1. The ESS high intensity proton source and the LEBT: status, planning & open points L. Celona on behalf the LNS team Istituto Nazionale di Fisica Nucleare Laboratori Nazionali del Sud INFN-LNL, Legnaro, 5 May 2014

2. General requirements Proton current :above 70 mA (total drain of 90 mA circa are expected) Proton energy: 75 keV Pulsed operation: 2.86 ms - 14 Hz High reliability:>99% Long lifetime:>> 1 month Low emittance:0.25 π mm mrad at RFQ entrance Short pulse rise time required: 100 ns Robust extraction system LEBT optimization with chopper insertion The peak beam current must be varied continuously from 6.3 mA to 62.5 mA with a maximum step size of 6.3 mA and with a precision of 1.6 mA.

3. Main tasks IS&LEBT Design of ion source body: magnetic system, plasma chamber, extraction column, extraction system Definition of LEBT optics and ion beam management issues Definition of the LEBT IRIS Thermo-mechanical study, design and construction of the RFQ input collimator Study, design and construction of the defocusing chopper Test at CEA-IRFU of RFQ input collimator and fast chopper to investigate the SCC issues. Vacuum definition according with ESS standardization. Draft of the computer control specifications & related meetings Start of IS procurement phase LNS Site in preparation: minor delay occurred in the design phase. Tenders in progress.

4. Roadmap IS-LEBT Proton Source Design refinement: minor changes in extraction column (external profile, triple point) and extraction electrodes profiles (smoothing) according to last electrostatic check. New 3D beam distribution will be provided soon. Integration of ion source body into the HV platform Procurement: high delivery time orders completed, body source completion to do. LEBT Conceptual & Technical design: single elements already designed, merging and reducing length strategy must be actuated Procurement & Test: chopper and RFQ entrance collimator prototypes already fabricated and tested at CEA. Procurement for LEBT: solenoids, iris, … Final LEBT layout: Final choice of diagnostics and its location Assembly strategy and Alignment strategy Definition of computer control specifications (in progress) and MPS related to the IS&LEBT operations (space needed at HV?) ESS Site: Final layout, Racks location, Technical spaces? Crane? If not, what about handling of weights? ….

5. PS-ESS Three coils magnetic system to test new plasma heating mechanism ARMCO magnetic shielding Copper plasma chamber Water cooling for plasma chamber Plasma chamber ends with BN disks Microwave injection Gas injection

6. PS-ESS Peek Alumina Electrodes water cooling AlN electric insulator with high thermal conductivity Four electrodes extraction system (75, 0, -5, 0 [kV]) First LEBT segment with two emittance measurements, a Faraday cup and a turbo molecular pump Repeller -3kV connection Triple point new geometry X-ray protection

7. Time schedule 2014-2015 LEBT activities which are strategic for the definition of the final layout started well before the planned dates.

8. Site preparation at LNS

9. Tunnel area Definition of PS-ESS area in the tunnel. What area is available for storage IS and LEBT spare parts? What area is available for maintenance and cleaning procedure? To be discussed!

10. Transport and mounting At ESS: -What about handling from the truck to the tunnel? -What will be available to handle high weights during the assembly? At LNS a big crane will be used, also at CEA a big crane can be used

11. Preliminary PS-ESS lab@Lund To be discussed!

12. Grounding issues What about Lund installation? Requirements needed: -equipotential point behind extraction -floating? -supplementary bonds To be discussed! INFN-LNS is adopting a supplemental bonding under the floating floor interconnecting all the racks involved in the PS-ESS installation and that improves the immunity from HV sparks.

13. Cabling What about cable path at Lund? @LNS @Lund

14. Alignment Alignment strategy inside the ESS accelerator tunnel Main important element for the alignment: 1.Plasma electrodes 2.Extraction electrodes 3.Two solenoids 4.RFQ entrance collimator 1 2 3 4

15. Beam Instrumentation comments A Residual Gas Analyzer must be inserted to evaluate gas contamination, vacuum contamination, partial pressure of additional gas LEBT collimator at RFQ entrance must me integrated in the lattice Measurement of beam profile, beam position and ion species fraction must be provided from the first step of the commissioning

16. Design must be focused to produce only one diagnostic box that can be used for commissioning and for operation Diagnostic box proposal EMU FC EMU TMP Doppler EMU can fit in a DN 200 CF? Doppler shift measurement will watch previous part of the beam line A Beam Stop will be mounted at the end of the box during commissioning phases. BS Beam Instrumentation comments

17. Faraday Cup must be provided with ns acquisition accuracy (at least for the commisioning with a scope) for the electronics and the electrical configuration should be made accordingly (RC time constant). Emittance Measurement cannot be done at the RFQ matching plane without the collimator at the end of LEBT. The requirements will be evaluated after the LEBT collimator, at two different position and with high vacuum after the collimator, the matching plane measurement will be interpolated. Beam Instrumentation comments

18. Setup shown in picture cannot be used: LEBT collimator is needed to dump chopped beam and need an integration with RFQ people. The AC Current Transformer must be compatible with the design of the collimator Valve and all integration must be as compact as is possible View ports of two NPM must be located to look the beam before the second solenoid and at the LEBT collimator entrance. NPM near the first solenoid are not mandatory Additional view port must be located to see the chopped beam shape Beam Instrumentation comments

19. Water treatment

20. Water & air treatment Water for HV devices at 0.5  s and pH=7.5 is ok. If 25C is the water temperature at the primary of the skid, what is the expected temperature of the water at the entrance of the coils and magnetron? LEBT can tolerate 0.5  s water if pH is neutral. Again, if 25C is the water temperature at the primary of the skid, what is the expected temperature of the water at the entrance of the LEBT solenoids? Final requirements of water cooling are reported in the following table: Cooling Water Collector (1) E.S.S. - temp. 20 °C DEVICEFlux Δ P l/mbar Solenoid 1 + steerer H & V265 Solenoid 2 + steerer H & V265 Beam Stop (*)104 Emittance Measurement Unit155 RFQ Input Collimator254 Iris104 Electrodes14 Spare34 8 pipe lines;Total:116 ESS Source - Cooling Demi Water 0.5µS ; temp. 20 °C DEVICEFlux Δ P l/mbar Coil 1-2-3 source (pipe 1)44 Camera source (pipe 1)44 Magnetron (pipe 1)44 Wawe Guide (pipe 1)44 Faraday Cup (pipe 2)106 2 pipe line; Total176 Any requirement for gas exhaust?

21. Neutron flux 1 W/m proton beam loss in DTL Tank 1 Preliminary calculations by R. Bevilacqua Damage of elecronics at high voltage? Shielding needed?...

22. Gamma flux 1 W/m proton beam loss in DTL Tank 1 Preliminary calculations by R. Bevilacqua Damage of elecronics at high voltage? Shielding needed?...

23. Next steps Different issues are on the table to design the source for proper operations at ESS site. The different issues has to be addressed with dedicated technical meetings. Recent new constraints from ESS need modifications in things already fixed or purchased (electronics at HV, water, aligment….). It is true that modifications at this time have a smaller impact with respect to afford them when the source is already installed in the tunnel, but it is important to minimize them if we want to follow the schedule.

24. People L. CelonaWU Leader L. Neri, D. MascaliBeam Physics G. TorrisiMicrowave Engineer A. Galatà (LNL), L. AndòBeam Extraction optics A. Caruso, A. Longhitano, A. SpartàChopper construction and tests G. Gallo, S. Passarello, L. AllegraMechanical design E. Zappalà, G. Manno, G. MessinaMechanical integration and design B. TrovatoMechanical workshop A. AmatoElectronics and diagnostics S. SalamoneMechanical integration and design S. MarlettaVacuum F. ChinesSite preparation and EMC issues S. PulvirentiResponsible of control system G. SchillaciResponsible of technical services

25. Thanks for the attention Comments are welcome

26. PS-ESS Flexible magnetic system under construction at  Simulation of extraction system Kobra (three-dimensional) chamber Optimized steps parameters with plasma and two Boro Nitride disks Extraction system thermal calculation All the electrodes are cooled (repeller indirectly through AlN insulators) LNS-PIC (Particle In Cell code) under development (3D)

27. Movable iris: from 1 to 80 mm, 600 W, 300 mm length

28. LEBT

29. Chopper and collimator test at CEA-Saclay BETSI Chopper Collimator HV chopper electronics

30. Different current measurement setups for fast transient 6,2 46,5 IN OUT C collimator= 534pF C beam stop = 183pF Rτ=((46,5+50)^-1+6,2^-1)^-1=5.8 V out =V in /(46,5+50)*50=0.52*V in IN OUT 50 Rτ=(50^-1+50^-1)^-1=25 IN OUT 6,2 Rτ=(50^-1+6,2^-1)^-1=5,5

31. Beam pulse width of 2.87 ms CH4: beam stop after the LEBT collimator CH2: beam at LEBT collimator CH1: chopper HV probe

32. Beam current measurement Ch4: Beam Stop IN OUT 6,2 Ch2: Collimator 30mV/5,5ohm=5,5mA 58mV/5,5ohm=10,55mA 10mV/5,5ohm=1,8mA -1mV/5,5ohm=-0.18mA Current measurement setup for fast transient τ coll = 3 ns τ bs = 1 ns

33. Beam stability in 2 ms window Variation of averaged current between different pulses : +1.99% and -2.28% Standard deviation inside a single pulse: between 2,38% and 3.62% Maximum peak deviation from avaraged current inside a single pulse: -8,57% and +9,06%

34. Beam pulse rise time Slow transition ≈ 250 ns Fast transition ≈ 50 ns

35. The fastest rise time: 60 ns ∆t=100ns/div Weak currenty intensity. Further measurements are planned (beginning of April) in a higher current domain.

36. Beam pulse fall time Ch4: Beam Stop (Rτ = 5,5 ohm; C = 183 pf ; Rτ * C = 1 ns) Ch2: Collimatore (Rτ = 5,5 ohm; C = 534 pf ; Rτ * C = 2,9 ns) Beam propagation delay ≈ 50ns fall time