High Field Dipoles for accelerators Etienne Rochepault PhD student - - PowerPoint PPT Presentation

▶
high field dipoles for accelerators
SMART_READER_LITE
LIVE PREVIEW

High Field Dipoles for accelerators Etienne Rochepault PhD student - - PowerPoint PPT Presentation

Jun 26, 2023 550 likes •799 views

CEA Saclay - Irfu High Field Dipoles for accelerators Etienne Rochepault PhD student Etienne Rochepault Toohig Presentation 07/05/12 1 Background 2009: Graduated from Ecole Normale Suprieure French famous school for

slide-1
SLIDE 1

1 07/05/12 Etienne Rochepault – Toohig Presentation

High Field Dipoles for accelerators

Etienne Rochepault PhD student

CEA Saclay - Irfu

slide-2
SLIDE 2

2 07/05/12 Etienne Rochepault – Toohig Presentation

Background

  • 2009: Graduated from “Ecole Normale Supérieure”

 French famous school for higher education and research.

  • 2009: Master degree in Electrical Engineering, University of Paris-Sud
  • PhD thesis at CEA Saclay

 Center for Atomic Energy, great research institution  Paris area  My department, IRFU, involved in many CERN projects

  • 2012, September: PhD defense
  • Teaching charge at university, during the PhD
slide-3
SLIDE 3

3 07/05/12 Etienne Rochepault – Toohig Presentation

Outline

I. Some issues in high field magnets

  • 1. High field magnets for LHC
  • 2. Innovative insulations

II. Theoretical work : Magnetic Design

  • 1. 2D cross-section design
  • 2. 3D coil-ends design
  • III. Experimental work : Ceramic Insulation Developments
  • 1. Critical current measurements
  • 2. Improvement outlooks
  • IV. Conclusion
  • 1. Contribution to high field magnet
  • 2. Interests in LARP
slide-4
SLIDE 4

4 07/05/12 Etienne Rochepault – Toohig Presentation

  • I. Some issues in high field magnets
slide-5
SLIDE 5

5 07/05/12 Etienne Rochepault – Toohig Presentation

  • I. Some issues in high field magnets
  • 1. High field magnets for LHC
  • LHC upgrades

 Increase energy: HE-LHC  Increase luminosity: HiLumi

  • Increase the bending field: NbTi limited, use Nb3Sn
  • Beam stability  Good field homogeneity
  • Avoid magnet quenching  Operational margins
  • Nb3Sn very sensitive to stress  Manage forces
  • Connect the straight parts  end-parts
  • Respect the bending limits of the cable
  • Keep field homogeneity and margin

Cross- section designs Coil-ends design

slide-6
SLIDE 6

6 07/05/12 Etienne Rochepault – Toohig Presentation

Magnetic agitation Impregnation process Drying tube Desized tape roller Ceramic solution Impregnated tape roller Thickness control by laser

  • 2. Innovative insulations
  • Ceramic insulation developed at CEA [2 patents, 2001 & 2003]
  • Porous material  excellent heat evacuation  [S. Pietrowicz, B. Baudouy, ICMC 2011]
  • Ceramic  withstands the 650 °C heat treatment 

 good resistance to irradiation   good electrical resistance 

  • Wind, Impregnate & React

 less risks 

  • Tests on small solenoids OK
  • Issues:

Is the mechanical strength sufficient ?  What is the electrical behavior

  • f insulated cables ?
  • I. Some issues in high field magnets
slide-7
SLIDE 7

7 07/05/12 Etienne Rochepault – Toohig Presentation

  • II. Theoretical work : Magnetic Design
slide-8
SLIDE 8

8 07/05/12 Etienne Rochepault – Toohig Presentation

  • II. Theoretical work : Magnetic Design
  • 1. 2D cross-section design
  • 2D model for the computation of field,

harmonics and forces  Analytic formulas for infinite rectangular blocks [G. Aubert, forthcoming book]

 Suitable for block design,

Rutherford cables, ribbons

  • Method to optimize cross-sections [E. Rochepault et al., IEEE 2011]

 4 degrees of freedom/block  Minimization of volume, forces…  Easy to implement, fast, precise   No need for Fourier decomposition   No analytical form for saturated iron 

slide-9
SLIDE 9

9 07/05/12 Etienne Rochepault – Toohig Presentation

FRESCA2 specifications: [HFM Magnet Design Working Group]

  • Nb3Sn
  • 100 mm aperture
  • 13 T bore field

Conductor section minimization:

  • 13 % margin
  • harmonics < 1 unit
  • stress < 100 Mpa
  • II. Theoretical work : Magnetic Design
  • 1. 2D cross-section design
slide-10
SLIDE 10

10 07/05/12 Etienne Rochepault – Toohig Presentation

  • 1. 2D cross-section design
  • II. Theoretical work : Magnetic Design

HE-LHC specifications: [Rossi, Todesco]

  • Bi2212, Nb3Sn, NbTi
  • Grading
  • 40 mm aperture
  • 20 T bore field

Financial cost minimization:

  • 20 % margin
  • aligned blocks

Bi2212 Nb3Sn low J Nb3Sn high J NbTi

slide-11
SLIDE 11

11 07/05/12 Etienne Rochepault – Toohig Presentation

  • II. Theoretical work : Magnetic Design
  • 2. 3D coil-ends design
  • 3D model for the computation of field in space

 Analytic formulas for blocks & arcs [G. Aubert, forthcoming book]  Suitable for a block design + “pancake model”

  • Method to optimize dipole ends [E. Rochepault et al., Numelec 2012]

 6 degrees of freedom/block  Minimization of the harmonic integrals along the tube  Need for Fourier decomposition 

Straight part

+ =

slide-12
SLIDE 12

12 07/05/12 Etienne Rochepault – Toohig Presentation

2D optimization :

  • 4 layers
  • 100 mm aperture
  • 13 T bore field
  • 13 % margin
  • B3 = B5 = B7 = B9 = B11 = 0

3D optimization :

  • 5 pancakes
  • ∫B3dz = 0
  • ∫B5dz = 0.145 T.m

Tricky cutting

500 mm end

  • II. Theoretical work : Magnetic Design
  • 2. 3D coil-ends design
slide-13
SLIDE 13

13 07/05/12 Etienne Rochepault – Toohig Presentation

  • II. Theoretical work : Magnetic Design
  • 2. 3D coil-ends design
  • 3D model for the computation of harmonic integrals

 Analytic formulas for geodesic strips [G. Aubert, forthcoming book]  Suitable for ribbons, approximation of Rutherford cables

  • Method to optimize dipole ends

 1 degree of freedom/strip  Formulas for integrated harmonics 

Radial  Sector coils Horizontal  Block design

slide-14
SLIDE 14

14 07/05/12 Etienne Rochepault – Toohig Presentation

2D optimization :

  • 1 angular sector
  • 100 mm aperture
  • 1.15 T bore field
  • B3 = 0

3D optimization :

  • 2 parts
  • minimum length
  • ∫B3dz = 0

350 mm end

  • II. Theoretical work : Magnetic Design
  • 2. 3D coil-ends design
slide-15
SLIDE 15

15 07/05/12 Etienne Rochepault – Toohig Presentation

  • III. Experimental work : Ceramic Insulation
slide-16
SLIDE 16

16 07/05/12 Etienne Rochepault – Toohig Presentation

  • III. Experimental work : Ceramic Insulation
  • 1. Critical current measurements
  • CEA experiment: design of a new sample holder

 U shape, adjustable force on the cable  Current measurement on a strand  Background field: up to 11 T  Ceramic insulation Are quenches stable when the pressure is applied ? Does cooling has a beneficial effect on quenches ?

FEM Modeling Drawing Assembly

slide-17
SLIDE 17

17 07/05/12 Etienne Rochepault – Toohig Presentation

  • III. Experimental work : Ceramic Insulation
  • 1. Critical current measurements
  • Collaboration with CERN: FRESCA experiment

 2 cables, soldered at the bottom  Adjustable pressure  Quench measurement on the cable  Background field: up to 9 T  3 types of insulation

Ceramic Epoxy impregnated Strand Impregnation Tape Wrapped

slide-18
SLIDE 18

18 07/05/12 Etienne Rochepault – Toohig Presentation

0,0 0,2 0,4 0,6 0,8 1,0 1,2 10 20 30 40 50 60 Iq/Ic0 P (MPa) Impregnated Wrapped Ceramic Ceramic strand

  • III. Experimental work : Ceramic Insulation
  • 1. Critical current measurements
  • No degradation

at very low pressure

0,75

  • Unacceptable degradation

at low pressure

  • Irreversible degradation

when pressure released Non-impregnated cables cannot withstand even a small pressure consistent with observations reported in literature

Quenches at high fields Vs applied pressure [E. Rochepault et al., IEEE 2012], [S. Le Naour, CERN report, 2012] Pressure sensitive films after 40 MPa 50-130 10-50

slide-19
SLIDE 19

19 07/05/12 Etienne Rochepault – Toohig Presentation

  • Improve the sintering

 650°C too low for ceramic sintering  maybe applicable to other superconductors (Nb3Al, MgB2, HTS…) ?

  • Fill the inter-strand interstices
  • III. Experimental work : Ceramic Insulation
  • 2. Improvement outlooks

Old process Aim Strand Ceramic Tape

Sintered ceramics can resist potentially up to 5 GPa pressures ! How to increase the mechanical strength of a ceramic insulation ?

  • The more mechanical strength, the less porosity

 heat evacuation   but thermal conductivity still 10-20x higher than resins !

slide-20
SLIDE 20

20 07/05/12 Etienne Rochepault – Toohig Presentation

  • III. Experimental work : Ceramic Insulation
  • 2. Improvement outlooks
  • Tests on different materials, different processes

 Mechanical characterizations on cable stacks and mini-racetracks  Presently no ceramic insulation withstands pressures > 40 MPa

Cable stack Deformation under the press

slide-21
SLIDE 21

21 07/05/12 Etienne Rochepault – Toohig Presentation

  • IV. Conclusion
slide-22
SLIDE 22

22 07/05/12 Etienne Rochepault – Toohig Presentation

  • IV. Conclusion
  • 1. Contribution to high field magnets
  • Theoretical work:

 Development of a 2D code and two 3D codes for magnet optimization  Proposition of 2D designs for actual projects  Proposition of 3D designs for Nb3Sn dipoles

  • Experimental work:

 Design of an experiment to measure critical current of Nb3Sn cables  Experimental testing of Nb3Sn cables  Research on new insulation methods

slide-23
SLIDE 23

23 07/05/12 Etienne Rochepault – Toohig Presentation

  • IV. Conclusion
  • 2. Interests in LARP
  • Skills acquired in high field magnets design, both theoretical…

 Mastering of field computation formulas  Computation of high field magnet configurations  Good knowledge of optimization programming …and experimental  Design of an experiment  Preparation & testing of superconducting cables (with all the issues !)

  • A good experience (and a lot of interest) in high field magnets:

 I already worked with CERN  I followed an high field dipole project

  • LARP is a great opportunity:

 High field magnets projects  Strong CERN partnership  4 laboratories of excellence with famous records in magnet technology

slide-24
SLIDE 24

24 07/05/12 Etienne Rochepault – Toohig Presentation

Thanks for your attention !

Some questions ?