The Need for Electron Cooling for ELENA Electron
- Slides: 10
The Need for Electron Cooling for ELENA • Electron cooling essential in ELENA to counter emittance blow-up caused by the deceleration process. • To prepare bunches with sufficiently low emittance for extraction to the experiments via the electrostatic extraction lines. • Cooling needed at 2 momenta: 35 Me. V/c and 13. 7 Me. V/c. • Expected emittances prior to cooling: @ 35 Mev/c: ε ~ 50 π mm mrad (Δp/p) = ± 2 × 10 -3 • Required emittances at extraction: ε ~ 3 π mm mrad (Δp/p) = ± 1 × 10 -3
§ Operate at very low electron energies (down to 55 e. V). § Operate at very low magnetic field to minimize disturbance to circulating low energy antiprotons – we have chosen 100 Gauss in the cooler. § Compact design to fit in short straight section. § Have extremely good vacuum. § Adiabatic expansion to reduce transverse temperatures. § Very good field quality – especially in the cooler solenoid (B /Bǁ < 5 × 10 -4 ). § Orbit correctors and solenoid compensators.
Electron Cooler Parameters Momentum (Me. V/c) 35 13. 7 b 0. 037 0. 015 Electron beam energy (e. V) 355 55 Electron current (m. A) 5 2 Electron beam density (m-3) 1. 38 x 1012 1. 41 x 1012 Bgun (G) 1000 Bdrift (G) 100 Expansion factor 10 Cathode radius (mm) 8 Electron beam radius (mm) 25 Twiss parameters (m) bh=2. 103, bv=2. 186, D=1. 498
Expected Cooling Performance • Betacool (A. Smirnov et al. ) – Code for long term beam dynamics simulation. • http: //betacool. jinr. ru • Model Beam Ion beam is represented by an array of model particles and each effect calculates a kick of the ion momentum components and changes the particle number • Results to be treated with caution, but gives an idea if we can actually cool the beam and what are the electron beam parameters.
Cooling @ 35 Me. V/c • • Initial beam parameters: eh, v = 50 p mm mrad, DP/P = ± 2 x 10 -3 Required parameters for deceleration obtained after 7 seconds
Cooling @ 13. 7 Me. V/c • • Initial beam parameters: eh, v = 15 p mm mrad, DP/P = ± 1 x 10 -3 Required parameters for extraction obtained in less than 2 seconds
Integration in ELENA expansion solenoid electron gun solenoids 90 degree toroids Beam position monitors collector
Where are we today? The magnet system will be built in European industry Market survey made in March 2014 Invitation to tender issued in July 2014 Company selected in November 2014 Contract signed with TESLA, UK in December 2014 Vacuum/mechanical systems designed and built at CERN EN-MME has produced the specification drawings Production drawings to follow Finalising the pick-up design Orbit correction scheme still to be decided 15 months for magnet design, production, measurement & delivery In parallel build the vacuum system at CERN Installation Q 2 2016.
