SC Elliptical cavities design and associated R&D MAX mid-term design review

1. SC Elliptical cavities design and associated R&D MAX mid-term design review 12/13 NOVEMBER 2012, SCK•CEN, Brussels R. Paparella, INFN Milano On behalf of the task 3.1 team

2. Layout of the talk • Elliptical cavities • RF design from ASH/TRASCO collaboration • Cavity manufacturing and cold test • Helium tank integration, magnetic shielding and fast tuner • ADS cryomodule test stand • Cryostat thermal design • Manufacturing and assembly at SIMIC • Experimental results • Commissioning at IPNO • Review of performed cold tests • Current status and perspectives R. Paparella, MAX mid-term design review, Brussels, November 12-13, 2012.

3. The b = 0.47 cavity – RF design • Cavity final design at 704.4 MHz has been the result of the TRASCO/ASH collaboration, exploiting a fully parameterized model of a SC cavity • Full parametric model of the cavity in terms of fewmeaningful geometrical parameters: • Ellipse ratio at the equator (R=B/A)Ruled by Mechanics • Ellipse ratio at the iris (r=b/a)Epeak • Side wall inclination (a) and position (d)Epeak vs. Bpeaktradeoff and coupling k • Cavity iris radius RirisCoupling k • Cavity Length L b • Cavityradius Dused for frequencytuning • Behavior of alle.m. and mechanical properties has been found as a function of the above parameters R. Paparella, MAX mid-term design review, Brussels, November 12-13, 2012.

4. The b = 0.47 cavity – figures R. Paparella, MAX mid-term design review, Brussels, November 12-13, 2012.

5. The b = 0.47 cavity – prototypes • Two low and two high RRR single-cell prototypes built within TRASCO: • Built by E. Zanon (Italy) • Treated at CEA-Saclay and JLAB with BCP, HPWR and class 100 CR assembly • Vertically tested at CEA-Saclay, JLAB and LASA R. Paparella, MAX mid-term design review, Brussels, November 12-13, 2012.

6. The b = 0.47 cavity – building the cavity • Dimensional and RF test on half-cells and on dumb-bells for QC • Soft-BCP to clean the welding region • Reduced number of welds, time-dominating factor is the pump down and the cooling after welding R. Paparella, MAX mid-term design review, Brussels, November 12-13, 2012.

7. The b = 0.47 cavity – 5 cell cavity • Defined the production choosing all the technological solutions • NbTi Flanges based on TTF/SNS solution • Ready for Titanium Helium Vessel (with stiffening TIG welded) • Dummy HOM ports R. Paparella, MAX mid-term design review, Brussels, November 12-13, 2012.

8. The b = 0.47 cavity – 5 cell cavity vert tests • Ep/Eacc=3.57 , Bp/Eacc=5.88 mT/(MV/m) • Z501 – JLAB 31/03/2004 , Z502 – Saclay 24/06/2004 Q0 R. Paparella, MAX mid-term design review, Brussels, November 12-13, 2012.

9. The b = 0.47 cavity – toward dressed cavity • A special setup has been built on purpose for cavity FF and goal frequency tuning • Helium tank realized to fulfill external stiffness requirements R. Paparella, MAX mid-term design review, Brussels, November 12-13, 2012.

10. The b = 0.47 cavity – magnetic shield • Both inner cryoperm shield in tank and outer m-metal shield in warm region solutions have been investigated • Finally, internal designed has been fixed • Pre-assembled to measure the shielding and compare to simulations R. Paparella, MAX mid-term design review, Brussels, November 12-13, 2012.

11. The b = 0.47 cavity – coaxial blade tuner • A coxial blade tuning system has been designed, inspired by the model realized by INFN for TESLA cavities. • A moving steel leverage transfers, through deforming Ti blades, the tuning action of stepper motor drive unit. • Design tuning range of 300 kHz with 1 Hz/step sensitivity • Two piezo actuators allow for fast and fine tuning • Design static tuning range of about 10 kHz with both actuators energized with 200 V R. Paparella, MAX mid-term design review, Brussels, November 12-13, 2012.

12. The ADS cryomodule test stand • Short, single-cavity module jointly realized by INFN Milano and IPN Orsayas EUROTRANS project deliverable: • INFN • Cavity+Module • IPNO • Coupler, Valve box & test infrastructure • Module based on theconcept of short independentlyfed and rapidly exchangeable units • Will be used for long testing for the reliability characterization of components R. Paparella, MAX mid-term design review, Brussels, November 12-13, 2012.

13. The cryomodule – cavity frame • Cavity power coupler orientation is vertical • Reference for supports is CEBAF solution • Cavity space frame simplifies assembly and handling of the cavity after CR • No need for vertical movements • Kept minimal longitudinal space (flat heads vs standard PV dome heads) R. Paparella, MAX mid-term design review, Brussels, November 12-13, 2012.

14. The cryomodule – cryogenics • Helium buffer in the module • Liquid helium line for coupler cooling • Valve box from IPN R. Paparella, MAX mid-term design review, Brussels, November 12-13, 2012.

15. The cryomodule – manufacturing • Cryomodule has beenmanufacturedby SIMIC firm at Camerana (Italy) • Delivery to IPNO in March 2010 R. Paparella, MAX mid-term design review, Brussels, November 12-13, 2012.

16. End 2007 The cryomodule – IPNO Experimental area Beginning 2011 • RF source • 160 kW DC PS • 80 kW IOT • Waveguide, doorknob transitions • Power coupler, test bench • Cryogenics valve box and controls R. Paparella, MAX mid-term design review, Brussels, November 12-13, 2012.

17. Power coupler Conditioning cavity Based on the SNS design (itself derived from the Tristan coupler) R. Paparella, MAX mid-term design review, Brussels, November 12-13, 2012.

18. Results – RF power supply & conditioning • Coupler conditioning: • Test bench equipped with tunable cavity with copper plunger, baking, vacuum management and diagnostics • Couplers and cavity baked at 130°C → vacuum up to 5.10-8 mbar, no leak detected on the ceramic window • A first travelling wave (CW) conditioning at 1kW has been successfully done (E. Rampnoux & S. Berthelot, IPNO) • RF circulator • Circulator efficiency is very sensitive to temperature & the regulation system of the coil is slow • Several Breakdowns / Flash occurred in the DC power supply (40 kV – 4 A). Two modules sent to Bruker for assessment. • DC power supply has been repaired and electric insulation improved. It can now be controlled through a Labview program (C. Joly, IPNO) • IOT • The IOT has been successfully re-re-re-tested with its RF circulator in full reflection until 80 kW. The current of the circulator coil had been tuned to enable fast RF power increase (switch on/off). (J. Lesrel, IPNO) • In Sept. 2012 the coupler test stand was assembled to the IOT: now almost ready for high power conditioning. R. Paparella, MAX mid-term design review, Brussels, November 12-13, 2012.

19. Results – critical coupling cold tests • Critical coupling – no power coupler: • Understand the complete cryogenic system behavior • Q0 measurement @ 4K & 2K • Check the good behavior of the RF Phase Locked Loop (PLL) • Measurement of the static capabilities of the tuning system : stepper motor • Fast tuning systems influence : range of detuning & piezos Transfer Function • Overview of the tests campaign • 1st test : - July 2010 - Big leakage on the He tank detected. Experiment stopped & cavity travelled back to ZANON. • 2nd test : - February/March 2011 - New leakage on the He tank – test at 4 K but we encountered problems with the PLL : not able to power correctly the cavity. • 3rd test : - October 2011 – cavity characterization at 1.9 K. • 4th test: - May 2012 – cryogenic characterization of cryomodule and cryo-plant. R. Paparella, MAX mid-term design review, Brussels, November 12-13, 2012.

20. Results – 1st cold test Repairing of the cold leak, Oct-Nov 2010 • Cavity send back to Zanon for repairing • The weld was partially removed and soldered with argon gas-filled • Then at LASA for leak check and field flatness measurements • Thermal cycles with nitrogen and no leak detected after warm-up R. Paparella, MAX mid-term design review, Brussels, November 12-13, 2012.

21. Results – 1st cold test Unflatness Field flatness has moved : bead-pull measurement Coupler side Pick-up side Guilty one cell on the coupler side detuned Matrix analysis give individual freq cell Cavity Performances expected to decreased by ~20 %. frequency & field shapes of the five modes R. Paparella, MAX mid-term design review, Brussels, November 12-13, 2012.

22. Results – 2nd cold test • Experimental results • Measurement of the cryogenic procedure only at 4K (2K pumping system was not ready). • Cryogenics control systems had been finalized (A. El Tarr, IPNO) • Siemens PLC to collect data, control valves and manage cryogenics and vacuum safety as vacuum loss or quenches • Labview interface to handle the whole cool-down procedure and acquire data • Stepper motor tuning range measured: ~ 270 kHz @ 4 K • Issues and adjustments after the test • Improvements of cool-down piping • A new leakage appeared on He tank • Repaired at IPNO and N2 thermal shock applied • New PLL filter loop hardware • Module RF feedthrough replaced R. Paparella, MAX mid-term design review, Brussels, November 12-13, 2012.

23. Results – 3rd cold test • No leak anymore on the tank → repairing procedure confirmed March 2011 October 2011 • Static losses : ~7.5 W (@ 2 K) (N. Chevalier) & ~ 5.5 W (@ 4 K - module closed on it self) • Further improvements: • « warm » point detected at the Cryomodule/valve box connection • Level probes in the helium pot need to be gauged • A direct reference for the pressure on the helium bath must be provided for accurate automated regulation • Some thermal sensors were poorly “thermalized” R. Paparella, MAX mid-term design review, Brussels, November 12-13, 2012.

24. Results – 3rd cold test Measurement at ~ 1.9 K (Rsurf ≈ 9 nΩ; RBCS≈ 3 nΩ → Rres~ 6 nΩ) 27/10/2011 afternoon (T~ 1,9K) Le 27/10/2011 morning (T~ 2.0 K) Processing multipacting Quench Coupling : _ Qi ≈ 2.0 1010 _ Qt ≈ 2.3 1011 the 12/10/2011 (T~ 4.2 K) RF cable limits (breakdown @ Pinc~ 170W) (@ βg=0.47) R. Paparella, MAX mid-term design review, Brussels, November 12-13, 2012.

25. Results – 3rd cold test SEIZED !? • Motor • Measured hysteresis on small displacement (~0.1 mm) of 2kHz • After a few cycle motor action was blocked : Screw and nuts seized!! • Piezo actuators • Effect below expectation by one order of magnitude: +150V → ~200 Hz detuning. • Measurement only achieved at 4K, with a high sensibility to pressure variation. • Cabling and installation sequence to be cross-checked R. Paparella, MAX mid-term design review, Brussels, November 12-13, 2012.

26. Results – understanding motor seizing • No large failing has been detected, just clear evidences of high level of friction. The rather large quantity of copper stripped in one point could be the major responsible for the actual seizing. • Analysis of the story of motor unit revealed that CuBe shaft has not been heat-treated / hardened: big impact on material strength as well as surface hardness. • These drive units produced by INFN and used so far are going to be replaced by XFEL-compliant drive units that have been already purchased (delivery expected within October) within MAX funding. • These units will be the exact replica of XFEL ones, taking therefore full benefit of DESY expertise and quest for reliability. 1.5 mm Copper deposition on one steel nut thread surface R. Paparella, MAX mid-term design review, Brussels, November 12-13, 2012.

27. Results – Cold actuators reliability M. Fouaidy et Al., CARE Report, 2004 • Reliability is taken into account when choosing actuators: • Both stepper motor and piezoelectric ceramic are robust and proven technologies, almost a standard solution in the field of SC cavities fast tuning. • Failures occurred in prototypes along their “learning curve” phase • The large data set available from manufacturers has been integrated in the last 15 years with continuous use and several dedicated cold tests in different labs • Warm vs. Cold motor is sometimes discussed • That is also accessibility vs. static heat loads (see S1G at KEK) • Piezoelectric actuators: • No moving parts, no lubricant, predictively functional at cryogenic temperature • Radiation hardness verified (M. Fouaidy, IPNO, 2004) • 100 times the expected dose in operation • Life-time tests conducted (A. Bosotti, R. Paparella, INFN, 2005 and 2012) • >10^9 (10 y equivalent work load) at cold in both unipolar and bipolar mode Jean-Luc Biarrotte, MAX 4th general meeting, Frankfurt, October 1-2, 2012.

28. Results – 4th cold test • The module and the cryogenic installation are fully qualified & we set-up a system which enable to have an accurate control of the helium bath temperature • Measured performances in agreement with expectations : at 1.9 K one can operate the module until ~35 W heat load on the cavity + ~ 6 W static losses • Further improvements: • Warm point at interconnection valves box / cryostat is confirmed and have small losses: not a big issue. • New probes with controls will be ordered to AMI in replacement of home-made ones • Investigation on thermal sensor shift in progress (maybe heat load from cables) 2 K tests balance • Control example at 1.9 k (P = 23 mbar) R. Paparella, MAX mid-term design review, Brussels, November 12-13, 2012.

29. Perspectives • Except few instrumentation details the module is now fully operational on the cryogenic point of view • We are currently moving the helium pumps (primary + roots) to its final configuration in a new building. Ready for January 2013. • The power coupler conditioning will start very soon and we plan a 2 months period for the test : October - November 2012 • A clean room session has to be foreseen for December 2012: for the power coupler assembly. • The Module preparation and wave guide installation is planned for: December 2012 / January 2013. • First High Power test : February / March 2013. R. Paparella, MAX mid-term design review, Brussels, November 12-13, 2012.