# Presentation: 260419

## Magnet Technology Support

_**US LHC Accelerator Research Program**_

***Magnet Technology Support***
***Summary***
- LARP Collaboration MeetingNapa, October 19-21, 2004
- Gian Luca Sabbi

## Presentations 

- - P. Wanderer (A. Ghosh)
- - E. Barzi
- - D. Dietderich
- Long magnet R&D
- - S. Bartlett
- - Round table discussion
- Sub-scale quadrupole
- - P. Ferracin

- Presentations

## Conductor & Cable Development 

- _Strand_:
- Target strand specification
- Strand characterization: Ic, RRR, stability limits etc.
- Strand procurement, inventory management
- _Cable_:
- Cable Parameters Optimization
- Cable characterization
- Ic, RRR, stability limits etc.
- Cabling degradation
- Stress degradation
- Cable fabrication for model magnets

## Strand development & procurement

- - high critical current (~ 3 kA/mm2 @ 12 T, 4.2 K)
- - small effective filament size (~40 m)
- - RRR > 20 (40)
-  Close coordination with HEP conductor program
-  OST is presently working on improving the strand designs
- - more SC fraction (higher Ic )
- - 2 approaches to smaller effective filament size:
- - Ta rods to split subelements
- - increased number of subelements
-  Increased strand diameter is also desirable (larger apertures, dipoles)
-  There is still a significant risk associated with strand procurements
- - need to procure strand well in advance of model magnet fabrication
- - create a strand inventory for LARP model magnets

## Cable Optimization

- - use less “width” compaction in Nb3Sn with respect to NbTi
- Narrow (keystone) cables (8-10 mm width):
- - full keystone and good mechanical stability
- Wide (keystone) cables (>15 mm):
- - ok with partial keystone; determine optimal keystone
- Flat cables (narrow/wide):
- - good mechanical stability and low degradation
- Material (strand) has significant influence on allowed parameter space
- - need to keep up with testing as wire fabrication processes evolve

## Cable Fabrication Procedure

-  Fabricate cable slightly oversized (thickness)
-  Anneal at ~210C/6h
-  Re-roll to final thickeness
- Results:
-  Mechanically more stable
-  Reduced dimensional change during reaction

## Cable Critical Current Measurements

- Sub-scale race track coils
- - Develop winding and assembly method for keystoned cables
- BNL
- - 7T dipole, 25,000A (narrow cables)
- CERN:
- - 10T, 32,000-40,000A (wide cables)
- FNAL
- - 28,000A superconducting transformer, 1 cable/day, self-field
- NHMFL
- - 12T split pair solenoid, 20,000A

## Stress Degradation

- - reduced effort wrt “full” cable tests allows rapid turnaround
- - comparisons of different materials and different cable configurations
- - New vs old PIT
- - Use of cores to improve stress tolerance
- - strand design optimization
- - comparison of different processes
- - Some questions in  “absolute” comparisons with magnet
- - cable tests
- - sub-scale and LARP model magnet tests
- - base programs

## Strand and Cable Stability

- - good indicator of stability limits of strands
- Cable tests in self field using SC transformer
- - also a good indicator of stability limits, with rapid turnaround
- RRR can have a critical impact on strand/cable stability.
- - Use RRR > 20 (40)
- Reduced filament size is the best strategy, but requires more time
- - Target: Deff ~ 40 m (in progress)
- Some unexpected limitations found in PIT
- - relatively small filament diameter and high (overall) RRR

## Long Magnet R&D

_*Main R&D issues:*_
-  stress control during coil reaction, cable treatment, pole design
-  tooling/handling of reacted coils
-  support structures (alignment, segmented shells, He containment)
-  assembly issues; design/fabrication/test of long bladders

- LAPAC recommendation: investigate length scaling as early as feasible

## Long Magnet R&D (2)

-  generate detailed list of issues & priorities
-  define what is required to address these issues
-  determine coil configuration & coil length
-  generate cost estimates for different options
-  discuss R&D phases
-  feasibility of FE analysis of coil reaction?
-  role of R&W?
- Need to be ready to start in FY06
-  Infrastructure procurement
-  Model coil design/plan

## Subscale Quadrupole R&D

- 1. General application:
-  Mechanical support structure optimization
-  Stress limits, pre-stress options
-  Validation of mechanical analysis models
-  Assembly/alignment with bladder & keys
-  Coil fabrication tolerances/reproducibility
-  Field correction (coil & magnetic shims)
-  Thermal and quench protection studies
- 2. Racetrack quad specific:
-  Evaluation of racetrack design performance
-  Internal bore support requirements

**Cost-effective, efficient tool to study many design/technology issues: **

**Subscale coils can also be effective as a tool for dipole-relevant R&D **