# Presentation: 768304

## Recent work on 750 - x 750 GeV Collider

- C. Johnstone and P. Snopok
- Fermilab and UC Riverside
- M. Berz
- MSU
- MCD Workshop
- BNL
- Dec 3-7, 2007

##  Current Design Overview

- 750 GeV
- Arc: FMC module ~5.3T dipole fields:
- Fits ~circumference, surrounds present Tevatron tunnel
- Direct piping  of existing electrical, water, cryo services
- Negative momentum compaction
- Can be isochronous up to 3rd order in 
- Peak beta functions are half of equivalent FODO cell
- 40% smaller beam size in arcs
- Lower fields allow potential for increased collider energy
- Potentially up to 1 x 1 TeV
- IR straight design:  currently *=1cm
- IR quads ~10T
- 6m IP to first quad spacing for detector
- Non-zero dispersion derivative at IP (D=0 @IP)
- Allows immediate linear chromatic correction

##  Magnetic components:

- Magnets, in particular SC arc magnets, will resemble design in feasibility I study – see figures below

- Dipole (left) and cryostat design (right) for arcs of SR racetrack: Feasibility I Study

## Site Considerations

- Depth
- Water tables
- Geological constraints for tunnel construction
- Civil engineering for tunnels “hundreds of meters” deep

## Example: Fermilab Site-specific constraints:  from Feas. I Study for a U.S. Neutrino Factory

- 50 GeV Fermilab Storage Ring:  racetrack
- 13 declination angle
- circumference, C = 1753 m
- 39% ratio (1 prod str./C)
- Design predicated on ~6T SC arc dipoles

| 600 | Feet | Ring Vertical Drop |
| --- | --- | --- |
| 10 | Feet | Tunnel ceiling to floor |
| 10  | Feet | Shielding above ring |
| 50  | Feet | Undisturbed bottom layer of Galena Platteville |
| 10 | Feet | For uncertainties in the above three numbers |
| 680 | Feet | Total  from Surface to Bottom of Galena Platteville |

## Example: BNL site specific constraints:from Feas. II study for a U.S. Neutrino Factory

- 20 GeV BNL Storage Ring: racetrack
- 10 declination angle
- C = 358 m
- 35% ratio
- Design predicated on ~7T SC arc dipoles- (hence the short circumference achieved at 20 GeV)

## General limitations

- Site depth and civil engineering:
- Fermilab and BNL have depth constraints, for example; the larger of the two, restricted to <200m down.
- Municipal water supply + substrate will not support tunnel.
- The NUMI project at Fermilab entailed considerable civil engineering for an ~1 km long tunnel only 100 m deep – (won the 2005 civil engineering award)
- Maintenance, water leaks are a problem even with the NUMI depth (muons are much nicer, however, from an activation standpoint)

## Ring Structures: IR + High – order correction insertion

## Ring Structures: FMC Arc module

## Ring Structures: General Information

- IR: final focus + aberration correction section:
- Relatively compact: ~425 m
- Peak Beta function ~43 km
- Linear chromaticity ~-500 to -700
- Arcs
- Flexible Momentum compaction, ~70 m long
- Momentum compaction corrected up to 3rd order
- Peak beta function, ~110 m
- Scraping and utility section
- Presently a simple representative R matrix
- Ring
- ~ 1 km radius for 750 x 750 GeV
- 2-fold symmetric
- 64 arc modules

## Preliminary results with present lattice:

-  DA – rough MAD optimization: sextupoles only
- Chromatic and tune-shift sextupole familiesno
- Envelope ~50
- Resonance correction
-  very crude tune optimization
- Momentum acceptance:
- Linear chromaticity correction only
- +/- 0.05% dp/p
- Oide-like lattice (beta functions are huge ~106 m and chromaticity is all in one plane) have much larger momentum acceptances

## Present and Future Work

- Implementation in COSY  for high-order studies and correction
- Kinematical corrections are important!
- Cannot be done in MAD
- Field-map codes such as ZGOUBI have limited optimization tools
- Tune optimiztion
- Tune sweep is automatically performed in COSY using a simple R matrix to jump fractional tune (preserves match to all optical functions)
- High-order correction
- Ocutpole families: DA was doubled using COSY to fit DA in 50 x 50 GeV collider
- Decapole – duo-decapole
- High-order chromatic correction
- 2nd order chromatic correction appears essential
- Final momentum compaction adjustment
- This is easy in FMC module – beta functions essentially do not change, dispersion change is small so re-matching is not a problem.
- Tracking with fringe fields – will be bad news

## Example: DA optimization in COSY using octupole families for 50 x 50 GeV collider

- Before:

- After:

- (x-x’):

- (y-y’):