# Unit 6 - Superconductor stability and margin

- Institution: CERN
- Department: Masterclass - Superconducting Accelerator Magnets
- Speaker: Ezio Todesco
- Year: 2020
- Language: English
- Source: [CERN](https://videos.cern.ch/record/3000426)
- Licence: [CERN](http://copyright.web.cern.ch)
- Who can watch: Teens profiles and older (sources give no ratings; placed by Invisible Network from the source's own words)

This unit belongs to the third part of the course, which is focussed on providing some elements of superconductivity. Here we outline the main reasons requiring a very peculiar layout for a high current density superconducting wires, namely (i) fine filaments and (ii) a copper matrix.

We will first discuss the magnetization in a superconductor, the Bean theory and the conditions for full penetration of the magnetic field. This mechanisms generates the conditions for stability of the superconductor: a bulk superconductor cannot transport large current densities, but it must be split in fine filaments. The relation between filament size, current density and temperature margin is therefore derived.

The second part is dedicated to prove that a copper matrix is needed to enhance the tolerance to transitions to normal conducting state induced by local deposition of heat.

Finally we will discuss the concept of margin for a superconducting magnets: we will start with the loadline margin, an empirical concept widely used in the magnet design. We will translate the loadline margin into a temperature and enthalpy margin for both Nb3Sn and Nb-Ti. .

0:06:24 Slide 1

0:12:48 Slide 2

0:19:12 Slide 3

0:25:36 Slide 4

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0:38:24 Slide 6

0:44:48 Slide 7

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1:04:01 Slide 10

## Lectures

1. [Unit 6 - Superconductor stability and margin](https://invisiblenetwork.ai/learn/cern/3000426/8a4a5e4bd1a4), 1 h 5 min (CERN's player)