212 research outputs found
New Particle Identification Approach with Convolutional Neural Networks in GAPS
The General Antiparticle Spectrometer (GAPS) is a balloon-borne experiment
that aims to measure low-energy cosmic-ray antiparticles. GAPS has developed a
new antiparticle identification technique based on exotic atom formation caused
by incident particles, which is achieved by ten layers of Si(Li) detector
tracker in GAPS. The conventional analysis uses the physical quantities of the
reconstructed incident and secondary particles. In parallel with this, we have
developed a complementary approach based on deep neural networks. This paper
presents a new convolutional neural network (CNN) technique. A
three-dimensional CNN takes energy depositions as three-dimensional inputs and
learns to identify their positional/energy correlations. The combination of the
physical quantities and the CNN technique is also investigated. The findings
show that the new technique outperforms existing machine learning-based methods
in particle identification.Comment: 7 pages, 10 figure
Thermal Control System to Easily Cool the GAPS Balloon-borne Instrument on the Ground
This study developed a novel thermal control system to cool detectors of the
General AntiParticle Spectrometer (GAPS) before its flights. GAPS is a
balloon-borne cosmic-ray observation experiment. In its payload, GAPS contains
over 1000 silicon detectors that must be cooled below -40^{\circ}\mbox{C}.
All detectors are thermally coupled to a unique heat-pipe system (HPS) that
transfers heat from the detectors to a radiator. The radiator is designed to be
cooled below -50^{\circ}\mbox{C} during the flight by exposure to space. The
pre-flight state of the detectors is checked on the ground at 1 atm and ambient
room temperature, but the radiator cannot be similarly cooled. The authors have
developed a ground cooling system (GCS) to chill the detectors for ground
testing. The GCS consists of a cold plate, a chiller, and insulating foam. The
cold plate is designed to be attached to the radiator and cooled by a coolant
pumped by the chiller. The payload configuration, including the HPS, can be the
same as that of the flight. The GCS design was validated by thermal tests using
a scale model. The GCS design is simple and provides a practical guideline,
including a simple estimation of appropriate thermal insulation thickness,
which can be easily adapted to other applications.Comment: 8 pages, 14 figures, 3 table
Fabrication of low-cost, large-area prototype Si(Li) detectors for the GAPS experiment
A Si(Li) detector fabrication procedure has been developed with the aim of
satisfying the unique requirements of the GAPS (General Antiparticle
Spectrometer) experiment. Si(Li) detectors are particularly well-suited to the
GAPS detection scheme, in which several planes of detectors act as the target
to slow and capture an incoming antiparticle into an exotic atom, as well as
the spectrometer and tracker to measure the resulting decay X-rays and
annihilation products. These detectors must provide the absorption depth,
energy resolution, tracking efficiency, and active area necessary for this
technique, all within the significant temperature, power, and cost constraints
of an Antarctic long-duration balloon flight. We report here on the fabrication
and performance of prototype 2"-diameter, 1-1.25 mm-thick, single-strip Si(Li)
detectors that provide the necessary X-ray energy resolution of 4 keV for
a cost per unit area that is far below that of previously-acquired commercial
detectors. This fabrication procedure is currently being optimized for the
4"-diameter, 2.5 mm-thick, multi-strip geometry that will be used for the GAPS
flight detectors.Comment: Accepted for publication at Nuclear Instrumentation and Methods A, 12
pages, 11 figure
Large-area Si(Li) Detectors for X-ray Spectrometry and Particle Tracking for the GAPS Experiment
Large-area lithium-drifted silicon (Si(Li)) detectors, operable 150{\deg}C
above liquid nitrogen temperature, have been developed for the General
Antiparticle Spectrometer (GAPS) balloon mission and will form the first such
system to operate in space. These 10 cm-diameter, 2.5 mm-thick multi-strip
detectors have been verified in the lab to provide <4 keV FWHM energy
resolution for X-rays as well as tracking capability for charged particles,
while operating in conditions (~-40{\deg}C and ~1 Pa) achievable on a
long-duration balloon mission with a large detector payload. These
characteristics enable the GAPS silicon tracker system to identify cosmic
antinuclei via a novel technique based on exotic atom formation, de-excitation,
and annihilation. Production and large-scale calibration of ~1000 detectors has
begun for the first GAPS flight, scheduled for late 2021. The detectors
developed for GAPS may also have other applications, for example in heavy
nuclei identification
Measurement of low-energy antiproton detection efficiency in BESS below 1 GeV
An accelerator experiment was performed using a low-energy antiproton beam to
measure antiproton detection efficiency of BESS, a balloon-borne spectrometer
with a superconducting solenoid. Measured efficiencies showed good agreement
with calculated ones derived from the BESS Monte Carlo simulation based on
GEANT/GHEISHA. With detailed verification of the BESS simulation, the relative
systematic error of detection efficiency derived from the BESS simulation has
been determined to be 5%, compared with the previous estimation of
15% which was the dominant uncertainty for measurements of cosmic-ray
antiproton flux.Comment: 13 pages, 7 figure
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