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G. Devanz

Status of HIPPI/WP3 developments at CEA/Saclay. Cavity “B” design Coupler design Power source Test stand Schedule. G. Devanz. RF design. Based on ASH b 0.47 design Design frequency 704.4 MHz. asymmetric. symmetric. RF design. RF design. Static Lorentz Detuning (1).

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G. Devanz

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  1. Status of HIPPI/WP3 developments at CEA/Saclay • Cavity “B” design • Coupler design • Power source • Test stand • Schedule G. Devanz

  2. RF design Based on ASH b 0.47 design Design frequency 704.4 MHz asymmetric symmetric

  3. RF design

  4. RF design

  5. Static Lorentz Detuning (1) Fixed ends, no rings

  6. Static Lorentz Detuning (2) Fixed ends, Nb thickness = 4 mm, rings When stiffeners are added on tube |k| drops below 3 Hz/(MV/m)², the optimal ring radius is unchanged, but …

  7. Static Lorentz Detuning (3) With a more realistic thinner weld region : Fixed ends Nb thickness = 4 mm

  8. Static Lorentz Detuning (4) Big changes arise when an external stiffness (tuner+ He tank) is taken into account Free ends Limit ~ 50 Fixed ends Limit ~ 3.6 Cavity stiffness

  9. Manageable zone Static Lorentz Detuning (5)  We are aiming at an external stiffness in 50 to 100 kN/mm

  10. Static Lorentz Detuning (6) Example of the cavity A test at Saclay: effect of the low frame stiffness • CASTEM computation with a simplified model of the frame: Low stiffness of 2.4 kN/mm due to buckling • Data from pressure sensitivity measurement : frame stiffness ~ 1 kN/mm • intrinsic K is -3.7 Hz/(MV/m2), effective K is ranging from -20 to -35 Hz/(MV/m2) • Cross-check with INFN for K calculation (ANSYS) OK

  11. Dynamic Lorentz Detuning (1) Computation of Lorentz coefficients for each mechanical mode: • Compute Mechanical modes with given B.C. (CASTEM code from CEA) and built a modal basis • Provide radiation pressure distribution on cavity surface (FISH) • Project on modal basis • Compute the cavity response to harmonic modulation in time domain for each mode. Assume a given damping coefficient for each mode ; wait for steady state • Compute the time dependant detuning of the cavity in steady state before : Superfish runs (many of them) now: Slater directly on the FEM mesh by external code coupled to CASTEM Most of the calculation are done with these conditions • cavity ends are not fixed : A given external stiffness of 70 kN/mm is assumed • Mechanical Qs are 50 or 100

  12. Dynamic Lorentz Detuning (2) Example : optimisation of the radius of the second family of ring R2 = 90 R2 = 100 R2 = 110 At lower frequencies, the R2 = 110 case (blue) is better : lower ks and higher frequencies for a given mechanical mode

  13. Dynamic Lorentz Detuning (3) Other methods provide more information on the cavity behavior : impulse response and step response Step response 1ring / 2rings

  14. Dynamic Lorentz Detuning (4) Scan of the Lorentz force modulation frequency  Transfer function What happens if the cavity is symmetric ? Only 1 mode is relevant for LFD below 500 Hz with a symmetric cavity ! Value @ 0 Hz is the static | K | Mode 1 of asym. Mode 1 of sym.

  15. Piezo tuner (preliminary) The harmonic scan method can be applied to a piezo-like element Warning : not normalized “Piezo” amplitude ~ 0.5 micron in this simulation Harmonic force, not harmonic displacement !

  16. Mechanics Regulations  the cavity must sustain twice the maximum pressure Max Pressure = 1.3 bar during test in vertical cryostat -> Preg = 2.6 bars Structural FEM calculations with fixed ends Sym + 1 familly of rings : max stress on beam tube iris 90 MPa Previous + stiffeners on beam tube iris : max stress around ring /cell junction 70 Mpa and 50 Mpa @ equator weld With second set of rings: max stress @ stiffener/outer cell junction 40 MPa stress @ equator 29 MPa

  17. Tuning *assuming sy = 40 MPa

  18. Conclusion on cavity • The best choice is a symmetric cavity with 2 series of rings • Dynamic behavior is more simple • Compared to asymmetric, RF performance is only slightly degraded • The second ring series is useful against Lorentz force detuning and strengthen the cavity w/ respect to external pressure Elliptical cavity ‘B’ with 2 sets of stiffening rings Equipped with cold tuning system (prelim. design) Helium tank with power coupler port & stiffening wings

  19. Schedule for cavity B Mechanical drawings ready Niobium order placed in August ‘05 (avail. in Dec. ‘05) Cavity order to be placed in November 2005 Fabrication (around 8 months) cavity B ready for June 2006

  20. Coupler Coupler architecture • Some proposed designs for SPL require peak powers exceeding 1 MW. The coupler should be specified with at least 1MW peak, 10 % duty cycle • HIPPI RF source will reach 1MW peak power • KEK/SNS type : coaxial warm window + He cooled coaxial part • We have developped a window at 700 MHz with IPN based on KEK/Toshiba design

  21. Coupler – window (1) Matching calculations (HFSS) Starting from SNS geometry  100 mm diameter, 50 W E H S11

  22. Coupler – window (2) 2 prototypes build by Toshiba

  23. Coupler (2) Thermal calculations • Thermo-mechanical model for the window ready (HFSS fields + CASTEM ) • Currently building a thermal model for the coaxial part Coupling calculations (HFSS) • Qext of 106 with a f=130 mm beam pipe is obtained with flush antenna • The coupling port location on the tube depends on the He tank side and stiffeners design. Multipactor simulations (MUPAC) for the coaxial part • TW and SW on 80 and 100 mm diameter 50 W coaxial lines

  24. Coupler MP TW 80 mm most stable barriers TW 100 mm most stable barriers TW 80-100 mm most stable barriers Lower power range SW 80-100 mm most stable barriers For all conditions, 100 mm behaves better

  25. Schedule for coupler Coupler: Mechanical drawings ready for Feb. 06 Order placed in June 06 Fabrication (10 Months) : coupler ready for March 2007

  26. Power source Klystron 704 MHz & 1.0 MW peak – 2 ms – 50 Hz (max. HT cathode = 95 kV) • Order placed in July ’05 • Fabrication : 16 months • Circulator 704 MHz & 1.0 MW peak & 100 kW average • Order placed in August ’05 • Fabrication : 8 months HV generator upgrade • Design of the HV tank : April - Dec. 2005 • Supply of mechanical and electrical components : May ‘06 • Order of the HV (110kV - 2.5 A) power supply in Nov. ‘06 • Fabrication of the HV power supply around 9 months • Modification of HV tank and cabling : June – Oct. 2006 Goal : elements at Saclay for Dec. ‘06

  27. Test Stand What still has to be done (from now to end of 2006): • Study of the implantation • Order of the missing WGs (we already have the power loads & bi-directional couplers) • Building of electronic racks (interlocks, diagnostics) • Preparation of the test area (cabling, water cooling, …) • Preparation of the acquisition/control system (already existing for tests at frep=1Hz) Test of the (HV generator + klystron): January 2007 Conditioning of power coupler(s): June 2007 We also have to move all our equipments to a new building in 2006 (liquefier, compressor, vertical and horizontal cryostats, RF power sources, …)

  28. Schedule

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