ABSTRACT
We observe a deuteron beam polarization lifetime near 1000 s in the horizontal plane of a magnetic storage ring (COSY). This long spin coherence time is maintained through a combination of beam bunching, electron cooling, sextupole field corrections, and the suppression of collective effects through beam current limits. This record lifetime is required for a storage ring search for an intrinsic electric dipole moment on the deuteron at a statistical sensitivity level approaching 10^{-29} e cm.
ABSTRACT
A new method to determine the spin tune is described and tested. In an ideal planar magnetic ring, the spin tune-defined as the number of spin precessions per turn-is given by ν(s)=γG (γ is the Lorentz factor, G the gyromagnetic anomaly). At 970 MeV/c, the deuteron spins coherently precess at a frequency of ≈120 kHz in the Cooler Synchrotron COSY. The spin tune is deduced from the up-down asymmetry of deuteron-carbon scattering. In a time interval of 2.6 s, the spin tune was determined with a precision of the order 10^{-8}, and to 1×10^{-10} for a continuous 100 s accelerator cycle. This renders the presented method a new precision tool for accelerator physics; controlling the spin motion of particles to high precision is mandatory, in particular, for the measurement of electric dipole moments of charged particles in a storage ring.
ABSTRACT
We report new measurements of inclusive pi production from frozen-spin HD for polarized photon beams covering the Delta(1232) resonance. These provide data simultaneously on both H and D with nearly complete angular distributions of the spin-difference cross sections entering the Gerasimov-Drell-Hearn (GDH) sum rule. Recent results from Mainz and Bonn exceed the GDH prediction for the proton by 22 microb, suggesting as yet unmeasured high-energy components. Our pi0 data reveal a different angular dependence than assumed in Mainz analyses and integrate to a value that is 18 microb lower, suggesting a more rapid convergence. Our results for deuterium are somewhat lower than published data, considerably more precise, and generally lower than available calculations.
ABSTRACT
The formation of hydrogenlike muonium (Mu) has been studied as a function of implantation energy in intrinsic Si, thin films of condensed van der Waals gases (N2, Ne, Ar, Xe), fused and crystalline quartz, and sapphire. By varying the initial energy of positive muons (mu+) between 1 and 30 keV the number of electron-hole pairs generated in the ionization track of the mu+ can be tuned between a few and several thousand. The results show the strong suppression of the formation of those Mu states that depend on the availability of excess electrons. This indicates that the role of H-impurity states in determining electric properties of semiconductors and insulators depends on the way in which atomic H is introduced into the material.
ABSTRACT
Antiprotons (p[over]) remain confined in a Penning trap, in sufficient numbers to form antihydrogen (H[over ) atoms via charge exchange, when the radial field of a quadrupole Ioffe trap is added. This first demonstration with p[over] suggests that quadrupole Ioffe traps can be superimposed upon p[over] and e(+) traps to attempt the capture of H[over] atoms as they form, contrary to conclusions of previous analyses.
ABSTRACT
The spatially oscillating electron spin polarization in the Ag spacer of a 4 nm Fe/20 nmAg/4 nm Fe(001) epitaxial trilayer has been determined by means of low energy muon spin rotation. It oscillates with the same period as the interlayer exchange coupling, but shows a much weaker attenuation at large distances x from the interface. The measured magnetization profile from the inner 14 nm of the spacer is described by an oscillating polarization decaying as x(-0.8(1)). This unusual behavior may arise from a full confinement of electron states within the spacer.
ABSTRACT
The variation of a magnetic field as a function of depth beneath the surface of an YBa(2)Cu(3)O(7-delta) thin film in the Meissner state has been measured using low energy muons. The depth of implantation was varied from 20-150 nm by tuning the energy of the implanted muons from 3-30 keV. These are direct measurements of the penetration of a magnetic field beneath a superconducting surface which illustrate the power of low energy muons for near surface studies in superconductivity and magnetism.
