Paper  Title  Other Keywords  Page 

SUPAG03  Challenges in Extracting PseudoMultipoles From Magnetic Measurements  multipole, induction, dipole, quadrupole  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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SUPAG05  Muon Background Studies for Beam Dump Operation of the K12 Beam Line at CERN  proton, target, background, simulation  93 


In the scope of the Physics Beyond Colliders study at CERN a future operation of the NA62 experiment in beam dump mode is discussed, enabling the search for dark sector particles, e.g. heavy neutral leptons, dark photons and axions. For this purpose, the 400 GeV/c primary proton beam, extracted from the SPS, will be dumped on a massive dump collimator located in the front end of the K12 beam line. Muons originating from interactions and decays form a potential background for this kind of experiment. To reduce this background, magnetic sweeping within the beam line is employed. In this contribution, the muon production and transport has been investigated with the simulation framework G4beamline. The high computational expense of the muon production has been reduced by implementing sampling methods and parametrizations to estimate the amount of highenergy muons and efficiently study optimizations of the magnetic field configuration. These methods have been benchmarked with measured data, showing a good qualitative agreement. Finally, first studies to reduce the muon background by adapting the magnetic field configuration are presented, promising a potential background reduction by a factor four.  
Slides SUPAG05 [1.885 MB]  
DOI •  reference for this paper ※ https://doi.org/10.18429/JACoWICAP2018SUPAG05  
About •  paper received ※ 19 October 2018 paper accepted ※ 28 January 2019 issue date ※ 26 January 2019  
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MOPLG01  Challenges in Simulating Beam Dynamics of Dielectric Laser Acceleration  laser, electron, focusing, acceleration  120 


Funding: ACHIP is funded by the Gordon and Betty Moore Foundation (Grant No. GBMF4744). U.N. acknowledges German BMBF Grant No. FKZ:05K16RDB. B.C. acknowledges NERSC, Contract No. DEAC0205CH11231. Dielectric Laser Acceleration (DLA) achieves the high est gradients among structurebased electron accelerators. The use of dielectrics increases the breakdown field limit, and thus the achievable gradient, by a factor of at least 10 in comparison to metals. Experimental demonstrations of DLA in 2013 led to the Accelerator on a Chip International Program (ACHIP), funded by the Gordon and Betty Moore Foundation. In ACHIP, our main goal is to build an acceler ator on a silicon chip, which can accelerate electrons from below 100keV to above 1MeV with a gradient of at least 100MeV/m. For stable acceleration on the chip, magnet only focusing techniques are insufficient to compensate the strong acceleration defocusing. Thus spatial harmonic and Alternating Phase Focusing (APF) laserbased focusing tech niques have been developed. We have also developed the simplified symplectic tracking code DLAtrack6D, which makes use of the periodicity and applies only one kick per DLA cell, which is calculated by the Fourier coefficient of the synchronous spatial harmonic. Due to coupling, the Fourier coefficients of neighboring cells are not entirely independent and a field flatness optimization (similarly as in multicell cavities) needs to be performed. The simu lation of the entire accelerator on a chip by a Particle In Cell (PIC) code is possible, but impractical for optimization purposes. Finally, we have also outlined the treatment of wake field effects in attosecond bunches in the grating within DLAtrack6D, where the wake function is computed by an external solver. 

Slides MOPLG01 [3.947 MB]  
DOI •  reference for this paper ※ https://doi.org/10.18429/JACoWICAP2018MOPLG01  
About •  paper received ※ 20 October 2018 paper accepted ※ 24 October 2018 issue date ※ 26 January 2019  
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MOPAF02  Realistic Modeling of the Muon g2 Experiment Beamlines at Fermilab  simulation, target, storagering, proton  134 


Funding: This work is supported by the U.S. Department of Energy under Award No. DEFG0208ER41546, by the PhD Accelerator Program at Fermilab, and by a Strategic Partnership Grant from the MSU Foundation. The main goal of the Muon g2 Experiment at Fermilab (E989) is to measure the muon anomalous magnetic moment (a, also dubbed as the "anomaly’’) to unprecedented precision. This new measurement will allow to test the completeness of the Standard Model (SM) and to validate other theoretical models beyond the SM. Simulations of the beamlines from the pion production target to the entrance of the g2 Storage Ring using COSY INFINITY contribute to the understanding and characterization of the muon beam production in relation to the statistical and systematics uncertainties of the E989 measurement. The effect of nonlinearites from fringe fields and highorder contributions on the beam delivery system performance are considered, as well as interactions with the beamline elements apertures, particle decay channels, spin dynamics, and beamline misalignments. 

Slides MOPAF02 [14.110 MB]  
DOI •  reference for this paper ※ https://doi.org/10.18429/JACoWICAP2018MOPAF02  
About •  paper received ※ 22 October 2018 paper accepted ※ 28 January 2019 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  quadrupole, multipole, 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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