Performance of Large Grain and Single Crystal Niobium Cavities P. - PowerPoint PPT Presentation

Performance of Large Grain and Single Crystal Niobium Cavities P. Kneisel, G. Ciovati, G.R.Myneni, Jlab J. Sekutowicz, DESY T. Carneiro, CBMM July 12, 2005 SRF 2005, Cornell University

Jlab/CBMM Technology(1) • Development started with the need for understanding mechanical properties of niobium from different manufacturers (G. Myneni) • Ingot material supplied by CBMM with large grains (T. Carneiro) • Mechanical properties –especially elongation – excellent, permitting forming of cavity cells • Investigate influence of grain boundaries on “Q-drop” Comparison of Single and Poly Crystal RRR niobium 1200 1000 Poly Crystal Single Crystal 800 Load (Pounds) 600 400 200 0 0 20 40 60 80 100 120 Percentage of elongatioon July 12, 2005 SRF 2005, Cornell University

Jlab/CBMM Technology(2) • Since the first ILC workshop we have fabricated and tested 5 single cell cavities ( 1300 MHz – 1500 MHz) from sliced material ( wire EDM and saw cut) from 3 different ingots (“A”,”B”,”C”),3 different shapes, CBMM • We have fabricated and tested 2 single crystal cavities from ingot “A” at 2.3 GHz, CBMM • We have fabricated two 2.3 GHz cavities with material from a second vendor (WC) with somewhat smaller grains (not yet tested) • We have fabricated a single cell cavity from large grain niobium from China-Ningxia (not yet tested) • We have fabricated a 7-cell HG –Jlab-Upgrade cavity, which has been tested with problems so far (leaks, FE) • We are in the process of fabricating an ILC_LL 7-cell cavity and intend to present results at the Snowmass meeting July 12, 2005 SRF 2005, Cornell University

Jlab/CBMM Technology(3) Ingot “B” HG Single Cell Cavity - "Single Crystal "-B Q 0 vs. E a cc "150 micron bcp,post-purified, 100 micron bcp " "In - situ" baked at 120C, 40 hrs 1.00E+11 Test 1.00E+10 Quench 1.00E+09 0 5 10 15 20 25 30 35 E ac c [M V / m ] July 12, 2005 SRF 2005, Cornell University

Jlab/CBMM Technology(4) Ingot “A” HG Single Cell Cavity - "Single Crystal "-A Q 0 vs. E a c c after baking before baking 1.00E+11 Test #4/4a 1.00E+10 Quench 1.00E+09 0 5 10 15 20 25 30 35 E a c c [M V / m ] July 12, 2005 SRF 2005, Cornell University

Jlab/CBMM Technology(5) Cavity Discs from Ingot E peak /E acc = 1.674 H peak /E acc = 4.286 mT/MV/m July 12, 2005 SRF 2005, Cornell University

Single Crystal Niobium Cavity (1) Test #1a: Treatment 100 µ m BCP, 800C hydrogen degassing, 100 µ m BCP, high pressure rinsing for 30 min 2.2 GHz Single crystal single cell cavity Q 0 vs. E acc T=2K T=1.7K T=1.5K 1.00E+11 Test #1 Q 0 1.00E+10 Q-drop 1.00E+09 0 5 10 15 20 25 30 35 40 July 12, 2005 SRF 2005, Cornell University E acc [MV/m]

Single Crystal Niobium Cavity (2) Test #2: T-dependence (before baking) 2.2 GHz Single crystal single cell cavity after post-purification, 70mm BCP 1:1:1, 30min HPR Data BCS Fit 1.00E-05 TEST #2 1.00E-06 Surface resistance [ohm] 1.00E-07 ∆ /kT c = 1.827 ± 0.032 R res = 0.8 ± 0.4 n Ω l = 291 ± 83 nm 1.00E-08 λ L = 32 nm ξ = 62 nm T c = 9.25 K 1.00E-09 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.7 1/Temperature [1/K] July 12, 2005 SRF 2005, Cornell University

Single Crystal Niobium Cavity (3) Test #1b: Treatment 100 µ m BCP, 800C hydrogen degassing, 100 µ m BCP, high pressure rinsing, “in situ” baked at 120C for 48 hrs 2.2 GHz Single crystal single cell cavity, 120C 48h bake Q 0 vs. E acc T=2K T=1.5K 1.00E+11 Test #1baked Transmitted signal Q 0 1.00E+10 Field emission pulsed 1.00E+09 0 5 10 15 20 25 30 35 40 45 July 12, 2005 SRF 2005, Cornell University E acc [MV/m]

Single Crystal Niobium Cavity (4) Test #2: post-purification heat treatment at 1250 C for 10 hrs, 100 µ m BCP ,high pressure rinsing 2.2 GHz Single crystal single cell cavity after postpurification Q 0 vs. E acc T=2K T=1.84K T=1.84K scaled to 1.3 GHz 1.E+11 Test #2 ERL gradient XFEL gradient ILC gradient Q 0 1.E+10 Quench 1.E+09 0 5 10 15 20 25 30 35 40 July 12, 2005 SRF 2005, Cornell University E acc [MV/m]

Jlab/CBMM Technology(6) Nb Discs LL cavity 2.3GHz E peak /E acc = 2.072 H peak /E acc = 3.56 mT/MV/m 1E+11 Baseline T = 2 K After 120 C, 24 h bake Q 0 1E+10 1E+09 0 5 10 15 20 25 30 35 40 45 50 E acc [MV/m] July 12, 2005 SRF 2005, Cornell University

Jlab/CBMM Technology(7) ILC_LL Cavities: no Q-drop w/o baking Large Grain ILC_LL_Cavity T=1.8K T=1.4K T=2K 1.00E+12 Test #4 T t #1 Can't follow the resonance! 1.00E+11 Q 0 1.00E+10 Quench @ 33 MV/m 1.00E+09 0 5 10 15 20 25 30 35 E acc [MV/m] 1500 ppm Ta July 12, 2005 SRF 2005, Cornell University

Surface Roughness (1) BCP provides very smooth surfaces as measured by A.Wu, Jlab RMS: 1274 nm fine grain bcp RMS 1274 nm 53 nm after ~ 35 micron, single Crys 27 nm after ~ 80 micron,single Crys 251 nm fine grain ep RMS 27 nm July 12, 2005 SRF 2005, Cornell University

Surface Roughness (2)(A. Wu) July 12, 2005 SRF 2005, Cornell University

Jlab/CBMM Technology(8) With a single cell cavity of the OC shape and fabricated from ingot “A” material we are investigating the “improvements” in cavity performance as a function of material removal employing T-mapping with the goal to: understand the loss mechanisms in the cavity, • especially in the region of the “Q-drop” • “streamline” the surface treatment by BCP with respect to the amount of material removal, which might result in cost savings July 12, 2005 SRF 2005, Cornell University

T-Mapping (1) T-mapping system: ~600 Allen-Bradley C-resistors a) a) b b ) ) July 12, 2005 SRF 2005, Cornell University

T-Mapping (2) 4 2 3 Large grain CEBAF Single cell cavity 70 µ m BCP 1:1:2 Large grain CEBAF Single cell cavity 70 µ m BCP 1:1:2 Large grain CEBAF Single cell cavity 70 µ m BCP 1:1:2 1E+11 1E+11 1E+11 T=2.0 K T=2.0 K T=2.0 K T=1.7 K T=1.7 K T=1.7 K Q 0 1E+10 Q 0 1E+10 Q 0 1E+10 1E+09 1E+09 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 1E+09 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 B p (mT) 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 B p (mT) Eacc = 25.9 Mv/m B p (mT) Eacc = 27.6 Mv/m Eacc = 29 Mv/m Q = 4.9 x 10 9 Q = 3.1 x 10 9 Q = 1.9 x 10 9 Tb = 1.7 K Tb = 2 K Tb = 1.7 K Tb = 2 K 1.00E+00 1.00E+00 1.00E-01 1.00E-01 70 micron ∆ T [K] ∆ T [K] 1.00E-02 1.00E-02 bcp 1:1:2 1.00E-03 1.00E-03 50 70 90 110 130 150 50 70 90 110 130 150 Bp [mT] Bp [mT] July 12, 2005 SRF 2005, Cornell University

T – Mapping(3) Add. 25 micron bcp 1:1:2 E acc = 28.5 MV/m Q = 3.6 x 10 9 1 4 2 3 Large grain CEBAF Single cell cavity 25 µ m BCP 1:1:2 1 1E+11 T=2.0 K T=1.7 K 0.1 13-8 ∆ T [K] 23-8 28-8 Q 0 1E+10 29-8 0.01 0.001 70 80 90 100 110 120 130 1E+09 Bp [mT] 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 B p (mT) July 12, 2005 SRF 2005, Cornell University

Jlab/CBMM Technology(9) What are the potential advantages of large grain/single crystal niobium ? • Reduced costs • Comparable performance • Very smooth surfaces with BCP, no EP necessary • Possibly elimination of “in situ” baking because of “Q-drop” onset at higher gradients • Possibly very low residual resistances (high Q’s), favoring lower operation temperature(B.Petersen) • Higher thermal stability because of “Phonon-Peak” • Good or better mechanical performance than fine grain material (e.g.predictable spring back..) • Less material QA (eddy current/squid scanning) July 12, 2005 SRF 2005, Cornell University

Cavities awaiting testing Wah Chang China CBMM 2.2 GHz, HG shape 1.5 GHz, OC shape 1.3 GHz ILC_LL shape July 12, 2005 SRF 2005, Cornell University

Acknowledgement This work would not have been possible without the support of several colleagues from Jlab: Bon Manus Gary Slack Larry Turlington Steve Manning Pete Kushnick Isiah Daniels July 12, 2005 SRF 2005, Cornell University