1. ESS RFQ B. POTTIN and RFQ team CEA-IRFU

2. RFQ design Strategy 3 RF codes to validate calculations Consideration of machining and assembly possibilities Hydraulic diagram Cooling system

3. RFQ design process We have presently done the thermo mechanical calculations We have presently done the thermo mechanical calculations To define the number and the position of cooling circuits for the RFQ, tuners, vacuum ports, extremities plates and RF loops (if necessary) To define the number and the position of cooling circuits for the RFQ, tuners, vacuum ports, extremities plates and RF loops (if necessary) To determine the operation temperature of the RFQ and flow velocity for each circuits To determine the operation temperature of the RFQ and flow velocity for each circuits To determine the hydraulic diagram and the cooling system like IPHI and SPIRAL2 To determine the hydraulic diagram and the cooling system like IPHI and SPIRAL2 IPHI SPIRAL2 IPHI

4. The ESS RFQ Global Design Global Schematic view of ESS RFQ T1 T5 T2 T3 T4 View of the end section of the RFQ with the tuning rod for a quadrant Transversal view of the RFQ across the tuners 40mm Cooling channels The ESS RFQ: The ESS RFQ: 5 x Sections for a total length = 4.58m 5 x Sections for a total length = 4.58m 2 x Vacuum ports per quadrant and per section except on T3 ( hosting the RF coupler) 2 x Vacuum ports per quadrant and per section except on T3 ( hosting the RF coupler) 3 x 80mm-diameter pistons per quadrant and per section acting as tuners 3 x 80mm-diameter pistons per quadrant and per section acting as tuners Endcells tuning with 4 x rods Endcells tuning with 4 x rods 8 x 10mm-diameter cooling channels per section (variable length) 8 x 10mm-diameter cooling channels per section (variable length) RFQ in CuC2 and Flanges in stainless steel RFQ in CuC2 and Flanges in stainless steel

5. RF calculations done with HFSS  Model realized with CATIA: imported in ANSYS and HFSS softwares (one quarter of RFQ) Power density transferred from HFSS to ANSYS workbench Voltage (kV) Length (m) Theorical voltage law HFSS calculation CATIA model Mesh in HFSS Power density  RF simulations in HFSS (calculation of cavity voltage and power density on the RFQ)

6. Cooling Strategy of the RFQ T1T2T3T4T5 InletOutlet Inlet Outlet A peak total RF power of 1MW can be deposited in the modules in pulse mode (~5% duty cycle) with an increase of the power density along the beam axis (Max power on T5) A peak total RF power of 1MW can be deposited in the modules in pulse mode (~5% duty cycle) with an increase of the power density along the beam axis (Max power on T5) The cooling system designed to remove a peak RF power 250kW The cooling system designed to remove a peak RF power 250kW Optimization of the cooling channel position, sizes and fluid velocity from 2D calculation (COMSOL) in order: Optimization of the cooling channel position, sizes and fluid velocity from 2D calculation (COMSOL) in order: to minimize the frequency shift between the RF on/off states (reviewer Jim Stoval’s remark) to minimize the frequency shift between the RF on/off states (reviewer Jim Stoval’s remark) Allow simple mechanical fabrication (minimum Cu thickness of 5mm close to the channels) Allow simple mechanical fabrication (minimum Cu thickness of 5mm close to the channels)  An average velocity of 3.5m/s is allowed in the cooling channels ( empirical estimation of the heat exchange coefficient ~ 13 000 W/m 2 /K) ( empirical estimation of the heat exchange coefficient ~ 13 000 W/m 2 /K)  Inlet Water temperature per section (for all sections) = 25°C Vacuum port are brazed on the RFQ sections (all in CuC2): good heat evacuation towards Vacuum port are brazed on the RFQ sections (all in CuC2): good heat evacuation towards the cooling channels the cooling channels Tuners are insulated from the RFQ by SS flanges (not a good heat conductor) => Tuners are insulated from the RFQ by SS flanges (not a good heat conductor) => cooling added using a brazed coaxial pipe cooling added using a brazed coaxial pipe End plates can be cooled End plates can be cooled Layout of the cooling system for the ESS RFQ View of a quadrant and the cooling channels View of an end plate and its the cooling channel View of a tuner and the coaxial cooling pipe

7. Thermal and mechanical calculation are done in 3D on the ¼ geometry of the RFQ (as in HFSS): Thermal and mechanical calculation are done in 3D on the ¼ geometry of the RFQ (as in HFSS): Calculation with ANSYS/HFSS: direct mapping of the RFQ power = 10 475W with the same geometry Calculation with ANSYS/HFSS: direct mapping of the RFQ power = 10 475W with the same geometry Take into account 3D effects (vs. 2D) : contacts, finite length of cooling channels, end cells, grids and tuners Take into account 3D effects (vs. 2D) : contacts, finite length of cooling channels, end cells, grids and tuners No natural convection is added (with surrounding) No natural convection is added (with surrounding) No cooling is implemented in the end plates => Not Necessary (see later) No cooling is implemented in the end plates => Not Necessary (see later) If no cooling is implemented in tuners: Temperature reaches 260°C locally = > Necessary If no cooling is implemented in tuners: Temperature reaches 260°C locally = > Necessary Numerical Modelling: Zoom on the mesh of T5: properly map the power density from HFSS to ANSYS thermal and mechanical analysis No direct contact between sections: Heat transfer through flanges only No direct contact between sections: Heat transfer through flanges only No direct contact between tuners and RFQ sections No direct contact between tuners and RFQ sections Grids are brazed locally on the RFQ section Grids are brazed locally on the RFQ section T1 T2

8. Energy balance and Water Temperature Rise: Global energy balance for the RFQ and for each section were consistent between HFSS and the ANSYS thermal analysis. Global energy balance for the RFQ and for each section were consistent between HFSS and the ANSYS thermal analysis. Energy dissipated in the cooling elements – ANSYS vs. HFSS balance Energy dissipated in the cooling channels in the # sections Water temperature rise in the cooling channels in the # sections Flow rate Inner/Outer channel =18L/min (duty cycle 5%)

9. Thermal Results: RFQ Sections T5 (max power deposition) Temperature almost uniform over a wide portion of the pole line Temperature almost uniform over a wide portion of the pole line Temperature peak in regions with the highest magnetic field Temperature peak in regions with the highest magnetic field T>22°C (Jim Stovall request : «The RFQ should run warm to avoid condensation and long term corrosion problems »)

10. Thermal Results: Vacuum Grids, Pistons, Flanges & End Cells Grid # 10 (T5) Tuner # 15 (T5) End cell + rod @ backend of RFQ Stainless steel flange # 15 (T5) Maximum temperature field are found on the last section T5 and the elements within: Maximum temperature field are found on the last section T5 and the elements within:

11. Mechanical Results: RFQ Sections Only stresses due to the thermal load are computed (no gravity or supports are included): Only stresses due to the thermal load are computed (no gravity or supports are included): The copper is annealed (brazing process) => Yield stress ~ 35MPa The copper is annealed (brazing process) => Yield stress ~ 35MPa Stainless steel elements in 316LN => Yield stress ~ 170MPa Stainless steel elements in 316LN => Yield stress ~ 170MPa Symmetry conditions and a central fixed point (center of the RFQ @ T3 ) constitute the boundary conditions. Two directional deformations of interest: Symmetry conditions and a central fixed point (center of the RFQ @ T3 ) constitute the boundary conditions. Two directional deformations of interest: The longitudinal deformation along the beam axis: limited effect on the frequency shift The longitudinal deformation along the beam axis: limited effect on the frequency shift Beam propagation Longitudinal deformation in the RF sections

12. Mechanical Results: RFQ Sections Transverse deformation does not exceed 16µm in the ESS RFQ for this set conditions. Transverse deformation does not exceed 16µm in the ESS RFQ for this set conditions. The maximum equivalent stresses in the Copper is at a vacuum grid port and is ~12MPa which is no plastic deformation in the RFQ The maximum equivalent stresses in the Copper is at a vacuum grid port and is ~12MPa which is no plastic deformation in the RFQ The 3D estimate of the deformation ratio between the pole tip and the cavity wall height varies between 3 (front end) and 2.6 (backend) along the RFQ => Consistent with the 2D results The 3D estimate of the deformation ratio between the pole tip and the cavity wall height varies between 3 (front end) and 2.6 (backend) along the RFQ => Consistent with the 2D results Transverse deformation Maximum equivalent stresses

13. Mechanical Results: Tuners Localized max equivalent stress on the Pistons (Cu): 12MPa < ~2/3 of the yield stress =23MPa Max equivalents stress on the flange (stainless steel): 55MPa < ~2/3 of the yield stress =115MPa. Transverse deformation of the Tuner (15th) surface in interaction with the cavity does not exceed 13µm. Transverse deformation for the 15 tuners

14. Mechanical Results: End cell with rod Transverse deformation the end plate with its rod Relative longitudinal deformation of the end plate with rod. With no cooling in the end plates, the rod deflection around its axis does not exceed 5µm With no cooling in the end plates, the rod deflection around its axis does not exceed 5µm (only 20W deposited on both plate on average)

15. A cavity with 2 RF loops + 1 pumping port + 1 adjustable tuner A cavity with 2 RF loops + 1 pumping port + 1 adjustable tuner RF loop: validation by conditionning with a new RF system in CEA  definitive ESS RF loop RF loop: validation by conditionning with a new RF system in CEA  definitive ESS RF loop  RFQ conditionning faster (RF loop already conditionned) Adjustable Tuners: the same geometry during adjustment and operation (same perturbation) Adjustable Tuners: the same geometry during adjustment and operation (same perturbation) – Definitive position just after adjustment : No delay of machining between adjustment and final position – Adjustment possible during the operation or after the transport To validate the industrial assembly for adjustment tuners and pumping ports To validate the industrial assembly for adjustment tuners and pumping ports The delay is 8 months (RF loops) only for machining, not with administration delay! The delay is 8 months (RF loops) only for machining, not with administration delay! – Be careful of the delay of management’s decision between CEA and ESS  The only interface between the RFQ and prototypes is the hole size : it’s possible to start the RFQ machining before the prototypes validation  Schedule adjustment  The only interface between the RFQ and prototypes is the hole size : it’s possible to start the RFQ machining before the prototypes validation  Schedule adjustment RF study already done and mechanic design in progress RF study already done and mechanic design in progress Prototyping plan

16. Interfaces We need to have interfaces and discussion between LEBT and MEBT because those parts are essentials for mechanical assembly, alignment…. We need to have interfaces and discussion between LEBT and MEBT because those parts are essentials for mechanical assembly, alignment…. Interfaces with building is very important concerning the RFQ integration (and the warm linac in general) Interfaces with building is very important concerning the RFQ integration (and the warm linac in general) It is necessary to have an infrastructure meetings 2 or 3 times per year It is necessary to have an infrastructure meetings 2 or 3 times per year – It is neccesary to exchange about the strategy of handling (crane, elevator…), assembly, alignment and test inside the tunnel… – The buildings group can’t know what is specific (stability and fragility) about accelerator equipments like RFQ… It is not possible to change the building design everyday !! It is not possible to change the building design everyday !!

17. Interfaces We must define the interfaces between RFQ and infrastructure, specially about : cooling system and RF distribution : the waveguide – coaxial transition included with RFQ We must define the interfaces between RFQ and infrastructure, specially about : cooling system and RF distribution : the waveguide – coaxial transition included with RFQ – Work in progress We need to access to 3D building pictures to simulate the RFQ integration inside the ESS tunnel (space around the RFQ : RF waveguide, vacuum…) We need to access to 3D building pictures to simulate the RFQ integration inside the ESS tunnel (space around the RFQ : RF waveguide, vacuum…)

18. Diagnostics and C&C: early in kind contribution « there was an overarching agreement between CEA and ESS to proceed on the early in-kind, and it was left to the technical people to finalise the technical details. » « there was an overarching agreement between CEA and ESS to proceed on the early in-kind, and it was left to the technical people to finalise the technical details. »  We have the « management authorization » to increase the collaborative technical work  We have the « management authorization » to increase the collaborative technical work Source and LEBT Source and LEBT – The work is in progress – Be careful of the delay of the ESS system standardization choices with the schedule impact behind Doppler shift Doppler shift – Start of technical discussion with ESS – First technical definition in June (Design, C&C, Tests…) during a diagnostics meeting in CEA EMU EMU – We are already working with Catania (mechanic and integration) and ESS (C&C) – ESS timing specification is important (end of this year) – Mechanical design is in progress

19. CEA In kind contribution Agreement between CEA and ESS is in progress for in kind contribution Agreement between CEA and ESS is in progress for in kind contribution A possible validation in June A possible validation in June  First hard order possible in September  First hard order possible in September Schedule time incompressible Schedule time incompressible – Impact on Source and LEBT schedule EMU : 17 months EMU : 17 months  First test in Catania without EMU ? – Possible flexibility for RFQ between prototype plan and RFQ machining : critical path