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Talk1 h 42 min

Unit 3 - The multipolar expansion of magnetic field

Ezio Todesco · CERN

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About

This unit belongs to the second part of the course, which is focussed on the physics of electromagnets.

In this unit we see how to express the magnetic field shape with a few coefficients, called the multipoles or field harmonics, thanks to the special form of the Maxwell equations. This formulations greatly simplifies the expression and the optimization of magnetic fields. It is based on the same principle of a Taylor expansion (power series), but applied to the complex domain.

We will discuss which are the multipoles of the simplest case: the field generated by a current line. This interesting example will also allow to outline the validity limits of this approach (i.e., where and why the multipole expansion fails) and give few elements about divergent series. We then show that the decay of the field harmonics are a powerful analysis tool to find the location of assembly errors and to check the consistency of measurements, and the precision.

Finally, we will summarize the beam dynamics requirements on the multipoles.

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0:10:11 Slide 1

0:20:23 Slide 2

0:30:35 Slide 3

0:40:46 Slide 4

0:50:58 Slide 5

1:01:10 Slide 6

1:11:21 Slide 7

The talk

  1. Unit 3 - The multipolar expansion of magnetic field 2020-05-14 · 1 h 42 min · CERN's player

Credits and licence

Institution
CERN
Department
Masterclass - Superconducting Accelerator Magnets
Speaker
Ezio Todesco
Year
2020
Language
English
Source
CERN
Licence
CERN, as CERN states it. CERN's terms
Attribution
© CERN. CERN provides its audiovisual media free of charge for educational and informational use, credited to CERN; this lecture is shown in CERN's own player.
Who can watch
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