1. 201 MHz Cavity Plans Derun Li Center for Beam Physics Lawrence Berkeley National Laboratory February 11, 2011 MAP Friday Video Conference Meeting

2. Summary of 201 MHz Cavity Activities – RF loop coupler damage (observation) Sparking at loop region due to a narrow gap between the loop and cavity body Sparking at loop region due to a narrow gap between the loop and cavity body Ceramic window damage: copper sputtered on the window with patterns Ceramic window damage: copper sputtered on the window with patterns – Understand/study and repair the damaged coupler A small section of the coaxial part of the coupler has been cut for measurement and analysis by J. Norem at ANL A small section of the coaxial part of the coupler has been cut for measurement and analysis by J. Norem at ANL The loop will be modified to increase the spacing between the loop and cavity body, including all couplers for MICE cavities The loop will be modified to increase the spacing between the loop and cavity body, including all couplers for MICE cavities – Field enhancement and RF heating power of the curved-in beryllium window Verify simulation results Verify simulation results 201 MHz Cavity Plan, D. Li, Lawrence Berkeley National Lab, Feb. 11, 2011 2

3. 201 MHz Cavity for MICE MICE cavity fabrication progressing well MICE cavity fabrication progressing well MICE RF cavities in advance of scheduled date (MICE CM28); we have ten cavities with brazed water cooling pipes (two spares) at LBNL (Dec. 2010) MICE RF cavities in advance of scheduled date (MICE CM28); we have ten cavities with brazed water cooling pipes (two spares) at LBNL (Dec. 2010) – First five cavities measured with low RF power (frequency and Q) – Received nine beryllium windows (with TiN coatings) – Ten ceramic RF windows ordered; two could be used for MTA – Tuner design complete, one tuner prototype tested offline – Six prototype tuners in fabrication, and to be tested this year – Design of RF power (loop) coupler complete, ready for fabrication – Design of cavity support and vacuum vessel complete – Cavity post-processing (surface cleaning and preparation for EP) to start this year at LBNL 201 MHz Cavity Plan, D. Li, Lawrence Berkeley National Lab, Feb. 11, 2011 3

4. Cavity Inspection 201 MHz Cavity Plan, D. Li, Lawrence Berkeley National Lab, Feb. 11, 2011 4

5. Damage on Ceramic Window 201 MHz Cavity Plan, D. Li, Lawrence Berkeley National Lab, Feb. 11, 2011 5

6. Sparking Marks of RF Coupler 201 MHz Cavity Plan, D. Li, Lawrence Berkeley National Lab, Feb. 11, 2011 6

7. Coupler Repair Borrow two MICE ceramic windows for high power tests (ten of them have been ordered) Borrow two MICE ceramic windows for high power tests (ten of them have been ordered) Refurbish the couplers Refurbish the couplers – Modify the loop design to increase spacing of the gap between the coupler and cavity body – TiN coating on the loop region – Clean surface exposed to RF Retune RF coupling Retune RF coupling Add more diagnostics Add more diagnostics – Arc detectors – Temperature sensors 201 MHz Cavity Plan, D. Li, Lawrence Berkeley National Lab, Feb. 11, 2011 7

8. Measurement Plan Using MICE Cavities Measurement of engineering and mechanical designs Measurement of engineering and mechanical designs – Prototypes: MuCool prototype cavity, tuners, tuning mechanism, support structure – Vacuum, water cooling and integration RF measurement RF measurement – RF parameters: frequency, Q, coupling (couplers) – Low power RF measurements of tuning range, sensitivity, mechanism and control circuit – W/O and with beryllium windows Single cavity vessel Single cavity vessel 201 MHz Cavity Plan, D. Li, Lawrence Berkeley National Lab, Feb. 11, 2011 8

9. Design of Single Cavity Vessel 9 201 MHz Cavity Plan, D. Li, Lawrence Berkeley National Lab, Feb. 11, 2011 o Keep as much as possible of the same dimensions and features of RFCC o One vessel to accommodate two types of MICE cavities (left and right) o Future LN operation RFCC module

10. Design of Single Cavity Vessel 201 MHz Cavity Plan, D. Li, Lawrence Berkeley National Lab, Feb. 11, 2011 10 o The single cavity vessel design is complete (LBNL) o Drawings will be generated for review soon o Design review soon: o Biding and identification of vendors o Fabrication of vessel and accessory components o Six prototype tuners in fabrication at Mississippi University

11. What Can We Learn? Prior to having MICE RFCC module, the single cavity vessel allows us to: Check engineering and mechanical design Check engineering and mechanical design Obtain hands-on experience on assembly and develop assembly procedures and fixture Obtain hands-on experience on assembly and develop assembly procedures and fixture – Cavity installation Beryllium windows Beryllium windows RF couplers and connections RF couplers and connections Water cooling pipe connections Water cooling pipe connections Vacuum port and connections Vacuum port and connections Tuners and circuit Tuners and circuit – Cavity support structures – Vacuum vessel support and handling 201 MHz Cavity Plan, D. Li, Lawrence Berkeley National Lab, Feb. 11, 2011 11

12. What Do We Plan to Measure? Low power RF measurements: – Cavity frequency in air and vacuum – Tuning sensitivity in air or vacuum High power RF measurements: – Cavity conditioning – Frequency variation due to RF heating on beryllium windows and cavity body (can be done using the MTA prototype cavity) – Frequency shift as a function of average RF power and time – Repeat above measurement with active tuners on the cavity and measure tuning range and sensitivity (tuner control circuits, etc.) Measurements with magnetic fields? Measurements with magnetic fields? 201 MHz Cavity Plan, D. Li, Lawrence Berkeley National Lab, Feb. 11, 2011 12

13. Summary Damage of RF couplers and ceramic windows observed, more RF tests will be resumed with new ceramic windows and repaired and modified couplers Damage of RF couplers and ceramic windows observed, more RF tests will be resumed with new ceramic windows and repaired and modified couplers RF cavity measurement plan (using MICE cavity) developed RF cavity measurement plan (using MICE cavity) developed Many MICE related issues can be explored and learned from the measurements of single cavity vessel Many MICE related issues can be explored and learned from the measurements of single cavity vessel In addition, we will continue In addition, we will continue – RF measurements of the second batch of the five MICE cavities – Cavity surface finish and EP – Corse tuning (by deforming the cavity body) of all MICE cavities to a center frequency – Fabrication of accessory components Coupling coil magnet for MuCool Coupling coil magnet for MuCool 201 MHz Cavity Plan, D. Li, Lawrence Berkeley National Lab, Feb. 11, 2011 13