[en] A new multiple scanning method is developed to detect the magnetic monopoles. The plastic track detectors CR-39 exposed to the heavily ionizing particles are over-etched in more dense agent 8.0N NaOH, higher temperature 80⁰C and much longer etching time 94h. The etched cones can be easily located on the over-etched plastic sheets without using the optical microscope. The trajectories of the heavily ionizing particles can be reconstructed with the naked eyes by superposing several over-etched sheets. The minimum detectable charge ratio z/β is obtained to be 10 in the observation of the cosmic heavy nuclei by this method. This value indicates that the magnetic monopoles with velocity greater than 2 x 10^-3c would have been detected. By adopting this method, CR-39 plastic chamber can be easily scaled-up to 100 m² yr of the exposure area X time. The upper limits for the possible flux of magnetic monopoles could be reduced to 2 x 10^-14 per cm² sec sr. (author)

[en] Two emulsion chambers composed with emulsion plates and lead plates were exposed to 303 GeV/c proton beam at FNAL to analyze precisely the event structure of proton - nucleus interaction. In the present analysis, large transverse momentum phenomena tagged by high energy gamma-ray emitted in most forward region were investigated. The analysis showed the strong correlation of the charged particles with large transverse momentum (>/GeV/c) with high energy gamma-ray. This result suggests that large transverse momentum protons and excited baryons decaying into neutral pions play important roles in the multiple production phenomena of elementary particles. In particular, the creation and decay of forward excited baryons in large transverse momentum events are discussed. (Yoshomori, M.)

[en] We have developed an underwater radon detector of the use of a PIN photodiode (PD) on 1996. This detector was put into the monitoring well at the depth of a meter, and has been monitoring the continuous radon concentration in the well. A microporous flat sheet membrane is attached to the window of the bottom of the detector. Gas dissolved in the underground water pass through the membrane of polypropylene with the hydrophobic properties. The principle of radon detection which is used in the detector is the electrostatic collection of the daughter nuclei of 222Rn, and the energy measurement of the alpha decay with PD. More than 90% of 218Po atoms, which was one of the daughter nuclei of 222Rn, tended to become positively charged. A negative high voltage is supplied to the p-layer of PD. The detector vessel is grounded. Then, an electric field is produced in the vessel. The daughter nuclei which ionized positively are collected on the surface of PD, the energy of alpha decay are measured. The small-sized underwater radon detector (PMT underwater radon detector) made of a Photomultiplier Tube and a ZnS scintillator. They say that the Photomultiplier Tube isn't influence by neutralization. We compare PMT underwater radon detector with PD underwater radon detector. (J.P.N.)

No abstract available

[en] A small-sized radon data logger and a electrostatic collecting radon monitor were developed for the continuous monitoring of environmental radon and radon daughters. A PIN photodiode (PD), an alpha particle defector, installed inside a container attracts radon daughters when charged electrostatically. Alpha particles are completely separated from each other according to the energy level. New logger has made it possible 10 analysts and save the radon data. Alpha particle count data from radon daughters are automatically integrated over preset time intervals and the energy regions. The desiccant P₂O₅ was placed in the bottom of the monitor, since the collection efficiency of ²¹⁸Po atoms depends on the humidity of the air. We can get the 30 days continuous data logging at 30 min sampling frequency at any place with the car battery. We observed the radon concentration of the air inside the Super-Kamiokande dome from Jan-30 to Feb-8-1996. The average of radon concentration was found to be (46±13) Bq/m³. (author)

[en] A 80 m² detector array consisting of two layers of CR-39 plastic track detector and an iron absorber was exposed at deep underground (2700 m.w.e.) in Kamioka mine for 1.8 yr. This plastic plate can detect tracks of penetrating monopoles with energy loss rate greater than that of a neucleus with Z/β > approx 10. Considering recoil of the C and O atoms in CR-39 due to diamagnetic repulsion, CR-39 plastic detector is considered to be sensitive to the monopoles at velocities down to about 10^-4c. We have found no monopole candidate, and this implies that the upper limit on the flux of grand-unified-theory monopoles with v ∼ 10^-4c or v > 5.5 x 10^-3c is 3.0 x 10^-14 cm^-2s^-1sr^-1 at 90 % confidence level. (author)

[en] Two Australia-Japan collaboration experiments by balloon flight were performed to study the high energy multiproduction phenomena of protons and heavy ions in the incident energy range of 10 - 100 TeV. To date, 90 jet shower events have been analyzed, and in two events, new elementary particles were found. The emulsion chamber used by the author is capable of determining the energies of charged particles and ν-ray in the energy range of a few TeV, and in the range of short lifetime (10₁₅ - 10₁₂ s), the loci of new elementary particles can be obtained. In addition, the super high energy multiproduction phenomena of protons, alpha particles and heavy nuclei can be studied. The integral energy spectra of singly charged particles, alpha particles and medium nuclei above 10 TeV are almost in agreement with the extrapolation of the low energy data by Ryan et al. The mean multiplicity of secondary charged particles above 7 TeV incident energy is 29 +- 6 when the target is lucite. The energy dependence of mean multiplicity is approximated by (ln E)₂, and this result suggests the violation of scaling law. Two events of charged X particle pair production were analyzed, and the lifetime was estimated to be (2.8 +- 0.9) x 10₁₃ s. (Yoshimori, M.)

[en] The balloon experiment of long duration using large and heavy detectors is required to observe the new particles produced by superhigh energy interaction. Six emulsion chambers were exposed to cosmic ray in the experiment of balloon flight by Australia-Japan collaboration. Exposure continued 32.5 hours, then the emulsion chambers were recovered. The cosmic ray with incident energy of 10 - 20 TeV was observed, and the increase of the production rate of new particles is expected by this increase of energy. The tracks of the new particles with lifetime of 10^-15 - 10^-12 s were able to be detected in the emulsion chambers. To date, 49 interaction events of protons, α particles and heavy nuclei were analyzed, and 2 events among them were accompanied by the pair production of new elementary particles. The present analysis shows that the production rate of new particles is 1 - 5% in the 10 - 20 TeV energy range, and this value is about ten times as large as that at 400 GeV. The mean lifetime and the distribution of transverse momentum of X-particles were obtained, and the results show that the mean lifetime and transverse momentum are (8 - 9) x 10^-13 s and 1.6 +- 0.5 GeV/C, respectively. (Yoshimori, M.)

[en] We newly developed an underwater radon detector for ²²²Rn concentration determinations in water. A PIN photodiode (PD), an alpha particle detector, installed inside a container attracts radon families when charged electrostatically. Alpha particles emitted from ²¹⁸Po (RaA), ²¹⁴Po (RaC'), ²¹⁰Po (RaF) and ²¹²Po (ThC') are completely isolated from each other. This system can be applied to a half year period observation for wide variation of radon concentrations from 0.5 Bq/m³ in pure water to 10000 Bq/m³ in underground water. The observed results of pure water radon concentration in the KAMIOKANDE tank showed that this technique is valid for the monitor of the degasification system. (author)

[en] 1.88 GeV/n Fe beams of LBL were vertically irradiated to the chambers composed of a pile of plastic track detector (CR-39) and nuclear emulsion plates. The charge number of projectile fragments in Fe interactions was carefully examined by use of CR-39. The angular distributions of emitted alpha particles have been investigated for several ranges of charge numbers of projectile fragments. The result of analysis shows that the emission angle distribution of alpha particles at large angles cannot be explained by the single mechanism of the fragmentation from a clean cut spectator. For events of central collisions with smaller charges of projectile fragments, the effective temperature for the production of alpha particles turns out to be much higher than that of the evaporation theory. The results are applied to the calibration of primary energy estimation by the opening angles of alpha particles. (author)