福家 英之

The Scientific Balloon Center of ISAS/JAXA has managed balloon-borne experiments in Japan. Since 1971 domestic balloon campaigns have been carried out at Sanriku Balloon Center. In 2007 ten scientific experiments were conducted by seven balloon flights at Sanriku. We have also developed next generation super-pressure balloons and ultra-thin balloons. In order to meet recent user requirements, i.e., stable flights of heavier payloads at the highest possible altitude, Japanese scientific balloons will be operated at Taiki, Hokkaido from 2008. This new balloon facility was constructed to launch the first balloon in May 2008. Standardization of balloons and the balloon system is also in progress, in order to maximize the reliability for our operation of larger balloons with heavier payloads. In this paper, we introduce the new balloon facility in Taiki and discuss the strategy of the Japanese scientific balloon activities. The status of the development of new balloon technologies and international collaborations will also be discussed.

The aims of the BESS-Polar experiment are precise measurements of the low-energy antiproton spectrum and search for cosmologically significant antimatter. After its first flight (BESS-Polar I), we had developed a new spectrometer based on the feedback from the results. Most of the detector components had been redesigned and upgraded to improve their performance and to increase the data taking period and capacity. The second flight (BESS-Polar II) was successfully carried out in December 2007 – January 2008. We performed 24.5 days scientific observation just at the solar minimum. In this paper, BESS-Polar II instrument and flight summary will be presented.

The Scientific Balloon Center of ISAS/JAXA has carried out two balloon campaigns at Sanriku, Iwate, Japan every year. Ten to twelve balloon vehicles are launched annually for scientific and engineering experiments. Since 2005, a Brazilian balloon campaign has also been conducted in cooperation with INPE. In the 2006 Brazilian campaign, large and heavy payloads up to 1500 kg for astronomy will be launched. New generation balloons, such as super-pressure balloons and high-altitude balloons with ultra-thin films, are being developed. The current status and prospect of the Japanese scientific ballooning are discussed. (C) 2007 COSPAR. Published by Elsevier Ltd. All rights reserved.

We are developing the CALorimetric Electron Telescope, CALET, mission for the Japanese Experiment Module Exposed Facility, JEM-EF, of the International Space Station. Major scientific objectives are to search for the nearby cosmic ray sources and dark matter by carrying out a precise measurement of the electrons in 1 GeV - 20 TeV and gamma rays in 20 MeV - several 10 TeV. CALET has a unique capability to observe electrons and gamma rays over 1 TeV since the hadron rejection power can be larger than 105 and the energy resolution better than a few % over 100 GeV. The detector consists of an imaging calorimeter with scintillating fibers and tungsten plates and a total absorption calorimeter with BGO scintillators. CALET has also a capability to measure cosmic ray H, He and heavy ions up to 1000 TeV. It also will have a function to monitor solar activity and gamma ray transients. The phase A study has started on a schedule of launch in 2013 by H-II Transfer Vehicle (HTV) for 5 year observation.

The General Antiparticle Spectrometer (GAPS) exploits low energy antideuterons produced in neutralino-neutralino annihilations as an indirect dark matter (DM) signature that is effectively free from background. When an antiparticle is captured by a target material, it forms an exotic atom in an excited state which quickly decays by emitting X-rays of precisely defined energy and a correlated pion signature from nuclear annihilation. We have successfully demonstrated the GAPS method in an accelerator environment and are currently planning a prototype flight from Japan for 2009. This will lead to a long duration balloon (LDB) mission that will complement existing and planned direct DM searches as well as other indirect techniques, probing a different, and often unique, region of parameter space in a variety of proposed DM models. Planes of coarsely pixellated Si(Li) detectors form the heart of the GAPS flight detector, providing both high X-ray energy resolution and good particle tracking. We will describe the proto-flight mission that will verify the performance of our Si(Li) detectors and cooling system in a flight-like configuration. We also will outline the LDB science payload design.

We discuss current progress and future plans for the general antiparticle spectrometer experiment (GAPS). GAPS detects antideuterons through the X-rays and pions emitted during the deexcitation of exotic atoms formed when the antideuterons are slowed down and stopped in targets. GAPS provides an exceptionally sensitive means to detect cosmic-ray antideuterons. Cosmic-ray antideuterons can provide indirect evidence for the existence of dark matter in such form as neutralinos or Kaluza-Klein particles. We describe results of accelerator testing of GAPS prototypes, tentative design concepts for a flight GAPS detector, and near-term plans for flying a GAPS prototype on a balloon. (C) 2007 COSPAR. Published by Elsevier Ltd. All rights reserved.

Historically, there are been many searches for fractionally charged particles in the cosmic radiation. However, few searches have been performed near the top of the atmosphere. We performed a search for relativistic 2/3e charged particles in cosmic rays using data collected during four BESS balloon flights from 1997 to 2000 carried out in northern Canada. The data were analyzed by examining energy deposition in the time-of-flight scintillator hodoscopes. No candidate was found. We derive an upper limit of 4.5 x 10(-7) (cm(2) s sr)(-1) for the flux of 2,e charged particles, at the 90% confidence level. (C) 2007 COSPAR. Published by Elsevier Ltd. All rights reserved.

The Balloon-Born Experiment with a Superconducting Spectrometer (BESS) has measured cosmic-ray spectra blow 1 TeV and searched for antiparticle of novel cosmic origin. The BESS program is extended to long duration balloon (LDB) flights in Antarctica (BESS-Polar) aiming at unprecedented sensitivity to search for primordial antiparticles. This report describes recent results from BESS and the progress in the BESS-Polar program.

An ultra-thin superconducting solenoid has been developed to provide a magnetic field of 0.8 T in a balloon-borne spectrometer for cosmic ray research, which is named BESS-Polar. The coil with a diameter of 0.9 m, a length of 1.4 m and a thickness of 3.5 mm was fabricated by using a mechanically strengthened aluminum stabilized superconductor. The coil winding is strong enough to eliminate the outer support cylinder which is necessary in the former thin solenoid type coils. Consequently 2 the coil weight and material thickness are 40 kg, and 2.52 g/cm, respectively. The BESS-Polar was launched near the US McMurdo Station in Antarctica on December 13th 2004, floated at an altitude of 37000 m around the South Pole for nine days. The solenoid was charged up on the ground and kept the field in a persistent current mode during launch and floating. This report describe the flight performance of the solenoid.

We performed a search for cosmic-ray antideuterons using data collected during four BESS balloon flights from 1997 to 2000. No candidate was found. We derived, for the first time, an upper limit of 1.9x10(-4) (m(2)s sr GeV/nucleon)(-1) for the differential flux of cosmic-ray antideuterons, at the 95% confidence level, between 0.17 and 1.15 GeV/nucleon at the top of the atmosphere.

We propose the CALorimetric Electron Telescope (CALET) mission for Japanese Experiment Module, Exposed Facilisty (JEM-EF) on ISS to address some of the most profound questions in particle astrophysics. CALET is composed of two kinds of calorimeter, an imaging calorimeter, IMC, at upper part and a total absorption calorimeter, TASC, at lower part. The IMC is employed to detect the shower profile by using scintillating fibers with 64-anode PMT read-out system. The TASC is consisted of BGO logs to measure the energy deposits in each shower. Total weight of the payload is nearly 2,500 kg and the geometrical factor for electrons is about 1 m2 sr. CALET has a unique capability to measure electrons and gamma-rays beyond 1 TeV since it can have a superior hadron rejection power of 106 for electrons and much better for gamma-rays. It can also measure protons and heavy nuclei in proximity of the Knee. The energy resolution for electromagnetic particles is better than a few % above 100 GeV. We will present a baseline design of the detector, and report the present status of detector development. Compatibility of the detector with the JEM Exposed Facility will also be discussed.

The CALorimetric Electron Telescope (CALET) mission is proposed for the observation of various components of cosmic-rays as well as ?-rays on the Exposure Facility of the Japanese Experiment Module ( EF/JEM ) on the International Space Station (ISS). The detector is composed of an imaging calorimeter of scintillating fibers (IMC), a total absorption calorimeter of BGO (TASC) and a silicon pad module at the top of IMC . The total thickness of absorber is 36 r.l for the electromagnetic particles and 1.8 m.f.p for protons. The total weight of the payload, including the detector, the support, the interface instruments with JEM so on, is nearly 2,500 kg and the geometrical factor for the electrons is about 1 m2 sr. The CALET has a unique capability to measure electrons and ?-rays beyond 1 TeV since the hadron rejection power is 106. The energy resolution for the electro-magnetic particles is better than a few % above 100 GeV. The detector is optimally designed to detect changes in the energy spectra caused by physical processes, or a line signature in the energy distribution expected from annihilations of dark matter candidates. This paper is the first presentation by the international team of the CALET collaboration.

We are developing the CALET (CALorimetric Electron Telescope) instrument for observing high energy electrons and gamma rays on ISS. For confirming the CALET capability expected by simulations, we made a small model of CALET with a size of 2/3 in thickness and had the experimental tests by using beams available in CERN. The beams used are 50GeV, 100GeV electrons and 150 GeV protons. The energy resolution is sigma/E = 4.0 +/- 0.1% and 2.25 +/- 0.04% for 50GeV and 100GeV electrons, respectively. About 97.3% of protons can be rejected by shower image, while approximately 96.8% of electrons are correctly identified. The performance of the model was also investigated by Monte Carlo simulation to compare with the results by beam tests. We confirmed good consistency between simulation and the beam test.

Although CALET is originally designed for detections of electrons and gamma rays, nuclear components of primary cosmic rays, from protons to iron nucleus and more, are also observable by CALET, utilizing the total absorption calorimeter (TASC). TASC has 1.6 m.f.p. for protons which is enough to measure the energy of protons up to 1000 TeV. Using the observed spectra, the following items will be discussed: (1) the detailed structure of the spectrum, checking the change of the spectrum index and comparing indices of various components. More than 300 iron nuclei with the energy greater than 1 TeV/n will be observed. (2) secondary/primary ratio. Especially we can observe the both of B/C ratio and sub-Fe/Fe ratio. At the space station, the observation is free from the atmospheric contamination corrections. These observations are essential for the acceleration mechanisms and the propagation of cosmic rays.

The CALorimetric Electron Telescope(CALET) mission is proposed to measure galactic electrons and gamma rays on ISS/JEM for three years[l]. In this paper we report the purpose of this project in solar physics and the expected results from precise measurement of electron energy spectrum in the 1-100GeV energy range. The CALET measurement of long-term variations of the energy spectrum will produce a wealth of data to investigate electron propagation in the heliosphere. CALET does not distinguish positive charge from negative one. However, we can evaluate the charge sign dependence of solar modulation using correlation with the neutron monitors, since most particles are negative electrons in this energy range. Further we estimate transport parameters, mainly the energy dependence of diffusion coefficient in the heliosphere. CALET will also have a capability of measuring the short-term variation of around ten Forbush decreases(Fds) for three years. Precise measurements of the energy spectral variation of Fds will give a conclusion of the energy dependence of Fds.

We are proposing the CALET (CALorimetric Electron Telescope) for the observation of high-energy electrons and gamma rays at the Exposed Facility of the Japanese Experiment Module on the International Space Station. The CALET has a capability to observe electrons (+positrons) in IGeV-IOTeV and gamma rays in 20MeV-10TeV with a high energy resolution of 2%(c) 100GeV, an angular resolution of 0.06deg (c) 100GeV, and a high proton rejection power of 10(6). CALET has the geometrical factor of nearly 1m(2)sr and three-years observation is expected. Precise electron observation of CALET enables us to identify cosmic-ray electron sources by the detection of distinctive features. in the energy spectrum and anisotropy toward nearby sources. The ISS orbit enables CALET to survey all of the sky in a wide field of view of 2 sr without attitude control of the instrument. In addition, by the hybrid observations of high-energy electrons and gamma rays, the CALET can search for WIMP dark matter.

The isotopic composition measurements of cosmic-ray hydrogen and helium were made during the most recent period of solar maximum using the Balloon-borne Experiment with a Superconducting Spectrometer (BESS). The data selection procedure and the mass histograms for proton, helium and their isotopes of BESS-2000 are presented in this paper.

We report a cosmic-ray antiproton spectrum measured with the BESS balloon experiment performed in 2002, which was in an intermediate period between the solar maximum in 2000 and the coming solar minimum. The observed antiproton spectrum and the antiproton to proton ratio are crucial for further development of the drift model of the solar modulation effect which has been generally supported by the previous measurements.

The first scientific flight of the BESS-Polar experiment was carried out in December 2004, aiming at elementary particle phenomena in the early Universe through observation of low energy antiprotons and search for antimatter in the cosmic radiation. The BESS-Polar payload was launched on December 13 from Williams Field near the US McMurdo Station in Antarctica, and circulated around the South Pole for 8 days and 17 hours. During the flight, the superconducting spectrometer including the solar-cell power supply system worked well, and two terabytes scientific data were recorded on the onboard hard disk drives. The flight was terminated on December 21, and the payload landed on the Ross Ice Shelf. The recovery operation continued for a week, and the spectrometer was recovered safely.

A flatter spectrum of low-energy cosmic ray antiprotons below 1 GeV measured by the BESS experiment in the last solar minimum period suggests the existence of possible novel and exotic sources of cosmic-ray antiprotons, such as evaporation of primordial black holes and annihilation of supersymmetric dark matter. In order to investigate these antiproton sources and to search for antimatter in the cosmic radiation, the BESS-Polar experiment was carried out with a NASA long duration balloon flight over Antarctica in December 2004. During this 8.5-day flight, the BESS-Polar superconducting spectrometer gathered 900 million cosmic-ray events. The data show that the newly developed particle detector system functioned well enough to observe the low energy antiprotons during the entire flight. Thus' we can expect to derive a precise energy spectrum of the low-energy antiprotons with several-times higher statistics than that from the flight of the previous solar minimum period.

The BESS-Polar balloon payload had its first flight on December 13th-21st, 2004 (UTC) from McMurdo Station, Antarctica. The flight duration was over eight days and more than 9 x 108 cosmic-ray events were recorded. An overview of the BESS-Polar flight, the status of the antiproton analysis, and a discussion of the low-power readout electronics and data acquisition system can be found elsewhere in these proceedings. In this paper we discuss the design, testing, and flight performance of the BESS-Polar Cherenkov counter, which operated in ambient conditions outside a pressure vessel. The silica-aerogel Cherenkov radiator had a nominal index-of-refraction, n = 1.02, yielding an lower limit for the most likely photoelectron (PE) number of 7 in the center of the counter and 9 near the photomultiplier tubes.

In nine flights between 1993 and 2002, the Balloon Borne Experiment with a Superconducting Spectrometer (BESS) has measured the energy spectrum of cosmic-ray antiprotons between 0.18 and 4.20 GeV, and the spectra of protons and helium to several hundred GeV. BESS has also placed stringent upper limits on the existence of antihelium and antiduterons. Above about 1 GeV, models in which antiprotons are secondary products of the interactions of primary cosmic rays with the ISM agree with the BESS spectrum. Below I GeV, BESS data suggest the presence of an additional source of antiprotons. The antiproton/proton ratios measured between 1993 and 1999, during the Sun's positive-polarity phase, are consistent with simple models of solar modulation. Results from the 2000 flight, following the solar magnetic field reversal, show a sudden increase in the antiproton/proton ratio and tend to favor a charge-sign-dependent drift model. To extend BESS measurements to lower energies, a new instrument, BESS-Polar, is under construction for a flight from Antarctica in 2004.

Prepared for 28th International Cosmic Ray Conferences (ICRC 2003), Tsukuba, Japan, 31 Jul - 7 Aug 2003. <br /> Published in *Tsukuba 2003, Cosmic Ray* 1163-1166<br /> <br /> 0&quot; target=&quot;_blank&quot;&gt;&lt;/a&gt;&lt;a href=&quot;http://www-rccn.icrr.u-tokyo.ac.jp/icrc2003/PROCEEDINGS/PDF/291.pdf

Prepared for 28th International Cosmic Ray Conferences (ICRC 2003), Tsukuba, Japan, 31 Jul - 7 Aug 2003. <br /> Published in *Tsukuba 2003, Cosmic Ray* 1797-1800<br /> <br /> 0&quot; target=&quot;_blank&quot;&gt;&lt;/a&gt; &lt;a href=&quot;http://www-rccn.icrr.u-tokyo.ac.jp/icrc2003/PROCEEDINGS/PDF/445.pdf

Prepared for 8th Accelerator and Particle Physics Institute (APPI 2003), Appi, Iwate, Japan, 25-28 Feb 2003. <br /> Published in *Appi 2003, Accelerator and particle physics* 284-293

BESS

J-GLOBAL ID 200902109906977366 <br /> 整理番号 02A0351952 <br /> JST資料番号 G0925B <br />

Prepared for 7th Accelerator and Particle Physics Institute (APPI 2002), Appi, Iwate Ken, Japan, 13-16 Feb 2002. <br /> Published in *Appi 2002, Accelerator and particle physics* 117-138 <br />

Prepared for 5th RESCEU International Symposium on New Trends in Theoretical and Observations Cosmology, Tokyo, Japan, 13-16 Nov 2001. <br /> Published in *Tokyo 2001, New trends in theoretical and observational cosmology* 111-118

Contributed to 27th International Cosmic Ray Conference (ICRC 2001), Hamburg, Germany, 7-15 Aug 2001, Hamburg, Germany. <br /> Published in *27th International Cosmic Ray Conference (ICRC 2001), Hamburg, Germany, 7-15 Aug 2001, Vol.3* 950-953<br /> <br /> 0&quot; target=&quot;_blank&quot;&gt;&lt;/a&gt; &lt;a href=&quot;http://www.copernicus.org/icrc/papers/ici7271_p.pdf