1. Slide 1 Overview Introduction Stochastic Cooling History of the Antiproton machines at CERN The AD and ELENA Conclusion

2. Introductory Remarks CERN’s flagship project is the LHC; BUT – In 2010 AD hit the media headlines with the capture of anti- hydrogen – In 2011 neutrino ToF?? Today is an important day for antiproton physics at CERN Antiproton beams became very important tools for particle physics, when it was shown that they could be “cooled”. ELENA (Extra Low ENergy Antiporoton Ring) will be a natural prolongation of the AD (already a highly regarded research facility) Some historical facts Slide 2

3. Stochastic Cooling at ISR (1975)

4. Slide 4 1977 Stochastic cooling demonstrated for the first time at CERN in the ICE (Initial Cooling Experiment) and electron cooling tested as well. Stochastic Cooling

5. Slide 5 By November 1979 the installation of the AA (Antiproton Accumulator) was well under way and commissioning began in June 1980. First observation of weak interacting boson in 1984 (Nobel prizes) in SPPS.

6. Slide 6 In the South Hall the LEAR (Low Energy Antiproton Ring) was ready to decelerate particles by 1982.

7. Slide 7 1987, to increase the antiproton production the AC was built around the AA to collect more antiprotons from the target.

8. Slide 8 Some LEAR highlights: – First machine to decelerate antimatter with a combination of stochastic and electron cooling – Ultra slow extraction (1hr @ 100 MeV/c to 15 hrs @ higher momenta) – Up to 3 experiments simultaneously – First Antihydrogen atoms created in 1995 – Around 1995 decision to discontinue the LEAR operation and to study the simplified low energy antiproton scheme (AD).

9. Slide 9 1999 commissioning of the AD machine.

10. AD Ring and Hall Target Area: 26 GeV/c protons -> 3.57 GeV/c pbars, yield ~ 4 10 -6 Protons via loop (TTL2) 4 arcs: chromaticity correction, dispersion suppression Stoch. Cooling kicker Stoch. Cooling pick-up 4 dispersion free straight sections: S-cool, E-cool, RF, diagnostics Experimental Area Electron Cooling

11. ELENA and AD Slide 11

12. 12 Motivation to build ELENA Most of AD experiments need antiprotons of 3 keV to 5 keV kinetic energy inside the trap, AD produces them at 5.3 MeV. How antiprotons are decelerated today by experiments: Antihydrogen experiments (ALPHA and ATRAP) use set of degraders to slow 5.3 MeV beam from AD further down Poor efficiency due to adiabatic blow up of beam emittances and scattering in degraders, less than 0.1 % of AD beam is used. For ASACUSA, RFQD is used for antiproton deceleration down to around 100 keV kinetic energy. The deceleration is accompanied by adiabatic blow up (factor 7 in each plane) which causes significant reduction in trapping efficiency and in addition to that, RFQD is very sensitive to trajectory and optics mismatch errors About 70% beam is lost after passing through RFQD (transverse beam size too big) about 3-5% of antiprotons are captured after passing through degrader.

13. Gain in intensity with extra deceleration and cooling Deceleration of the antiproton beam in a small ring down to 100 keV with electron cooling increases the beam density. Emittances of beam passing through a degrader will be much smaller due to the use of the thinner degrader (100 keV beam instead of 5.3 MeV) => a gain of a factor 100 in intensity is expected for ALPHA, ATRAP and AEGIS. Because of the cooling, beam emittances after deceleration in ELENA will be much smaller than after RFQD => a gain of a factor 10 in intensity is expected for ASACUSA 13

14. Summary ELENA has been approved as a CERN project Which means that we now have to build it and make it work as a successful facility for this important research at low energy. ELENA will begin a new era for antiproton physics for many years to come CERN is now engaged at two extreme fronts of particle physics, the very high and the very low energy side. Thanks to everyone for making this project such a success. Slide 14