Development of Infrastructure Facilities for Superconducting RF Cavity Fabrication, Processing and 2 K Characterization at RRCAT Satish Chandra Joshi, S Raghavendra, VK Jain, A Puntambekar, P Khare, J Dwivedi, G Mundra, P K Kush, P Shrivastava, M Lad and P D Gupta Raja Ramanna Centre for Advanced Technology, Indore ICEC 26 – ICMC 2016, March 7-11, 2016, New Delhi

RRCAT S C Joshi |ICEC 26 – ICMC 2016, March 7-11, 2016, New Delhi Outline DAE’s Program of High Intensity Proton Accelerators Infrastructure required for SCRF cavity development Test facilities for cavity qualification Results Summary 2

RRCAT S C Joshi |ICEC 26 – ICMC 2016, March 7-11, 2016, New Delhi High Power Proton Accelerators Programs Programs of Department of Atomic Energy: –Superconducting linac based Spallation Neutron Source –Accelerator Driven Sub-critical System –Indian Institutions and Fermilab Collaboration Program  R&D activities initiated for the above programs  Large number of superconducting cavities to be made  Dedicated infrastructure and trained man-power crucial  Industry partnership to be developed 3

RRCAT S C Joshi |ICEC 26 – ICMC 2016, March 7-11, 2016, New Delhi 4 Proposed ISNS Facility Front End SCRF Linac 1 GeV Accumulator Ring Target > 1GeV SCRF Cavities Nuclear Physics NC / SC structures 150 – 200 MeV RFQLow Beta SCRF Cavities Elliptical SCRF cavities IS The SRF infrastructure to support : ISNS activity and Participation in IIFC related activities

RRCAT S C Joshi |ICEC 26 – ICMC 2016, March 7-11, 2016, New Delhi 5 SRF Infrastructure facilities Laser scanning confocal microscope Universal Testing Machine SIMS Facility Optical Inspection Bench 3D CMM 15 kW EBW Machine Cavity fabrication & inspection facility Material Characterization facility Cavity Forming Facility

RRCAT S C Joshi |ICEC 26 – ICMC 2016, March 7-11, 2016, New Delhi 6 Electropolishing SetupBarrel Polishing MachineHigh Pressure Rinsing Setup SCRF Cavity Processing Facilities Ultrasonic cleaner Cavity polished & processed High Vacuum Annealing Furnace SRF Infrastructure facilities

RRCAT S C Joshi |ICEC 26 – ICMC 2016, March 7-11, 2016, New Delhi Beam power15 kW Gun Voltage90 to 150 kV Duty cycle100% Beam current range mA or wider Beam current setting resolution 0.1 mA Beam oscillations1 – 1000 Hz or more Beam focus diameter0.25 mm Inner size of chamber3650 x 1500 x 1800 mm 3 X-Y table size1780 m x 710 mm Vacuum ready pressure < 1x10 -4 mbar in 15 min Ready for welding pressure < 1x10 -6 mbar in 60 min Electron Beam Welding Machine Cavity Fabrication Facility 7

RRCAT S C Joshi |ICEC 26 – ICMC 2016, March 7-11, 2016, New Delhi 8 Welding of single-cell 650 MHz cavity

RRCAT S C Joshi |ICEC 26 – ICMC 2016, March 7-11, 2016, New Delhi Cavity Fabrication Facility Nd-YAG laser beam welding facility – for 1.3 GHz single-cell cavity A novel technique of fabrication of SRF cavities using Nd-YAG laser welding process, has been developed at RRCAT. The process has received patent from Japan. A 1.3 GHz single-cell cavity fabricated using the facility was processed and tested at Fermilab. The cavity produced an accelerating gradient > 31 MV/m 9

RRCAT S C Joshi |ICEC 26 – ICMC 2016, March 7-11, 2016, New Delhi 10 Optical Inspection Bench  Cavity internal surface measurement using a digital CCD camera with 10X- 200X magnification.  Tri-color LED for illumination  Smallest measurable feature size : 10 microns SRF Cavity Inspection Facility Images from optical bench (650 MHz cavity) Inspection of single-cell 650 MHz cavity Inspection of five-cell 1.3 GHz cavity

RRCAT S C Joshi |ICEC 26 – ICMC 2016, March 7-11, 2016, New Delhi Laser Scanning Confocal Microscope Imaging Method 3-D Laser Scanning Confocal system Z - Resolution (Depth) 1 nm Z - Measurement repeatability 12 nm X-Y Resolution0.12  m Confocal image of replicaMeasurement of bead profile SRF Cavity Inspection Facility 11

RRCAT S C Joshi |ICEC 26 – ICMC 2016, March 7-11, 2016, New Delhi Secondary Ion Mass Spectrometer (SIMS) To develop understanding of impurity distribution near the top layer (~ nm) of niobium by 2-D, 3-D ion mapping of the impurities. Quantification of the elemental impurity distribution using niobium standards. Analysis Gun : Bi + at 30 kV C 60 at 20 kV Sputter Gun : Cs + ; 0-2 kV O 2 + ; 0-2 kV Xe + ; 0-2 kV Ar + ; 0-2 kV SRF Cavity Material characterization Facility "Study of impurity distribution in chemically treated and high pressure rinsed pure Niobium samples for SCRF cavity applications using TOFSIMS technique", A. Bose and S. C. Joshi, Superconductor Science and Technology, July

RRCAT S C Joshi |ICEC 26 – ICMC 2016, March 7-11, 2016, New Delhi 13 Centrifugal Barrel Polishing (five-cell 650 MHz cavity) Main features of CBP machine Turret speed – 0 – 200 rpm ( variable ) Barrel speed – 0 – 200 rpm ( variable ) Machine size – 4 m X 5 m X 3 m Temperature is maintained by closed loop air conditioner Barrel Polishing Machine at RRCAT Cavity Processing Facility

RRCAT S C Joshi |ICEC 26 – ICMC 2016, March 7-11, 2016, New Delhi 14 Electropolishing setup for 1.3 GHz & 650 MHz Cavities Cavity Processing Facility Electropolishing of single-cell 650 MHz cavity Electropolishing of nine-cell 1.3 GHz cavity

RRCAT S C Joshi |ICEC 26 – ICMC 2016, March 7-11, 2016, New Delhi 15 Thermal Processing Facility Specification of High Vacuum Furnace OrientationHorizontal Maximum Temperature 1400  C Max Working Vacuum <1 x mbar (600  C  C ) <1 x mbar (> 1000  C) Working Volume Dia : 825 mm Depth :1500 mm High Vacuum Annealing Furnace Single-cell 650 MHz cavity prepared for annealing

RRCAT S C Joshi |ICEC 26 – ICMC 2016, March 7-11, 2016, New Delhi High Pressure Rinsing Setup Cavity Processing Facility Rotational speed: 2-20 RPM Stroke: 1300 mm Vertical speed: mm/min Pressure: 80 – 100 bar 16

RRCAT S C Joshi |ICEC 26 – ICMC 2016, March 7-11, 2016, New Delhi 17 SRF Cavity Tuning Machine Separate Semi-automatic tuning facility for 1.3 GHz A prototype nine-cell1.3 GHz cavity has been successfully tuned using the facility  Field flatness improved from 24% (as fabricated) to 92%

RRCAT S C Joshi |ICEC 26 – ICMC 2016, March 7-11, 2016, New Delhi Operating temperature Range of frequency shift with piezo actuator excitation to 200V Hysteresis 300 K82 kHz11 kHz 77 K31.5 kHz2.9 kHz 2 K10.8 kHz950 Hz  Tuner mechanism is tested at 2K in VTS with single-cell SCRF cavity under superconducting state.  A piezo driver has been developed to drive the actuator by half sine wave. Characteristic of single-cell cavity tuner assembly for piezo DC excitation at 2 K. Comparison of fast tuner characteristics at different temp. Tuner testing with 1.3 GHz single cell SCRF cavity Single-cell SCRF cavity with tuner Assembly for testing in VTS Tuner development for SCRF cavity

RRCAT S C Joshi |ICEC 26 – ICMC 2016, March 7-11, 2016, New Delhi First 5-cell, 1.3 GHz SCRF cavity First 5-cell, 1.3 GHz SCRF niobium cavity on October 8, The cavity showed E acc of 20.3 MV/m at 2 K and 42 MV/m at K with Q 0 of 2 x cell 1.3 GHz cavity on VTS insert Q0 v/s Eacc plot of cavity cold test

RRCAT S C Joshi |ICEC 26 – ICMC 2016, March 7-11, 2016, New Delhi 650 MHz Single-cell Niobium Cavity First 650 MHz single-cell niobium cavity fabricated by RRCAT and IUAC was processed and tested at Fermilab. It reached E acc of 19.3 MV/m and Q o of of 7x10 10 at 2K. This performance exceeds the design parameters.

RRCAT S C Joshi |ICEC 26 – ICMC 2016, March 7-11, 2016, New Delhi Vertical Test Stand (VTS) Facility A vertical test facility for RF characterization of SCRF cavities at 2 K has been commissioned. A single-cell 1.3 GHz cavity has been successfully tested using the facility. Transfer of liquid helium in the VTS cryostat Testing of single-cell 1.3 GHz SCRF cavity in the VTS facility at RRCAT 21

RRCAT S C Joshi |ICEC 26 – ICMC 2016, March 7-11, 2016, New Delhi Electropolishing Assembly in clean room High pressure rinsing Cavity on VTS insert Total liquid helium collected in cryostat1400 liters Minimum temperature achieved1.65 K Processing & Testing of single-cell 650 MHz cavity Maximum Quality factor3.7x10 10 Accelerating gradient10.25 MV/m

RRCAT S C Joshi |ICEC 26 – ICMC 2016, March 7-11, 2016, New Delhi One Helium liquefier with a liquefaction capacity of 50 l/h. One Helium liquefier with a liquefaction capacity of 145 l/h Cryogenic facility Liquid Dewar 10,000 liters and Cold Box: LR 280 Cyclic Compressor 23

RRCAT S C Joshi |ICEC 26 – ICMC 2016, March 7-11, 2016, New Delhi LASER BEAM WELDING STATION EP SETUP CBP FACILITY HIGH PRESSURE RINSING SET UP PRESS Exisiting & Planned Facilities ELECTRON BEAM WELDING STATION ULTRASONIC CLEANERS A ANNEALING FURNACE Ultrapure Water Plant Under Construction ETP Facility TUNING MACHINE 24

RRCAT S C Joshi |ICEC 26 – ICMC 2016, March 7-11, 2016, New Delhi 25 Summary…. A large infrastructure has been setup at RRCAT for SCRF cavity fabrication, processing, characterization and testing. A few 1.3 GHz and 650 MHz cavities have been fabricated, processed and tested under IIFC and exhibited good performance 1.3 GHz and and 650 MHz cavities also have been fabricated, processed and undergoing test at 2 K in RRCAT. A large VTS facility is operational along with a LHe distribution and pump down facility for 2K operation. Work is under progress to test multi-cell SCRF cavities using VTS facility at RRCAT.

RRCAT S C Joshi |ICEC 26 – ICMC 2016, March 7-11, 2016, New Delhi Acknowledgement Thanks to all our colleagues at RRCAT and collaborators: Cryo-engineering and Cryomodule Development Division, Pulsed High Power Microwave Division, Accelerator Control Section, Accelerator Components Design and Fabrication Section, Power Supplies & Industrial Accelerator Division. Inter University Accelerator Centre, Delhi Fermilab, USA Proton Linac and Superconducting Division,