# Presentation: 709824

## Magnet Systems

- Jim Kerby
- 20 Apr 2007
- With thanks to my colleagues

## Current Program

- _Current_ focus:  Demonstrate by the end of 2009 that Nb3Sn magnets are a viable choice for an LHC IR upgrade
- Known major issues
- Nb3Sn technology; Peak field on coil; Length; Consistency
- Three pronged approach:
- Predictable and reproducible performance
- TQ models (1m, _90mm bore, G__nom__ > 200 T/m_, Bcoil > 12T)
- Long magnet fabrication
- LQ models (_4m_, 90mm bore, Gnom > 200 T/m, Bcoil > 12T)
- Predictable and reproducible performance
- HQ models (1m, 90+mm bore, Gnom ~ 250 T/m, _B__coil__ > 15T_)
- _But_ several new initiatives are under discussion—slim Q0 options, for instance—we can not be completely locked in the box, and must be willing to contribute in the best way possible for LHC

## Quadrupole Designs for the LHC IR

- From ASC06 HQ Paper

## TQC and TQS Design Concepts

-  Aluminum shell over iron yoke
-  Assembly with bladders and keys
-  Aluminum rods for axial pre-load

- Axial rod

- Shell

- Key

- Yoke

- Pad

- Filler

- TQC

- TQS

-  Stainless steel collars and skin
-  Control spacers to limit pre-load
-  End support plates, no pre-load

## TQC01 and TQS01 Quench Training 

- TQC01 and TQS01 Quench Training

-  TQC01: limited to 70% of short sample at 4.5K, but achieves 85% at 1.9K
-  TQS01: start training at 80% of 4.5 K short sample, limited to 87% in one coil
-  Maximum quench gradient was close to 200 T/m in TQC01 and TQS01

## TQS01b & TQS01c Test Results

-  TQS01b: starts training at 75% of 4.5 K short sample, plateau at ~82% (1 coil)
-  TQS01c: Trained at and 4.5K and 1.9K,  ~80% plateau is conductor-limited

## Field quality analysis:

**Field quality analysis:**
**First TQ models show that the random coil block displacements are *****mostly***** within ± 50 microns which is factor of three larger than in production MQXB at the same fraction of coil aperture. ****This is an encouraging result given the differences between NbTi and Nb3Sn technologies and the fact that MQXB field quality was polished on many preceding short models.****The measurements reveal opposite ramp-rate dependences in TQC01 and TQS01 transfer functions that may be related to different interstrand contact resistances. **

## TQ Next Steps

-  Coils use new Ti pole pieces to confirm adequacy
-  Assembly to be completed by the end of April
-  Test in May at FNAL (4.5K & 1.9K)
-  *Discussion*: cause of the 80%-87% plateau & planned corrections
-  Same coil design as TQC01 (bronze pole with stress relief cut)
-  Significantly higher collaring pre-load (addressing TQC01 problem)
-  Two coils *possibly* damaged during collaring (shim displacement)
-  *Discussion*: revise plan, minimize impact on schedule & milestones
-  Converged on coil design (Ti poles and no stress-relief cut)
-  Need to start parts procurement & coil winding (after TQ02 spares)
-  *Discussion*: can we converge on a single structure for TQ03?

*Starting from TQ02, we are switching to RRP strand: *
-  Higher current density, possibly different stress & stability characteristics

- _TQS02_
- _TQC02_
- _TQ03_

## LQ Status & Plans

- LQ “Design Study” is proceeding:
-  Finalized coil envelope and design (TQ); structure decision in June 2007 (?)
-  Feb 07 Workshop focused on integration with other program components
-  *TQ, LR, other supporting R&D and materials (conductor)*
- LQ “Task” FY07 plan: design & procure coil parts & tooling; start practice coils
* **Winding/curing tooling design approved by internal review on April 9*
* **End parts will be same as TQ  *
- _Next steps_:
- Release drawings for winding & curing tooling
- Confirm use of Ti pole pieces, determine length
- Discuss reaction and impregnation tooling and procedures
- Further clarify how/when feedback from rest of program will be integrated
- Further clarify participation of LBNL and BNL

## LQ Design study – G. Ambrosio

- Technological
- Quadrupoles

- Long Quad.
- Design Study

- Long Racetrack

- Long mirror

**Long Quadrupole**

***Practice coils***

- Goal: 4m long, G  200 T/m,  = 90 mm

## Long Racetrack

- Support structure assembled at LBNL with dummy coils
- Tested at BNL at 77 K
-  Ready to be used for LR01

##  LR coils – LR01

- LRSC01:
- Coil impregnation – completed 4/ 16/ 07
- Prep for assembly - underway
- LRSC02
- Coil reaction – heat cycle completed 4/ 19/ 07
- Coil prep for impregnation – through end of April
- Coil impregnation – early/ mid May
- Prep for assembly – mid May
- 1st LONG RACETRACK
- Coil assembly – mid/ late May
- Hang, wire, cool down – end of May
- Cold test –start early June

## LQ Mech Design Development

- With Al shell

- With collars

- Hybrid concepts: SS shell + bladders

- Analysis of TQC with Ti coils: OK!

## LQ: Next Steps

- Conductor:
- TQ02 series results  choice for LQ01 54/61 or 60/61
- Coil Fabrication Technology:
- TQ02 series results  Pole material (Ti or Bronze)
- Mechanical Design:
- Complete design of LQ with Al shell
- Analysis of TQC01b, TQ02s and TQ03s
- Generate mechanical design selection criteria
- Quench Protection:
- Design QP heaters for LQ, upgrade VMTF QP system

## HQ Status & Plans

- HQ “_Design Study_”: goals, magnetic, mechanical, quench analysis reported at ASC
- Main focus is on _fundamental technology issues_ – HQ is not a prototype
- 4-layer coil w/TQ cable width – option of “standalone” test of outer double-layer
* **We need a “technology” HQ as part of the achieving the FY09 goal *
* **HQ can be designed to facilitate the transition towards a prototype*
- Significant progress on mechanical design & analysis in recent months * *
- FY07 HQ “_task_” plan is to get started on tooling design – requires radial envelope
- Recently, more emphasis on “standalone” outer double-layer test (130 mm aperture)
- Responding to CM7 comments, considered increasing cable _width_ in outer layers
* **No significant advantage in terms of stress*
* **Quench protection issues not analyzed yet – high priority*
* **Strand diameter TBD based on materials feedback*
- We have confirmed the choice of a 10 mm cable – comments?

## FY07 progress:

-  Magnetic optimization of coil cross-section and ends
- Mechanical design concepts with coil alignment
-  Detailed magnetic/mechanical analysis & comparisons

## Summary of mechanical analysis

|  | HQ1 | HQ2 | HQ3 | HQ1out | HQ3out |  |
| --- | --- | --- | --- | --- | --- | --- |
| Gradient SS (T/m) | 312 | 319 | 308 | 185 | 205 |  |
| Iss (A) | 10600 | 12450 | 11010 | 13500 | 17030 |  |
| Peak field ss (T) | 15.74 | 16.03 | 15.49 | 14.54 | 15.37 |  |
|  |  |  |  |  |  |  |
| Gradient comparison (T/m) | 300 | 300 | 300 | 185 | 185 | 205 |
| Peak field (T) | 15.06 | 14.99 | 15.04 | 14.37 | 13.9 | 15.37 |
| Fx (MN/m) | 3.76 | 3.38 | 4.04 | 2.73 | 3.19 | 3.9 |
| Fy (MN/m) | -4.93 | -4.62 | -4.95 | -3.48 | -4.18 | -5.14 |
|  |  |  |  |  |  |  |
|  at 4.2 K in high field (MPa) | -165 | -152 | -136 | -149 | -153 | -179 |
|  after excitation (MPa) | -196 | -177 | -185 | -194 | -181 | -219 |

**Model1** = coil#i pole#i glued
- 20 MPa tension between pole and coil

## Nb3Sn Strand Specification Rev-D7/26/06

## RRP-54/61 Production 490 kg

## RRP Strand for LARP

- For FY08 LARP could use strands with the *127-stack design*
*High Jc design has been achieved*
*Stability improves with decreasing sub-element diameter*
*Smaller low field magnetization*
*Option to increase strand diameter **** wider cable*

## Small Magnet R&D

- SQ03:
- Fabrication and test of 4 new coils
- 108/127 strand
- Possible candidate for LQ02
- Conductor evaluation in operational conditions similar to the TQ/LQ magnets
- Cabling degradation
- Transverse stress degradation
- Short sample current
- Possibly use to address “bubbles”
- Seen in TQs after 1.9K test

## Radiation study – N. Mokhov

- Based on detailed MARS15 modeling and thorough analyses of coil apertures, distances to IP, low-Z spacers, stainless steel and high-Z liners, magnet splitting, and a set of TAS/TAN-type absorbers through final focus region, it is shown that dipole-first, and shell-type & block-type quad layouts are feasible for the LHC luminosity upgrade up to 1035 cm-2 s-1.
- Work has started on design of radiation damage tests of materials for the superconducting magnets for the luminosity of 1035.
-  Q3-Q4 FY07 plans: further studies of block-type coil option; address a kW-scale heat loads in the triplet; (possibly) perform calculations on a slim dipole; design Rad-Dam beam tests in an emulated LHC-like environment.
- We have everything to respond to all energy deposition Oliver’s requests, but need someone!

## Rad-Hard Insulation R&D

- Goal: Develop insulation/impregnation scheme that can withstand the expected dose at Max luminosity

|  | Plan A | Plan B |
| --- | --- | --- |
| FY07 | Develop plans, schedule, cost | Select alternative material |
| FY08
Q1-Q2 | Prepare samples and fixtures |  |
| FY08
Q3-Q4 | Irradiation & tests | Irradiation & tests |
| FY09 |  | SQ and/or TQ |

***Rad-Hard Insulation Workshop***
**Fermilab, ***** April 20, 2007  (1:30 – 6:00 pm)***

## Improved insulation for Nb3Sncables in superconducting magnets

- Improved insulation for Nb3Sncables in superconducting magnets

- The result: robust insulation fabric with half the conventional thickness:
- The silane sizing is stable through Nb3Sn heat treatment.
- The tight weave (80 ct) is strong and flexible, no broken yarns, no Cu show through
- Conformation with cable is excellent, promotes easy coil winding.
- Silane survives heat treat, provides enhanced bonding with epoxy in final coil.
***New insulation has 20% higher shear strength!***
***Good electrical properties***
***We could coordinate materials and braiding process to make this new direct-braid insulation available to be applied to cable for LARP magnets.***
********* ******Question: are you (we) interested?***

## D2 challenges:

**D2 apertures have the same polarity and negative coupling so most of the magnetic flux returns through the iron that needs to be relatively thick.**
**In spite of high current density, the quench field is ~10T and the operating field may probably be 9T instead of 14.1T quoted in the PAC03 paper. It extends magnet length from 10.0m to 15.7m.**
**The next optimization steps will attempt to reduce the yoke OR, while keeping the field quality at a reasonable level. **

## New initiatives – P. Wanderer

- LHC/LARP can benefit from BNL experience in developing
- Slim magnets
- “direct wind” CAD/CAM staff + machine produced NbTi magnets for:
- HERA IR upgrade (multielement)
- BEPC IR upgrade (multielement)
- ILC IR R&D (now underway)
- Can we use this technology with Nb3Sn?
- Magnetized TAS
- Discussions with R. Gupta  High Temperature Superconductor for quad coil in TAS
- Basis: successful design, construction, operation of HTS superferric quadrupole for RIA R&D
- Fast-cycling superconducting magnets for PS2 and SPS upgrade
- BNL modified RHIC dipole for GSI and fabricated and tested short model
- Infrastructure for fast cycling magnet testing is available

## Closeout

- New initiatives and participation...welcome!
- Magnet tests exploring the phase space...as upgrades become more real, we will be able to suggest real phase space to operate in.
- Proposal for new strand made....options for larger diameter as required
- Continued R&D and studies on materials and cooling to make a real upgrade of LHC
- Thanks to all collaborators on an active and open meeting!