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An analysis is made of the sound produced by vorticity generated as high pressure fluid is forced through an aperture in the wall of a duct in the presence of an exterior baffle plate. The aperture typically behaves as a ‘pressure release’ opening when the flow is ideal and irrotational, corresponding to the traditional interpretation of the action of a finger hole of a woodwind instrument, although theoretical predictions that neglect vorticity are irrelevant in practice except at very high frequencies. The theory of vortex sound is applied to derive an approximate nonlinear equation for the volume flux through the baffled aperture that generalises Cummings's empirical equation for a jet exhausting through a fully open orifice in a large wall. The equation takes account of the impingement of the jet on the baffle and of the nonlinear ‘inertial blocking’ of the aperture flow. Application is made to the problem of compression wave generation by a high-speed train entering a tunnel fitted with an entrance hood whose windows are partially ‘closed’ by the presence of a side-wall of a railway cutting or embankment. Theoretical predictions are found to be in good agreement with measurements made at model scale at train speeds ∼ 300 – 400 km / h .

A low-background gamma-ray detector of NaI(Tl) comprising a core surrounded by an annulus was developed for nuclear astrophysics experiments with radioactive ion beams, mostly for detailed studies of low-energy radiative capture reactions that involve proton and alpha particles. Monte Carlo simulations using EGS4 were performed to calculate the full-energy detection efficiency. The background was satisfactorily reduced as designed. The best S / N ratio for very low-event rate was obtained using the annulus in anticoincidence with the core. A consideration of an experiment of astrophysical interest, the 19 Ne(p,γ) 20 Na reaction, is also briefly discussed.

A series of experiments were made to investigate the early stage of the rapid-proton process. Specifically, the nuclear reaction chain at N=11 was discussed, including a recent result on 25 Si. A discussion with nova model calculations using the present experimental results is also made.

An ISOL-based radioactive nuclear beam facility is just about to come into operation at INS. The present status of the INS radioactive nuclear beam project is reported. The capability of the facility and possible experiments are also discussed, including research programs of nuclear physics and nuclear astrophysics.

Experimental studies on bottled neutrons have been carried out using a supermirror turbine facility and are compared with the results of numerical simulations. The gravity effects for 1 m elevation and fall with guides are observed. Measured exhausting and storage lifetimes agree with the numerical results, which indicate the collision loss probability of about 10 −4 to be expected in the bottle studied.

A superconducting kaon spectrometer has been installed in the north experimental hall of the KEK 12-GeV proton synchrotron. The spectrometer was designed to serve for nuclear physics experiments with meson beams in the 1 GeV/c region, particular emphasis being laid on study of Λ-hypernuclei via (π+, K+) reactions. In order to obtain Λ-hypernuclear data with better statistics and energy resolution, it was designed to have a good momentum resolution of 0.1% FWHM and a large acceptance of 100 msr. It consists of a large superconducting dipole magnet, tracking chambers, and trigger counters that can efficiently select kaons from large background of pions and protons. The overall energy resolution for scattering is realized together with a beam-line spectrometer in the K6 beam line, the momentum resolution of which was also designed to be better than 0.1% FWHM. A good energy resolution of better than 2 MeV FWHM has been confirmed in π−-12C elastic scattering and in the (π+,K+) reaction on 12C.

A spectroscopic study of Λ hypernuclei by the ( π + , K + ) reaction has been performed for the wide hypernuclear mass range using a new superconducting kaon spectrometer (INS-SKS) at the KEK 12 GeV PS. A Λ 12 C spectrum with 2 MeV (FWHM) energy resolution was measured and core excited states of Λ 12 C were clearly identified for the first time. It is discussed that the excitation energies and cross sections of these states will be closely related with the choice of ΛN interaction models as well as hypernuclear structure. Hypernuclear spectra of Λ 10 B, Λ 28 Si, Λ 89 Y, Λ 139 La and Λ 208 Pb were also obtained and binding energies of a Λ hyperon were deduced for each Λ orbital. The mass number dependence of the Λ binding energies is, within the present experimental errors, consistent with a calculation based on the Woods-Saxon potential.

The first measurement of two-nucleon pion absorption in 4 He at 1 GeV/ c has been performed at the KEK 12 GeV proton synchroton. Both the (π + , pp) and (π + , pn) modes were measured and clearly identified, even at this energy. An isospin dependence was obtained which was different from that in the Δ-energy region.

Attempts have been made to improve the characteristics of glasses suitable for Cherenkov counters of the total-absorption type. Many kinds of new lead glasses were prepared and examined in the transmittance, radiation lengths, and methods of manufacturing. Several kinds of glass blocks having the dimension of 65 × 65 × 235 mm 3 were manufactured successfully. The transmittance of one of the new glasses is higher than the usual lead glass of F-2 ∗ . It was also found that the discoloration of the new glasses is smaller than the usual lead glasses upon irradiation of 60 Co γ rays of 10 4 to 10 7 Roentgens. The Cherenkov counters of the total-absorption type with the new glasses, together with the ones with usual lead glasses of F-2, SF-2, SF-5, and SF-6, were tested by using electron beams with energies from 300–1000 MeV. It was found that the energy resolution of the first ones is better by a few percents than that of the latter in the whole energy region.

The linear polarization of the coherent bremsstrahlung from a single crystal of silicon was measured by observing the one-dimensionally projected angles of electron and positron pairs. The coherent bremsstrahlung was produced by injecting the 1153 MeV electrons to the silicon crystal nearly along the [110] axis. The emission angles, η + and η − , of pair particles were determined event by observing their tracks with a set of four wire spark chambers. From the ( η + , η − ) distribution of events, the polarization of photons was evaluated. The obtained polarization was consistent with the calculated values, and the technique gives a new approach to the measurement of the linear polarization of photons.

An experimental investigation of the reaction γ p → p p p at photon energies 4.7 ⩽ E γ ⩽ 6.6 GeV is described. The main results are the measurement of the cross section as a function of energy, a discussion of the main dynamical features of the reaction and the observation of a narrow p p mass state at 2.024 ± 0.005 GeV with a width of 29 ± 13 MeV.

The differential cross section of the reaction ( γ p → p φ ) has been measured in the t range 0 ⩽ t ⩽ 0.4 GeV 2 and for photon energies from 3.0 to 6.7 GeV. In particular for the small t region the measurement accuracy was better than 10%. We obtained for the slope parameter B in an exponential parametrization of the differential cross section d σ /d t = A e − Bt values of B ⋍ 6 ± 0.5 GeV −2 which are significantly larger than the slopes obtained by most other experiments at higher t values. This indicates a t dependence of B particularly in the small t region. An energy dependence of the optical point (d σ /d t ) t =0 , observed in our measurements, has been explained as a kinematic effect due to the VDM relation. A fit of our measurements is in excellent agreement with all other published values of (d σ /d t ) t =0 ( γ p → φ p), this implies that σ tot (φp) must be essentially energy independent in this energy range. Spin density matrix elements of the φ have been evaluated and an analysis of the helicity amplitudes has been carried out. This analysis confirmed s -channel helicity conservation. Moments of spherical harmonics of the K K angular decay distribution have been computed for 10 MeV K K mass-bins from threshold to 1.3 GeV. The mass dependence of the normalized moments is generally smooth. Contributing amplitudes have essentially only even moments. The moment 〈 Y 2 0 〉/〈 Y 0 0 〉 changes sign above the φ mass. Differential cross sections for the inelastic φ production γ p → φ X have been evaluated for the first time both with respect to t − t min and M K . The integrated inelastic cross sections are comparable in size with the elastic ones. The slopes of the differential cross sections d σ /d t appear to become flatter with increasing M X .

A mass-dependent asymmetry was observed in the decay angular distribution of a photoproduced K+K− system near the K+K− threshold. The corresponding moments 〈Y10〉 have been evaluated. Interpreting the asymmetry as an S-P wave interface due to the states S993∗(0+) and o1019(1−) one can compute the moments 〈Y10〉 through an amplitude analysis. The theoretical calculation reproduces the experimental results well, if one assumes a real S-wave amplitude for the S993∗. The data cannot be explained by a non-resonant real S-wave. Other possibilities have been discussed. An estimate of the photoproduction cross section of the S∗ → K+K− can be given on the basis of the above hypothesis.

A Si single crystal has been mounted on the conventional internal target holder of the 1.3 GeV electron synchrotron at the Institute for Nuclear Study, Tokyo. The energy spectrum measured with the pair spectrometer has a clear enhancement due to the coherent bremsstrahlung process. The linear polarization of the photon beam thus obtained is estimated to be 27% and 10% at the photon energy of 200 and 540 MeV, respectively.

Differential cross sections of proton Compton scattering have been measured in the energy range between 375 MeV and 1150 MeV in steps of 25 MeV at c.m. angles of 130°, 100° and 70°. The recoil proton was detected with a magnetic spectrometer. In coincidence with the proton, the scattered photon was detected with a lead-glass Cerenkov counter of the total absorption type. Theoretical calculations based on an isobar model with two components, that is, the resonance plus the background, were practiced. The photon couplings of the second resonance region were determined from the proton Compton data for the firs time. The results were that the helicity 1 2 photon couplings of P11(1470) and S11(1535), and the helicity 3 2 photon coupling of D13(1520) were consistent with those determined from the single-pion photoproduction data; however, the helicity 1 2 photon coupling of D13(1520) required a somewhat larger value than that from the single-pion photoproduction data.

A search for K + → π + γ, π + γγ, π + γγγ was made detecting pions from stopped kaons in the kinetic energy region between 117 MeV and 127 MeV. New Limits of 1.4 ×10 −6 , 8.4 × 10 −6 and 1.0 × 10 −4 for the branching ratio were obtained assuming a phase-space spectrum on the pion energy. The first limit also aplies to another process K + → π + + a, where a is a light meson with mass smaller than 100 MeV/ c 2 and decays into n γ's with lifetime less than 10 −9 s.

The π + and π − momentum spectrum of the reaction γ p → ππ N have been measured at lab angles 20°, 40°, 60° and 90° and photon energies 0.744, 0.844, 0.944 and 1.044 GeV with a magnetic spectrometer using the photon subtraction method. Both spectra show a peak corresponding to the production of the πΔ(1236) state. The analysis has been carried out with amplitudes for the quasi two-body process γ p → πΔ (1236) and a phase-space background so as to reproduce both π + and π − spectra. The ratio of cross sections σ ( γ p → π + Δ 0 )/ ( γ p → π − Δ ++ ) is found to vary 0.0 to 1.8, depending on kinematical conditions.

The recoil proton polarization of the reaction γp → π0p was measured at a c.m. angle of 100° for incident photon energies between 451 and 1106 MeV, and at an angle of 130° for energies from 400 to 1142 MeV. One photon, decayed from a π0 meson, and a recoil proton were detected in coincidence. Two kinds of polarization analyzer were employed. In the range of proton kinetic energy less than 420 MeV and higher than 346 MeV, carbon plates and liquid hydrogen were used for determining the polarization, respectively. The data given by the two polarimeter systems are in good agreement. Results are compared with recent phenomenological analyses. From the comparison between the present data and the polarized target data, the invariant amplitude A3 can be estimated to be small.

Using stopped kaons, rare decay modes K + → π + ν v and K + → π + a 0 is the light pseudoscalar meson (axion), have been measured. The upper bound of the branching ratio was found to be 1.4 × 10 −7 for K + → π + ν v and 3.8 × 10 −8 for K + → π + a 0 .

Momentum distributions for inclusive photoemission of deuterons from nitrogen have been measured at laboratory angles of 43° and 50°, and for maximum energies of the bremsstrahlung photon beam of 725, 775 and 825 MeV. The double differential cross sections of deuterons emitted from nitrogen are obtained for photon energies of 750 and 800 MeV and for laboratory angles of 43° and 50°. The photon energy is determined by the photon subtraction method. Results are examined by a π 0 photoproduction process off a quasi-deuteron in nitrogen ( γ ″d″→ π 0 d) and by a two-step process. The two-step process means the following: first, a nucleon is produced by a photo-pion production process from a quasi-free nucleon in the nitrogen nucleus ( γ ″N″→ π N); second, the nucleon produced at the first step picks up another nucleon in the nucleus and then a deuteron is emitted (N+A→d+anything).

The muon range spectrum in the stopped K+ decay has been measured in order to search for a discrete line associated with heavy-neutrino emission in Kμ2 decay. An upper bound of 0.5 ∼ 2 × 10−5 for the mixing ratio between νμ and a massive neutrino has been obtained for a mass range of 160–230 MeV/c2.

The differential cross sections for the reactions γ d → π 0 d have been measured for photons from 500 to 1000 MeV. We discuss the effect of the double scattering term and suggest no indication for the dibaryon resonances of the mass around 2.5 GeV.

The decay of 12.9 d 136Cs was studied with a delayed coincidence circuit. It was found that the 2211 keV (6+) state in 136Ba is delayed with respect to the 342 keV beta rays with a half-life of T 1 2 = 3.3±0.3 nsec , and the half-life of the 2144 keV (5−) state is smaller than about 1 nsec. Gamma rays and conversion electrons were measured with Ge(Li) and Si(Li) detectors to obtain gamma-ray intensities and conversion coefficients of some of the transitions. Transition probabilities of the four transitions de-exciting the 2211 keV state are deduced as follows: 0.45 (340 keV, E2), 4.8 (153 keV, E2), 2.2 × 10−6 (176 keV, E1) and 2.7 × 10−5 (67 keV, E1) in Weisskopf units. The excited states in 136Ba are discussed in terms of two-particle excitations on the basis of data thus far obtained in the decay of 136Cs.