# Presentation: 402150

## Electron Cooling in the Accumulator

- Dave McGinnis

## Install Electron Cooling in the Accumulator AP50 Pit

- A50 Straight Section was used for the E835 detector
- Straight section no longer used for anything
- Large pit beneath beam pipe (~4ft below floor level)
- Counting room no longer used
- AP50 Drop hatch available
- 15 meters of straight section between Q1’s
- Zero dispersion
- Lattice functions could be modified with Q1,Q2,Q3 settings

## Install Electron Cooling in the Accumulator AP50 Pit

- AP50
- Pit

## Install Electron Cooling in the Accumulator AP50 Pit

## Accumulator Momentum Aperture

- Accumulator Momentum Aperture measured to be 206 mm at A314 scraper (J. Morgan – 5/19/03)

## Accumulator Aperture with Electron Cooling

- Accumulator Aperture would be Divided into 3 Regions
- 208 mm required for 10-mm-mrad Aperture
- Injection Region
- Beam is injected from the Debuncher every 1.5 seconds
- The transverse beam size is 5-mm-mrad
- The momentum spread is 5 MeV
- The Stacktail Region is shielded from the injection kickers by shutters

- h=21m
- Dh=9m

- 10-mm-mrad
- Aperture
- (un-normalized)

## Accumulator Aperture with Electron Cooling

- Stacktail Region
- The beam is bunched with RF and decelerated from the injection orbit to the Stacktail deposition orbit
- The beam is stochastically stacked with a 4-8 GHz stacktail system and a 4-8 GHz Core system
- The Stacktail is shielded from the high density core in the electron cooling region by means of a shutter in the stochastic cooling pickup region.
- The beam is transversely cooled from 5 to 1 -mm-mrad with a stacktail betatron cooling
- The momentum aperture of the entire stacktail region is 43.5 MeV
- The stacktail system fills 10 eV-sec (6 MeV) every 55 minutes

- h=21m
- Dh=9m

- 10-mm-mrad
- Aperture
- (un-normalized)

## Stacktail Performance with an Input Flux of 90x1010 pbars/hr

## 4-8 GHz High Dispersion Pickups

## Accumulator Aperture with Electron Cooling

- Electron Cooling Region
- Once 10 eV-sec of the core is filled up:
- The Stacktail is gated off
- The shutter to electron cooling is opened
- The stochastic core is bunched and decelerated to the deposition orbit of the electron cooling region
- The electron cooling shutter is closed and stochastic stacking is restarted.
- Electron Cooling Rate – 11 eV-Sec/hr (6.8 MeV/hr)

## Advantages

- Machine circumference
- 7x smaller than Recycler
- No Rapid transfers
- No beam loss
- No transverse emittance dilution
- No longitudinal emittance dilution
- No waiting for transfer
- Electron cooler can be placed closer to ring
- 8 GeV beam only in Accumulator
- Shielding requirements much less
- Accelerator Performance
- Vacuum
- Ring Size
- Equipment
- Pumping speed
- Bakeout system
- Aperture
- No Main Injector ramps to contend with

## Disadvantages

- Stacktail Betatron cooling
- Cooling section length
- Recycler -> 20 meters
- Accumulator - > 12 meters
- Available longitudinal phase space

## Things to Do

- Come up with a physics design for 4-8 GHz Betatron Cooling – Derwent
- Verify 4-8 GHz stacktail envelope calculations with detailed Fokker-Plank Simulations – Derwent
- Determine how to modify beta functions in A50 Sector – Werkema
- Electron Cooling Calculations – Burov
- Come up with a design of 4-8 GHz Pickups – Sun,McGinnis
- Civil Construction Aspects – Harms
- Schedule – McGinnis, Nagaitsev