High-power test and thermal characteristics of a new radio-frequency quadrupole cavity for the Japan Proton Accelerator Research Complex linac

We performed a high-power test of a new radio-frequency quadrupole (RFQ II) for the J-PARC linac. RFQ II was developed as a spare RFQ because the operating J-PARC RFQ has suffered from a sparking problem. First, the conditioning of RFQ II was carried out; after 50 h of conditioning, RFQ II became very stable with a nominal power and duty of 330 kW and 3%, respectively. Next the thermal properties were measured because the resonant frequency of RFQ II is tuned by changing the temperature of the cooling water. The frequency response was measured and compared to finite-element method simulation results, confirming that the simple two-dimensional model reproduces the experimental data well. The differences in the field distribution with changes in the rf loading and the cooling-water temperature were also measured, and no serious field distortion was observed. Therefore, we conclude that RFQ II can perform well as a high-power rf cavity

Study of Strangeness Photo-production in the Threshold Region at LNS-Tohoku(I. Nuclear Physics)

We have successfully measured neutral kaons, bombarding a liquid deuterium target with a photon beam in the threshold region from 0.8 to 1.1GeV. It was the first data for K^0 photoproduction on the deuteron in this energy region. The momentum spectra of K^0 production were compared with theoretical spectra calculated assuming isobar models for the elementary process and a realistic deuteron wave function for the target The present experiment has demonstrated a usefulness of the neutral kaon measurement for the investigation of photo strangeness production reactions

Double Pion Photoproduction on Deuteron(I. Nuclear Physics)

Exclusive cross sections for double-pion photoproductions on proton and deuteron were measured in an energy range from 0.8 to 1.1GeV using tagged photons at Laboratory of Nuclear Science, Tohoku University. We employed the Neutral Kaon Spectrometer (NKS) to detect two pions in the final state, and deduced the cross section for the π^+π^- photoproduction on the "free" and "bound" proton. We have discriminated between the quasi-free and non-quasi-free process applying the kinematical cut on the missing momentum. We found that the total cross section for the γ"p"→pπ^+π^- reaction was about 60% of that for the "free" proton, and this is consistent with the previously obtained data. The one of the dominant part of the non-quasi-free process was found to be the double Δ production. Its cross section is smaller than the previous investigations