# Presentation: 157398

## TQC Mechanical Design Overview 

***bnl - fnal- lbnl - slac***

_**US LHC Accelerator Research Program**_

- A. Zlobin, Fermilab

## Outlines

- This talk introduces basic features of collar based mechanical structure used for LARP TQC series and provide answers on some review questions formulated in review charge and in document called “Criteria for LQMSR v.5”.
- The details and other specific questions will be addressed in the following presentations on TQC mechanical structure:
- TQC mechanics, coil pre-stress and support - Igor Novitski
- TQC mechanical structure, assembly procedure and production quality control - Rodger Bossert
- TQC structure scale up - Fred Nobrega
- TQC performance - Mike Lamm

## TQC Magnetic Design and Parameters

- LARP Technology quadrupole (TQC):
- 90-mm diameter bore
- Design gradient Gmax~230/250 T/m at 4.5/1.9 K (Bmax~12-13 T)
- 0.7-mm Nb3Sn strand
- 27 strand cable
- 2-layer coil
- Cold 400-mm iron yoke
- Above parameters are consistent with the LQ target parameters.
- 2D and 3D magnetic analysis has been done (LQ design report)
- Bmax in coil outer layer end
- TQC and TQS maximum gradients are slightly different due to larger iron inner radius.

## TQC structure – cross section

- TQC coil support structure is based on the MQXB collar based design:
- Stainless steel collar blocks
- Two piece iron yoke
- Thick welded stainless steel skin
- Iron OD and ID, collar OD and ID are the same for MQXB and TQC

**MQXB**

**TQC**

## TQC Mechanical Structure – End support

- TQC cold mass end design is also similar to MQXB:
- thick stainless steel plates each with 4 bullets to reduce coil end motion under the Lorentz force in the axial direction.
- magnet ends are in contact with the bullets during all phases of cool-down and operation.

## TQC Structure specific features

**TQC Structure specific features**

- Based on structural analysis, MQXB structure have been modified to meet TQ performance requirements:
- Round collar - to accommodate Nb3Sn coils with glued poles.
- Midplane collar/yoke shims – to control interference to transfer radial Lorentz force to the iron yoke and skin, and for additional coil preload from skin.
- A radial cut in each yoke quadrant - more symmetrical iron properties.
- Control spacers –  to control collar/yoke alignment and interference, and increase structure radial rigidity.
- 12 mm thick stainless steel skin - to increase structure radial and longitudinal rigidity.

##  Coil target pre-stress

** ****Coil target pre-stress**

**Collared coil at 300K**

**Completed magnet at 300K**

**Magnet at 1.9K**

**Magnet at Gmax~240T/m**

- Lorentz forces: azimuthal, radial, axial
- Material properties are temperature dependent
- Boundary conditions:
- Coil peak stress <150 MPa at all conditions
- Tension at the pole 0 or less than 20 MPa on all elements
- 2D and 3D ANSYS analysis
- TQC mechanical concept
- _provide_ sufficient (120-140 MPa) and acceptable (<150 MPa) azimuthal stress for Nb3Sn coil at 300K and _preserve_ it during operation at 1.9K.
- Coil end support (not pre-load) at all temperatures.

## Magnet Assembly Issues

- TQC model magnet R&D program performed in FY05-07 addressed the following magnet assembly issues:
- Coil measuring and shimming
- 4 coil handling, assembly and ground insulation
**Collaring - capability to deliver safely the required high prestress at room temperature using partial collaring procedure**
- pre-stress control
- Collared coil OD measurement, strain gauges
- Collared coil handling, shimming, yoking and skinning
- Yoke ID measurement
- Skin welding
- bolted skin vs. welded skin
- End plate installation, splicing, bullet pre-load
- Cold mass electrical and magnetic measurements
- Transportation
- The mechanical concept and process have been developed using several mechanical models and 3 short quadrupole models - TQC01a, TQC01b and TQC02E.

## TQC structure performance demonstration

- Nb3Sn is brittle material. Final evaluation of magnet design and fabrication procedures requires model cold test.
- Test program includes:
- 4.5 K quench performance (short sample current/gradient, achieved current/gradient, percentage of SSL, training, ramp rate, quench origin)
- 1.9 K quench performance (short sample current/gradient, achieved current/gradient, percentage of SSL, training, ramp rate, quench origin)
- Mechanical measurements
- Magnetic measurements
- Quench heater test
- Coil RRR measurement
- Splice measurement
- Performance evaluation includes:
- Comparison of magnet assembly and test data with design parameters.
- Comparison models of TQC and TQS series.

## TQC Quench Performance

- 3 TQC models were tested:
- TQC01a/b, low Jc MJR strand
- TQC02E, high-Jc RRP strand
- TQC01 (MJR) models:
- Gmax~200 T/m at 1.9K
- degradation at 4.5 and 1.9K
- TQC02E (RRP) model:
- Gmax~200 T/m at 4.5K
- Limited performance at both 4.5K and 1.9K

- Field gradient of 200 T/m has been achieved with TQC structure in all 3 models.
- Open questions – limited quench performance at 4.5 and 1.9 K, correlation with conductor and mechanical structure.

## TQC Structure Length Scale Up

- TQC structure is totally compatible with the LARP length scale up goals and requirements
- MQXB experience.
- Scale up issues to be addressed:
*Long coil handling, measuring and shimming* - LM
- 4 coil handling, assembly and ground insulation
- Coil alignment inside collar (possibilities for LQ2) – TQC02b
- Collaring and handling
- Collared coil OD measurement and pre-stress control
- Collared coil warm magnetic measurements
- Yoke ID measurement
- Collared coil shimming, yoking and skinning
*Skin welding* (issues for long skin) - LM
- End plates welding, splicing, bullet pre-load
*Transportation *- LM
*Cold test* - LM
- Positive experience from long mirrors (LM) which use similar yoking and skinning procedures, and the same fabrication and test infrastructure.

## Relevance to and Scalability toward HQ/QA/QB

- Possibility of adopting the same concept for accelerator magnets with larger aperture and higher forces:
-   Prestress level ~150 MPa at the operation temperature, high structure rigidity
- Up to 100% can be provided during collaring at room temperature
- - HGQ experience with 30 mm coil
- High radial rigidity provided by SS collar, yoke stoppers and skin_** **_

## Summary

- 3 1-m long quadrupole models of TQC series have been fabricated and tested.
- The target field gradient of 200 T/m was reached in all 3 TQC models.
- The possibility of traditional collar-based structure and assembly procedure for Nb3Sn quadrupole coils was successfully proven.
- Possibility of adopting the same concept for accelerator magnets with larger aperture and higher forces was also demonstrated.
- Open questions:
- limited quench performance at 4.5 and 1.9 K
- correlation with conductor properties and mechanical structure
- TQC02 with virgin coils will address conductor degradation issue in TQC structure (December 2007, LARP and Fermilab core program)
- TQC03 with RRP 114/127 strand will address conductor stability issues (June-July 2008, Fermilab core program)
- TQC structure is ready to be used for LQ – no change is expected.
- The scale up issues for LQ based on TQC structure have been identified
- Some positive experience have been achieved by testing a 2-m and 4-m long Nb3Sn dipole coils in a mirror configuration (Fermilab core program).