1. DTL RF properties F.Grespan LNL - 2015_06_22 CDRF. Grespan

2. Contents RF properties of tanks Tuning Thermo-mechanical simulations RF couplers Post couplers Pick up PMQ prototype Steerer EM design LNL - 2015_06_22 CDRF. Grespan

3. ESS DTL RF properties LNL - 2015_06_22 CDR Tank12345 Cells6134292623 E 0 [MV/m]3.003.163.073.043.13 E max /E k 1.55 φ s [deg]-35,-25.5-25.5 L Tank [m]7.627.097.587.857.69 Diam Tank [mm]520.5 R Bore [mm]1011 12 N.PMQ - 1 st /last cover 31 - Y/N18 -Y/Y15 - N/Y13 - N/N12 - Y/N Radius PMQ [mm]1112 13 L PMQ [mm]5080 Tun. Range [MHz]±0.75 Q0/1.254251244455443444389443415 Optimum β2.012.032.011.911.84 Optimum Detuning [kHz]+2.3+2.0 +1.8 P cu [kW] (no margin)870862872901952 E out [MeV]21.2939.1156.8173.8389.91 P TOT [kW]21922191219621892195 F. Grespan

4. DTL cells and tank design LNL - 2015_06_22 CDR Even if the cells, different in length, have the same frequency, the accelerating field is not constant because there is NOT a perfect mode matching between the adjacent cells built individually. The phase variation implies a cell length variation. The tilt that results from a cell length variation, have been compensated cell by cell tuning of Face Angle. Face Angle fine tuning also compensated frequency effect of STEM R. De Prisco et al.THPME041, IPAC 2014 proceedings F. Grespan

5. DTL tank design LNL - 2015_06_22 CDR This tuning can be verified only by 3D simulation 3D simulation of tank5 show a 2.5% error on field flatness (simulation of tank 1 error is 5%) A margin of 2 on the tuning range is considered in order to compensate field flatness error F. Grespan

6. Breakdown risk mitigation LNL - 2015_06_22 CDR Enhancement of sparking risk in presence of magnetic field. Assumption of scaling with Kilpatrick criterion (MuCool program at FermiLab). 3D simulation of first 15 ESS DTL cells with Halbach PMQ inside the tube. PMQ MAX Gradient = 62 T/m. PMQ Length = 50 mm in the first tank. Maximum surface field is at R=12 mm. In the first cell: E limit =1.45 Ekilp. - Design : 1.20 Ekilp. Risk of multipacting reduced by minimizing parallel surfaces: F = 0.3cm. F. Grespan

7. Static frequency budget and tuners LNL - 2015_06_22 CDR Tuners compensate construction errors Evaluation with realistic tolerances on important dimensions (tank diameter, drift-tube lengths, drift tube diameter, face angles) Movable tuners compensate thermal deformations in operation 1 st cell of Tank 1 is the most sensitive → taken for all cells as a margin Cell 1 of Tank 1Nominal [mm] Sensitivity [KHz/mm] Tolerance [mm] Static Error [KHz] GAP_Length13.135187±0.025±130 FACE_Angle5.72 deg6684±0.025±167 DT_Diameter90-1191±0.025 ∓ 30 TANK_Diameter520.5-451±0.100 ∓ 45 STEM_Diameter28132±0.025±3 Total±375 Static error compensated by Tuners = ±750 KHz (+100% margin) Superfish frequency target (stem included)= 352.21 MHz – 0.75 MHz = 351.46 MHz The tuner sensitivity (diam=100mm) = 7.0 (kHz/mm)×m Extra power for tuners (24 tuners/tank, Nom. Penetration=35mm) = +2.1% F. Grespan

8. Thermo mech. simulation LNL - 2015_06_22 CDR 1 st cell tank 1 Δf=-10 kHz Last cell tank 5 Δf=-25 kHz F. Grespan

9. Frequency tuning in operation Max simulated cell detuning in operation= - 25kHz (tank 5) Water nominal temperature = 30deg Temp sensitivity= -10 kHz/deg water frequency range = +40 kHz (@26°C), -100 kHz (@40°C) Operating water temperature will be optimized in RF conditioning phase 3 movable tuners/tank, tuning range= +120 kHz (@ penetration=80mm), - 90 kHz (@penetration=0mm) LNL - 2015_06_22 CDRF. Grespan

10. RF Tuning sequence 1.Alignment of DTs (0.1mm) provides cell by cell field flatness 2.End walls and tuners provide Higher order harmonics tuning 3.Tuning of RF coupler perturbation 4.Field flatness goal = 2% 5.Insertion of post coupler 6.Post coupler average length fixed with dispersion curve method 7.Artificial tilt of field changing end cell tuning 8.Fine tuning of post coupler length 9.Fine frequency tuning for nominal temperature 30°C 10.Final machining of post couplers, tuners, end plates 11.Measure of Qvalue 12.Fine tuning of RF couplers to achieve optimum coupling β 13.High power conditioning 14.Fine temperature tuning to minimize movable tuner stress in operation LNL - 2015_06_22 CDRF. Grespan

11. Longitudinal misalignment of Cells (Tank 1) F. GrespanLNL - 2015_06_22 CDR Error ranges: ± 50 - ± 100 - ± 200 micron Statistic: 100 runs per range Distribution: uniform 50 micron = +0.1% error 100 micron = +0.2% error 200 micron = +0.4% error

12. RF coupler design LNL - 2015_06_22 CDR MDT Fish DataHFSS T1_C26_27 P tot W47.13 Q03016630591 MHz351.764351.082 F. Grespan

13. RF coupler design LNL - 2015_06_22 CDR  Aperture=50 mm  Heigth = 76.8 mm  Beta rescaled = 1.23  Detuning cells 26-27 = -3.2 MHz (local detuning on 23 cm)  Dedicated tuner located RF at coupler section F. Grespan

14. RF coupler design H0=3.7 kA/m (superfish) H max = 11 kA/m Rs=0.004896 Ohm Max Power density = (H max 2 )x Rs/2 x 5%=1.5 W/cm 2 LNL - 2015_06_22 CDRF. Grespan

15. Bandwidth and Beam loading LNL - 2015_06_22 CDR Parameter/Tank12345 Peak P cu [MW] (1.25 margin) 10871077109011261190 Pbeam [MW] 11031113110510241004 Optimum coupling 2.012.032.011.911.84 Q0 (margin 1.25) 4251244455.6443454389543416 Optimum detuning [MHz] 352.2123352.2120 352.2118 3dB bandwidth (0.5 power) ±12.5 kHz±12 kHz±12.0 kHz±11.7 kHz±11.5 kHz 1dB bandwidth (0.8 power) ±6.2 kHz ±6 kHz±6.0 kHz±5.8 kHz±5.7 kHz Filling Time [micros] 12.713.213.313.613.8 Required Pgen/(Pcu+Pbeam) in case of detuning=0 1.0211.016 1.014 Effective sync.phase Optimum coupling Optimum detuning F. Grespan

16. RF coupler phase and tuning LNL - 2015_06_22 CDR i1 i2 Z1 Z2 R Unbalance between RF couplers generates reflected power. RF Coupler tolerances (phase Δθ, coupling β, power splitting) should take into account power margin coupling β is responsibility of INFN-LNL Accuracy around β=1 → 1mm on short length = 1% on β F. Grespan

17. RF windows Linac4 RF windows: duty cycle applied was 1 ms pulses at 2 Hz, @1 MW Request to Mega for -Half heigth WR2300 -freq = 352.21 MHz -return loss > 30 dB -insertion loss > 30 dB -FWD peak power: 1.3 MW all phase -FWD average power: 70 kW -Vacuum: 10e-8 mbar Order for 10 RF windows, confirmed after high power test of 1 st window (contact with CEA ESS test bench) LNL - 2015_06_22 CDRF. Grespan

18. Post couplers LNL - 2015_06_22 CDR Parameter /Tank12345 Cells per cavity 6134292623 PC distance [m] 0.350.330.350.320.33 N PCs 2423282522 N PCs / N cells First 12 cells: 1/4 Second 18 cells: 1/3 Others: 1/2 First 20 cells: 1/2 Others: 1/11/1 Detuning [MHz] L_post = 19cm 0.17 0.200.17 Power [MW] (no duty cycle considered) 0.0310.0360.0440.031 F. Grespan

19. Post coupler Post coupler distribution is compliant with stabilization requirements and mechanical constraints Thermal and static results for Copper Post coupler are: –Temp: + 10.7°C –Thermal elongation: + 44 micron –Static bend: -9 micron LNL - 2015_06_22 CDRF. Grespan

20. Pick-up LNL - 2015_06_22 CDR Pick-up characteristics Pick-up location along the tank 9 pick-ups are symmetrically located with respect to the tank center in order to suppress higher order TM modes for LLRF control. F. Grespan

21. PMQ prototype LNL - 2015_06_22 CDR Rare earth block specifications (Sm2Co17): -Error Br < 3% -Error an Angle < 2deg -Dimension tolerances < 0.05mm – 0.1mm -Br=1.1 T → Simulated Gradient=65 T/m Assembly specifications: -Housing Material - Stainless Steel (316LN) -Outgassing rate per magnet below 4.10-6mbar l s-1 -Gradient integral error (rms) -+ 0.5 % -Magnetic versus geometric axis: < 0.1 mm -Harmonic content at 10 mm radius: Bn/B2 for n=3,4,...10: < 0.01 -Roll: 1 mrad Goal: -define assembly criticalities -verify feasibility of specifications -define magnetic measurement bench and procedure -tunability of PMQ -Company qualification F. Grespan

22. PMQ prototype LNL - 2015_06_22 CDR See vacuum presentation F. Grespan

23. Steerer EM design LNL - 2015_06_22 CDR Vector potential Dipole Strength0.0016T*m Dipole Length30mm Inner radius28mm maximum external radius33mm B0.0533T ampere turn976.33A conductor radius2.3mm water channel radius1.5mm cu-area9.55mm^2 n turns4 current244.1A current density25.56A/mm^2 condutor length2m copper resistivity1.70E-08Ohm*m Conductor resistance0.0036Ohm Volt0.869V Power DC (single steerer)212.10W Magnetic flux density T F. Grespan

24. Conclusions RF properties of 5 tanks are defined Static and dynamic tuning range is defined (Mechanical tolerances, RF simulation and thermo-mechanical simulations) Size of RF couplers is defined, effect on frequency and field detuning will be compensated by dedicated tuner, power density is calculated. Multiple coupler unbalances (phase, coupling, amplitude) must be negotiated with ESS RF group. N° and distribution of Post couplers is compliant with Stabilization and mechanical constraints. Thermo-mechanical simulations done. Pick up design and distribution is done PMQ prototype produced and characterized Steerer preliminary EM design is done, compatible with available space in the drift tube. F. GrespanLNL - 2015_06_22 CDR

25. Back up slide 1 F. GrespanLNL - 2015_06_22 CDR

26. Back up slide 2 F. GrespanLNL - 2015_06_22 CDR