backward production of the relativistic hadron. The incident energy is a principal factor responsible for the forward relativistic hadron production, implying that this system of particle production is a creation system. However, the target size is an effective parameter as well as the projectile size considering the geometrical concept regarded in the nuclear fireball model. The data are analyzed in the framework of the FRITIOF model.

Analysis system of submicron particle tracks in the fine-grained nuclear emulsion by a combination of hard x-ray and optical microscopy.

Analyses of nuclear emulsion detectors that can detect and identify charged particles or radiation as tracks have typically utilized optical microscope systems because the targets have lengths from several μm to more than 1000 μm. For recent new nuclear emulsion detectors that can detect tracks of submicron length or less, the current readout systems are insufficient due to their poor resolution. In this study, we developed a new system and method using an optical microscope system for rough candidate selection and the hard X-ray microscope system at SPring-8 for high-precision analysis with a resolution of better than 70 nm resolution. Furthermore, we demonstrated the analysis of submicron-length tracks with a matching efficiency of more than 99% and position accuracy of better than 5 μm. This system is now running semi-automatically.

Testing the Weak Equivalence Principle with an antimatter beam at CERN

The goal of the AEgIS experiment is to measure the gravitational acceleration of antihydrogen – the simplest atom consisting entirely of antimatter – with the ultimate precision of 1%. We plan to verify the Weak Equivalence Principle (WEP), one of the fundamental laws of nature, with an antimatter beam. The experiment consists of a positron accumulator, an antiproton trap and a Stark accelerator in a solenoidal magnetic field to form and accelerate a pulsed beam of antihydrogen atoms towards a free-fall detector. The antihydrogen beam passes through a moiré deflectometer to measure the vertical displacement due to the gravitational force. A position and time sensitive hybrid detector registers the annihilation points of the antihydrogen atoms and their time-of-flight. The detection principle has been successfully tested with antiprotons and a miniature moiré deflectometer coupled to a nuclear emulsion detector.

Measurement of the muon beam direction and muon flux for the T2K neutrino experiment

The Tokai-to-Kamioka (T2K) neutrino experiment measures neutrino oscillations by using an almost pure muon neutrino beam produced at the J-PARC accelerator facility. The T2K muon monitor was installed to measure the direction and stability of the muon beam which is produced together with the muon neutrino beam. The systematic error in the muon beam direction measurement was estimated, using data and MC simulation, to be 0.28 mrad. During beam operation, the proton beam has been controlled using measurements from the muon monitor and the direction of the neutrino beam has been tuned to within 0.3 mrad with respect to the designed beam-axis. In order to understand the muon beam properties,measurement of the absolute muon yield at the muon monitor was conducted with an emulsion detector. The number of muon tracks was measured to be $(4.06\pm0.05)\times10^4$ cm$^{-2}$ normalized with $4\times10^{11}$ protons on target with 250 kA horn operation. The result is in agreement with the prediction which is corrected based on hadron production data.

Emulsion detectors for the antihydrogen detection in AEgIS

The AEgIS experiment at CERN aims to perform the first direct measurement of gravitational interaction between matter and antimatter by measuring the deviation of a cold antihydrogen beam in the Earth gravitational field. The design of the experiment has been recently updated to include emulsion films as position sensitive detector. The submicrometric position accuracy of emulsions leads indeed to a significant improvement of the experimental sensitivity. We present results of preliminary tests and discuss perspectives for the final measurement.

LET dependence of bubbles evaporation pulses in superheated emulsion detectors

Superheated emulsion detectors are suspensions of metastable liquid droplets in a compliant inert medium. Upon interaction with ionizing radiation, the droplets evaporate, generating visible bubbles. Bubble expansion associated with the boiling of the droplets is accompanied by pressure pulses in both the sonic and ultrasonic frequency range. In this work, we analyzed the signal generated by bubble evaporation in the frequency and time domain. We used octafluoropropane (R-218) based emulsions, sensitive to both photons and neutrons. The frequency content of the detected pulses appears to extend well into the hundreds of kHz, beyond the range used in commercial devices to count bubbles as they are formed (typically 1–10kHz). Kilohertz components characterize the early part of the waveforms, potentially containing information about the energetics of the explosive bubble initial growth phase. The power spectral density of the acoustic signal produced by neutron-induced evaporation shows a characteristic frequency pattern in the 200–400kHz range, which is not observed when bubbles evaporate upon gamma ray-induced irradiation. For practical applications, detection of ultrasonic pulses associated with the boiling of the superheated drops can be exploited as a fast readout method, negligibly affected by mechanical ambient noise.

Development of Nuclear Emulsion Detector for Muon Radiography

Muon radiography is the non-destructive testing technique of large-scale constructions with cosmic ray muon. Cosmic ray muon has high penetrating power and it always comes from the whole sky. In the same way of taking a X-ray photograph, we can obtain integrated density of constructions which thickness are several tens to several hundreds. We had ever applied this technique to nuclear reactors, volcanos, and so on. Nuclear emulsion is three dimensional track detector with micrometric position accuracy. Thanks to high position resolution, Nuclear emulsion has mrad angular resolution. In addition, the features which require no power supply and can observe in a large area suitable for muon radiography. In Nagoya University, we launched emulsion manufacturing equipment at 2010. It has become possible to flexible development of our detector and succeeded to development of high sensitive nuclear emulsion film (Nagoya emulsion). An important factor is the temperature characteristic to withstand the outdoor observation as a detector to be used in the muon radiography. There is a phenomenon of a latent image fading, whichit is well known in the photographic industry, and this phenomenon is known that temperature and water are involved. So we examined temperature and humidity characteristic of latent image fading about Nagoya emulsion. As a result, we found latent image fading is strongly depends on both temperature and humidity. By dehydrating emulsion film in RH8%, over 95% (Grain Density>40) detection efficiency of muon track keeps over 3months in 25degree, for 2months in 35degree. Additionally it was showed in this test that increasing back ground noise “fog”, which may have occurred by sealing emulsion film in a narrow space, is reduced by buffer space in the bag.

Comparison of Planar and 3D Silicon Pixel Sensors Used for Detection of Low Energy Antiprotons

The principal aim of the AEgIS experiment at CERN is to measure the acceleration of antihydrogen due to Earth's gravitational field. This would be a test of the Weak Equivalence Principle, which states that all bodies fall with the same acceleration independently of their mass and composition. The effect of Earth's gravitational field on antimatter will be determined by measuring the deflection of the path of the antihydrogen from a straight line. The position of the antihydrogen will be found by detecting its annihilation on the surface of a silicon detector. The gravitational measurement in AEgIS will be performed with a gravity module, which includes the silicon detector, an emulsion detector and a scintillating fibre time-of-flight detector. As the experiment attempts to determine the gravitational acceleration with a precision of 1%, a position resolution better than 10 μm is required. Here we present the results of a study of antiproton annihilations in a 3D silicon pixel sensor and compare the results with a previous study using a monolithic active pixel sensor. This work is part of a larger study on different silicon sensor technologies needed for the development of a silicon position detector for the AEgIS experiment. The 3D detector together with its readout electronics have been originally designed for the ATLAS detector at the LHC. The direct annihilation of low energy antiprotons ( ~ 100 keV) takes place in the first few μm of the silicon sensor and we show that the charged products of the annihilation can be detected with the same sensor. The present study also aims to understand the signature of an antiproton annihilation event in segmented silicon detectors and compares it with a GEANT4 simulation model. These results will be used to determine the geometrical and process parameters to be adopted by the silicon annihilation detector to be installed in AEgIS.

Target dependence of clan model parameter in 84 Kr 36 – Emulsion interactions at 1 GeV per nucleon

This article focusses on the study of clan model parameters and their target dependence in light of void probability scaling for heavy (Ag and Br) and light (C, N and O) groups of targets present in nuclear emulsion detector using 84Kr36 at ∼1 A GeV. The variation of scaled rapidity-gap (rap–gap) probability with single moment combination has been studied. We found that experimental points lie approximately on the negative binomial distribution (NBD) curve, indicating a scaling behaviour. The increase in average clan multiplicities ( $\bar {N}$ ) for interactions with the pseudorapidity interval (Δη) was also observed. The values of $\bar {N}$ for AgBr targets are larger than those for C/N/O target and also average number of particles per clan ( $\bar {n}_{\mathrm {c}}$ ) increases with increase in pseudorapidity interval. We further observed that for a particular target, the average number of particles per clan ( $\bar {n}_{\mathrm {c}}$ ) increases with an increase in the size of projectile nucleus.

A moiré deflectometer for antimatter.

The precise measurement of forces is one way to obtain deep insight into the fundamental interactions present in nature. In the context of neutral antimatter, the gravitational interaction is of high interest, potentially revealing new forces that violate the weak equivalence principle. Here we report on a successful extension of a tool from atom optics—the moiré deflectometer—for a measurement of the acceleration of slow antiprotons. The setup consists of two identical transmission gratings and a spatially resolving emulsion detector for antiproton annihilations. Absolute referencing of the observed antimatter pattern with a photon pattern experiencing no deflection allows the direct inference of forces present. The concept is also straightforwardly applicable to antihydrogen measurements as pursued by the AEgIS collaboration. The combination of these very different techniques from high energy and atomic physics opens a very promising route to the direct detection of the gravitational acceleration of neutral antimatter.

Measuring the gravitational free-fall of antihydrogen

Antihydrogen holds the promise to test, for the first time, the universality of free-fall with a system composed entirely of antiparticles. The AEgIS experiment at CERN’s antiproton decelerator aims to measure the gravitational interaction between matter and antimatter by measuring the deflection of a beam of antihydrogen in the Earths gravitational field (\(\overline {\textrm {g}}\)). The principle of the experiment is as follows: cold antihydrogen atoms are synthesized in a Penning-Malberg trap and are Stark accelerated towards a moire deflectometer, the classical counterpart of an atom interferometer, and annihilate on a position sensitive detector. Crucial to the success of the experiment is the spatial precision of the position sensitive detector. We propose a novel free-fall detector based on a hybrid of two technologies: emulsion detectors, which have an intrinsic spatial resolution of 50 nm but no temporal information, and a silicon strip / scintillating fiber tracker to provide timing and positional information. In 2012 we tested emulsion films in vacuum with antiprotons from CERN’s antiproton decelerator. The annihilation vertices could be observed directly on the emulsion surface using the microscope facility available at the University of Bern. The annihilation vertices were successfully reconstructed with a resolution of 1–2 μmon the impact parameter. If such a precision can be realized in the final detector, Monte Carlo simulations suggest of order 500 antihydrogen annihilations will be sufficient to determine \(\overline {\textrm {g}}\)with a 1 % accuracy. This paper presents current research towards the development of this technology for use in the AEgIS apparatus and prospects for the realization of the final detector.

Experimental study of source of background noise in muon radiography using emulsion film detectors

Abstract. The aim of this study is to ascertain and confirm the source of background noise in cosmic-ray muon radiography (muography) using emulsion film detectors. For this, we build two types of emulsion detectors with different momentum thresholds and perform test measurements of an actual geoscientific target. This experiment reveals that contamination of nonsignal particles with momenta of less than 2 GeV c−1 cause significant systematic errors for the density estimation of muography. Utilizing the results of precedent studies, we conclude that the origin of these low-momentum particles is either electromagnetic components of air showers or cosmic-ray muons scattered in topographic material. In this paper, we analyze the emulsion data in detail, including the film-inefficiency compensation and momentum selection by applying an upper bound to the chi-square distribution for the data.

Fast 4π track reconstruction in nuclear emulsion detectors based on GPU technology

Fast 4π solid angle particle track recognition has been a challenge in particle physics for a long time, especially in using nuclear emulsion detectors. The recent advances in computing technology opened the way for its realization. A fast 4π solid angle particle track reconstruction based on GPU technology combined with a multithread programming is reported here with a detailed comparison of processing time by CPUs with respect to using GPUs. By employing 3 state-of-the-art GPUs with a multithread programming, a 60 times faster processing of 3D emulsion detector data has been achieved with an excellent tracking performance in comparison with a single-thread CPU processing, corresponding to processing of 15 cm2 emulsion surface scanned per hour.

Measuring GBAR with emulsion detector

The motivation of the AEgIS experiment is to test the universality of free fall with antimatter. The goal is to reach a relative uncertainty of 1% for the measurement of the earth's gravitational acceleration [Formula: see text] on an antihydrogen beam. High vertex position resolution is required for a position detector. An emulsion based detector can measure the annihilation vertex of antihydrogen atoms with a resolution of 1-2 μm, which if realized in the actual experiment will enable a 1% measurement of [Formula: see text] with less than 1000 [Formula: see text] atoms. Developments and achievements on emulsion detectors for the AEgIS experiment are presented here.

Characteristics of compound multiplicity in 84Kr36 with various light and heavy targets at 1 GeV per nucleon

Present article focuses on the interactions of 84 Kr 36 having kinetic energy around 1 GeV per nucleon with NIKFI BR2 nuclear emulsion detectors targets, that can reveal important features of some compound multiplicity. The observation showed that the width of the compound multiplicity distributions and value of the mean compound multiplicity have linear relation with the mass number of the projectile as well as colliding system.

Prospects for measuring the gravitational free-fall of antihydrogen with emulsion detectors

The main goal of the AEgIS experiment at CERN is to test the weak equivalence principle for antimatter. AEgIS will measure the free-fall of an antihydrogen beam traversing a moir'e deflectometer. The goal is to determine the gravitational acceleration ḡ with an initial relative accuracy of 1% by using an emulsion detector combined with a silicon μ-strip detector to measure the time of flight. Nuclear emulsions can measure the annihilation vertex of antihydrogen atoms with a precision of ∼ 1–2 μm r.m.s. We present here results for emulsion detectors operated in vacuum using low energy antiprotons from the CERN antiproton decelerator. We compare with Monte Carlo simulations, and discuss the impact on the AEgIS project.

Double-Λhypernuclei observed in a hybrid emulsion experiment

A hybrid experiment with nuclear emulsion and scintillating-fiber detectors (KEK-E373) has been performed to search for double-strangeness systems. Among about 10${}^{3}$ events of ${\ensuremath{\Xi}}^{\ensuremath{-}}$ hyperons captured at rest by emulsion nuclei, we have observed four events which clearly show the topology of cascade weak decays of double-$\ensuremath{\Lambda}$ hypernuclei including the ``Nagara'' event. Regarding the Nagara event, values of the two-$\ensuremath{\Lambda}$ binding energy (${B}_{\ensuremath{\Lambda}\ensuremath{\Lambda}}$) and the $\ensuremath{\Lambda}$-$\ensuremath{\Lambda}$ interaction energy ($\ensuremath{\Delta}{B}_{\ensuremath{\Lambda}\ensuremath{\Lambda}}$) of ${}_{\ensuremath{\Lambda}}^{}{}_{\ensuremath{\Lambda}}^{6}\mathrm{He}$ have been revised to 6.91 $\ifmmode\pm\else\textpm\fi{}$ 0.16 and 0.67 $\ifmmode\pm\else\textpm\fi{}$ 0.17 MeV, respectively, due to the recent change of the ${\ensuremath{\Xi}}^{\ensuremath{-}}$ mass value (Particle Data Group). For another three events, we have determined possible species of double-$\ensuremath{\Lambda}$ hypernuclei together with their binding energies.

Gamma photon techniques for detection of nucleation in superheated emulsion detectors for neutron dosimetry

Application of transmission and scattering gamma photon techniques for calibration of superheated emulsion detectors used for neutron dosimetry is described. The bubbles nucleated in the detector due to neutron exposure generate detectable changes in both attenuation and scattering properties of the medium, and the magnitude of change in properties depends on population density of bubbles nucleated and in turn is proportional to neutron dose. The experimental set-up consists of (137)Cs and (241)Am sources and an HPGe detector-based gamma-ray spectrometer. An indigenously developed bubble detector and a commercially available one (BTI, Canada) are used in the present study. Theoretical models for the variation in transmitted and scattered intensities through the bubble detector as a function of neutron dose are formulated, and the experimental results obtained are found to be in good agreement with the models. In the neutron dose region studied, the transmission technique shows better sensitivity than scattering technique.

Search for the νμ → ντ oscillation with the OPERA hybrid detector

This work reviews the status of the international OPERA experiment aimed at searching for the νμ → ντ oscillation. Development of the emulsion techniques in the preceding DONUT and CHORUS experiments is described. A brief overview of the NOMAD experiment is given, in which properties of ντ interactions were thoroughly investigated. Characteristics of the CERN-Gran Sasso (CNGS) neutrino beam are given, the structure of the OPERA hybrid detector and the functions of its subsystems are considered, and the automatic emulsion scanning technique is briefly reviewed. Uncertainties in reconstruction of event parameters using the electronic and emulsion detectors are discussed and the procedure adopted in the experiment for identification of ντ interactions is described. The main sources of background in the search for νμ → ντ oscillation are considered. Topologies of the first two ντ candidates observed in the OPERA emulsion detector are presented. Possibilities of increasing the ντ interaction selection efficiency using multidimensional criteria are briefly discussed.

The nucleation parameter for heavy-ion induced bubble nucleation in superheated emulsion detector

The values of the nucleation parameter, k, for bubble nucleation induced by high energy heavy ions 12C (180 MeV/u), 20Ne (400 MeV/u) and 28Si (350 MeV/u) in superheated emulsion detector are determined by comparing the experimentally obtained normalized count rates with those obtained from simulations done using the GEANT3.21 simulation code.The results show that the nucleation parameter depends on the mass number of the incident heavy ions, and decreases with increasing mass number.