ISG3 Injector Working Group (WG2) l/26/99. NLC Damping Ring RF Cavity development. R. A. Rimmer LBNL

Transcription

1 ISG3 Injector Working Group (WG2) l/26/99 NLC Damping Ring RF Cavity development R. A. Rimmer LBNL

2 outline: Parameters Baseline design (scaled PEP-II) R&D HOM damping waveguides HOM loads Window and Coupler Tuner Tapers Fabrication issues Conclusions

3 Parameters: lx frequency 714 MHz number of cells total voltage MV voltage/cell 500 kv wall power 4-l.7 kw beta 57 beam current forward power/cell 7iO ma 238 kw eauiv. window Dower 238 kw klystron power L 733 kw PPDR 714 MHz 4 2 MV 500 kv 41.7 kw 5.7 (opt=3.1) 800 ma 142 kw 238 kw 582 kw

4 Baseline design: Scaled PEP-II cavity meets requirements Peak surface field below Kilpatric (similar to PEP-II) Wall power density high but within design limits (72 W/cm2, c.f. PEP-II operating 67 W/cm2, max design 116 W/cm:!) High window power (238 kw, 44% area of PEP-II) But: Expensive to manufacture Stresses caused by HOM-port hot spot R&D effort focused on scaling and simplifying designs

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6 357 MHz -476 MHz 2856 MHz

7 Kilpatrick Chart 3 Kiloatrick criterion 25 I. I 0, I I I I I I I I I I I I I I. 1 I I Freauencv NtlHz\ Page 1

8 R&D: HOM damping waveguides Peak surface power loss at ends of HOM waveguides look at alternative shapes reduce heat load eliminate iris but: must not lose effectiveness of damping!

9 ~ 1#3DCONTOIJR I C\::,?DINATES /P! FL -?. W\PJtiE, ;: I: 8-L O>J 2 [.oooo, oooo. ' 'i.%r:604, %604, Z, -.ZiSOO, , FRAME: 3 11/01

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11 AFIA RAKE: I 24/01/99-10:40:54 VERSIONfV WG2.DRC FREQUENCY/HZ MAXIMUM ERROR OF CURLCURL-E MEAN ERROR OF CURLCURL-E MAXIMUM ERROR OF DIVERGENCE-D creal PART OF TIME HARMONIC ELECTRIC FIELD IN V/M #ARROW :GQRDINATES/M ULL RANGE / WINDOW :r , 'I : [ , :ymbol = ERE-1 NTERPOLATE.= 0,CGSCALE...= 0. w( ARROW =

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13 Alternative HOM port profiles * 1 0 b (PEP-II, fc=600 MHz) * 8.25 b

14 R&D: HOM loads Lower beam current may reduce power but variable fill patterns may make things worse baseline design is scaled PEP-II load assess heating once impedance spectrum is confirmed investigate all likely fill patterns lower heat load would allow simpler design must be very broad-band (900 MHz GHz)

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16 i lo2 PEP-II Cavity HOM s ns bunch spacing, 5% gap, 3A Total power 3.6 kw 10 loo 10-l 1o-2 1o-3 lo4 10" 1.5 Frequetxy (GHZ) Fl.-.., E!.._-.-. B F =r g Frequency (GHZ)

17 Low-End Frequency Measurement of Production Horn Load REF 0.0 d ❻ a MCiRKER MHz I d VSWR 2:l I. I WI I I l--ywprii MQRKER MHz MWIKER MHz -12,025 d STFSRT STOP 0,600QK2mzHm Gtiz GHZ 1 03 OCT 9Ej 1 09:58:

18 R&D: Window and Coupler Follow PEP-II scheme power density similar to PEP-II rugged pre-stressed window aperture coupling into cavity coupler box incorporates HOM filter

19 WR2100 PEP-II RF cavity window module

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21 COMPRESSED ASSEMBLY SEQUENCE COPPER PLATED STAINLESS STEEL WATER JACKET ALUMINA WINDOW, METALLKED AND NI PLATED CRITICAL GAP AT ROOM TEMP GAP AT ROOM TEMP THE MOLY KEEPER RING COMPRESSES THE STAINLESS STEEL RING AT BRAZE TEMPERATURE FOR A SUFFICIENT REDUCTlON IN DIAMETER TO CREATE 10,DDOPSl COMPRESSION AT ROOM TEMPERATURE 1 BRAZE USING 6&S (CU/All) AT 1050 C ~WlTH,ttOlO PERJOD,eT 450 C FOR TEN BRAZE FIXTURE BASE TO SET CRlTlCAL SPAClNGS BETWEEN CERAMlC AND WATER JACKET

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23 FIA FRAME: 2 24/01/99-14:21:50 VERSION[V /WG3.DRC FREQUENCY/HZ E+08 RIDGED CIRCULAR WAVEGUIDE MAXIMUM ERROR OF CURLCURL-E E-06 MEAN ERROR OF CURLCURL-E I MAXIMUM ERROR OF DIVERGENCE-D REAL PART OF TIME HARMONIC ELECTRIC FIELD IN V/M #ARROW :OORDINATES/M FULL RANGE I WINEOW KI , [ , Y[ , [ , SYMBOL - ERE-1 INTERPOLATE.= 0 LOGSCALE !4AX ARROW = Y t L+ X

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25 I window module -L - ---m---w---, I I I I I I II P--f-.-v-.-r~-.. r~-l-t-l-r-l--i, Ll,I,LJ,LJ,II I I I II I I II r-~-i-ti-r cavity flange High-power coupler, plan view.

26 R&D: Tuner Follow PEP-II scheme water-cooled piston type tuner moderate gap to accommodate alignment tolerances straight Glidcop fingers with silver plating rhodium plated tuner body commercial actuator (if available)

27 PEP-II RF Cawity Glidcop Fingers

28 IPEP-II Production Tuner... :.,... :r.. I

29 bi R&D: Tapers Tapers needed to transition to small beam pipe add transverse impedance (kl) comparable to cavity! need long smooth transition look at non-linear tapers look for HOMs trapped by tapers / between cavities

30 transverse loss parameter (V/PC/m) a3 CD d- cv 0 I I I I I I, Lo i-. -0 m / I I I I i I j I : 1 4 I 1: I I I I I I I I I /,, i,,,, /,,, I, / /, d- cc) nl (0~) awepadw! ~unys

31 Cl R&D: Fabrication issues PEP-II cavity successful but expensive some simple geometry changes may simplify design e.g.: HOM ports reordering assembly e.g.: port cooling. reduced e.g.: sequence may reduce parts count jackets size may allow alternative materials / parts forgings, flanges some ideas already tried on ALS Landau cavity but: Easy to spend more on R&D than saved in manufacture!

32 nose pick-up -loop/view port

33 . PEP-II RF Cavity produced by Lawrence Livermore National Laboratorv The RF surface is finish turned ml-u-001

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35 hl Mondey. January Page: 1

36 2 0 0 E 0 u L d =1 d LQ&