CERN 12 December 2016 Trim tuning of the
CERN, 12 December 2016 Trim tuning of the CERN-DQW-001 cavity Silvia Verdú-Andrés | Brookhaven National Lab “Trim tuners” Rama Calaga, James Alexander Mitchell, Silvia Verdu-Andres with contributions from Ofelia Capatina, Paula Freijedo Menendez, Marco Garlasche, Raphael Leuxe and Laurent Prever-Loiri and many others in the CERN main workshop
9. 2 mm longer h = 26 Silvia Verdú-Andrés (BNL)| CERN, 12 December 2016 | Slide 2 11. 2 Measurement #0
9. 2 mm longer h = 26 f = 404. 60 MHz for htop = hbottom = 17. 5 mm; thus there are still 0. 7 mm overlength w. r. t. nominal height (note that in addition there are 0. 5 mm reserved for weld shrinkage and 1. 5 mm in case the cavity needs to be cut shorter than nominal) Silvia Verdú-Andrés (BNL)| CERN, 9 December 2016 | Slide 3 11. 2 Measurement #3 – TODAY Saturday 10 Dec 2016
Frequency measurement of clamped cavity [CERN-DQW-001] 13 d. Bm, 6000 points, 200 – 500 Hz Silvia Verdú-Andrés (BNL)| CERN, 12 December 2016 | Slide 4
Clamping cycles for CERN-DQW-001 [f#2] Good reproducibility from cycle to cycle No need for strong clamping to reach high Q (very flat subassembly edges) Cavity deformation with clamping is +/-0. 1 mm to improve Q from 3000 to 5000 with frequency variation less than 10 k. Hz 409. 8000 409. 7000 409. 6000 Cycle_1 Cycle_2 Cycle_3 409. 5000 409. 4000 409. 3000 0 1000 2000 3000 4000 5000 Silvia Verdú-Andrés (BNL)| CERN, 12 December 2016 | Slide 5 6000
Frequency evolution during trim tuning of CERN-DQW-001 nominal shorter (1. 5+1. 5) Frequency [MHz] 420 418 416 414 412 410 408 406 404 402 400 -5. 00 -2. 6 longer (9. 2+9. 2) f #0 Measured Target f #3 GOAL 401. 17 MHz 0. 00 1. 4 5. 00 10. 00 Trim tuning sensitivity [MHz/mm] 1. 00 (target frequency for clamped cavity 15. 00 20. 00 before two last welds) may need to be revisited as it assumes 1 mm total shrinkage Instantaneous and 0. 98 MHz/mm sensitivity 0. 90 0. 80 df/dl for Niowave cavity increased for extra material length < 10 mm. Currently still is below value from simulations, 0. 98 MHz/mm. 0. 70 0. 60 -5. 00 0. 00 5. 00 10. 00 Overlength [mm] 15. 00 20. 00
Strategy for week 12 -17 December 2016 STEP 1: asymmetric trim; aims at bringing cavity frequency close to target Trim 2 mm in top subassembly Trim 0 mm in bottom subassembly STEP 2: weld top and center subassemblies together weld Silvia Verdú-Andrés (BNL)| CERN, 12 December 2016 | Slide 7
Shrinkage of two last welds – tests on ellipsoidal tube Measured shrinkage in the ellipsoidal test for the final weld W 03 is 0. 6 mm, except for the overlap (R) in which the value obtained is 1 mm, being the length of this area of around 50 mm. Silvia Verdú-Andrés (BNL)| CERN, 12 December 2016 | Slide 8
Improvement of Q with clamping Clamping adjustment was refined from cycle 1 to cycle 2 by using the nut faces as reference: 1 face is 60 degrees or 1/6 of a full turn. Highest Q achieved with less than full turn (after manual tightening) excellent planarity. 1. 6 Cycle 1 1. 4 Cycle 2 Cycle 3 1. 2 may vary due to different manual tightening Turns 1 0. 8 0. 6 0. 4 0. 2 0 0 1000 2000 3000 4000 Quality factor 5000 Silvia Verdú-Andrés (BNL)| CERN, 12 December 2016 | Slide 9 6000
Deformation of cavity with clamping Displacement of clamping plate [mm] Cavity deformation with clamping is +/-0. 1 mm to improve Q from 3000 to 5000 with frequency variation less than 10 k. Hz. Quality factor 0 -0. 1 0 2000 4000 -0. 2 -0. 3 -0. 4 -0. 5 -0. 6 -0. 7 -0. 8 -0. 9 -1 Silvia Verdú-Andrés (BNL)| CERN, 12 December 2016 | Slide 10 6000
Electric field center For symmetric cavity, the electric field center offset is -0. 23 mm, that is 0. 23 mm closer to the bottom (asymmetry introduced by port distribution). If the bottom subassembly is made shorter than the top subassembly, the electric field center will move towards the top, thus centering the electric field lines. Silvia Verdú-Andrés (BNL)| CERN, 12 December 2016 | Slide 11
Trim tuning sensitivity for NWV-DQW-001 Trim tuning sensitivity df/d. L Trim tuning sensitivity [MHz/mm] 1. 00 Instantaneous Absolute 0. 90 0. 80 0. 70 0. 60 -2. 00 0. 00 2. 00 4. 00 6. 00 8. 00 Section length [mm] 10. 00 Silvia Verdú-Andrés (BNL)| CERN, 12 December 2016 | Slide 12 12. 00 14. 00
Setup
Frequency measurement setup - at CERN Equipment prepared by James Mitchell and Rama Calaga Couplers • set of hooks with different apertures • spacers of different length • flanges with enlarged through holes #1 SET OF HOOKS #2 #3 allow changing Qext: 105 – 108 Network Analyser Rhode & Schwarz COUPLER ASSEMBLY Clamping system hook • compliant surface (rubber) • torque wrench 0. 3 -20 N m Measurements conducted in Bldg. 72 – metrology (access to hygrometer and thermometer) Excel spread sheet available to assist trim tuning Silvia Verdú-Andrés (BNL)| CERN, 28 November 2016 | Slide 14 spacer
HOMs [James Alexander Mitchell] f_580 582. 5 581. 5 580. 5 579. 5 578. 5 577. 5 576. 5 0 1000 2000 3000 4000 5000 f_958 6000 959. 2 959 958. 8 958. 6 958. 4 958. 2 958 0 1000 2000 3000 4000 5000 Silvia Verdú-Andrés (BNL)| CERN, 12 December 2016 | Slide 15 6000 7000 8000 9000
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