Status of ELENA – Technical Report, Status of External Contributions Christian Carli on behalf of the ELENA teams ADUC, 13 th June 2012  Recap on ELENA machine and challenges, …  Topics studied recently (mostly work in progress)  Lattice and acceptance  Bending magnets with very low fields  Electron cooling at low energy and equilibrium with IBS  Vacuum system and residual gas interactions  Stray Field measurements  Status of external Contributions  Summary

Recap on ELENA machine and challenges (Not that) short synchrotron decelerating p-bars from the AD to very low energy of 100 keV Increase of phase space density by electron cooling at (two) low energy  Weak magnetic field (100 G planned at present) to limit lattice perturbations  Twiss parameter at cooler D ≈ 1.4 m,  x ≈  y ≈ 2 m  Challenge for studies: equilibrium beam parameters with IBS and other blow-up sources, cooler imperfections … optimization of (lattice) parameters  Electron beam potential creates parabolic electron velocity profile (plotted for 0.5 and 1 mA at 100 keV) Transfer lines  Electrostatic lines proposed: cheap and magnetic shielding simpler H - (or other ion) source for commissioning 13th June 2012 ELENA Status C.Carli on behalf of the ELENA team Interaction length reduced to 0.8 m now

Recap on ELENA machine and challenges Direct space charge effects  Additional defocusing due to Coulomb repulsion  Non-linear, depending on position in bunch  Tune shift and spread (rule of thumb: maximum -0.1 to -0.3 just an indication – true for low periodicity and energy?)  Limits intensity per bunch (or bunch length) Very low energy and, in consequence, low beam rigidity and magnetic fields  Deflection due to ~0.5 G earth magnetic field at 100 keV (beam rigidity 457 Gm): > 1 mrad/m  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  Good field quality of very low field magnets a challenge Instabilities  Possibly despite low intensity with small emittances (momentum spread) and energy  Large direct space charge impedance due to low energy 13th June 2012 ELENA Status C.Carli on behalf of the ELENA team Anti-

Recap on ELENA machine and challenges Intra Beam Scattering (IBS)  Consider coordinate system moving with (average velocity of) beam  Still unordered motion of beam particles  Can be associated with temperature (beam cooling = reduction of this unordered motion)  IBS: Coulomb scattering between beam particles  ELENA: longitudinal temperature (and relative velocities) small compared to longitudinal ones (longitudinal electron cooling faster than transverse one)  Likely to transfer heat from transverse plane to longitudinal plane  Likely the main limitation for equilibrium emittances with electron cooling  Several theories exist and give similar results taking into account: “Dispersion” (describing how beam position depends on (relative) momentum offset) tends to generate horizontal emittance growth due to IBS Variations of beta-functions (beam sizes) around ring, coupling between transverse planes… 13th June 2012 ELENA Status C.Carli on behalf of the ELENA team s (long. position) x (trans. position)

Lattice and Layout Challenges (usual for low small rings) for lattice design and optics  Many constraints and few “free parameters” (quads) Suitable working point and sufficient acceptances (small maximum beta function, but also large dynamic aperture with non-linearities) Long straight with small dispersion for electron cooling..  Modeling of magnets with not that small gaps (compared to bending radius) Many geometries and lattices studied since last autumn  Square, hexagonal, triangular shape, different quadrupole locations Baseline lattice (Q X ≈2.3, Q Y ≈1.3) chosen for further detailed studies Discussion e.g. on acceptances and apertures on-going 13th June 2012 ELENA Status C.Carli on behalf of the ELENA team Pavel Beloshitsky

Lattice and Layout Integration and mechanical design started (details later in Francois presentation) 13th June 2012 ELENA Status C.Carli on behalf of the ELENA team Francois Butin and team

Bending magnets with very low fields Magnets with very low fields (0.35 T to 0.05 T) required  Non-linearities due to low fields a possible issue  Was this the limitation for low energies in other machines?  “Dilution”, i.e. mixing of magnetic steel and non-magnetic (stainless steel laminations) Higher field in magnetic laminations Mitigation of non-linearities due to low fields Many simulations carried out  2D and 3D, static and dynamic effects, hysteresis effects …  C-shape and H magnets … 13th June 2012 ELENA Status C.Carli on behalf of the ELENA team Daniel Schörling Inhomogeneity at low field: - Dominated by a gradient - Compensation with quad settings  B/B      ~half the field at 100 keV ~1.5 the field at 100 keV

Bending magnets with very low fields Bending magnet prototype (planned) to verify: Production process of a magnetic yoke diluted with stainless steel plates. Field quality with chosen steel and hysteresis Mechanical deformations Wish: test heating during bake-out (NEG activation) Edge angle and end shim design. 13th June 2012 ELENA Status C.Carli on behalf of the ELENA team Ratio Magnetic Steel: Stainless Steel 1:2 Magnetic: Non-Magnetic Minimum field 0.05T Maximum field 0.4T Magnetic length (straight) 1.0 m Ramp rate 0.4T/s Good field region (square) ±30/cos(30°)mm Local field quality ≤ ±2· B/B ref Integrated field quality ≤ ±2· ∫Bdl/∫B ref dl Total gap height 100mm Approximate pole width 330mm Edge angles 12deg

Electron cooling at low energy and equilibrium with IBS Code betacool  Developed at JINR, Dubna  Models electron cooling, Intra Beam Scattering (IBS), RF system ….) Cooling at 100 keV plateau  Electron cooling current 0.5 mA  Strong blow-up due to IBS limits final momentum spread  Energy spreads expected at experiments increased by one order of magnitude!! (see presentation by Pavel)  Cooling times around 1 s  Final physical rms emittances of ≈0.25  m and ≈0.17  m ! 13th June 2012 ELENA Status C.Carli on behalf of the ELENA team A. Smirnov (JINR), P.Beloshitsky, G.Tranquille, M.Martini RMS emittances and rel. momentum spread

Capture after electron cooling RF capture after switching off cooler  Sufficiently slowly to avoid non-adiabaticities  Sufficiently fast to avoid (longitudinal) blow-up due to IBS  Four bunches with pbars each Characteristics for experiments (with V RF,h=4 ≈ 500 V)  Rms bunch length: ≈0.25 m  Rms energy spread: ≈0.5 keV (impact on experiments & design of lines!) 13th June 2012 ELENA Status C.Carli on behalf of the ELENA team A.Smirnov (JINR), S.Hancock, P.Beloshitsky, G.Tranquille, M.Martini RMS emittances and rel. momentum spread Required RF voltage under discussion (could be less than 500 V)

Vacuum system and rest gas interactions Very first simulations of pressures around the ring  Only H 2 desorption with Torr l s -1 cm -2 (realistic for baked machine everywhere)  Some pressure variations since H 2 not pumped efficiently by NEGs (assumed in the whole ring) Next (more realistic simulations for gas compositions and more realistic hardware):  Realistic gas loads for heavier molecules  Injection/ejection equipments  Transfer lines (differential pumping close to ring)  Electron cooler  Final apertures (smaller apertures reduce conductance) 13th June 2012 ELENA Status C.Carli on behalf of the ELENA team Torr Position along a sector between bends R.Kersevan

Vacuum system and rest gas interactions Very low pressure and velocity at 100 keV  Most p-bars do not interact with rest gas molecules (black): in average ~40 s between interactions!  Nuclear interactions (red): very rare  Large angle scattering outside acceptance (orange): large cross section due to low energy (losses slow due to low pressure and velocity)  Small angle scattering (blue): several deflections of one p-bar at 100 keV very unlikely Rms angles (and blow-up) strongly overestimated if p-bars undergoing large angle scattering angles are taken into account 13th June 2012 ELENA Status C.Carli on behalf of the ELENA team Nucleus Electrons

Stray field measurements in the AD hall Motivation:  Beam at very low energy in not that short machine sensitive to stray field  Make sure that stray fields in the hall are not too strong First - preliminary for the moment - selected results  Earth magnetic field dominates at the position of future ELENA ring (few locations with higher and lower fields understood and not an issue) …. Excellent news for ELENA ring  Stronger fields a few meters from an experimental solenoid (AEGIS).. Watch out for lines 13th June 2012 ELENA Status C.Carli on behalf of the ELENA team General field level B VERTICAL ≈ 35  T B HORIZONTAL ≈ 30  T Scaffolding structure behind kicker spools: 150  T (70  0.2 m) Field at AD ring concrete shielding blocks: |B|≈ 10  T No gross time dependence observed M. Buzio

Beam Transfers and Lines Studies on beam transfers (injection/ejection, lines) underway (see presentation tomorrow by W.Bartmann and G.Vanbavinckhove)  Extraction channels  Geometry of lines  Optics Design  Test triplet (by and at ASACUSA) 13th June 2012 ELENA Status C.Carli on behalf of the ELENA team ASACUSA triplet (Courtesy: D.Barna, M.Hori and T.Koichi) W. Bartmann, G.Vanbavinckhove many contributions from ASACUSA

Status of external Contributions 13th June 2012 ELENA Status C.Carli on behalf of the ELENA team Univ. Tokyo and MPQ-MPI: - 2 MCHF (possibly electron cooler) - 7 FTE (identified, electrostatic transfer lines and devices) Cockcroft Institute & Univ’s and Swansea University: - Costing of the order of 500 kGBP has been applied by U Liverpool, - A proposal has been submitted for work : this would cover 2 Postdocs, some PhD students and equipment; the overall funding requested is about 1 M€; a decision is expected until June. Denmark: - Applied for the money for bends and quadrupoles (Danfysik), possibly funding for a postdoc IKP-FZ Julich: - Several aspects of the source have been discussed in meeting on 27 th of March in Juelich - Work has started and will be again discussed tomorrow afternoon: substantial development work is required to make such a source operational for ELENA commissioning. Many interfaces to be clarified (vacuum with differential pumping, design of lines, integration, infrastructure …). Univ. Brescia: 50 kEuros (to be transferred after ADUC) RIKEN (new since last ADUC) - Compensation solenoids for electron cooler - Manpower (student) TRIUMF: Help for design of electrostatic transfer lines Hemholtz Institute Mainz: Construction of supports Manne-Siegmann: Help with ELENA commissioning Berkeley: DOE does not (yet) support – MoU not signed, but discussion not yet abandoned! CEA-IRFU Saclay-SIGMAPHI: only prototypes are interesting for them – did not sign MoU, but still discussions

Summary/Status Studies on-going on several technical issues  Better understanding of limitations at low energy  Intra Beam Scattering (IBS) seems the dominant limitation for ELENA  Expect larger energy spreads at the experiments  Still many studies work in progress …. and some studies to be started (e.g. instabilities, IBS on ramps ….) Status  Aim: Technical Design Report (TDR) to be ready in autumn  For other milestones and more details on some topics (parameter, new building, experimental zones …) see presentations by Stephan, Pavel, François and Wolfgang  Memory of Understanding of collaboration signed this morning On track for first ELENA physics at the beginning of 2017 Thanks  To everybody who helped with the preparation of this presentation  For your attention 13th June 2012 ELENA Status C.Carli on behalf of the ELENA team