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Abstract Two single-

crab cavities Modes (HOM)designed and pproject at theBaseline cavitybeen verticallspecification wAlternate cavwaveguide daimpedance saffabricated by machine and idesign, layoucomponents ar

The SPX pruse supercondat 2.815GHz selected users usage for othestatus will be requires 2MVproduction secfor each cryomwith maximumcavity. Only sto satisfy the vfabrication reqmost promisinhave been sum

The LOM challenging fdevelopments small apertureand prototypinout at Jeffersonensure the beaimpedance safpreferred. In apower from thiris on the caLOM/HOM enhancement.

CAVITY F

* Work supportedOffice of Basic En06CH11357 #haipeng@jlab.or

AVITY A

g#, G. Chengosser, R.A. R

A. Nass

-cell, superconwith wavegui) and Lower Oprototyped for e Advanced Py with LOM dly tested andwith over 0.5vity design amper is prefefety margin. Ita Computer N

is subject to fuut and analysre presented.

INTRODroject at Argonducting radio fr

to produce shwithout disru

r users aroundreported in [

V deflecting voction in Sectormodule will bem surface magsingle-cell cavivoltage performquirements. Thng two candid

mmarized in [2]and HOM d

for the crabdue to 200mA

e due to the hng activities forn Lab [3] [4] inam stability offety margin on addition it prohe beam. It alsavity cell’s opdamping with

FABRICATd by the U.S. Depanergy Sciences, un

rg

AND CRYOTHE ADV

g, C. CiovatiRimmer, G. Ssiri, G. Wald

nducting, squaides to damp

Order Mode (LOthe Short Puls

Photon Sourcdamper on the d exceeded it5MV deflectinwhich uses

erred due to itts prototype cNumerical Conurther testing. Tsis for variou

DUCTION nne National Lfrequency (SRFhort (~2ps) pu

upting the regud the APS. The 1]. The scopeoltage on eachr 6 at the APS utilized to att

gnetic field at ity designs havmance, impedahe design parates, Baseline ]. damping becob cavity andA CW beam chigh cavity frer the cavity han collaborationf machine opethe Alternate c

oduces less LOso features a dpen slot whichh reduced m

ION, PROCartment of Energy, nder Contract No.

OMODULVANCED

i, B. ClemenSlack, L. Tudschmidt, G.

ashed ellipticaHigher Orde

OM) have beense X-ray (SPXce (APS). Th

beam pipe hats performancng voltage.Th

an “on-cellts larger LOM

cavity has beenntrolled (CNCThe conceptuaus cryomodul

Lab (ANL) wilF) crab cavitieulse x-rays foular x-ray puls

current projec of the projech side of SPXS. Four cavitieain the 0.5 MV98mT on eachve been shown

ance budget andrameters of th

and Alternate

ome especiallyd cryomodulcurrent and thequency. R&Dve been carried

n with ANL. Toeration, a largecavity design iOM and HOMdog bone shaph can improvmagnetic field

CESS AND Office of ScienceDE-AC02-

LE PROTD PHOTON

ns, J. Henry, urlington, JLa

Wu, ANL, A

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The firmade by jwaveguidElectron Bused for tfirst base

Figure 1: impedanc

e,

OTYPE DN SOURC

P. Kneisel, Pab, NewportArgonne, IL

TESrst prototype ojoining a saddl

de adapter [4]. Beam Weldingthe proof of peline cavity C

8 Baseline (redces againt to AP

DEVELOPCE*

P. Kushnick,t News, VA 60439 USA

ST RESULTon-cell damperle piece from aUnfortunately

g (EBW) paramprinciple in veCCB1’s cell w

d) and AlternatPS impedance

PMENT F

K. Macha, J23606, USA

A

T r cavity CCAa stamped cell y this trial articmeter study hadertical tests [4]was stamped

te (black) cavitbudegt (blue).

FOR

J. A

1 was to the

cle for d been ]. The

from

ties’

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Tech 07: Superconducting RF

the same die, but the Y HOM waveguide was machined from bulk RRR>250 fine grain niobium by CNC machine [3].

Baseline cavity After grinding off a trench-like welding ripple on the cavity equator, the CCB1 cavity went through following processes: 90+10+80um Buffer Chemistry Polish (BCP) with ∆T <10°C, etching rate=1um/min to allow equal amounts of material removal from iris and equator. Inlet to outlet acid ∆T<1.5°C

600oC bake for 10hrs Final 5um BCP on bench Ultrasonic degreasing High Pressure Rinsed (HPR) in R&D system for

~1hr Dried in a class-10 clean area overnight Assembled with indium seals on RRR~ 80 Nb blank-

off flanges in class-10 clean area Attached to test stand, leak checked and evacuated to

<5e-8 mBar in class-100 room Set up variable coupling in vertical staging area

The cavity was in a vertical free hanging position with a variable coupling link for the probe coupler on the bottom. The input RF coupling can reproduce the setup at room temperature and be changed at 2K temperature.

The coupling antenna is a copper L shape electric probe. In the first power rise of test #2, the cavity reached 116mT maximum magnetic field on the iris which corresponds to a 0.59 MV deflecting voltage (in Figure 2). There was no sign of x-ray radiation or multipactoring (MP). The Lorentz Force Detuning (LFD) coefficient was measured as -14.9Hz/(MV/m)2. The helium pressure sensitivity was measured also as -1.1kHz/Torr. The ANSYS simulations later confirmed these numbers quantitatively and found that they are critically dependent on the constraining conditions and detail feature regarding the EBW joint welds.

Figure 2: Baseline CCB1 cavity vertical #2 test result.

In the #3 test setup, the LOM waveguide blank-off flange was changed from Niobium to Stainless Steel (SST) material. Process procedure followed above steps after HPR. The measurement showed that the low power

Q0 at 2K dropped to 8×108 which indicated an error of the LOM waveguide alignment relative to the long axis of racetrack crab cell. The loss due to the beam pipe blank-off flanges using SST was calculated by MWS to be ~3e9 in unloaded Q.

Alternate cavity The CCA1 cavity has been tested for number of times

with the highest Bp field of 95mT [3] but with the signs of low Q0, soft MP barrier, early quench and weak coupling. A high resolution optical inspection revealed an interior weld crack (with chemical residual around it) on the saddle joint which could be caused by a non-penetration EBW and opened up by later grinding and chemistry. This find could explain the low Q and the contaminated surface which emitters the MPs.

The fabrication of CCA2 cavity was decided then all parts except beam pipes are to be machined from the RRR>250 bulk, large grain niobium ingot directly to avoid the electrical centre (EC) alignment error and the difficulty of forming the dog bone iris by sheet metal. The final geometry of CCB2 and CCB3 cavities followed the frequency recipe previous developed have been finalized.

Figure 3: Bare crab cavity prototypes. A: two half CCB1 cavity groups before the final equator EBW; B: Y HOM waveguide group made by CNC machining for CCB1 cavity with RRR>250 Nb; C: CCA2 cavity fabricated on CNC machine; D: Finished Nb and Al prototype cavity.

CRYOMODULE COMPONENTS DEVELOPMENT

The cryomodule components of cavity tuner, LOM/HOM loads, RF windows, bellows and alignment device are all critical to the schedule and success of the SPX project. The R&Ds and conceptual designs of loads, RF windows have been presented in Ref. [2]

Alignment Due to the tight tolerance of individual cavity assembly

in the cryomodule string [6], a wire-stretching technique based on the S21 of RF signal has been proposed [5] for the clean room assembly on the rails. The tuning sensitivity on the vertical offset is about 20dB/0.5mm. Special fixtures to do this mock-up experiment have been developed. A beam based feedback alignment scheme using the crab cavity as the beam position monitor (BPM) has been proposed. The accuracy of EC using cold (2K) actuators’ adjustment is estimated to be ±0.1mm.

Proceedings of 2011 Particle Accelerator Conference, New York, NY, USA WEOCS7

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to be used [Fmeasured an4.64kHz/lbf athickness. Fomicrometer reand the 4mmcompromise th

Figure 4: Bscissor jack tun

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use the WR28coupling. The inside of spacecryomodule bo

Figure 5: Powaveguide. Th

Cavity-to-caThis space

Sector 5 and 7flange confinecan have a <hardware volu4. Figure 6 speriodic boundplanes which aof the neighbostring in the A

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Figure 4]. Thend simulated and 8.84kHz/µr the ±200kHsolution is nee

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mode couplerpower couple

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avity spacingis dominated

7 at the APS. ed space, the m<-80dB deflectume could dropshows the MWdary conditionalso representsur cavities. Fig

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design uses ons calculated by

g (CCS) d by the strai

Within a 2.8mminimum CCSting mode isop the cavity nuWS calculatedn (BC) on the the both resongure 7 lays out le which leave

k tuner is goingtivity has been

cavity being3mm Nb walange, the subzo tuner devict this point to

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AuthorsJefferson scientific

[1] A. N(SPXThese

[2] G. Wfor SSourc

[3] H. Wtowarfor th

[4] H. WCana

[5] H. WMini-Appli1-3, 2

[6] M. B

omponent deveave been also p

6: RF isolationcavity for mi

Four-cavity sf the APS strabetween in 10

ACKNOWs would like

Lab and Aand technical c

REFassiri, et. Al.,

X) Project at thee proceedings.

Waldschmidt, “Short-Pulse Xce” these proce

Wang, et. al., rd a Superconhe APS,” Proc. Wang, et. al.,ada, p. 2138. Wang, talk pre-Workshop oication in Acce2010. orland, PRST-

elopment. Theplanned in the

n calculation foinimum cavity

string’s cryomoight section. S

00mm space.

WLEDGEMto thank all

Argonne Natiocontributions i

FERENCES“Status of the

e Advanced Ph

“SuperconductX-Ray at the eedings. “Design and

nducting Crab IPAC’10, Kyo

, Proc. PAC

esented at ICFon Deflectingelerators, Cock

-AB, Vol 8, 07

e schemes of 5design stage.

or Alternate CCspacing.

odule layout wShield bellows

MENT other staff bo

onal Lab for n this R&D pr

S e Short-Pulse Xhone Source (A

ting Cavity DAdvanced P

Prototype ProCavity Cryomoto, Japan, p. 3

2009, Vanco

FA Beam Dyng/Crabbing Ckcroft Inst. UK

4001, (2005).

5 to 8

CA3

within are to

oth at their

oject.

X-Ray APS),”

Design Photon

ogress module 3061. ouver,

namic Cavity

K, Sep.

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Tech 07: Superconducting RF