# Presentation: 398647

## Nb3Sn LHC IR QuadMagnet Workshop – Archamps France March 17-18, 2003Shlomo Caspi

- s_caspi@lbl.gov

## Design parameters  

-  First Generation IR quadrupoles (KEK and FNAL)
- (Nominal luminosity: 1034 cm-2s-1)
- Aperture: 70 mm
- Gradient: 205 T/m
- NbTi technology at 1.9K
- Next generation Interaction Region quadrupoles:
- (Ultimate luminosity: 2.51034 cm-2s-1)
- Aperture: 90 mm
- Gradient: 205 T/m
- Nb3Sn technology at 1.9K

- s_caspi@lbl.gov

## Outline

-  LBNL Nb3Sn magnet experience
** **IR quad mechanical** **and** **magnetic** **conceptual design
** **Future Plans

- s_caspi@lbl.gov

## LBNL Nb3Sn Magnet Experience

-  **11 **years of Nb3Sn experience.
-  **6** Nb3Sn 1m long magnets built and tested.
-  Magnet reached design field ranging from  6 T to 14.7 T.
** ****3** magnets (D19H, D20, RD3C) addressed field quality.
-  **3** magnets addressed conductor, structure and technology.
-  **4 **types of structures were tested.

- s_caspi@lbl.gov

## Mechanical Experience - I

-  Unacceptable “spring-back”   and cool-down losses

-  No Self supporting collars in Nb3Sn magnets
-  Large Lorentz forces  ~15 MN/m (LHC dipole 3.5 MN/m)

-  Key and Bladder Technology
-  No spring back loss
-  Pre-stress gain during cool-down – >100 Mpa
- Never overstress coil

- s_caspi@lbl.gov

## Mechanical Experience - II

-  Four ways to assemble and pre-stress magnets were tested.
-  D19: thin collars (3mm) and a welded shell
-  D20: spacer and wire-wrap
-  RT1:  structural beams and tie rods
-  RD, SM, HD series:
-  Collars replaced by low pre-stress sub-assembly pads
-  Final pre-stress using key and bladder technology

- s_caspi@lbl.gov

## Conceptual Design

-  Magnetic
-  Mechanical

- Coil

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** **Magnetic

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## Two types of cos2 designs 
     - 90 mm bore,  1.9 K 
 Two layers – fully keystoned
 using an internal copper core

-      - 90 mm bore,  1.9 K
-  Two layers – fully keystoned
-  using an internal copper core

- Magnetic - Cross Section

-  Four layers – fully keystoned

- s_caspi@lbl.gov

## Field Quality  

-  Reference radius: assumed 22 mm, to reflect larger bore size
-  Geometric Harmonics:
- Design: all components within 0.05 units
-  Systematic harmonic correction:
- b10 : Inner layer wedge allows +/- 0.05 units with 	+/- 150 m
- b6   : Magnetic shims within the yoke gaps allow 	+/- 0.5 units with +/- 3 mm
-  Saturation effect:
- No yoke optimization: 1 unit
- With yoke optimization: 0.1 unit

- s_caspi@lbl.gov

## Cable parameters

- 4-layer cables: conventional techniques
- 2-layer keystone angle >> conventional angle

- s_caspi@lbl.gov

## Magnetic parameters

- Operational gradient: 205 T/m
- Assuming TOP = 1.9 K

- At 4.2 K  2-layer: 230 T/m, 4-layer: 248 T/m

- s_caspi@lbl.gov

** **Mechanical

- s_caspi@lbl.gov

## Two Sub-assembly Packs

- Coil Pack – low pre-stress

- Iron Pads

- Structural Pack

- Aluminum Shell

- Iron Yoke

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## Final Assembly and Pre-stress

- Total diameter: 440 mm

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## Shell, Keys and Bladders – SM type

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## Shell Stress History – 14.7 T (RD3)

-  Initial stress 130 MPa
-  No creep
-  Gain of 120 MPa during  	cool-down
-  No increase in stress  	up to 14.7 T
-  Reversible stress upon 	warm-up
-  Reversible stress upon 	2’nd cool-down

- s_caspi@lbl.gov

## Mechanical Summary

-  Inflatable bladders
- “internal press”
- Generates large forces
- Minimize spring back

-  Interference Keys
-  Lock in pre- stress
-  Allow bladder removal
-  Confine high tolerances to key regions
-  Allow adjustment of magnetic errors

-  Aluminum Shell
- Reduces assembly pre-stress
- Monitor average coil pre-stress.

- s_caspi@lbl.gov

## Bladders pressurized
Keys inserted, bladder deflated
Cool-down
Lorentz forces – 5 MN/m

- Keys inserted, bladder deflated
- Cool-down
- Lorentz forces – 5 MN/m

- Finite element model – 4 Steps

- s_caspi@lbl.gov

## Assembly and Operation

- Coil

- Shell

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## Coil Pre-Stress and Key Position

- s_caspi@lbl.gov

** **Future Plans

- s_caspi@lbl.gov

## Mechanical Structure Test

- Cost consideration
- Use an inner instrumented tube instead of coil

- Goals:
-  Build and test support structure (full pre-stress)
-  Vary key size and position

- s_caspi@lbl.gov

## Mechanical Model- Final assembly

- s_caspi@lbl.gov

## Magnet Tests

- Cost consideration
- D20 dipole tooling can be used
- Wind Quad with dipole type ends (1/2 coils and spacers)
- Replace inner mechanical pack with coil pack

- Goals:
- Reach Short Sample
- No training below operation
- Assure field quality

- s_caspi@lbl.gov

## Prototype assembly

- s_caspi@lbl.gov

## Goals for Next Magnet Workshop 

- Complete one full design iteration:
-  Cross-section, Ends, Structure, Assembly procedure etc ...
-  Field quality
-  Structural and Thermal analysis
-  Complete a 3D CAD model
-  Complete a 3D ANSYS model - structural and thermal
-  Build and test a 1 m long mechanical model

- s_caspi@lbl.gov