~ ~ ~ ~ FERMILAB-SLIDES-18-121-TD Status of HOMS Spectra Measurements in 1.3 GHz Cavities for LCLS-II --------• ~· & ,. NATIONAL -- -- e ACCELERATOR ... LABORATORY Andrei Lunin CFermilab (on behalf of TD/SRF Group, Fermilab) HOMSC2018 ICFA Mini Workshop • 1-3 October 2018 @ ENERGY Office of Science This document was prepared by [COLLABORATION NAME] using the resources of the Fermi National Accelerator Laboratory (Fermilab), a U.S. Department of Energy, Office of Science, HEP User Facility. Fermilab is managed by Fermi Research Alliance, LLC (FRA), acting under Contract No. DE-AC02-07CH11359. This docu ment was prep ared by [COL LAB ORA TION NAM E] using the resou rces of the Ferm i Natio nal Accel erato r Labo rator y (Fer milab ), a U.S. Depa rtme nt of Ener gy, Offic e of Scien ce, HEP User Facili ty. Ferm ilab is mana ged by Ferm i Rese arch Allian ce, LLC (FRA ), actin g unde r Contr act No. DE- AC02 -07C H113 59.
Outline • Overview of the LCLS-II 1.3 GHz Cryomodule (CM) assembly • CM RF quality control (RF/QC) procedure at Fermilab • Measurement of HOM spectra at CM Test Facility (CMTF) • HOMs data processing • Operating passband statistics • Dipole HOMs statistics • Monopole HOMs statistics • Cavity vendors performance • Summary -----------------------0 Fermilab 2 10/01/2018 HOMSC2018 ICFA Mini Workshop
► ► ► ~ ~ Motivation HOMSC2014, A. Sukhanov et., all Motivation • SRF cavities are very good resonance systems with multiple eigenmodes (HOMs) with very low losses (high Q-factors) • Beam of charged particles interacts with HOMs in SRF cavities Single bunch interaction - incoherent losses and wake fields ??? CW beam may have beam harmonics closet ,, - resonance excitation of HOMs ,,'r ,, - at exact resonance beam power loss may be high ,, ,,,, Plass = / 1 ~ (R/Q) r@ • for monopole modes: For a single cavity analysis of non-propagating modes is sufficient • Measurement of actual HOMs parameters @2K insures a reliable model of resonant HOMs excitation in the LCLS-II linac • HOMs statistics allows to estimate and to compare a consistency of cavities mechanical tolerances for different vendors OFermilab HOMSC2018 ICFA Mini Workshop 10/01/2018 3
LCLS-II Linac LO L1 L2 L3 (fJ = * (p =- 21 ° (fJ = - 21° (fJ = 0 HL V 0 =94 MV V 0 =223 MV V 0 =1447 MV V 0 =2409 MV (p =- 165° / pk = 1.0 kA / pk = 12 A / pk = 12 A / pk = 50 A Lb =2.0 mm V 0 =55 MV Lb = 2.0 mm Lb= 0.56 mm Lb = 0.024 mm CM04 .. CM16 .. CMOl CM2,3 3.9GHz CMlS CM35 Func ti on al Requirements Specification Docum en t Document Title: 1 .3 GH z Su pe, rconduc ti ng IR F Cryomod ul e Document ! Number: LCLSll-4.5-FR ~00 53-R1 Page 3 of 15 1 Introduction Fermi ab and Je ff erso Lab are collaboratiing w· h SLAG on their LCLS-I1 1 1 upgrade project by supplying SRF design and fabricaitiion expertise W- The .aocelernt in g strudures wi ll l ut ilize • 4 GeV CW SRF Linac: 35 (+5) 1.3 GHz CMs , 50/50 by JLab & Fermilab • Single 1.3 GHz CM: eight 9-cell TESLA-type cavities (280 cavities in linac) • CW Beam: 0.1-0.3 nC bunch charge, 1 MHz rep. rate, 0.3 mA (max) average beam current • HOM damped Q- value: ≤ 10 6 for HOMs with high R/Q OFermilab HOMSC2018 ICFA Mini Workshop 10/01/2018 4
1.3 GHz LCLS-II Cavity Coupler Ports Changes HOM antenna FPC antenna ILC LCLS-II ILC, XFEL LCLS-II Original antenna Antenna tip cut by 8.5 mm ..,....- -- - -, I O ext ~ 4e7 I Ø11 x 0.1 mm Ø7.8 x 0.5 mm Changes to accommodate CW operation: • Smaller size of HOM antenna tip and larger the f-part gap for minimization of local RF losses • Weaker FPC coupling (~ by one order) for matching with beam current and lowering input RF power OFermilab HOMSC2018 ICFA Mini Workshop 10/01/2018 5
~ ~ ~ ~ .c WEST - I. ca - z I 0 ■- E SRFCAVITY 1 JGHz.CAVITY VACUUM BAKE SRFCAVJTY ~ J: HELIUM VESSE L 1 20C BAKE FURNACE AREA 6 WELDING AREA OVENS AREA TOTIJNHEL ... J: "" ! 1- , ~E O> ::, ,, MP9 !I 0 .f ,.. 0 V) •~ I 5 ANTE i CLEAN ROOM CAVITY STRING ASS EM Bl y iEA fLASS100 ~ so fs'oE~:~~ . CLASS 1000 ( 311FT . X 24 FT. ) <> .l' a "•' '"J -·~ [ Cl,.E#JIIIQOMMI HAIIDUMOUNIT EAST 25 FT. 200 FT. CLOSED AREA CLASS 1000 ONE 25 TON CRANE SOFTWW. OPENAAEA CLEAHROOM CLEANROOM DOORS t l shipping Cables Integrity Cavity RF/QC: FPC tune-up HOM Notch IB1 (VTS) I RT Spectra 2K Spectra ICB CM assembly RF/QC at Fermilab CMTF Income RF/QC) HOMSC2018 ICFA Mini Workshop [ :.: 2K HOM Spectra · "' 7 Q) E · .::: I 0.. ~ t: ;I (") ~ IB4 ' • ll I ~ i (/) ~ s ~ ~ w "' "' ----i > w ,. 5 . j t 10/01/2018 V I :l " ' a: I~ " receiving @ > I g I <> :i: I I ii I '.J.,j 09
Cryomodule Cold Test @CMTF HOMs 2K Spectra Measurements Cables: 20m ⅜” Heliax, ~3dB loss HOM1 to HOM2 S21 signal Agilent E5071C NWA, <4.5GHz LabVIEW data acquisition Frequency sub-ranges: 5 Step: 0.25 .. 2 kHz Max Qext: 5E6 -----------------------0 Fermilab HOMSC2018 ICFA Mini Workshop 10/01/2018 7
HOMs 2K Spectra @CMTF 10 3 0 S21 raw data • R/Q - Dipole Bands 1&2&3 R ǁ /Q, R ⊥ /Q, [ , / cm 2 ] • • R/Q - Monopole Bands 2&3 10 2 -20 • R/Q - Monopole Bands 4&5 S 21 [dB] 10 1 -40 10 0 -60 • 10 -1 -80 -· 10 -2 -100 1500 2000 2500 3000 3500 4000 • Dipole Bands 1&2&3&4 • E Monopole Bands 2&3 • Frequency [MHz] 1e+6 ., , • •· Monopole Band 5 I I • Quadrupole Band 1 • I • \. ' . ..... • Q EXT • 1e+5 ~-- ~: .- 1e+4 - 1e+3 1500 2000 2500 3000 3500 4000 Frequency [MHz] • High risk HOMs: Dipole bands 1&2&3, Monopole band 2&5 • Dipole #3 and Monopole #5 bands interferes with other HOMs (difficult to sort out) -----------------------0 • Logged CM HOMs data: Dipole bands 1&2 and Monopole band 2 Fermilab HOMSC2018 ICFA Mini Workshop 10/01/2018 8
■ ■ ■ Operating Passband 2K Spectrum l.000E+09 <Q> I 1.000E+08 I • • I l.000E+07 1 2 3 4 5 6 7 8 9 -- -- R/Q<Q> -------- - 1.00E+07 ~ 1W ' / ' - { l \ -- / ' ..... 1.00E+06 ----- 1.00E+0S 1.00E+04 2 3 4 5 7 8 9 1 6 • Operating band monopole modes may generate up to 1 W power, if in resonance with the harmonic frequencies of 0.3 mA average beam current • High Q-value (up to 10 9 ): difficult to locate and measure • Slow S21 data acquisition: BW <20 Hz • We take data for 3 cavities in the CM (left, right and middle) -----------------------0 Fermilab HOMSC2018 ICFA Mini Workshop 10/01/2018 9
t- ➔ -~ HOMs Data Processing Mathcad script for finding F&Q 10 ~- ~ ~ ~ ~ - ~~ --- - ---- - - ----- ~ ~ ------------------ +- --- -+ ~ ---i i,- -,.,- ....,.,,.--- --, - 20 9 -- 8 - 30 7 6 - 40 A ' 5 Et - 50 3 2 - 60 O '-- ----' - 70 :! .9"103 Sorted HOMs data . . . . ' ' . 1e+9 --------------------------- . . . CAVITY#1 ! • . . . CAVITY#2 CAVITYl1 • i --~---------~---------~------ 1· l e+6 . I . . CAVITYt3 CAVITY#2 CAVITY#1 . CAVITY fl . CAVITY#2 CAVITYU ' ' ' ' . ------t---- . • ----+-----t-----i-----r-- . CAVITYIM . . CAVITY#3 CAVITY#S e+6 CAVITYU . CAVITY#4 CAVITYl6 CAVITY IN CAVITY#S CAVITYt7 ! ' CAVITYf7 CAVITYl6 CAVITY#S .. ' CAVITY ff CAVITY#7 I I . . CAVITY#8 r ' ! le+S -- ',:. -L---~--------- ,·---------+--------- . .. I • I I • • j 1e+8 ' . LCLS-11 Cryomodule Testing at CMTF (RFCG) .. . .. ' ~ • . ' ~---- \ - e+5 .. ' , .. - .. ' . 464255 Rev. G • . . . . -- . .; I • ____ J __ • ___ i • ------1,-----L, • L, --- e .J, _____ :- • .-. -~-----!-----.J-----!----- e+4 • l e+3 2360 2370 2380 2390 2400 2410 2420 2430 2440 2450 2460 2470 1e+7 1600 1650 1700 1750 1800 1850 1900 1275 1280 1285 1290 1295 1300 Freq., [MHz] Freq., [MHz] Freq ., [MHz] • Data filtering issues: noise, spurious peaks, bands overlapping • Final sorted HOMs data are attached to each CM traveler OFermilab HOMSC2018 ICFA Mini Workshop 10/01/2018 10
■ ■ ~ ■ ~ ■ EZ ■ ~ ~ RI I I ■ I ■ ■ ■ AES ~ Statistics: Operating Passband Frequencies RI, EZ - Monopole Band 1 1.400 1.200 RI 1.000 <EZ>-<RI> 0.800 8 Z 0.600 II - - · II II VI 0.400 D •• 1 Ill -- RI II 0.200 EZ 6 0.000 1 2 3 4 5 6 7 8 9 Mode# Count 4 RI, EZ, AES Monopole Band 1 2 EZ 1.000 0.800 N 0 :::c -2 -1 0 1 2 0.600 G: Q.400 Cavity Length Error [mm] 0 •• ·- -- I- VI 0.200 - - - 0.000 1 2 3 4 5 6 7 8 9 Mode# • Cavity Vendors: pCM01 – 8 by AES, 9 production CMs – 50 by RI & 22 by EZ • AES cavities were procured for the ILC prototyping and passed many clean&tune steps • There is a large systematic frequency span between RI & EZ spectra (dies error, e/b welding ?) • The average length of RI’s cavities is ~1.5 mm shorter than the EZ’s after field flatness tuning OFermilab HOMSC2018 ICFA Mini Workshop 10/01/2018 11
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