1. AD Electron Cooler Consolidation Review

3. Agenda: Welcome and Review charges Speaker: Mike Lamont (CERN)
09:45 → 10:15 History, design and spares of the current AD cooler ( discussion) Speaker: Gerard Alain Tranquille (CERN)
10:15 → 10:45 AD & e-cooling – operational experience ( discussion)
Speaker: Tommy Eriksson (CERN)
10:45 → 11:00 coffee break 15m
11:00 → 11:30 The collector issues in 2018 The collector issues in 2018 & general spares situation ( discussion) Speaker: Lars Varming Joergensen (CERN)
11:30 → 12:00 Collector repairs in 2018 & mechanical considerations for the future ( discussion) Speaker: Federico Carra (CERN)
12:00 → 12:30 New collector design and planning for manufacture & installation ( discussion) Speaker: Gerard Alain Tranquille (CERN)
12:30 → 14:00 Lunch 1h 30m
14:00 → 14:30 Optics layout and specifications for the new electron cooler ( discussion)
Speakers: Pavel Belochitskii (CERN), Tommy Eriksson (CERN)
14:30 → 15:00 Design of the new AD cooler ( discussion)
Speaker: Lars Varming Joergensen (CERN)
15:00 → 15:30 Group contributions, planning and budget for the new AD cooler ( discussion) Speaker: Gerard Alain Tranquille (CERN)
15:30 → 15:45 Coffee 15m
15:45 → 16:30 Closed session

4. Electron Cooling Hardware
Beam dump: collector
Source: cathode
Vacuum, diagnostics
Acceleration system: electron gun
Beam transport: solenoids, steering magnets

5. Initial Cooling Experiment (1977-1980)
Low Energy Antiproton Ring ( )
Antiproton Decelerator (2000……)
Present cooler is 40 years old :
Biggest modifications/upgrades made for LEAR :
Upgrade of vacuum system
Renovation of power supplies
New electron beam collector
New electron gun

7. SPARES
Electron gun
Spare unit and cathodes available.
Collector
Spare unit has been repaired. New collector construction.
Magnets:
gun sol
toroid
drift sol
Used on test stand. Power connections to be modified.
col sol
Vacuum system
Complicated toroid chamber
Power supplies
Responsibility of TE/EPC.
Principle cause of concern is the lack of spare magnets.
More than one year stop in case of magnet problem (e.g. short circuit)
Any vacuum intervention takes a long time because accessibility and bake-out.

8. Parameters for the new AD Electron Cooler
Maximum energy: 80 keV
Magnetic field in drift: 600 G
Electron beam energy: keV
Expansion factor: 2
Antiproton beam momentum: 500 MeV/c
Beam radius in drift: 2.5 cm
Accelerating voltage: kV
Ne x 1013 m-3
Relativistic beta:
Drift solenoid length: 1.5 m
Maximum electron current: 3.5 A
Cooler orientation: horizontal
Cathode radius: cm
Vacuum chamber diameter: 140 mm
Magnetic field in gun: G

9. What will be different?
Cooling at a higher antiproton momentum (≤500 MeV/c)
Horizontal orientation
Electrostatic plates in each toroid.
NEG coated vacuum chambers.
Fast ramping of the expansion solenoid to adapt the electron beam size during cooling.
New solenoid design using pancakes and iron bars for the return-flux.
Compact orbit correctors (as used on ELENA).

10. Cooler more accessible. No need for working at heights.
Vertical orientation (present situation)
Horizontal orientation (proposal)
5 x 5cm coils
2cm gap
12 x 1cm iron rods for the return flux
33cm coil
1cm iron shield
Fine adjustment of magnetic field possible
Only a handful of spare coils will be needed
Easier mounting
Lighter structure

11. New electron gun design (courtesy of Alexander Pikin)
Collector studies at 65 keV, 3.5 A

12. Advantages of a new Cooler
Present cooler
New cooler
Gain
Max Ee (keV) for cooling 27 68
Corresponding beam momentum (MeV/c)
300
500
Shorter deceleration ramp from 2 GeV/c. Smaller initial emittances. Faster cooling with lower equilibrium emittances.
Gun perveance (10E-6 mP)
0.58
2.6
Ie at 100 MeV/c (mA)
105
470
Four times faster cooling at extraction energy.
Expansion factor 1 2
Electron beam transverse temperature (meV)
100 25
Four times reduction in electron beam transverse temperature resulting in faster cooling and smaller equilibrium emittances.
Bt/Bl
1.00E-03
1.00E-05
Electron beam losses losses
1.00E-04
Better collector efficiency with electrostatic plates in the toroid magnets.
Vacuum pressure in cooling section (torr)
2.00E-11
4.00E-12
Pressure reduction with extra pumping from NEG. Less outgassing from secondary beam loss. Less blow-up due to vacuum.

13. Cost Comparison (new cooler vs spare parts)
Total budget : MCHF
For new cooler
Design, drawings
250 kCHF
>4500 hours
Magnetic system
1000 kCHF
Incl. spare coils
Raw materials & production
750 kCHF
Vacuum chambers, BPM…..
Vacuum
50 kCHF
NEG (coating,strips), acceptance tests
HT platform
100 kCHF
Cabling
Misc.
227 kCHF
Total budget : MCHF
For spare parts
New collector
350 kCHF
Spare magnetic elements
550 kCHF
1.3m gun & 0.7m collector solenoids, toroid
Design, drawings
100 kCHF
Spare cathodes, vacuum cons.
165 kCHF
Ion pump, NEG cartridges, toroid chamber

14. Timeline (new cooler vs spare parts)
2019: Design of new collector. Produce drawings. Start production.
Specification of the magnetic system. Produce tender documents. Market survey (?).
Finish integration study (incl. magnets reshuffle).
Finalise gun study and design.
2020: Call for tender for the magnetic system.
Production of the new collector (ready for autumn).
Produce drawings for the electron gun. Start production (?).
Design of the vacuum system. Drawings ready for end of year.
Test new collector on ecool test stand.
2021: Install new collector on AD. Exchange electron gun. Ready for start-up.
Magnets production. Production of the vacuum system. Chamber coating. Vacuum acceptance tests.
2022: Continue production and acceptance tests/measurements of magnets and vacuum system.
Mounting in bld 236 (ecool test stand).
2023: First tests of the new cooler.
LS3: Consolidate vacuum system.

15. Review Conclusions
A preliminary proposal for the construction of a new e-cooler was presented.
The new e-cooler will not ready for installation before end 2023 at the earliest, leaving potential operation in presently schedule Run 3 of 1 year.
A re-designed collector is in the design stage. Tight schedule for installation in LS2.
AD will be continued to be exposed to risk of gun, collector solenoids, toroids in Run 3. A recommendation on this requires a risk benefit analysis, which requires further input from BE-BI.
Spare magnetic elements would cost of order 700 kCHF, these plus new collector and other measures would guarantee life of AD e-cooler but without listed benefits of new system. In any case these additional spare components will not be available much earlier than a new e-cooler and can therefore not really be considered as a risk mitigation measure. The review panel think it needs to be justified why spare parts are not possible in a shorter time frame. A recommendation on this requires a risk benefit analysis, which requires this input from BE-BI.
Present degraded operation not understood.
Choice appears to be between: new e-cooler with benefits, but costly (material, labour) and only realistically available after LS3; and production of spares and other consolidation allowing continued operations until end of life.

16. Summary of recommendations
At the present time it is not possible to give a clear recommendation on building a new cooler. We propose the following set recommendations in order to reach a conclusion.
For End June 2019
1. Produce an alternative scenario for spares (starting from what is already received).
2. Discussion with TE-MSC about responsibility for magnet design and production (both scenarios)
3. Of the possibilities mentioned at the review (present spares, spares for a new cooler, layout changes, changes to power converters if needed) – clarify which are in the consolidation request.
4. Assessment if optics improvements, and the layout configuration, can be made independently of the new cooler – and budget and timeline estimate.
Assessment if the gun improvements (to 4 times higher perveance) are alone sufficient faster cooling, and could this be implemented on the existing cooler.
These questions are presently being addressed

17. Follow up on recommendations from reviewers (questions to be finally answered by the end of June 2019):
1. Produce an alternative scenario for spares (starting from what is already received).
• New collector is common to both present and new e-cooler design.
• Drawings of present magnets nor available. Reverse engineering would take as long as a new design. Even if drawings found, EN-MME should be involved to make production drawings and tender documents. A complete magnetic system would be available by end of 2022.
2. Discussion with TE-MSC about responsibility for magnet design and production (both scenarios)
• Davide Tommasini is available for collaboration at any level of involvement desired by BE-BI.
• The collaboration between TE-MCS and BE-BI should be well specified from the beginning. ACTION BE-BI: meeting with TE-MCS to draw terms of collaboration.
3. Of the possibilities mentioned at the review (present spares, spares for a new e-cooler, layout changes, changes to power converters if needed) – clarify which are in the consolidation request. Pin down what is actually included in the budget request, as it was not well understood by the panel:
• Power Converters for HV already included. Note, one 80kV already ordered to use on the test stand.
• Power Converters for Magnets NOT included. Note that all magnets are in series and bending angle does not scale with energy. Present PC could be used for the new e-cooler.
ACTION BE-BI: enquire with TE-EPC if present PC (which are dated) should be replaced.
• Spares included for the new e-cooler: 1 gun, 1 collector, 1 coil for the pancake structure.
• E-Cooler instrumentation consolidation NOT included in the option of present spares.
• Layout changes NOT included.
4. Assessment if optics improvements, and the layout configuration, can be made independently of the new e-cooler – and budget and timeline estimate.
• Layout changes are independent of whether we go for spares of the present e-cooler or installation of the new e-cooler. The idea presented was to re-shuffle the magnets at the same time as the new e-cooler installation, profiting from the big intervention.
Vice versa, the new e-cooler design does not depend on the layout changes, only its performance (improved).
• ACTION BE-OP (Laurette Ponce), EN-EA (Francois Butin) and BE-ABP (Davide Gamba): follow up on layout changes.
5. Assessment if the gun improvements (to 4 times higher perveance) are alone sufficient faster cooling, and could this be implemented on the existing e-cooler.
• It is feasible to design a new gun with 4 times higher perveance, working possibly at higher HV.