There is a great advantage in signal to noise ratio (S/N) that can be obtained in nuclear magnetic resonance (NMR) experiments on very small samples (having spatial dimensions ∼100 μm or less) if one employs NMR “micro” receiver coils, “microcoils,” which are of similarly small dimensions. The gains in S/N could enable magnetic resonance imaging (MRI) microscopy with spatial resolution of ∼1–2 μm, much better than currently available. Such MRI microscopy however requires very strong (>10 T/m), rapidly switchable triaxial magnetic field gradients. Here, we report the design and construction of such a triaxial gradient system, producing gradients substantially greater than 15 T/m in all three directions, x, y, and z (and as high as 50 T/m for the x direction). The gradients are switchable within time ∼10 μs and adequately uniform (within 5% over a volume of [600μm3] for microcoil MRI of small samples.
We present density-matrix elements and single-spin correlations for the reaction p , p -p~+ n at 1.18, 1.47, 1.71, and 1.98 GeV/c, using both longitudinal and transverse beam polarizations. For the p , p -h + + n subprocess we find quite different energy dependence for the helicity-i and helicity-+ A+ + -production asymmetries. The helicity-f asymmetry has pi,, dependence similar to the polarization in p,p-.ntd, while the helicity-4 asymmetry changes sign between 1.18 and 1.47 GeV/c. By fitting the production angle dependence of the spin correlations, we obtain joint moments which are easily related to the partial-wave structure. We have carried out a partial-wave analysis with the moments data. We find that the production wave intensities are qualitatively consistent with the elastic phase-shift analyses, and the phases vary smoothly with plab. From the absence of Breit-Wigner phase behavior, we conclude that the dinucleon resonances seen in the pp elastic waves are not true coupled-channel Briet-Wigner states in N N and N A .
A trigger track processor is being designed for CDF Run 2. This processor identifies high momentum (P T > 1.5 GeV/c) charged tracks in the new central outer tracking chamber for the CDF II detector. The design of the track processor, called the eXtremely Fast Tracker (XFT), is highly parallel and handle an input rate of 183 Gbits/sec and output rate of 44 Gbits/sec. The XFT is pipelined and reports the results for a new event every 132ns. The XFT uses three stages, hit classification, segment finding, and segment linking. The pattern recognition algorithms for the three stages are implemented in Programmable Logic Devices (PLDs) which allow for in-situ modification of the algorithm at any time. The PLDs reside on three different types of modules. Prototypes of each of these modules have been designed and built, and are working. An overview of the hardware design and the system architecture are presented.
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