Paper  Title  Other Keywords  Page 

SUPAF10  Reconstruction of Particle Distributions at RFQ Exit at SNS Beam Test Facility  rfq, simulation, emittance, lattice  76 


Fluctuations of beam parameters and uncertainties of quadrupole gradients during measurements have effects on the reconstruction of initial particle distributions. To evaluate these effects, the concept of a distribution discrepancy is proposed. Results suggest effects of fluctuations of beam parameters are small, while uncertainties of quadrupole gradients are the main factors that affect the reconstructed distributions. By comparing the measured distributions with distributions produced by tracking the reconstructed initial distributions, it is proved that the real or quasireal (closest to real) initial distribution can be obtained as long as the minimum distribution discrepancy is found.  
Slides SUPAF10 [8.261 MB]  
DOI •  reference for this paper ※ https://doi.org/10.18429/JACoWICAP2018SUPAF10  
About •  paper received ※ 18 October 2018 paper accepted ※ 27 January 2019 issue date ※ 26 January 2019  
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SUPAG03  Challenges in Extracting PseudoMultipoles From Magnetic Measurements  multipole, induction, dipole, experiment  87 


Extracting the coefficients of FourierBessel series, known as pseudomultipoles or generalized gradients, from magnetic measurements of accelerator magnets involves technical and mathematical challenges. First, a novel design of a short, rotatingcoil magnetometer is required that does not intercept any axial field component of the magnet. Moreover, displacing short magnetometers, stepbystep 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 content with the low signaltonoise ratio of the measurands, which are integrated voltages corresponding to spatial flux distributions. Finally, the compensation schemes, as implemented on long coils used for measuring the integrated field harmonics, cannot be applied to short magnetometers. 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 pseudomultipoles 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 saddleshaped, rotatingcoil magnetometer.  
Slides SUPAG03 [4.548 MB]  
DOI •  reference for this paper ※ https://doi.org/10.18429/JACoWICAP2018SUPAG03  
About •  paper received ※ 18 October 2018 paper accepted ※ 27 January 2019 issue date ※ 26 January 2019  
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TUPAF15  A Holistic Approach to Simulating Beam Losses in the Large Hadron Collider Using BDSIM  collimation, simulation, beamlosses, ECR  221 


To fully understand the beam losses, subsequent radiation, energy deposition, backgrounds and activation in particle accelerators, a holistic approach combining a 3D model, physics processes and accelerator tracking is required. Beam Delivery Simulation (BDSIM) is a program developed to simulate the passage of particles, both primary and secondary, in particle accelerators and calculate the energy deposited by these particles via material interactions using the Geant4 physics library. A Geant4 accelerator model is built from an existing optical description of a lattice by procedurally placing a set of predefined accelerator components. These generic components can be refined to an arbitrary degree of detail with the use of userdefined geometries, detectors, field maps, and more. A detailed model of the Large Hadron Collider has been created in BDSIM, validated with existing tracking codes and applied to study beam loss patterns.  
Slides TUPAF15 [2.065 MB]  
DOI •  reference for this paper ※ https://doi.org/10.18429/JACoWICAP2018TUPAF15  
About •  paper received ※ 31 October 2018 paper accepted ※ 08 December 2018 issue date ※ 26 January 2019  
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TUPAG22  Main and Fringe Field Computations for the Electrostatic Quadrupoles of the Muon g2 Experiment Storage Ring  multipole, experiment, storagering, FEL  313 


Funding: This work was supported by the U.S. Department of Energy under Contract DEFG0208ER41546 and by Fermi Research Alliance for U.S. Department of Energy under Contract DEAC0207CH11359. We consider semiinfinite electrostatic deflectors with plates of different thickness, including plates with rounded edges, and we calculate their electrostatic potential and field using conformal mappings. To validate the calculations, we compare the fringe fields of these electrostatic deflectors with fringe fields of finite electrostatic capacitors, and we extend the study to fringe fields of adjacent electrostatic deflectors with consideration of electrostatic induction, where field falloffs of semiinfinite electrostatic deflectors are slower than exponential and thus behave differently from most magnetic fringe fields. Building on the success with electrostatic deflectors, we develop a highly accurate and fully Maxwellian conformal mappings method for calculation of main fields of electrostatic particle optical elements. A remarkable advantage of this method is the possibility of rapid recalculations with geometric asymmetries and mispowered plates. We use this conformal mappings method to calculate the multipole terms of the high voltage quadrupole used in the storage ring of the Muon g2 Experiment (FNALE0989). Completing the methodological framework, we present a method for extracting multipole strength falloffs of a particle optical element from a set of Fourier mode falloffs. We calculate the quadrupole strength falloff and its effective field boundary (EFB) for the Muon g2 quadrupole, which has explained the experimentally measured tunes, while simple estimates based on a linear model exhibited discrepancies up to 2%. 

Slides TUPAG22 [3.780 MB]  
DOI •  reference for this paper ※ https://doi.org/10.18429/JACoWICAP2018TUPAG22  
About •  paper received ※ 15 October 2018 paper accepted ※ 28 January 2019 issue date ※ 26 January 2019  
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