Conference Paper

The injection kicker system for the muon g-2 experiment

Brookhaven Nat. Lab., Upton, NY
DOI: 10.1109/PAC.1995.505409 Conference: Particle Accelerator Conference, 1995., Proceedings of the 1995, Volume: 3
Source: IEEE Xplore

ABSTRACT The muon g-2 experiment is designed to measure the anomalous
magnetic moment of the muon to an accuracy of 0.35 ppm by measuring the
difference between the spin precession frequency and the cyclotron
frequency of the particle in a known magnetic field. The injection
kicker is designed to deflect 3.094 GeV/c muons by an angle of 10 mrad
into a storage ring with a radius of 7.112 m. No magnetic materials can
be used in or near the beam line because of the high precision with
which the field of the main dipole magnets must be known. Eddy currents
induced in the vacuum chamber by the fast kicker pulse, and their effect
on the main dipole field must also be considered. An air core magnet
which is driven by an underdamped capacitor discharge modulator using a
spark gap switch has been designed. This design, as well as test data,
will be presented

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    ABSTRACT: The goal of AGS E821 is a precision measurement of the muon magnetic moment (g-2) value to 0.35 ppm. A problem with muon injection is the effect of the residual magnetic field during the measurement period due to the eddy currents in the vacuum chamber induced by the kicker pulse. The paper presents a mainly analytical look at the nature of the eddy currents as an equivalent RL circuit and describes a method to solve 2D Maxwell's operations under pulse excitation with some quantitative estimates of the decay time constants. Analysis of the results show that the field due to eddy currents is dependent on the chamber dimensions, type of material, and duration of pulse rise, flattop and fall. The field created by the rising edge of the waveform is largely cancelled by the falling edge, providing the pulse is short compared to the diffusion time of the eddy current. The simulation results agree with the theoretical analysis and confirm the residual integral field at the start of the measurement period is acceptable
    Particle Accelerator Conference, 1995., Proceedings of the 1995; 06/1995


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