Search Results (4 total)

Thin carbon foils are used as strippers for charge exchange injection into high intensity proton rings. However, the stripping foils become radioactive and produce uncontrolled beam loss, which is one of the main factors limiting beam power in high intensity proton rings. Recently, we presented a scheme for laser stripping an H^- beam for the Spallation Neutron Source (SNS) ring. First, H^- atoms are converted to H⁰ by a magnetic field, then H⁰ atoms are excited from the ground state to the upper levels by a laser, and the excited states are converted to protons by a magnetic field. In this paper we report on the proof-of-principle demonstration of this scheme to give high efficiency (around 90%) conversion of H^- beam into protons at SNS in Oak Ridge. The experimental setup is described, and comparison of the experimental data with simulations is presented.

The cross section of the process e⁺e^-→π⁺π^-π⁰ was measured in the Spherical Neutral Detector experiment at the VEPP-2M collider in the energy region sqrt[s]=980–1380 MeV. The measured cross section, together with the e⁺e^-→π⁺π^-π⁰ and ωπ⁺π^- cross sections obtained in other experiments, was analyzed in the framework of the generalized vector meson dominance model. It was found that the experimental data can be described by a sum of ω, φ mesons and two ω^′ and ω^″ resonances contributions, with masses m_ω^′∼1490, m_ω^″∼1790 MeV and widths Γ_ω^′∼1210, Γ_ω^″∼560 MeV. The analysis of the π⁺π^- invariant mass spectra in the energy region sqrt[s] from 1100 to 1380 MeV has shown that for their description one should take into account the e⁺e^-→ωπ⁰→π⁺π^-π⁰ mechanism also. The phase between the amplitudes corresponding to the e⁺e^-→ωπ and e⁺e^-→ρπ intermediate states was measured for the first time. The value of the phase is close to zero and depends on energy.

Analytic calculation and numerical simulations reveal a multiline structure in the spectrum of coherent dipole oscillations in the colliding beam system due to coupled synchrobetatron beam-beam modes. The model employed in the analysis involves linearization of the beam-beam kick and takes into account the fact that the length of the colliding bunches is finite. In the present paper, we discuss the behavior of the synchrobetatron beam-beam modes, obtained both analytically and numerically, and compare it with the experimental results for the VEPP-2M collider. A particular case of the betatron tune close to the half-integer resonance is considered on the basis of the presented models.

The process e⁺e^-→μ⁺μ^- has been studied by the SND detector at the VEPP-2M e⁺e^- collider in the φ(1020)-resonance energy region. The measured effective φ meson leptonic branching ratio B(φ→l⁺l^-)≡sqrt[B(φ→e⁺e^-)B(φ→μ⁺μ^-)]  =  (2.89±0.10±0.06)×10^-4 agrees well with the Particle Data Group value B(φ→e⁺e^-)  =  (2.91±0.07)×10^-4, confirming μ- e universality. Without additional assumption of μ- e universality the branching ratio B(φ→μ⁺μ^-)  =  (2.87±0.20±0.14)×10^-4 was obtained.