Supervised learning-based reconstruction of magnet errors in circular accelerators

Magnetic field errors and misalignments cause optics perturbations, which can lead to machine safety issues and performance degradation. The correlation between magnetic errors and deviations of the measured optics functions from design can be used in order to build supervised learning models able to predict magnetic errors directly from a selection of measured optics observables. Extending the knowledge of errors in individual magnets offers potential improvements of beam control by including this information into optics models and corrections computation. Besides, we also present a technique for denoising and reconstruction of measurements data, based on autoencoder neural networks and linear regression. We investigate the usefulness of supervised machine learning algorithms for beam optics studies in a circular accelerator such as the LHC, for which the presented method has been applied in simulated environment, as well as on experimental data.

Constrained stellarator coil curvature optimization with FOCUS

Finding less complicated coils that have adequately low field errors is a crucial step in stellarator development. One coil metric that is of high importance is the maximum curvature of the coil centreline, or coil single filament. Conductors cannot be bent below some threshold minimum radius of curvature. High coil curvatures can cause strains to exceed acceptable levels, especially in superconducting coils. We investigate three ways to optimize coil curvature and find that applying penalty functions to the coil curvature solves for coils that have a constrained maximum curvature and low field error. Penalty functions are implemented in FOCUS and coil solutions optimized for an HSX-like ‘plasma boundary’ are presented.

Polarization issues in circular electron–positron super-colliders

We study a possibility of obtaining transversely polarized electron/positron beams in the CEPC collider. Also, original results are presented for another project, the FCCee collider, which allows us to identify some features and differences of these similar machines. Important is the comparison of the data obtained with the expected and measured polarizations at LEP. In estimation of the depolarizing effect of field errors, in addition to the usual nonresonant spin diffusion, an attempt was made to take into account the resonant diffusion, which is due to a large spin tune spread. We consider a possibility to obtain polarization by accelerating polarized particles in the CEPC booster and then injecting them into the main ring. This option can be crucial for obtaining longitudinal polarization. We propose a scheme in which long-term preservation of such polarization is possible.

Development of a rotating-coil scanner for superconducting accelerator magnets

The High-Luminosity upgrade project for the Large Hadron Collider (HL-LHC) at CERN (Conseil Européen pour la Recherche Nucléaire) will require new superconducting magnets for the insertion regions. Among these magnets, the new triplet quadrupoles, based on Nb3Sn technology, require magnetic-field measurements of a high precision in the field angle and multipole field errors. In this paper, we present a scanning system based on a rotating-coil magnetometer and its transport system, including the design of the mechanical structure and the induction coils based on printed-circuit-board (PCB) technology. The system and its components are cross-calibrated with other field transducers, such as stretched-wire systems, and their measurement precision is established in a measurement campaign of 2 m long reference quadrupoles.

Challenges in extracting pseudo-multipoles from magnetic measurements

Extracting the coefficients of Fourier–Bessel series, known as pseudo-multipoles or generalized gradients, from magnetic measurements of accelerator magnets involves technical and mathematical challenges. First, a novel design of a short, rotating-coil magnetometer is required that does not intercept any axial field component of the magnet. Moreover, displacing short magnetometers, step-by-step along the magnet axis, yields a convolution of the local multipole field errors and the sensitivity (test function) of the induction coil. The deconvolution must then contend with the limited signal-to-noise ratio of the measured quantities, which are integrated voltages corresponding to spatial flux distributions. Finally, the compensation schemes, as implemented on long coils and based on scaling laws derived for the integrated field harmonics, cannot be applied to short magnetometers intercepting only a local field distribution. All this requires careful design of experiment to derive the optimal length of the induction coil, the step-size of the scan, and the highest order of pseudo-multipoles in the field reconstruction. This paper presents the theory of the measurement method, the data acquisition and deconvolution, and the design and production of a saddle-shaped, rotating-coil magnetometer.

Language Error Analysis in MPBI-UMS Students Speech Who Roled as Police Officers

This study aims to describe language errors made by the Klaten police officers when giving speeches. The method used in this study is qualitative. The data collection technique used is refer to and record. The data analysis method used is the Agih method. Data analysis techniques use extending techniques and reading merkah techniques. The results of this study were (1) phonological errors 5. (2) spelling field errors 1. (3) morphological errors, 1 pleonasms, and 9 prepositions. (4) syntax errors, 6 word waste errors, 6 repetition errors and 1 sentence ineffectiveness. (5) sociolinguistic errors, 3 code switching errors.

Cramér type moderate deviations for random fields

We study the Cramér type moderate deviation for partial sums of random fields by applying the conjugate method. The results are applicable to the partial sums of linear random fields with short or long memory and to nonparametric regression with random field errors.