Y. Nakamura

Measurement of high energy cosmic rays by the new Tibet hybrid experiment

We have started a new hybrid air shower experiment at Yangbajing (4300 m a.s.l.) in Tibet in February 2014. This new hybrid experiment consists of the YAC-II comprised of 124 core detectors placed in the form of a square grid of 1.9 m spacing covering about 500 m2, the Tibet-III air shower array with the total area of about 50,000 m2 and the underground MD array consisting of 80 cells, with the total area of about 4,200 m2. This hybrid-array system is used to observe air showers of high energy celestial gamma-ray origin and those of nuclear-component origin. In this paper, a short review of the experiment will be followed by an overview on the current results on energy spectrum and chemical composition of CRs and test of hadronic interaction models.

Interplanetary Coronal Mass Ejection and the Sun's Shadow Observed by the Tibet Air Shower Array

We continuously observed the Sun’s shadow in 3 TeV cosmic-ray intensity with the Tibet-III air shower array since 2000. We find a clear solar-cycle variation of the deficit intensity in the Sun’s shadow during the periods between 2000 and 2009. The MC simulation of the Sun’s shadow based on the coronal magnetic field model does not well reproduce the observed deficit intensity around the solar maximum. However, when we exclude the transit periods during ICMEs towards to the Earth, the MC simulation shows better reproducibility. In the present paper, we report on the MC simulation and the analysis method of the Sun’s shadow observed by the Tibet-III array.

The Tibet AS+MD Project; status report 2017

We built a large (approximately 4,000 m**2) wateru3000Cherenkov- ntype muon detector array under the existing Tibet air shower array at n4,300 m above sea level, to observe 10-1000 TeV gamma rays from ncosmic-ray accelerators in our Galaxy with wide field of view nat very low background level. A gamma-ray induced air shower has nsignificantly less muons compared with a cosmic-ray induced one. nTherefore, we can effectively discriminate between primary gamma rays nand cosmic-ray background events by means of counting number of nmuons in an air shower event by the muon detector array. We make a nstatus report on the experiment.

ALPAQUITA Array in the ALPACA Project

We are now proposing a new project which consists of a large air shower array (83,000 m^2) and a muon detector array (5,400 m^2) located at the altitude of 4,740 m near La Paz in Bolivia to observe 100 TeV gamma rays in the southern sky. The ALPAQUITA array is a prototype air shower array which will be constructed at the ALPACA site. This array consists of 45 scintillation counters of 1 m^2 in area each, and its effective area is approximately 8,000 m^2 (1/10 of ALPACA air shower array). In the present paper, we report on the current status and the performance of the ALPAQUITA array

Solar magnetic field strength and the “Sun's Shadow”

The angular displacement of the center of the observed Suns shadow from the center of the optical solar disc tells us the information of average solar magnetic field strength in the space between the Sun and the Earth. We analyze the displacement of the Suns shadow observed in 5 ~ 240 TeV cosmic-ray intensity with the Tibet-III air shower array during 10 years between 2000 and 2009, and compare with the MC simulations based on the coronal magnetic field model and Parkers spiral interplanetary magnetic field model. We find that the observed North-South displacement is significantly larger than the prediction of simulations. This result uniquely suggests the underestimation of the average field strength between the Sun and the Earth in our model. In this work, we will report the actual solar magnetic field strength evaluated from the observed Suns shadow.

Development of faster front end electronics for the SciCRT detector at Sierra Negra, Mexico

The SciBar Cosmic ray telescope (SciCRT) is installed on the top of the Sierra Negra volcano with the main goal of observing solar neutrons to investigate the ion acceleration process during solar flares. Using scintillator bars as a medium to stop energetic particles, the SciCRT is capable of recording both energy deposited on the bars and direction of the incoming particles with high resolution. The original DAQ system was used in neutrino oscillation experiment (low event rate), therefore operation of the electronics on cosmic ray experiment is limited. To improve the SciCRT performance as a solar neutron telescope, development of custom made DAQ electronics is essential. Our first step onto this task was the design and construction of a new fast readout back-end board using SiTCP. The installation of this new system on Sierra Negra and its further improvement on the data acquisition for the detector will be analyzed on separate paper on this conference. The development of new front end electronics is the next stage of the upgrading process. To achieve this goal, we are developing new electronics applying the time over threshold (ToT) technique, using a FPGA to process the signal from one 64 channel multi anode photomutiplier tube (MAPMT). In this paper we will present the details of this new system and several tests performed to guarantee its proper operation to detect solar neutrons.

The overview of the ALPACA Experiment

The ALPACA experiment is a new project aimed at wide field-of-view nhigh-sensitivity observations of high-energy cosmic rays and cosmic ngamma rays, launched between Bolivia and Japan in 2016. It is composed nof an 83,000 m

Current status of SciCRT experiment and its expected future performance

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Development of a pattern recognition algorithm for particle identification on the SciCRT in the Sierra Negra Volcano Summit

air shower array and a 5,400 m

Upgrade of a data acquisition system for SciBar Cosmic Ray Telescope (SciCRT) at Mt. Sierra Negra, Mexico

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