Shigeru Isagawa

RF systems for the KEK B-Factory

This paper describes the design features and operational status of the RF systems for the KEK B-Factory (KEKB). Two types of new RF cavities have been developed to store very high-intensity beams with many short bunches. The design and performance of the cavities and other critical components, such as the input couplers and HOM dampers, are reported. The configuration of the RF systems is given and descriptions of various control loops are made, including a direct RF feedback loop and a 0-mode damping loop. The effects of transient beam loading due to a bunch gap on bunch phase modulations were simulated and measured. The development of a superconducting crab cavity, which is a component of luminosity upgrade strategy, is also presented.

Slow Neutron Polarization by Longitudinally Polarized Proton Filter

The neutron beam with the energy between 10-2 eV and 10 eV could be polarized by the longitudinally polarized proton filter. In this experiment, we found that the polarization cross section for the longitudinally polarized filter is approximately the same value as that for the transversely polarized one.

Analysis of deuteron NMR spectrum in propanediol for polarization measurement

Abstract An analysis of the deuteron NMR spectrum is given to determine the deuteron polarization and the quadrupole coupling parameters in deuterated 1, 2-propanediol-D6 and 1, 2-propanediol-D8. Deuterons are polarized by the dynamic method in a spin frozen target. The deuteron line-shape function is calculated for a polycrystalline solid. Agreement between the theoretical and experimental spectrum is satisfactorily good. The following parameters are obtained for the deuteron quadrupole coupling; e2qQ/h = (166.3 ± 1.0) kHz, η = 0.03 ± 0.01 for the C-D bond, and e2qQ/h = (197.9 ± 3.0) kHz, η = 0.17 ± 0.02 for the O-D bond. The deuteron polarization reaches around 40% and is determined with a relative error less than 10%. A possible application of the dynamic polarization method to the study of molecular structure is discussed.

A Spin-Frozen Polarized Target of Proton and Deuteron

A spin-frozen polarized target of proton and deuteron was constructed for the measurement of spin dependent parameters of hadron-hadron scatterings at the 12 GeV KEK proton synchrotron. The target was also used for experiments at LAMPF-HRS. As the proton and deuteron targets, 1,2-propanediol and fully deuterated propanediol (D-8) with stable Crv complex (EHBA) were used, respectively. The characteristics and performance of the targets are described. Data on the nuclear spin lattice relaxation time (Tln) with proton beam give us information on the Kapitza resistance between the target material and liquid 3He/4He mixture.

Microwave Surface Resistance of Bi 2Sr 2CaCu 2Ox Thick Films on Large-Area Metallic Substrates

As a feasibility study for application of a high-T c material to an accelerator cavity, Bi2Sr2CaCu2Ox thick films were formed on large-area metallic substrates. The microwave surface resistance of the films was measured over a temperature range from 4.2 K to 300 K using a demountable cylindrical copper cavity operated at 3 GHz in the TE011 mode. The area of the end plate was 177 cm2 and the thickness of the films was around 50 µm. The films were formed either on silver foils (on copper) or on a silver plate, coated by either a screen-printing or a spray-coating method, sintered either in air or in a Bi2O3 atmosphere, both at 885–890°C, and either annealed in nitrogen gas at 600°C or not annealed. The ratio of the microwave surface resistance of the best film to that of the copper was 0.18 at 10 K and 0.65 at 77.3 K. A comparison of the microwave surface resistance is made between Bi2Sr2CaCu2Ox and YBa2Cu3O7-x films.

rf Field dependence of surface resistance for a-b plane-textured YBa2Cu3O7-δ films deposited on copper substrate

Low rf loss at high rf field levels should be realized in order to apply high-Tc films to accelerator cavities. It is well known that c-axis perpendicular to the surface is essential to reduce Rs and its field dependence However, the effect of a–b plane texturing on Rs is not so clear because lack of experiments, especially for films deposited on metallic substrates. We developed a deposition technique that enables a–b plane texturing as well as c-axis orientation of YBCO films on a copper substrate. We prepared four samples with c-axis normal to the surface: two of them were a–b plane well textured films and the other two were a–b plane weakly textured films. The a–b plane well-textured films in low rf field exhibited a Rs higher than that of weakly textured films below 80 K. The rf field dependence measurements showed that the increase of Rs with increasing rf field for the a–b plane well-textured films was slower as compared with that of the weakly textured films.

Precise measurement of the microwave surface impedance of a YBa2Cu3O7−δ film on copper substrate

In measurement of the microwave surface resistance, Rs(T), of a high-Tc film with a host-cavity method, in which the cavity material is usually copper, the systematic error in Rs at low temperature can be significantly reduced through calibration with the data obtained by a niobium host cavity. Using a cavity excited in the TE011 mode at 13.6 GHz, the procedure is illustrated for a c-axis oriented YBa2Cu3O7−δ film fabricated on 36 mm diameter copper disk with yttria-stabilized-zirconia and chromium buffer layers. The temperature dependence in Rs(T) was consistent with that of the penetration depth; both quantities behavior could be fit well by a modified two-fluid model, in which the fraction of the pairing normal carriers obeyed (T/Tc)2 rather than (T/Tc)4 with some 20% of the charge carriers remaining normal.

Measurement of the polarization for the reactions K+n → K+n and K0p at 1.06, 1.28, 1.39 and 1.49 GeV/c

Abstract The polarization for the K+n elastic and charge-exchange reactions was measured at the momenta of 1.06, 1.28, 1.39 and 1.49 GeV/c. It was found to be negative for the K+n elastic process and generally positive for the charge-exchange process. The present results are compared with the predictions of phase shift analyses.

Dependence on the microwave field of the surface resistance for YBa2Cu3O7−δ films fabricated on copper substrates

The microwave field dependence of the surface resistance for YBa2Cu3O7−δ films was studied at field levels up to 400 A/m. The c-axis normal YBa2Cu3O7−δ films were deposited onto copper disks 36 mm in diameter by a laser ablation method. The surface resistance increased linearly below 50 K as the microwave magnetic field increased, which is explained better by the critical-state model than by the coupled-grain model. The critical current density decreased almost linearly with increasing temperature from 2.8×105 A/cm2 at 20 K to 4×104 A/cm2 at 77 K.

The TELAS spectrometer

Abstract A magnetic spectrometer TELAS was constructed for experiments with a polarized target to measure various spin dependent variables. The system was first used for the measurement of polarization parameters on K + n elastic and charge exchange reaction and pn elastic scattering in the momentum range between 1 GeV/ c and 2 GeV/ c .