# Presentation: 547473

## MCTF Magnet and HTS Conductor R&D

## MCTF Magnet R&D Directions

- Magnet R&D (with Muons Inc.)
- Conceptual design studies of Helical Cooling Channel Magnet System
- Development of Helical Solenoid for Cooling Demonstration Experiment (CDE)
- Very High Field Solenoid R&D
- R&D for SC Materials in support of magnet program (with National Labs and Industry)
- Participation in National HTS Program
- Contribute where possible to the conceptual design of detector magnets

## HCC Magnet System Design Studies

- The helical solenoid concept (Fermilab)
- Alternative to straight solenoid with helical D and Q coils
- Ring coils follow the helical beam orbit produsing solenoi-dal, helical D and Q fields
- Multi stage HCC study
- Wide range of fields, helical periods, apertures
- Straight solenoid concept does not work for high-field/small-aperture sections
- Field tuning more complicate at high fields
- NbTi, Nb3Sn/Nb3Al and probably HTS in final stage
- Studies will continue

## HS for Cooling Demonstration Experiment

- _Status_: conceptual design complete
-  solenoid
-  matching sections
- _Next_: engineering design
-  mechanical structure
-  field quality, tolerances
-  cryostat
-  quench protection

- _Goals_: cooling demonstration, HS technology development
- _Features_: SSC NbTi cable, Bmax~6 T, coil ID ~0.5m, length ~10m => Complex magnet, significant magnetic forces and stored energy, must eventually incorporate RF.

## 4-coil Helical Demonstration Model

- Goals:
- validate mechanical structure and fabrication methods
- study quench performance and margins, field quality, quench protection
- Features:
- use existing SSC cable
- fields and forces as in the HS for CDE
- Funded by MCTF and Muons Inc.

## 4-coil model Analysis

- Magnetic and mechanical engineering design complete:
-  3D field distribution
-  3D stress/strain analysis in coils and mechanical structure

## 4-coil fabrication status

- Parts:
- design complete
- procurement in progress
- Cable:
- Extracted strand samples were tested
- Practice winding complete:
- cable stability and support during hard bend winding
- coil size control
- Instrumentation:
- development started
- Model test:
- September 2008

## HCC R&D Plans for the next few years

- Directions of magnet R&D program are dictated by muon collaboration and MCTF goals
- Possible directions:
- Design and build 1/4 period section of NbTi HCC incorporating RF
- Solve RF/magnet integration issues, cryostat design, etc.
- Design and build multi-period helical solenoid for 6-D Cooling Demonstration Experiment
- Validate tracking
- Better understand and optimize matching sections
- Design magnet integrated with experiment

## High Field Solenoid Development

- Used in the final muon cooling stage
- Basic Parameters
- Inner bore diameter 50 mm
- Length 1 meter
- Fields 30 T or higher 
- HTS materials
- Required R&D
- Design Studies
- Identify key issues
- Determine R&D directions
- Advances in Conductor R&D

## 50 T Solenoid Conceptual Design Study

**BSCCO**

**Nb3Sn**

**NbTi **

**B**

**Coil radius, m**

- Key design issues:
- superconductor Jc
- effect of field direction on Ic in case of HTS tapes
- stress management
- quench protection
- cost
- Solutions:
- hybrid coil design
- coil sections

## 50 T Solenoid: next steps

- Build and test smaller HTS and HTS/Nb3Sn hybrid solenoid models
- Field range: up to 20-25 T
- HTS material: BSCCO (G1) or YBCO (G2)
- Conductor type: round strands, cables or tapes
- Technologies: React-&-wind or wind-&-react
- Motivate progress in HTS conductor technology
- National Conductor Program (*see Alvin’s talk*)

## MCTF Conductor Program

- Emphasis on HTS strands, tapes and cables
- Nb3Sn and Nb3Al strand and cable R&D is supported by other programs (DOE, LARP, NIMS/FNAL/KEK, CARE, etc.)
- Collaborator as part of National HTS Program
- R&D infrastructure
- Two Oxford Instrument Teslatron stations with 16T and 17T solenoids, and test temperatures from 1.9K to 70K
- 42-strand cabling machine
- Probes to measure
- Ic of HTS strands and tapes as a function of field, temperature, and field orientation
- transverse pressure sensitivity of strand Ic in a cable
- 28 kA SC transformer to test cables at self-field in LHe

## Strand and Tape Samples

## HTS and LTS Performance at 4.2 K

- October 30, 2007

- Measurement on round strands and tapes in magnetic fields up to 17T
- Ic for tapes depends on field orientation
- Detailed measurement of Ic angular dependence for HTS tapes at fields up to 15-16 T
- LTS samples show better performance than HTS at low fields
- Input data for High Field HTS Solenoid design studies

## High field HTS tests

- HTS tape Ic measurements at 4.2 K (with NIMS, Japan)
- transverse fields up to 28T
- two field orientations
- Input data for High Field HTS Solenoid design studies
- reduce uncertainty in conductor performance at high fields

## BSCCO Rutherford Cables

- Goals:
- increase conductor Ic
- reduce magnet inductance
- Important for magnet quench protection
- Issues:
- Ic degradation after cabling
- Determine design criteria and cabling procedures
- low degradation at packing factors <87%
- Cable HT optimization
- reduce Ag leaks and Ic degradation
- Transverse pressure sensitivity studies
- determine pressure limits

## Present and Future HTS R&D Plans

- HTS reaction site for strands and small coils
- Convert existing small oven
- Go through a safety review
- Collaborate with DOE labs, industries and Universities through National HTS Conductor program
- Round Robin test of HTS round wire
- Collaboration with NHFML on short sample and coil reaction cycle
- Start small coil test program to study technology and quench issues
- Support SBIR on HTS development

## NF Detector R&D: Magnetic Cavern

- Cable based design (Fermilab)
- Features
- 10 solenoids
- 15-m long 15 m ID each
- Bnom~0.5 T (50% margin)
- 1 m iron wall, B~2.4 T
- Good field uniformity
- Solve technical problems
- Reduce detector cost

## 2-turn Solenoid Model (proposal)

- Goals:
- Optimize cable design, thermal shield and support structure
- Needs modification to provide long piece length (~5-7 km) and flexibility (bending diameter 15m)
- Fabricate and test ~100-m long cable prototype
- Test solenoid support structure and assembly procedure
- Test cable support structure (axial and radial mechanics)
- Measure heat leaks to LN and LHe
- Unique opportunity to model a short section of the detector before fabrication.

## Summary

- Magnets are one of the enabling technologies for the Muon Collider/Neutrino Factory
- The development of practical muon collider magnets is a long term investment
- MCTF Magnet program has already created a strong foundation and has made progress in all key directions
- Important on going and near term activities
- Support the National HTS R&D program
- Design and possibly build relevant demonstration magnets
- NbTi Helical Solenoids without and with RF
- Moderate field solenoids and very high field solenoids in support of Muon Cooling Experiments
- Continue the conceptual design studies of collider ring, IR and detector magnets
- It is critical for the community to increase the support of advanced magnet and HTS R&D
- i.e. stable funding and manpower resources