# Presentation: 934396

## DESIGN STUDIESIR Magnet Design

- P. Wanderer
- LARP Collaboration Meeting
- April 27, 2006

## Thanks ...

- Thanks to Paolo, Giorgio, and Vadim, who prepared summaries of their work and many of the following slides.

## Topics

- #1: Analysis and comparison of IRQ based on shell-type and block-type coils (Ferracin, Maura Monville + N. Mokhov)
- #2: Analysis of a 110-mm shell-type IR quads with different supporting structures (Ambrosio)

## Topics

- #3: Analysis of aperture and field quality limitations for double-bore IR Quads (Vadim Kashikhin)
- #4: Field quality analysis and error tables for Nb3Sn IRQ (Kashikhin, Zlobin)

## #1: Compare block, shell quads

- Status: For a reasonable set of IR quad requirements, a block quad was developed.  The mechanical and magnetic properties of this quad and a shell quad which met the same requirements have been compared.
- Next: Study response of these quads to IR radiation, iterate designs.

## Shell-type vs. block-type

- Previous work: V.V. Kashikhin, *et al.*, “2nd generation LHC IR quadrupoles based on Nb3Sn racetrack coils”, *EPAC 2004.*

## Upgrade scenario*

- Phase 1:  increase of luminosity with hardware changes only in the interaction regions
*β*** **= *0.25 m
- σ = 2.185 mm
- Dtrip = 78.5 mm
-  77 mm (T. Sen, *et al.*, 2001)
-  Increase the triplet magnet diameter
-  Same gradient
- Gnominal ~ 200 T/m
- Gshort sample ~ 250 T/m
- L = 4 - 5 x 1034 cm-2s-1
- *O. Bruning, *et al.*, “LHC luminosity and energy upgrade: a feasibility study”, ***LHC Project Report*** 626 (2002)

## Coil aperture and beam envelope

- Dtrip = 78.5 mm

- 80mm

- 105mm

## Magnetic design: gradient and field quality

- TQ-v1 cable (27 strands)
- Jc = 3000 A/mm2
- 1.9 K
- Harmonics < 0.05 at Rref

|  | Inner | Outer |
| --- | --- | --- |
| Iss [kA] | 13.3 |  |
| N turns | 26 | 37 |
| Bss [T] | 13.9 | 13.3 |
| Gss [T/m] | 251 |  |
| SC area [cm2] | 52 |  |

## Mechanical design: support structure

- Aluminum shell
- Iron yokes
- Stainless steel pad
- Stainless steel poles
- Stainless steel mid-plane spacers
- Aluminum bore

## Mechanical analysis: coil and bore stresses

- Coil stress < 170 MPa

- Bore stress < 150 MPa (293 K, 4.3 K and excitation)

## #2: Study of different support structures in quads

- 110 mm aperture, shell-type, 228 T/m.
- Generic structures for high forces
- Not specific to a particular coil
- Two types of coil arrangements:
- Four layers, all glued together (complete)
- Four layers, glued together in pairs (now starting)

## Structure for 4 layers as 1

- Needs & solutions:
- Very rigid structure  ss collars + (ss skin or Al skin with bladders & keys)
- Extra coil support at midplane  collar-yoke support only at midplane
- Yoke open when warm
- Stresses < 150 MPa under all conditions  dummy cable at midplane of outer coil

## Best solution up to now

- Yoke with gap at 45 deg.
- Open @ 300 K
- Closed at 4.2 K
- Closed at 228 T/m
- Gap control spacers
- 15 mm SS collar ring
- Collar-Yoke contact 0-6 deg.
- Outer shell:
- 15 mm SS skin or
- 30 mm Al (bladders & keys)

## #3: Study double-bore quads

- Quads for dipole-first optics
- Two cases:  warm and cold iron
- 100 mm aperture, 205 T/m
- 194 mm beam separation
- Determine dynamic aperture (10-4 FQ)
- Achieving good FQ a challenge
- Correctors = LHC baseline
- Results presented April 19.

## Warm yoke design

**Maximizing the aperture at the fixed nominal gradient and the beam separation distance brings the adjacent coils close to each other;**
**There is not enough space for a ferromagnetic screen of sufficient thickness to individually shield each coil and avoid mutual influence;**
**In the “warm” yoke design the ferromagnetic part was removed from the cold mass and the coils are of an unusual asymmetric type to achieve a good field quality.**

## Cold yoke design

**It is possible to bring the iron closer to the coils in the “cold” yoke design that increases the gradient and eliminates the eccentricity forces between the coils and the yoke;**
**The yoke inner surface has to be optimized simultaneously with the coil geometry to achieve good geometrical field quality and correct the yoke saturation effect;**
**The coils are still asymmetric, but the degree of asymmetry is lower than in the “warm” yoke design;**
**The coil aperture limit is ****100 mm**** for both designs.**

## Geometrical harmonics @half-aperture radius

**Field quality**

| Harmonic | IRQ design |  |
| --- | --- | --- |
|  | Warm yoke | Cold yoke |
| b1 | 0.0002 | -0.0005 |
| b3 | 0.0001 | 0.0005 |
| b4 | 0.0001 | 0.0042 |
| b5 | -0.0070 | -0.0049 |
| b6 | 0.0014 | -0.0305 |
| b7 | 0.0130 | -0.0151 |
| b8 | -0.0013  | 0.0996 |
| b9 | -0.1016 | 0.0212 |
| b10 | 0.1797 | 0.3404 |

- LHC has correctors for b3, b4, and b6.

## 2-in-1 quad good field region

- Green: 27 mm radius beam envelope
- Red: warm yoke, 10-4 FQ
- Blue:  cold yoke, 10-4 FQ

## Comparison

- MQXB beam envelope (2x9) = 40 mm
- MQXB FQ (measured) at 40 mm = 10-4
- 2-in-1 quads 10-4 region = 54 mm
- LARP beam envelope (1.1x18) = 70(60) mm
- LARP beam envelope (18) = 64(54) mm

##  #4: Error tables

- Error tables will combine calculated and measured errors from magnets of different radii.
- Status:  underway.  There are more magnets to measure this FY, so the database is still being expanded.