# Presentation: 742541

## Model Quadrupoles

*DOE Review of the LHC Accelerator Research Program*
*June 19-20, 2008*
- Gian Luca Sabbi

_***BNL - FNAL - LBNL - SLAC***_

## Outline

- Technology Quads – TQ:
*Goals*
*Design*
*Model Magnet Program*
*Test Results & Analysis *
*Status and Next steps*
- High Gradient/Aperture Quads – HQ:
*Goals and R&D Issues*
*Coil and Structure Design*
*Progress toward start of fabrication*
*Status and next steps*

## Technology Quadrupoles (TQ)

***Technical objective: develop technology base for the Long Quadrupole***
-  Evaluation of conductor and cable performance
-  Development and optimization of coil fabrication procedures
-  Comparison of mechanical design concepts & support structures
***Magnet parameters:***
-  1 m length, 90 mm aperture, cos2 coil geometry
-  Maximum gradient 200-260 T/m, 10-13 T coil peak field
_**Goal**_**: predictable and reproducible performance***** *****above 200 T/m**
_***Two series of models, same coil design, different mechanical support***_***:***
-  TQC models: collar & stainless steel shell; low axial pre-load
-  TQS models: aluminum shell over iron yoke; high axial pre-load

## TQC and TQS Designs

-  Aluminum shell over iron yoke
-  Assembly with bladders and keys
-  Full preload after cool-down
-  Rods/plates for high axial pre-load

- TQC (Collar)

- TQS (Shell)

-  Stainless steel collars and skin
-  Control spacers to limit pre-load
-  Full pre-load at room temperature
-  End support plates, low pre-load

## TQ Conductor and Coils

-  TQ01: OST-MJR strand
-  TQ02: OST-RRP strand
-  27-strand, 10.05 mm width
-  Insulation: S-2 glass sleeve
-  Double-layer, cos2 coils
-  One wedge/octant

_**Winding & curing (FNAL - all coils)**_

_**Reaction & potting (LBNL - all coils)**_

## TQ Short Sample Limit

**MJR strand (TQ01 Models)**
- Jc = 1.9 kA/mm2
*(12 T, 4.2 K)*

**RRP strand (TQ02 models)**
- Jc = 2.7 kA/mm2
*(12 T, 4.2 K)*

| Magnet | Top [K] | Gss [T/m] | Iss [kA] |
| --- | --- | --- | --- |
| S01a,b,c | 4.4 | 216 | 12.1 |
|  | 1.9 | 234 | 13.2 |
| C01a (b) | 4.4 | 209 (201) | 12.6 (12.1) |
|  | 1.9 | 228 (218) | 13.7 (13.1) |

| Magnet | Top [K] | Gss [T/m] | Iss [kA] |
| --- | --- | --- | --- |
| S02a,b,c | 4.4 | 239 | 13.6 |
|  | 1.9 | 260 | 14.9 |
| C02a,e | 4.4 | 224 | 13.6 |
|  | 1.9 | 244 | 14.8 |

-  TQC iron yoke is located further away from the coil than TQS (SS collar)
*- Causes shallower load line, lower short sample gradient *
-  From TQC01b, iron yoke was extended above the ends for mechanical reasons
*- End peak field increase causes further loss of short sample gradient *

*Same fraction of short sample results in ~6% lower gradient for TQC than TQS*

## TQC Tests

| Magnet | Conductor | Coils | Island | Temperature | Test |
| --- | --- | --- | --- | --- | --- |
| TQC01a | MJR | 9,10,12,13 | Bronze | 4.4 K & 1.9K | August 2006
FNAL |
| TQC01b | MJR | 7,8,10,12 | Bronze | 4.4 K & 1.9K | August 2007
FNAL |
| TQC02e | RRP | 20, 21, 22, 23 | Titanium | 4.4 K & 1.9 K | October 2007
FNAL |
| TQC02a | RRP | 17, 19, 24, 27 | Bronze | 4.4 K & 1.9 K | January 2008
FNAL |

- New models & virgin coils are in **bold font. **Rebuilt models & pre-trained coils are in *italic font.*** **

## TQS Tests

| Magnet | Conductor | Coils | Island | Temperature | Test |
| --- | --- | --- | --- | --- | --- |
| TQS01a | MJR | 5, 6, 7, 8 | Bronze | 4.4 K | April 2006
LBNL |
| TQS01b | MJR | 14, 15, 7, 8 | Bronze | 4.4 K | Nov. 2006
LBNL |
| TQS01c | MJR | 5, 15, 7, 8 | Bronze | 4.4 K & 1.9 K | March 2007
FNAL |
| TQS02a | RRP | 20, 21, 22, 23 | Titanium | 4.4 K & 1.9 K | June 2007
FNAL |
| TQS02b | RRP | 22, 23, 28, 29 | Titanium | 4.4 K & 1.9 K | March 2008
CERN |
| TQS02c | RRP | 22, 23, 28, 20 | Titanium | 4.4 K & 1.9 K | June 2008
CERN |

- New models & virgin coils are in **bold font. **Rebuilt models & pre-trained coils are in *italic font.*** **

## Performance Expectations

- TQ02 models should perform better than TQ01 models
* **Experimental feedback, optimization of design and procedures*
* **RRP conductor has much higher critical current than MJR*
- Revised models should perform better than new models
* **Use best coils from previous tests*
* **Optimized pre-loading conditions*
- Revised models with no new coils should have faster training
-  *Nb**3**Sn coils retain their training*
- Performance at 1.9K should be better than at 4.4K

- Significant departures from these expected trends in some of the tests

## Quench Training (New Models)

*Ramp rate, intermediate temperature and spurious (system triggered) quenches are not included*

## Quench Training (Rebuilt Models)

*Ramp rate, intermediate temperature and spurious (system triggered) quenches are not included*

##  TQ Quench Performance Summary

| Model | First Training at 4.4K |  |  | First Training at 1.9K |  |  | Highest Quench* |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
|  | GStart
(T/m) | GMax 
(T/m) | Gmax/Gss
(%) | GStart
(T/m) | GMax 
(T/m) | Gmax/Gss
(%) | GMax 
(T/m) | GMax quench
conditions |
| TQC01a | 131 | 154 | 74 | 151 | 196 | 86 | 200 | 1.9K, 100A/s |
| TQC01b | 142 | 177 | 88 | 179 | 200 | 92 | 200 | 1.9K |
| TQC02E | 177 | 201 | 90 | 198 | 198 | 81 | 201 | 4.4K |
| TQC02a | 124 | 156 | 70 | 145 | 165 | 68 | 169 | 1.9K, 50 A/s |
| TQS01a | 180 | 193 | 89 | n/a | n/a | n/a | 200 | 3.2K |
| TQS01b | 168 | 182 | 84 | n/a | n/a | n/a | 182 | 4.4K |
| TQS01c | 159 | 176 | 81 | 176 | 191 | 82 | 191 | 1.9K |
| TQS02a | 182 | 219 | 92 | 214 | 221 | 85 | 222 | 2.2K |
| TQS02b | 190 | 200 | 84 | 196 | 205 | 79 | 205 | 1.9K |
| TQS02c | 216 | 222 | 93 | 205 | 209 | 80 | 222 | 4.4K |

*(*) Highest Quench value includes all Training, Ramp Rate & Intermediate Temperature Quenches*

## TQC Models Analysis

- _TQC01a_:
- Viability of collaring process demonstrated
- Low preload limited the quench plateau in TQC01a at 4.5K and resulted in outer layer mid-plane damage at 1.9K at the end of magnet test.
- _TQC01b_:
- Analysis incorporated plastic coil behavior, resulting in appropriate preload.
- Reached 88% of its short sample gradient at 4.5K and 92% at 1.9K.

- _TQC02E_:
- Coils re-used from TQS02a, collared without damage.
- Achieved 90% of its short sample gradient at 4.5K and 81% at 1.9K
- After disassembly, coils were re-used in TQS02b/c, with no indication of degradation during assembly, testing or disassembly of TQC structure.

## TQC Models Analysis (2)

- _TQC02a_:
- TQC02a was first collared in March 2007: results from strain gauges as well as collar deflection measurements were consistent with analysis.
- The magnet was re-assembled in November 2007 with increased preload during the collaring phase.
- The reassembled magnet included two new coils, replacing two that may have been damaged due to a misplaced mid-plane shim during the initial assembly.
- Limited quench plateau in the new coils indicates probable degradation during construction due to higher collaring preload and large increments during early collaring steps.
- Return to TQC01b preload parameters and additional early collaring steps in TQC02b will allow return to TQC02E/TQC01b performance or better.

## TQS Models Analysis

- _TQS01 (a,b,c)_:
-  Quenches originated at pole gaps, where high axial tension occurred
-  3D FEA+SG data guided the change from Bronze to Titanium poles
- _TQS02 (a,b,c)_:
- New Titanium poles eliminated pole-gap quenches
- All models used the same structure and loading conditions
- Performance limits in each model are in specific coils/locations:
-  TQS02a: limited by coil 21 at outer layer pole *(both 4.4K & 1.9K)*
-  TQS02b: limited by coil 29 at end of straight   *(both 4.4K & 1.9K)*
-  TQS02c: limited by coil 23 at inter-layer ramp *(both 4.4K & 1.9K)*
- All models used the same conductor and heat treat
- For TQS02b, weakness could be traced back to coil winding phase
- Ramp area limiting TQS02c is also problematic (geometry, handling)
- TQS02 models identified areas for improving coil design and fabrication

## TQ Summary

- _TQC_:
-  Incorporation of analysis using plastic coil behavior and new coil measurement techniques provide tools for control of preload
-  Collaring parameters and procedures established through model program
-  Although the maximum gradient reached by TQC models is lower than in TQS, it corresponds to a similar fraction of the short sample limit
-  TQS02a coils were not significantly degraded after collaring and de-collaring in the TQC structure

- _TQS_:
-  Demonstrated accurate, repeatable control of warm and cold pre-load
-  Delivered safe, fast assembly and disassembly for all 6 models
-  Training starts high and improves rapidly to maximum; no retraining
-  Reliable structure performance allows to identify conductor/coil issues
-  Selectively replaced coils to understand limits and improve coil quality
-  S02 models consistently surpassed the 200 T/m target at 4.4K & 1.9K
-  TQS02c never quenched below 200 T/m during 4.4K and 1.9K training

## TQ Next Steps

- TQS02: additional tests with modified loading conditions (e.g. end pre-load) will be performed at CERN
*Helene Felice (Toohig Fellow) is playing a key role in coordinating planning, testing and analysis with CERN*
- TQC02b: currently under construction at FNAL. It will be tested to understand conductor properties and verify refined collaring procedures
- Four new coils will be fabricated using 108/127 strand
-  Cable fabrication completed
-  Winding/reaction/potting before the end of the year
-  Plan to assemble first as a TQS then as a TQC

## QA and HQ Goals

_**QA**_**:**
- This series of ~4 m long quads will be **designed using the parameters and accelerator quality specifications of the Phase 1 NbTi quads** (except for length), to facilitate their evaluation for use in the LHC.  The goal is to **demonstrate large performance margins with respect to the NbTi quads**, on the timescale of the Phase-1 upgrade.
_**HQ**_**:**
- The HQ (High gradient/aperture Quad) series of short models will be **used to develop the design of the mechanical support structure and the coils of QA**.  The full set of **accelerator magnet features will be gradually incorporated** into successive magnets in this series.

- Representatives from each Lab coordinate the mechanical design features

## Phase 1 NbTi IR Quad Development

| Phase | Task | Start | Completion |
| --- | --- | --- | --- |
| Model | Tooling installation | 01/02/2008 | 01/02/2009 |
|  | Models construction | 01/09/2008 | 01/07/2009 |
| Prototype | Prototype and series tooling installation | 01/02/2008 | 01/01/2010 |
|  | Prototypes construction | 01/10/2009 | 01/09/2010 |

- Case 2: “normal grading”:
- Aperture: 120 mm
- Nb turn of cable 01/coil: 18
- Nb turn of cable 02/coil: 17
- SS gradient:  152.1 T/m

- Case 1: “special grading”:
- Aperture: 120 mm
- Nb turn of cable 1: 19
- Nb turn of cable 2: 19
- SS Gradient:  152.8 T/m

- _Magnet aperture_ will be defined in the conceptual design report (June 08)
-  Jan. 08: considering values between 90 and 140 mm
-  May 08: considering values between 110 and 120 mm

***P. Fessia, WAMSDO***

## HQ Design Space

## Optimized HQ Cross-Sections

## Coil Design Optimization

- Mechanical considerations are driving the HQ coil cross-section design

**TQS (1-meter):**
** **
- - 90 mm aperture
- - 12 T peak field
-  240 T/m
-  F Layer 1 = -1.5 MN/m
-  F Layer 2 = -1.02 MN/m

**LQS (3.6-meter):**
- - 90 mm aperture
- - 12 T peak field
-  240 T/m
-  F Layer 1 = -1.5 MN/m
-  F Layer 2 = -1.02 MN/m

**HQ (1-meter)**
- - 114 mm aperture
- - 15 T peak field
-  230 T/m
-  F Layer 1 = -2.5 MN/m
-  F Layer 2 = -2.99 MN/m

- Key optimization

- Xsection optimization

**20 MPa**

**20 MPa**

**20 MPa**

## Cable Prototypes and Test Winding

-  First pass: 8 cable samples made
-  End parts designed for prelim. cross-sections
-  Poles fabricated using rapid prototyping
-  Two turns wound with 30 lb of cable tension
-  Samples rated for winding characteristics
-  Cables also evaluated for critical current
-  Feedback to cable & cross-section design
-  Baseline cable selected, longer length made
-  Further optimization in the near future

## HQ Tooling

- Coil Winding

- Coil Curing

-  Conceptual design and CAD models completed, obtained quotes from vendors
-  Parametric spreadsheets to control coil build and relevant dimensions
-  Final drawings based on aperture determination, procurements will follow

## Mechanical Design Concept

| Coil Stress | Gnom=230 T/m | Gnom=200 T/m |
| --- | --- | --- |
| Pressurization | -77 / -32 MPa | -35 / -15 MPa |
| Key inserted | -83 / -18 MPa | -30 / -5 MPa |
| After cool-down | -176 / -15 MPa | -133 / 4 MPa |
| Excitation, Gnom | -177 / 20 MPa | -136 / 20 MPa |

- _Guidelines:_
- Full contact between pole and coil at short sample (200 – 230 T/m)
- Optimization of the mechanical stress in the coil during bladder operation: bladder location
- Optimization of the mechanical stress in the coil after cool-down and during excitation: key location
- Alignment with gradual implementation
- _Preliminary results_:
- Coil stresses can be maintained at safe levels up to the short sample limit

## Mechanical Assembly

## Model Magnet Budget

- FY08 budget:
-  Supported completion of TQC02a, TQC02e
-  No funding for TQS02b, TQS02c (supported by LBNL core program and CERN)
-  No funding for TQC02b (supported by FNAL core program)
-  Supported fabrication of 4 new TQ coils using 108/127 conductor
-  HQ funding directed toward magnet design, fabrication of tooling and coil parts
- FY09 preliminary proposal & cost estimate (under discussion):
-  Fabrication and test of the first HQ model: 1.8 M$
-  Start of coil fabrication for second HQ model: 0.4 M$
-  No funding for TQ (core program support)

## Slide 28

## Summary

_*TQ Models*_*:*
- The main TQ goal was achieved:
-  Surpassed 200 T/m with 10% margin
-  Consistent, reproducible results obtained in several models
*However, no convergence yet on structure evaluation and selection*
_*HQ models*_:
-  Goals and strategy for HQ and QA have been clearly defined
-  Planning to match the “Phase 1” short quadrupole development
-  Considerable progress in FY08 on magnet and tooling design
-  High field design is best suited to fully exploit Nb3Sn properties
-  Unique opportunity to qualify Nb3Sn magnets for use in LHC
-  *Significant support required to complete first model in Sept. 2009*