40 research outputs found
Fundamental physics activities with pulsed neutron at J-PARC(BL05)
"Neutron Optics and Physics (NOP/ BL05)" at MLF in J-PARC is a beamline for
studies of fundamental physics. The beamline is divided into three branches so
that different experiments can be performed in parallel. These beam branches
are being used to develop a variety of new projects. We are developing an
experimental project to measure the neutron lifetime with total uncertainty of
1 s (0.1%). The neutron lifetime is an important parameter in elementary
particle and astrophysics. Thus far, the neutron lifetime has been measured by
several groups; however, different values are obtained from different
measurement methods. This experiment is using a method with different sources
of systematic uncertainty than measurements conducted to date. We are also
developing a source of pulsed ultra-cold neutrons (UCNs) produced from a
Doppler shifter are available at the unpolarized beam branch. We are developing
a time focusing device for UCNs, a so called "rebuncher", which can increase
UCN density from a pulsed UCN source. At the low divergence beam branch, an
experiment to search an unknown intermediate force with nanometer range is
performed by measuring the angular dependence of neutron scattering by noble
gases. Finally the beamline is also used for the research and development of
optical elements and detectors. For example, a position sensitive neutron
detector that uses emulsion to achieve sub-micrometer resolution is currently
under development. We have succeeded in detecting cold and ultra-cold neutrons
using the emulsion detector.Comment: 9 pages, 5 figures, Proceedings of International Conference on
Neutron Optics (NOP2017
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
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 ultracold neutrons (UCNs) on a mirror bounded by the Earth's
gravitational field. The Searches require detectors with higher spatial
resolution. We are developing a UCN detector for the with a high spatial
resolution, which consists of a Si substrate, a thin converter layer including
BC, and a layer of fine-grained nuclear emulsion. Its resolution
was estimated to be less than 100 nm by fitting tracks of either Li
nuclei or -particles, which were created when neutrons interacted with
the BC layer. For actual measurements of the spatial
distributions, the following two improvements were made: The first 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 m and 5
m diameter with an interval of 50 m and 500 m, respectively, on
the Si substrate by electron beam lithography and realized a position accuracy
of less than 30 nm. The second was to build a holder that could maintain the
atmospheric pressure around the nuclear emulsion to utilize it under vacuum
during exposure to UCNs. The intrinsic resolution of the improved detector was
estimated by evaluating the blur of a transmission image of a gadolinium
grating taken by cold neutrons as better than 0.56 0.08 m, which
included the grating accuracy. A test exposure to UCNs was conducted to obtain
the spatial distribution of UCNs in the Earth's gravitational field. Although
the test was successful, a blurring of 6.9 m was found in the
measurements, compared with a theoretical curve. We identified the blurring
caused by the refraction of UCNs due to the roughness of the upstream surface
of the substrate. Polishing of the surface makes the resolution less than 100
nm
Charge identification of highly ionizing particles in desensitized nuclear emulsion using high speed read-out system
We performed an experimental study of charge identification of heavy ions from helium to carbon having energy of about 290 MeV=u using an emulsion chamber. Emulsion was desensitized by means of forced fading (refreshing) to expand a dynamic range of response to highly charged particles. For the track reconstruction and charge identification, the fully automated high speed emulsion read-out system, which was originally developed for identifying minimum ionizing particles, was used without any modification. Clear track by track charge identification up to Z 1?4 6 was demonstrated. The refreshing technique has proved to be a powerful technique to expand response of emulsion film to highly ionizing particles
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