# Presentation: 333459

## LHC IR Upgrade Post Lumi 06  Valencia Workshop 16-20 October 2006

-  Tanaji Sen

- T. Sen: LHC IR Upgrade

- LARP Meeting - 11/08/06

## IR Optics Themes

- Quads First optics
-   - Large aperture Nb3Sn (LARP)
-   - Low gradient, larger aperture NbTi (CERN-AB)
-   - Early separation with D0 dipole (CERN-AT)
-   -  Early focusing with Q0 doublet (CERN-AT)
- Dipoles First optics
-   - Triplet and doublet focusing (LARP)
-   - Triplet focusing (CERN)
-  Reducing L* - Luminosity gains and detector constraints

- T. Sen: LHC IR Upgrade

- LARP Meeting - 11/08/06

## Luminosity gain - reducing L*

-  Gains are limited if crossing angle has to scale as 1/√β*
-  Crossing angle needs to be reduced for significant gains

- T. Sen: LHC IR Upgrade

- LARP Meeting - 11/08/06

## Early separation – D0

- D0

- D0

- Triplet

- Triplet

- D1

- D1

-  Early separation dipoles D0 placed inside the detector
-  Beams collide with no crossing angle (D0 less than 3.75m from IP) or
-  with a small crossing angle (D0 more than 3.75m from the IP).
-  Luminosity loss due to crossing angle much smaller

- Issues
-  Integrating the dipoles into the
-     detectors CMS and ATLAS
-  Energy deposition in the detectors
-  Impact of a few parasitics at small
-     separations (< 4 σ)
-   Choice of magnet technology:
-      NbTi or Nb3Sn (shorter)

- IP

- T. Sen: LHC IR Upgrade

- LARP Meeting - 11/08/06

##  Early Focusing – Q0

- Q0A/B are slim (~40mm) NbTi quads,  B’~165T/m
- NbTi Triplet
- βmax with β* = 0.25m is the same as with β* = 0.55m
- Issues
- Integration into detectors
- Alignment sensitivity
- Energy deposition
- Luminosity gain

- Q0A

- Q0B

- Q1

- L*=13m

- IP

- 0.25m

- 0.55m

- T. Sen: LHC IR Upgrade

- LARP Meeting - 11/08/06

## Quads 1st vs Dipoles 1st 

|  | Quads 1st  | Dipoles 1st  |
| --- | --- | --- |
|  Lowest β* at L* = 19.5m |  0.22 | 0.23 |
| Lumi gain: L*=19m vs L*=23m | 1.04 – 1.15 | 1.02 – 1.09 |
|      L* = 23m |  |  |
| βMax [m] at β* = 0.25m |  9484 |  26092 |
| Max aperture [mm] |  101 |  107 |
| Max pole tip field [T] |  10.1 | 10.7 |
|  Q’ of ring |   -200, -194 |  -333, -340 |
| Max 3rd order bb resonance |  0.9 x 10-3 |  0.5 x 10-3 |
| Max 10th order bb resonance |  0.16 x 10-3  |  0.3 x 10-5 |
| Beam-beam diffusion | Jump at 7 | Jump at 8 |
| Max Energy Deposition in quads [mW/g] | ~ 1.0 | ~ 0.6 |

- T. Sen: LHC IR Upgrade

- LARP Meeting - 11/08/06

##  Summary of Options

- Quads first options
-    1) Baseline with Nb3Sn quads, perhaps at smaller L*
-    Pros: Experience gained during 1st phase, easier to commission (?)
-    Cons: Limited luminosity gain without additional measures
-   2) D0 dipole inside detector & Nb3Sn triplet
-    Pros: Larger gain in luminosity, reduces crossing angle
-    Cons: Integration with detector, energy deposition (?)
-   3) Quad doublet (NbTi) inside detector & NbTi triplet
-   Pros: Proven NbTi technology, smaller βmax in triplet
-   Cons: Integration in detector, limited luminosity gain, very sensitive to alignment
- Dipoles first optics
-    Pros: weaker beam-beam effects, lower energy deposition in triplets
-    Cons:
-     - Requires open mid-plane dipole D1 – no effort on this at present
-     - Much larger chromaticity
-     - Greater length of absorbers

- T. Sen: LHC IR Upgrade

- LARP Meeting - 11/08/06

##  Next Steps for LARP

-  I. Quads first options
-  - Optics variations with magnets inside detector
-  - L* dependence for all options – luminosity, beam-beam effects, chromaticity
-  - Energy deposition with magnets in detector
-  - Magnet parameters: apertures, gradients, field quality
-  II. Beam-beam compensation
-    - Wire compensation
-    - Electron-lens compensation
-  III. Dipoles first – wrap up studies
-  IV. Crab cavities with small crossing angle
-    Optics design with global crab cavities

- T. Sen: LHC IR Upgrade

- LARP Meeting - 11/08/06