Nuclear Emulsion Plates Research Articles

Development of High-Resolution Nuclear Emulsion Plates for Synchrotron X-Ray Topography Observation of Large-Size Semiconductor Wafers

Characterization of defects in semiconductor wafers is essential for the development and improvement of semiconductor devices, especially power devices. X-ray topography (XRT) using synchrotron radiation is a powerful methods used for defect characterization. To achieve detailed characterization of large-size semiconductor wafers by synchrotron XRT, we have developed nuclear emulsion plates reaching a high-resolution and wide dynamic range. We have shown that higher-resolution XRT images could be obtained using emulsions with smaller iodobromide crystals, and demonstrated clear observation of threading edge dislocations in a SiC epitaxial layer having small contrast. Furthermore, we demonstrated XRT image acquisition for almost all of a 150-mm SiC wafer with one plate. Our development will contribute to advances in electronic materials, especially in the field of power electronics, in which defect characterization is important for improving the performance and yield of devices.

Development of glass-based nuclear emulsion plate as an ultra-high precision tracking detector in the era of fully automated readout systems

The positional accuracy of a nuclear emulsion can reach a submicrometric resolution owing to the size of its detection elements, i.e., 200 nm sized AgBr crystals. However, when used as a film in an experimental environment, the film is deformed by temperature and various mechanical stresses, and it becomes difficult to maintain the accuracy of the submicrometric absolute position throughout the detector. In this study, we attempted to solve this problem by using a glass base instead of a plastic base, which has been widely used thus far. To evaluate the deformation effect, sets of nuclear emulsion plates with a size of 10cm×12.5cm using various base materials were exposed to 5GeV/c pion beams. The magnitude of the deformation between the two films was evaluated using the beam pattern discrepancy. For the commonly used 180 μm thick polystyrene base, the magnitude of the deformation within the 3cm×4cm region was evaluated to be 1.77 μm on average, whereas for the 500 μm thick glass base, it was improved to 0.31 μm. This was approximately the same level as the measurement accuracy of the fully automated nuclear emulsion readout system, and the effect of the film deformation can be ignored. Through an analysis of this experiment, it became clear that the angle of the track had a systematic correlation with the material of the base. Because it can be inferred that the origin is owing to the difference between the refractive index of the base and the designed refractive index of the optical system of the readout system, an equation for correcting this systematic error was proposed. Nuclear emulsions with glass supporting bases are suitable for applications that require submicrometric positional accuracy throughout the detector, such as the precise measurement of momentum using a magnetic field and multiple scattering, and for use in outdoor experiments where the temperature changes widely.

Track formation in nuclear emulsion plates for cosmic-ray imaging with stabilized Ag nanoparticles

In cosmic-ray imaging system with nuclear emulsions, silver halide (AgX) grains capture muon-created electrons to form a latent image composed of small Ag nanoparticles (latent image centers), which could be as small as three atoms. Since it needs such a long time as several months for the grains to capture sufficient number of muon-created electrons for imaging, the stabilization of latent image is inherently important. There are two kinds of latent image fading; the first- and second-order reactions. The former is the oxidation of latent image centers by oxidants, which are not formed by cosmic-ray irradiation, and the latter is the re-halogenation of latent image centers by irradiation-created X2. It was revealed that the latter became to be predominant over the former within several days after irradiation as the volume ratio of gelatin in emulsion layers decreased, indicating that gelatin is very effective to depress this type of latent image fading. Following the previous paper, we have extended our study on the property and behavior of new additives by means of photoelectron spectroscopy to prove the mechanism of the latent image fading with the first-order reaction, according to which a latent image center with electric charge of +1/2 degrades via the repetition of the ionic process (detachment of an Ag+ion) and the electronic process (losing of an electron) one after the other, its electric charge changing to -1/2 and back. The mechanism thus proved has provided several ideas to depress latent image fading in nuclear emulsions for cosmic-ray imaging.

X-ray topography of crystallographic defects in wide-bandgap semiconductors using a high-resolution digital camera

A high-resolution CMOS camera equipped with a scintillator and relay lenses was used to record X-ray topographic images of wide-bandgap semiconductor wafers, including 4H-SiC, GaN, AlN, and β-Ga2O3. The images were compared with those recorded with nuclear emulsion plates (NEPs) and a CCD camera at the same sample site. Fine structures of dislocation contrasts, which allowed for accurate identification of the dislocation types, could be observed using the CMOS camera. The results suggest that the CMOS camera can provide high-quality images that are comparable with the NEPs; hence, the reported approach is a promising one for real-time dislocation observation in power devices under operation.

Characteristics of double hypernuclei revealed by nuclear-emulsion plates

Characteristics of double hypernuclei revealed by nuclear-emulsion plates

Detection of the Rare Interaction of a Neutral Particle with Energy Higher than 15 TeV in the Stratospheric X-ray Emulsion Chamber (According to the RUNJOB Experiment Data)

A rare event observed in a nuclear emulsion is reported. The RUNJOB Russian-Japanese balloon experiment detected the interaction of a high-energy neutral particle in a nuclear emulsion plate of an X-ray emulsion chamber exposed in 1999.

21pAA-10 J-PARC E07実験における大型原子核乾板現像手法の研究開発

21pAA-10 J-PARC E07実験における大型原子核乾板現像手法の研究開発

Dark matter directional detection: comparison of the track direction determination

Several directional techniques have been proposed for a directional detection of Dark matter, among others anisotropic crystal detectors, nuclear emulsion plates, and low-pressure gaseous TPCs. The key point is to get access to the initial direction of the nucleus recoiling due to the elastic scattering by a WIMP. In this article, we aim at estimating, for each method, how the information of the recoil track initial direction is preserved in different detector materials. We use the SRIM simulation code to emulate the motion of the first recoiling nucleus in each material. We propose the use of a new observable, D, to quantify the preservation of the initial direction of the recoiling nucleus in the detector. We show that in an emulsion mix and an anisotropic crystal, the initial direction is lost very early, while in a typical TPC gas mix, the direction is well preserved.

Cosmic ray nuclei detection in the balloon borne nuclear emulsion gamma ray telescope flight in Australia (GRAINE 2015)

Nuclear emulsion plates for studying elementary particle physics as well as cosmic ray physics are very powerful tracking tools with sub-micron spatial resolutions of charged particle trajectories. Even if gamma rays have to be detected, electron-positron pair tracks can provide precise information to reconstruct their direction and energy with high accuracy. Recent developments of emulsion analysis technology can digitally handle almost all tracks recorded in emulsion plates by using the Hyper Track Selector of the OPERA group at NAGOYA University. On the other hand, the potential of time resolutions have been equipped by emulsion multilayer shifter technology in the GRAINE (Gamma Ray Astro-Imager with Nuclear Emulsion) experiments, the aims of which are to detect cosmic gamma rays such as the Vela pulsar stellar object by precise emulsion tracking analysis and to study cosmic ray particle interactions and chemical compositions. In this paper, we focus on the subject of cosmic ray nuclei detection in the GRAINE balloon flight experiments launched at Alice Springs, Australia in May 2015.

Cosmic ray nuclei detection in the balloon borne nuclear emulsion gamma ray telescope flight in Australia (GRAINE 2015)

Nuclear emulsion plates for studying elementary particle physics as well as cosmic ray physics are very powerful tracking tools with sub-micron spatial resolutions of charged particle trajectories. Even if gamma rays have to be detected, electron-positron pair tracks can provide precise information to reconstruct their direction and energy with high accuracy. Recent developments of emulsion analysis technology can digitally handle almost all tracks recorded in emulsion plates by using the Hyper Track Selector of the OPERA group at NAGOYA University. On the other hand, the potential of time resolutions have been equipped by emulsion multilayer shifter technology in the GRAINE (Gamma Ray Astro-Imager with Nuclear Emulsion) experiments, the aims of which are to detect cosmic gamma rays such as the Vela pulsar stellar object by precise emulsion tracking analysis and to study cosmic ray particle interactions and chemical compositions. In this paper, we focus on the subject of cosmic ray nuclei detection in the GRAINE balloon flight experiments launched at Alice Springs, Australia in May 2015.

Development of fast neutron pinhole camera using nuclear emulsion for neutron emission profile measurement in KSTAR.

We have developed a compact fast neutron camera based on a stack of nuclear emulsion plates and a pinhole collimator. The camera was installed at J-port of Korea superconducting tokamak advanced research at National Fusion Research Institute, Republic of Korea. Fast neutron images agreed better with calculated ones based on Monte Carlo neutron simulation using the uniform distribution of Deuterium-Deuterium (DD) neutron source in a torus of 40 cm radius.

21pCF-9 大型原子核乾板の現像手法最適化

21pCF-9 大型原子核乾板の現像手法最適化

Emulsion Scanning Systems for Double-strangeness Nuclei

Nuclear emulsion is so far the best detector to investigate double-strangeness nucleus including double Lambda hypernucleus, which is a nucleus made up of two lambda hyperons in addition to nucleons. Two types of scanning system are being developed to search for more events of double Lambda hypernucleus rapidly. One is a system for automated Xi− hyperon tracking. The other is “Overall scanning”, high-speed scanning and image recognition for vertex-like-shapes from microscopic images of the tracks in nuclear emulsion plates.

Experimental Study of the Interaction between Two Lambda Hyperons

The knowledge of \({\Lambda{-}\Lambda}\) interaction is quite limited. At present, only Nagara event gives a definite information for its interaction among nine samples of double hypernucleus in the world. To obtain nuclear mass dependence of the interaction with one thousand double hypernuclei, a system for fully automated scanning of \({\Xi^-}\) hyperons was developed by the success of precise position alignment (1 μm) of nuclear emulsion plates. Production and decay of double hypernuclei have typical topologies with three vertices. The development of a system to search for such topologies in overall emulsion is ongoing.

NUCLEAR STRUCTURE OF 97Mo FROM THE (d, p) REACTION

The reaction 96 Mo (d, p)97 Mo has been studied at 12 MeV using the tandem Van de Graaff accelerator and a multi-channel magnetic spectrograph at the Atomic Weapon Research Establishment, Aldermaston, England. Angular distributions of protons are measured at 12 different angles from 5° to 87.5° at an interval of 7.5° and the reaction products are detected in nuclear emulsion plates. Thirty levels in the energy range from 0.000 to 2.458 MeV have been observed and absolute differential cross-sections for these levels have been measured. The data are analyzed in terms of the distorted-wave Born approximation (DWBA) theory of the direct reactions, and spins, parities and spectroscopic factors are deduced for various levels. Ambiguity in the spin assignments of d5/2 and d3/2 which is allowed in ln = 2(d, p) transition is removed by using the corresponding L-value of the 95 Mo (t, p)97 Mo reaction at Et = 12 MeV . Determined value of the sum of spectroscopic factors for transfers of d5/2 neutrons suggests configuration mixing in the ground state of 96 Mo . The properties of the levels in 97 Mo are compared with previous experimental results and theoretical predictions.

10.1007/s11496-008-2004-3

Interactions of relativistic heavy ions with total energies above 30 GeV in thick Cu and Pb targets (≥ 2 cm) have been studied with various techniques. Radiochemical irradiation experiments using thick Cu targets, both in a compact form or as diluted “2π-Cu targets” have been carried out with several relativistic heavy ions, such as 44 GeV 12C (JINR, Dubna, Russia) and 72 GeV 40Ar (LBL, Berkeley, USA). Neutron measuring experiments using thick targets irradiated with various relativistic heavy ions up to 44 GeV 12C have been performed at the JINR. In addition, the number of “black prongs” in nuclear interactions (due to protons with energies less than 30 MeV and emitted from the target-like interaction partner at rest) produced with 72 GeV 22Ne ions in nuclear emulsion plates has been measured in the first nuclear interaction of the primary 22Ne ion and in the following second nuclear interaction of the secondary heavy (Z > 1) ion. Some essential results have been obtained. (1) Spallation products produced by relativistic secondary fragments in interactions ([44 GeV 12C or 72 GeV 40Ar] + Cu) within thick copper yield fewer products close to the target and many more products far away from the target as compared to primary beam interactions. This applies also to secondary particles emitted into large angles (Θ > 10°). (2) The neutron production of 44 GeV 12C within thick Cu and Pb targets is beyond the estimated yield as based on experiments with 12 GeV 12C. These rather independent experimental results cannot be understood within well-accepted nuclear reaction models. They appear to present unresolved problems.

NUCLEAR STRUCTURE OF 99Mo FROM THE (t,p) REACTION

The 97 Mo (t,p)99 Mo reaction has been studied with the triton beam energy of 12 MeV obtained from tandem Van de Graaff accelerator at the Atomic Weapon Research Establishment, Aldermaston. Proton spectra were obtained at 12 different angles from 5° to 87.5° at an interval of 7.5° and were detected in nuclear emulsion plates. Angular distributions for transitions to 46 levels in the energy range from 0 to 2.054 MeV have been measured. Absolute differential cross-sections for the levels have been measured. The experimental angular distributions are compared with the distorted-wave Born approximation calculations (DWBA) to determine L and Jπ values. The present results are compared with the previous experimental results and model predictions.

A STUDY OF 97Mo FROM THE (t, p) REACTION

The 97 Mo nucleus has been studied with the reaction 95 Mo (t, p) 97 Mo using a multichannel magnetic spectrograph. The isotopically enriched thin target 95 Mo was bombarded with the 12 MeV triton beam obtained from the tandem Van de Graaff accelerator at the Atomic Weapon Research Establishment, Aldermaston. Proton spectra are obtained at 12 different angles from 5° to 87.5° at an interval of 7.5° and are detected in nuclear emulsion plates. Forty-eight levels in the energy range from 0.000 to 3.189 MeV have been observed. Absolute differential cross-sections for these levels have been measured. The angular distributions are compared with the theoretical distorted-wave Born approximation calculations to determine L and Jπ values. The nuclear properties of 97 Mo are compared with previous experimental results and model predictions.

Interactions of relativistic heavy ions in thick heavy element targets and some unresolved problems

Interactions of relativistic heavy ions with total energies above 30 GeV in thick Cu and Pb targets (≥ 2 cm) have been studied with various techniques. Radiochemical irradiation experiments using thick Cu targets, both in a compact form or as diluted “2π-Cu targets” have been carried out with several relativistic heavy ions, such as 44 GeV 12C (JINR, Dubna, Russia) and 72 GeV 40Ar (LBL, Berkeley, USA). Neutron measuring experiments using thick targets irradiated with various relativistic heavy ions up to 44 GeV 12C have been performed at the JINR. In addition, the number of “black prongs” in nuclear interactions (due to protons with energies less than 30 MeV and emitted from the target-like interaction partner at rest) produced with 72 GeV 22Ne ions in nuclear emulsion plates has been measured in the first nuclear interaction of the primary 22Ne ion and in the following second nuclear interaction of the secondary heavy (Z > 1) ion. Some essential results have been obtained. (1) Spallation products produced by relativistic secondary fragments in interactions ([44 GeV 12C or 72 GeV 40Ar] + Cu) within thick copper yield fewer products close to the target and many more products far away from the target as compared to primary beam interactions. This applies also to secondary particles emitted into large angles (Θ > 10°). (2) The neutron production of 44 GeV 12C within thick Cu and Pb targets is beyond the estimated yield as based on experiments with 12 GeV 12C. These rather independent experimental results cannot be understood within well-accepted nuclear reaction models. They appear to present unresolved problems.

Sub-micron alignment for nuclear emulsion plates using low energy electrons caused by radioactive isotopes

Nuclear emulsion plates are employed in three-dimensional charged particle detectors that have sub-micron position resolution over 1 m 2 with no dead space and no dead time. These detectors are suitable for the study of short-lived particle decays, and direct detection of neutrino interactions of all flavors. Typically emulsion plates are used in a stacked structure. Precise alignment between plates is required for physics analysis. The most accurate alignment method is to use tracks passing through the emulsion plates. The accuracy is about 0.2 μ m . However, in an experiment with low track density alignment accuracy decreases to 20 μ m because of plate distortion and it becomes more difficult to perform the analysis. This paper describes a new alignment method between emulsion plates by using trajectories of low energy electrons originating from environmental radioactive isotopes. As a trial emulsion plates were exposed to β -rays and γ -rays from K 40 . The trajectories which passed through emulsion layers were detected by a fully automated emulsion readout system. Using this method, the alignment between emulsion plates is demonstrated to be sub-micron. This method can be applied to many nuclear emulsion experiments. For example, the location of neutrino interaction vertices in the OPERA experiment can benefit from this new technique.