Status of the 201 MHz Cavity and Coupling Coil Module Steve Virostek Lawrence Berkeley National Laboratory MICE Video Conference March 10, 2004

MICE Video Conference Status of 201 MHz Cavity and Coupling Coil S. Virostek LBNL Page MHz Cavity Concept Spinning of half shells using thin Cu sheets and e-beam welding to join the shells Water cooling channels Cavity design accommodates different windows Extruding ports

March 10, 2004 MICE Video Conference Status of 201 MHz Cavity and Coupling Coil S. Virostek LBNL Page 3 The Cavity Body Profile De-mountable pre-curved Be windows to terminate RF fields at the iris 2 o tilt angle Spherical section at the equator to ease addition of ports (± ~ 6 o ) Elliptical-like (two circles) nose to reduce peak surface field 6-mm Cu sheet permits spinning technique and mechanical tuners similar to SCRF ones Stiffener ring Bolted Be window

March 10, 2004 MICE Video Conference Status of 201 MHz Cavity and Coupling Coil S. Virostek LBNL Page 4 The Cavity Parameters The cavity design parameters –Frequency: MHz – β = 0.87 –Shunt impedance (V T 2 /P): ~ 22 M  /m –Quality factor (Q 0 ): ~ 53,000 –Be window radius and thickness: 21-cm and 0.38-mm Nominal parameters for cooling channel in a neutrino factory –Up to 17 MV/m peak accelerating field –Peak input RF power ~ 4.6 MW per cavity (85% of Q 0, 3τ filling) –Average power dissipation per cavity ~ 8.4 kW –Average power dissipation per Be window ~ 100 watts

March 10, 2004 MICE Video Conference Status of 201 MHz Cavity and Coupling Coil S. Virostek LBNL Page 5 ACME Spinning a bowl Spinning tools An example of the spinning technique!

March 10, 2004 MICE Video Conference Status of 201 MHz Cavity and Coupling Coil S. Virostek LBNL Page 6 RF & CMM Measurements at LBNL CMM scans, RF frequency and Q measurements of half shells; Cu tape for better RF contacts. 3 CMM scans per half shell conducted at 0 o, 45 o, 90 o, respectively. Measured frequency: MHz (simulated frequency: MHz)

March 10, 2004 MICE Video Conference Status of 201 MHz Cavity and Coupling Coil S. Virostek LBNL Page 7 E-Beam Welding Preparation for e-beam welding of the stiffener ring (left); after the e-beam Welding (above) Stiffener ring

March 10, 2004 MICE Video Conference Status of 201 MHz Cavity and Coupling Coil S. Virostek LBNL Page 8 Extruding Tests at JLab Extruding tests on a flat Cu plate going through e-beam joint Possible improvement: Anneal around the extruding area or Combination between pilot hole dimensions and lid heights, … Successful extruding recently!

March 10, 2004 MICE Video Conference Status of 201 MHz Cavity and Coupling Coil S. Virostek LBNL Page 9 Be Windows R&D Ideal windows – Transparent to muon beams – Perfect electric boundary to RF field – No detuning of cavity frequency Engineering solutions – Pre-stressed flat Be (low-Z) windows – Pre-curved Be windows – Grids A pre-curved Be window: 0.25 mm thick and 21 cm in radius Window profile evolutions

March 10, 2004 MICE Video Conference Status of 201 MHz Cavity and Coupling Coil S. Virostek LBNL Page 10 Curved S.S. Windows Succeeded in the S.S. window with Cu frame for 805 MHz cavity (scaled version of the window for 201 MHz cavity) Pre-formed at room temperature by holding foil edge then brazing the Cu frames A finished curved S.S. window with brazed Cu frame

March 10, 2004 MICE Video Conference Status of 201 MHz Cavity and Coupling Coil S. Virostek LBNL Page 11 Curved Be Window Failed in forming Be window at room temperature The curved Be windows can be formed at higher temperature by the Brush- Wellman Company. Order was placed for two 805 MHz windows. The Be foil cracked during forming at room temperature (LBNL) A successfully formed Be foil (Feb. 5th 2004 at Brush-Wellman)

March 10, 2004 MICE Video Conference Status of 201 MHz Cavity and Coupling Coil S. Virostek LBNL Page 12 Curved Be Windows Brush-Wellman recently succeeded in making two curved Be windows with Cu frames for the 805 MHz cavity Fabrication Methodology Fabricated dies in the shape of the windows Press Be into shape at high temperature Braze Cu frames to curved Be in a separate process

March 10, 2004 MICE Video Conference Status of 201 MHz Cavity and Coupling Coil S. Virostek LBNL Page MHz Cavity Status Four half shells have been formed by spinning Cu stiffener rings were e-beam welded to two half shells The shells were mechanically cleaned at JLab Shells are being machined prior to e –beam welding of equator joint Equator weld fixturing has been fabricated at LBNL Cavity nose piece rings (fab. By U. Miss.) have been brazed at LBNL Conceptual design of RF loop coupler is complete Prototype pre-curved Be windows complete (805 MHz size)  E-beam welding of equator joint and nose rings  Extruding of four ports (2 RF, 2 vacuum)  Brazing of cooling lines to cavity exterior  Chemical cleaning and electro-polishing of the cavity  Design and fabrication of tuner system  Final design and fabrication of RF coupling loops  The cavity should be ready for test in MTA at Fermilab this fall

March 10, 2004 MICE Video Conference Status of 201 MHz Cavity and Coupling Coil S. Virostek LBNL Page 14 MICE RF Module Layout Status New layout has several changes and additions: New coupling coil design incorporated RF coupling loops modified Vacuum system for cavities and vessel added AFC module vessel flanges extended 62 mm on downstream ends to make flanges symmetric to coils Various vessel joint concepts being explored

March 10, 2004 MICE Video Conference Status of 201 MHz Cavity and Coupling Coil S. Virostek LBNL Page 15 MICE RF Module Layout

March 10, 2004 MICE Video Conference Status of 201 MHz Cavity and Coupling Coil S. Virostek LBNL Page 16 MICE RF Module Coupling Loops

March 10, 2004 MICE Video Conference Status of 201 MHz Cavity and Coupling Coil S. Virostek LBNL Page 17 MICE RF Module Vacuum System