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For high luminosity in electron-positron linear colliders, it is essential to generate low vertical emittance beams. We report on the smallest vertical emittance achieved in single-bunch-mode operation of the Accelerator Test Facility, which satisfies the requirement of the x-band linear collider. The emittances were measured with a laser-wire beam-profile monitor installed in the damping ring. The bunch length and the momentum spread of the beam were also recorded under the same conditions. The smallest vertical rms emittance measured at low intensity is 4 pm at a beam energy of 1.3 GeV, which corresponds to the normalized emittance of 1.0x1.0(-8) m. It increases by a factor of 1.5 for a bunch intensity of 10(10) electrons. The measured data agreed to the calculation of intrabeam scattering within much better than a factor of 2.

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Vapor-liquid-solid (VLS) growth of position-controlled InP nanowires (NWs) with 10–100 μm pitches was investigated on SiO2-mask-patterned InP substrates. In addition to the vertical VLS NWs formed by Au catalysts, excess group-III materials that were diffused from the large mask region formed plural inclined NW-like structures from single openings. The introduction of HCl gas during the NW growth was found to remove the excess group-III materials effectively. Vertical InP NWs with minimal tapering were formed by controlling the HCl flow rate while suppressing the formation of tilted NWs. InP NWs having lengths independent of the pattern pitches, which were regulated by the VLS mechanism, were obtained.

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