Spectral computed tomography (CT) is a promising technique with the potential for improving lesion detection, tissue characterization, and material decomposition. In this paper, we are interested in kVp switching-based spectral CT that alternates distinct kVp X-ray transmissions during gantry rotation. This system can acquire multiple X-ray energy transmissions without additional radiation dose. However, only sparse views are generated for each spectral measurement; and the spectra themselves are limited in number. To address these limitations, we propose a penalized maximum likelihood method using spectral patch-based low-rank penalty, which exploits the self-similarity of patches that are collected at the same position in spectral images. The main advantage is that the relatively small number of materials within each patch allows us to employ the low-rank penalty that is less sensitive to intensity changes while preserving edge directions. In our optimization formulation, the cost function consists of the Poisson log-likelihood for X-ray transmission and the nonconvex patch-based low-rank penalty. Since the original cost function is difficult to minimize directly, we propose an optimization method using separable quadratic surrogate and concave convex procedure algorithms for the log-likelihood and penalty terms, which results in an alternating minimization that provides a computational advantage because each subproblem can be solved independently. We performed computer simulations and a real experiment using a kVp switching-based spectral CT with sparse-view measurements, and compared the proposed method with conventional algorithms. We confirmed that the proposed method improves spectral images both qualitatively and quantitatively. Furthermore, our GPU implementation significantly reduces the computational cost.

The muon anomalous magnetic moment has been measured in a new experiment at Brookhaven. Polarized muons were stored in a superferric ring, and the angular frequency difference, v a , between the spin precession and orbital frequencies was determined by measuring the time distribution of highenergy decay positrons. The ratio R of v a to the Larmor precession frequency of free protons, v p , in the storage-ring magnetic field was measured. We find R 3.707 220͑48͒ 3 10 23. With m m ͞m p 3.183 345 47͑47͒ this gives a m 1 1 165 925͑15͒ 3 10 29 (613 ppm), in good agreement with the previous CERN measurements for m 1 and m 2 and of approximately the same precision.

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We report on performance results achieved for recently produced LAPPDs -largest comercially available planar geometry photodetectors based on microchannel plates. These results include electron gains of up to 10 7 , low dark noise rates (∼100 Hz/cm 2 at a gain of 6 · 10 6 ), single photoelectron (PE) timing resolution of ∼50 picoseconds RMS (electronics limited), and single photoelectron spatial resolution along and across strips of 3.2mm (electronics limited) and 0.8 mm RMS respectively and high (about 25% or higher in some units) QE uniform bi-alkali photocathodes. LAPPDs is a good candidate to be employed in neutrino experiments (e.g. ANNIE [1], WATCHMAN [2], DUNE [3]), particle collider experiments (e.g. EIC [4]), neutrinoless double-beta decay experiments (e.g. THEIA [5]), medical and nuclear non-proliferation applications.

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