Low Energy Antiproton Facility at CERN Christian Carli

Low Energy Antiproton Facility at CERN Christian Carli on behalf of the AD and ELENA team …. with special thanks to P. Beloshitskii, T. Eriksson and S. Maury for help with the slides • • Brief History of Antiproton Machines at CERN Antiproton Decelerator (AD) Extremely Low ENergy Antiproton ring (ELENA) Summary

Brief History of Antiproton Machines at CERN Conversion of the SPS into a 1970’ies: n n collider (to become ) in the Conversion of a brand-new machine into a collider First proof of stochastic cooling (proposed several years earlier by S. van der Meer) in ISR ICE for systematic investigations on stochastic cooling and later on electron cooling (proposed by and proof of principle test at BINP) Construction of the Antiproton Accumulator AA with target area … AA commissioning in 1980 ¨ Discovery of the W bosons in 1984 in the ¨ 11 th October 2011 Low Energy Antiproton Facility C. Carli on behalf of the ELENA and AD team

Brief History of Antiproton Machines at CERN Construction and commissioning of the Low Energy Antiproton Ring LEAR n n n Additional facility making use of the p-bar accumulation complex Ultra-slow (and fast) ejection to experiments in south hall and internal targets Commissioning in 1982 with stochastic cooling First machine with electron cooler used for operation First observations of antihydrogen … First proposal to construct ELENA to decelerate to even lower energies (7. 85 m circumference to reach 200 ke. V !!) 11 th October 2011 Low Energy Antiproton Facility C. Carli on behalf of the ELENA and AD team

Brief History of Antiproton Machines at CERN Construction and commissioning of the Antiproton Collector AC n n n Motivation: increase of the p-bar accumulation rate to increase antiproton intensity in Additional ring with large acceptances to collect and (pre-)cool p-bars before transfer to the AA Commissioned in 1987 ➠ Elaborate complex and operation for antiprotons ¨ Linac + PSB + PS for p-bar generation ¨ Two rings AC + AA for accumulation ¨ LEIR with PS again required for transfer ¨ with PS again required as injector (until 1990? ) 11 th October 2011 Low Energy Antiproton Facility C. Carli on behalf of the ELENA and AD team

Brief History of Antiproton Machines at CERN AD Construction and commissioning n Around 1995: ¨ AC & AA running only for LEAR ¨ Decision to discontinue p-bar physics with LEIR (several machines and transfers involved … free resources for LHC) n Conversion of AC to AD proposed as simplified scheme for low energy p-bar physics ¨ Only one p-bar machine ¨ PS used only for p-bar production n Start of AD Commissioning in Autumn 1998 First physics run in summer 2000 n 11 th October 2011 Low Energy Antiproton Facility C. Carli on behalf of the ELENA and AD team

AD – Hall and Layout Stoch. Cooling kicker Protons via loop (TTL 2, not operational) Target Area: 26 Ge. V/c protons -> 3. 57 Ge. V/c pbars, yield ~ 4 -5 10 -6 4 dispersion free straight sections: S-cool, E-cool, RF, diagnostics 4 arcs: chromaticity correction, dispersion suppression Experimental Area Stoch. Cooling pick-up 11 th October 2011 Low Energy Antiproton Facility Electron Cooling C. Carli on behalf of the ELENA and AD team

AD – Main Parameters n n n Circumference 182 m Production beam 1. 5*1013 protons at 26 Ge. V Injected beam 5*107 pbars/cycle Beam momenta max-min 3. 57 – 0. 1 Ge. V/c Momenta for beam cooling: Stochastic ¨ Electron 3. 57 and 2. 0 Ge. V/c 0. 3 and 0. 1 Ge. V/c ¨ n Acceptances: Transverse ¨ Longitudinal ¨ n 200 (p) mm ± 30 10 -3 Ejected beam at 100 Me. V/c or 5. 3 Me. V: Intensity ~3 107 ¨ Transverse emittances 5 p mm (dense core ~1 p mm ) ¨ Momentum spread 1*10 -4 ¨ Bunch Length ~200 ns ¨ n n Vacuum pressure, average Cycle length 100 s 11 th October 2011 4*10 -10 Torr Low Energy Antiproton Facility C. Carli on behalf of the ELENA and AD team

ELENA – Motivation n Further deceleration of p-bars coming from the AD to 100 ke. V Separation of vacuum system of experiments from the transfer line ➠ 100 ke. V fits the needs of the experiments ¨ Very low energy for synchrotrons ¨ Operation at 100 ke. V challenging due to very low magnetic fields (in average 94 G along whole circumference, 493 G in Bends) ¨ n n Electron cooling to reduction emittances – compensate increase due to deceleration Expected gain for experiments About two orders of magnitude more intensity for experiments with thick degraders ¨ About one order of magnitude more intensity for ASACUSA and no delicate RFQD operation ¨ Several experiments operated in parallel ¨ n Sketch of ELENA magnetic cycle ¨ Expected duration around 10 s to 15 s 11 th October 2011 Low Energy Antiproton Facility C. Carli on behalf of the ELENA and AD team

ELENA – Proposal in 1982 From the proceedings of the Workshop on “Physics at LEAR with Low-Energy Cooled Antiprotons”, ERICE (1982) n n n 11 th October 2011 Low Energy Antiproton Facility Proposal for very short ring (11. 4 m circumference … longer than in proposal from Jan. 1982) Energy down to 200 ke. V (discussion on feasibility of 100 ke. V) Cooler current 0. 16 m. A C. Carli on behalf of the ELENA and AD team

ELENA – Present Layout n n Circumference increased to 1/6 the AD Space for all equipment required ¨ ¨ ¨ Magnets (bends, quadrupoles, correctors) with low fields RF cavities with very low fields Fully bakeable vacuum system for pressure ~3 10 -12 Torr (beam life-time) Electron cooler (plus compensators) Injection and two ejection lines possible (all in dedicated straight) Instrumentation suitable for low intensity and energy n Machine compatible with 11 th October 2011 Low Energy Antiproton Facility C. Carli on behalf of the ELENA and AD team

ELENA – Present Layout in AD/ELENA Hall 11 th October 2011 Low Energy Antiproton Facility C. Carli on behalf of the ELENA and AD team

ELENA – present estimate for parameter n Momentum range 100 - 13. 7 Me. V/c Energy range 5. 3 - 0. 1 Me. V Circumference C 30. 4 m Tunes horizontal/vertical ~1. 34 / ~2. 45 Electron cooling 100 ke. V and ~650 ke. V Intensity of injected beam 3 × 107 Intensity of ejected beam 1. 8 × 107 Efficiency 60 % Number of extracted bunches 1 to 4 Transverse emittances (95%) at ejection at 100 ke. V 4 / 4 mm ∆p/p after cooling, [95%] 10− 4 Bunch length Lb at 100 ke. V 1. 3 m (300 ns) Required (dynamic) vacuum, Torr 3 × 10− 12 Torr Parameters to be revised and refined for Technical Design Report (TDR) 11 th October 2011 Low Energy Antiproton Facility C. Carli on behalf of the ELENA and AD team

ELENA – Present Lattice E-cooler Injection E-cooler D (m) b. V (m) b. H (m) With perturbation due to cooler (100 G only) periodicity reduced from two to one n Few quadrupoles and constraints imply somewhat irregular lattice, but with small beam sizes n No section without dispersion – difficult without adding many more quad’s (giving longer 11 th October 2011 Low Energy Antiproton Facility C. Carli on behalf of the ELENA and AD team machine) n

ELENA – possible limitations, questions n Direct space charge effects Additional defocusing due to Anti. Coulomb repulsion ¨ Non-linear, depending on position in bunch ¨ Tune shift and spread (rule of thumb: maximum -0. 2 just an indication – true for low periodicity and energy? ) ¨ n Lattice and stray fields Deflection due to ~0. 5 G earth magnetic field at 100 ke. V (beam rigidity 457 Gm): > 1 mrad ¨ Careful investigations on stray fields to be expected … good closed orbit control ¨ Ratio between magnet gap and curvature radius not (that) small: correct modeling of magnet entrance/exit ¨ 11 th October 2011 Low Energy Antiproton Facility C. Carli on behalf of the ELENA and AD team

ELENA – possible limitations, questions n Electron cooling Weak magnetic field (100 G planned at present) to limit lattice perturbations ¨ Twiss parameter at cooler D ≈ 3 m, bx≈ by ≈ 2 m ¨ Expected (cooled) p-bar parameters erms=(2/3) mm and sp/p = 0. 25 10 -4 ¨ Temperatures of cooled pbars k. TT ≈ 0. 07 e. V ¨ Electron beam potential creates parabolic electron velocity profile (plotted for 0. 5, 1 and 2 m. A at 100 ke. V) ¨ Azimuthal electron drift velocity (crossed magnetic and electric field) for 2 m. A: vf/v|| = r/3. 4 m ¨ n Studies Cooling times and equilibrium parameters (with cooling and blow-up mechanisms) ¨ Optimum lattice functions and cooler parameter ¨ 11 th October 2011 Low Energy Antiproton Facility C. Carli on behalf of the ELENA and AD team

ELENA – possible limitations, questions n Instabilities Possibly despite low intensity with small emittances (momentum spread) and energy ¨ Large direct space charge impedance due to low energy ¨ n Mechanisms provoking blow-up and beam loss ¨ n Transfer lines ¨ n IBS , scattering on gas molecules, heating by electron cooler => equilibrium with cooling, blow-up after cooling until ejection Electrostatic lines proposed: cheap and magnetic shielding simpler H- (or other ion) source for commissioning Motivation: ELENA commissioning in parallel to AD run, H- with same mass and charge ¨ Life-time (gas stripping) probably o. k. , start commissioning at low energy ➠ Possibly switch to H- after very first commissioning with p-bars ¨ 11 th October 2011 Low Energy Antiproton Facility C. Carli on behalf of the ELENA and AD team

ELENA - Tentative Planning n Tentative planning ¨ Next step: detailed study and Technical Design Report TDR 11 th October 2011 Low Energy Antiproton Facility C. Carli on behalf of the ELENA and AD team

Summary and Outlook n Antiproton Rings now have a long tradition at CERN In the 1980’ies: p-bars for the high energy frontier and at low energy ¨ Now: ¨ n n n Protons for the high energy frontier (luminosity in LHC) but still a low energy program with very active & successful experiments ELENA has been approved as a CERN project and will become reality Thanks to everybody involved for making this project reality ¨ Help and contributions to ELENA construction from interested institutes vital (see ADUC & ELENA meeting on 28 th and 29 th September) ¨ We now have to build it and make it work successfully ¨ n n ¨ n ELENA a synchrotron operated at an unusually low energy range Next step: detailed study and Technical Design Report (TDR) AD to be operated for at least one more decade and, thus, serious consolidation required New era for antiproton physics at CERN for many years 11 th October 2011 Low Energy Antiproton Facility C. Carli on behalf of the ELENA and AD team

Thanks for your attention ! 11 th October 2011 Low Energy Antiproton Facility C. Carli on behalf of the ELENA and AD team