# Presentation: 658672

## A Proposal for a 50 T HTS Solenoid

- Steve Kahn
- Muons Inc.
- March 14, 2006

- S. Kahn--Proposal for a 50 T HTS Solenoid

- March 14, 2006

## Slide 2

- S. Kahn--Proposal for a 50 T HTS Solenoid

- March 14, 2006

## Alternating Solenoid Lattice for Cooling

- We plan to use high field solenoid magnets in the near final stages of cooling.
- The need for a high field can be seen by examining the formula for equilibrium emittance:
- The figure on the right shows a lattice for a 15 T alternating solenoid scheme previously studied.

- S. Kahn--Proposal for a 50 T HTS Solenoid

- March 14, 2006

## From R. Palmer

- S. Kahn--Proposal for a 50 T HTS Solenoid

- March 14, 2006

## Slide 5

- S. Kahn--Proposal for a 50 T HTS Solenoid

- March 14, 2006

## A Proposal for a High Field Solenoid Magnet R&D

- The availability of commercial high temperature superconductor tape (HTS) should allow significantly higher field that can produce smaller emittance muon beams.
- HTS tape can carry significant current in the presence of high fields where Nb3Sn or NbTi conductors cannot.
- We would like to see what we can design with this commercially available HTS tape.

- S. Kahn--Proposal for a 50 T HTS Solenoid

- March 14, 2006

## Comparison of JE for HTS Conductors

**We have chosen to use Bi2223 since it is available as a reinforced tape from AMSC**
**The conductor can carry significant current at very high fields.  NbTi and Nb****3****Sn can not.**

- S. Kahn--Proposal for a 50 T HTS Solenoid

- March 14, 2006

## Properties of American Superconductor’s High Temperature Superconductor Wire

- 6% more current per turn
- 10 % more turns per radial space

- S. Kahn--Proposal for a 50 T HTS Solenoid

- March 14, 2006

## Cross Sections of HTS Tape

- High Strength Tape

- High Compression Tape

- High Current Tape

- S. Kahn--Proposal for a 50 T HTS Solenoid

- March 14, 2006

## Why Do We Want to Go to Liquid Helium?

- The parallel field orientation is the most relevant for a solenoid magnet.
- Previous calculations had used the perpendicular field.  (We can view this not as a mistake, but as a contingency).

- S. Kahn--Proposal for a 50 T HTS Solenoid

- March 14, 2006

## Current Carrying Capacity for HTS Tape in a Magnetic FieldScale Factor is relative to 77oK with self field

- S. Kahn--Proposal for a 50 T HTS Solenoid

- March 14, 2006

## Fit to High Field to Extrapolate Beyond 27 T

- We are using BSSCO 2223 which has been measured only to 27 T in the perpendicular configuration.  We are using it in the parallel configuration.
- We have to extrapolate to high field.
- We know that BSSCO 2212 has been tested to 45 T, so we *think* that the AMSC tape will work.
- The high field measurements of BSSCO 2212 has a different falloff from BSSCO 2223.
- We certainly will need *measurements *of the AMSC tape at high field

- S. Kahn--Proposal for a 50 T HTS Solenoid

- March 14, 2006

## A Vision of a Very High Field Solenoid

- Design for 40 Tesla.
- Inner Aperture Radius: 2.5 cm.
- Axial Length chosen: 1 meter
- Use stainless steel ribbon between layers of HTS tape.
- We will vary the thickness of the SS ribbon.
- The SS ribbon provides additional tensile strength
- HTS tape has 300 MPa max tensile strength.
- SS-316 ribbon: choose 660 MPa (Goodfellow range for strength is 460-860 MPa)
- Composite strength = SS SS +  (1-SS) HTS (adds like parallel springs).
- We use the Jeff associated to 40 Tesla.
- We operate at 85% of the critical current.
- All parameters used come from American Superconductor’s Spec Sheets.

- S. Kahn--Proposal for a 50 T HTS Solenoid

- March 14, 2006

## Case 3: Constraining Each Layer With A Stainless Steel Strip

- Instead of constraining the forces as a single outer shell where the radial forces build up to the compressive strain limit, we can put a mini-shell with each layer.  Suggested by R. Palmer, but actually implemented previously by BNL’s Magnet Division for RIA magnet.  (See photo)

- S. Kahn--Proposal for a 50 T HTS Solenoid

- March 14, 2006

## Case 3: Using Stainless Steel Interlayer

- The figure shows tensile as a function of the radial position for the cases of 1.5 and 2 mil stainless steel interleaving tape which will take some of the stress.  These stresses are calculated for a 40 Tesla solenoid!
- The effective modulus for the HTS/SS combination increases with increased SS fraction:
- 90 GPa for no SS
- 96 GPa for 1.5 mil SS
- 98 GPa for 2 mil SS
- 101 GPa for 3 mil SS
- 104 GPa for 4 mil SS
- 110 GPa for 5 mil SS
- The maximum strain limit for this material is 0.35%.
- With 4 mil Stainless Steel we have achieved 40 Tesla!

- S. Kahn--Proposal for a 50 T HTS Solenoid

- March 14, 2006

## 40 Tesla Solenoid Parameters When Varying the Stainless Steel Fraction

- S. Kahn--Proposal for a 50 T HTS Solenoid

- March 14, 2006

## A Slightly More Aggressive Approach

- Bob Palmer has suggested that we can vary the amount of stainless steel interleafing as a function of radius.
- At small radius where we have smaller stress, we could use a smaller fraction of stainless steel.  (See previous slide)
- In the middle radial region we would use more stainless where the tensile strength is largest.
- Following this approach Bob finds that he can build a 60 Tesla solenoid.  (We need to check this but it seems plausible).
- I was only able to achieve 50 T.
- A 60 Tesla solenoid will require significantly more HTS and will consequently cost more.

- S. Kahn--Proposal for a 50 T HTS Solenoid

- March 14, 2006

## Case 4b: Naively Increasing The Field to 50 T

- S. Kahn--Proposal for a 50 T HTS Solenoid

- March 14, 2006

## Case 5: Vary SS Thickness to Achieve 50 T

- HTS Length: 7.27105 m
- HTS Cost: M$ 14.6

- S. Kahn--Proposal for a 50 T HTS Solenoid

- March 14, 2006

## Case 5: Varying SS Thickness in Different Radial Regions to Achieve 50 Tesla

- S. Kahn--Proposal for a 50 T HTS Solenoid

- March 14, 2006

## R&D Issues Associated with HTS

- Mechanical Fatigue performance is good:
- For strain <0.1% Ncycles>1.5105 observed
- For strain 0f 0.26% Ncycles4000 have been observed
- There are *thermal cycling *issues that have been observed.
- Figure shows degradation with cycling between LN2 and RT.
- ASC has solution (next transparency)

- S. Kahn--Proposal for a 50 T HTS Solenoid

- March 14, 2006

## Special HTS Solutions for Special Problems

- Nominal High Strength Wire used in our study

- Special Reasonably High Strength Wire that prevents cryogens from contact with conductor

- Good for Leads?

- We may need to use up some of our Je contingency by using Hermetic Wire to address thermal cycling issue

- S. Kahn--Proposal for a 50 T HTS Solenoid

- March 14, 2006

## Possible Phase 1 R&D Program

- Measure the current carried by HTS at 4.2°K and under tensile strain.
- This measurement would be performed at a number of strain points up to and beyond the recommended tensile strain limit of 0.35-0.45%.
- This could be done at self field.
- Measure the current carried at the HTS at 4.2°K and under 0.35% tensile strain and thermal cycle the conductor ~10 times.
- This could be done at self field.
- Wind a small number of test coils with the new *high strength plus* HTS conductor both with and without the stainless steel interleaving.
- The dimensions should be chosen to fit into existing test solenoids:
- 11 Tesla available at BNL
- 15 Tesla available at FNAL
- 45 Tesla available at NHFML in Florida.  (This may need to be done in phase II.

- S. Kahn--Proposal for a 50 T HTS Solenoid

- March 14, 2006

## Conclusions

- Commercially available HTS appears to make very high field solenoid magnets viable.
- These very high field magnets can permit the necessary muon phase space cooling to once again think about muon colliders.

- S. Kahn--Proposal for a 50 T HTS Solenoid

- March 14, 2006