Spoke Cavity for ESS

31 Pages·2014·6.03 MB·English

Design of the 352MHz, beta 0.50, Double-
Spoke Cavity for ESS
Patricia DUCHESNE, Guillaume OLRY
Sylvain BRAULT, Sébastien BOUSSON, Patxi DUTHIL, Denis REYNET
Institut de Physique Nucléaire d’Orsay
SRF 2013, PARIS, September 27, 2013
P. 1
CONTENTS
 CONTEXT
 RF DESIGN OF THE RESONATOR
 MECHANICAL DESIGN OF THE RESONATOR
 INTEGRATION IN THE CRYOMODULE
 STATUS OF THE PROTOTYPES
P. 2
CONTENTS
 CONTEXT
 RF DESIGN OF THE RESONATOR
 MECHANICAL DESIGN OF THE RESONATOR
 INTEGRATION IN THE CRYOMODULE
 STATUS OF THE PROTOTYPES
P. 3
ESS SPOKE SECTION
 ESS Superconducting Spoke section:
ESS Accelerator layout (2012_10_02)
 28 Double Spoke cavities (3 accelerating gaps)
 beta=0.50
T
X
E
T  frequency: 352.2 MHz
N
O
C  grouped by pair in 14 cryomodules
 operating temperature: 2K
 Accelerating gradient: Eacc = 8 MV/m
 Peak field specifications: Epk < 35 MV/m, Bpk < 70 mT
P. 4
ESS SPOKE SECTION
 Activities of IPN Orsay Laboratory on ESS Spoke section:
Cold Tuning System
N. Gandolfo
 DDeessiiggnn THP078
Power coupler  FFaabbrriiccaattiioonn ooff pprroottoottyyppeess
E. Rampnoux
 tteessttss ooff pprroottoottyyppeess::
THP065
-- VVeerrttiiccaall tteessttss ooff ccaavviittiieess
--PPoowweerr ccoouupplleerrss ccoonnddiittiioonniinngg ((TTeesstt bbeenncchh @@CCEEAA//SSaaccllaayy))
--TTeessttss ooff CCTTSS
T
X --LLooww ppoowweerr tteessttss ooff ccrryyoommoodduullee
E
T ((HHiigghh ppoowweerr tteessttss aatt UUPPPPSSAALLAA))
N D. Reynet
O
MOP089
C
Cavity
Cryomodule
P. 5
CONTENTS
 CONTEXT
 RF DESIGN OF THE RESONATOR
 MECHANICAL DESIGN OF THE RESONATOR
 INTEGRATION IN THE CRYOMODULE
 STATUS OF THE PROTOTYPES
P. 6
SPECIFICATIONS FOR THE DOUBLE SPOKE CAVITY
Parameters established by the beam dynamics simulations:
DOUBLE-SPOKE CAVITY
Beam mode Pulsed (4% duty cycle)
R Frequency [MHz] 352.2
O
T Beta_optimal 0.50
A
N
Temperature (K) 2
O
S
E
R

E Bpk [mT] 70 (max)
H
T
Epk [MV/m] 35 (max)
F
O
Gradient Eacc [MV/m] 8
N
G
I Lacc (=beta optimal x nb of gaps x λ /2) [m] 0.639
S
E
D Bpk/Eacc [mT/(MV/m)] < 8.75

F
R
Epk/Eacc < 4.38
Beam tube diameter [mm] 50 (min)
RF peak power [kW] 300 (max)
P. 7
OPTIMIZATION OF THE GEOMETRY
 Main goal: fulfil the criteria of the peak surface field to accelerating gradient ratios
E B
< <
pk 4.38 pk 8.75
[mT/MV/m]
E E
acc acc
 The optimization method of the RF design:
Hspokebase
Rspokebase
R  Parameterization of the geometry
Dspoke
O Rtop1
T
A
 Sensitivity analysis on the ratios Epk/Eacc &
N Rtop2
O Bpk/Eacc
S Rtop3
E
R
 CST MicroWave Studio (MWS)

E
Rbeamtube
H
 Results cross-checked with to mesh types:
T Hbottom

F
hexahedral and tetrahedral
O
Lcav
Htop

N
G Parameters list for Spoke optimization –G. Olry
SI  Geometry of the spoke bars:
E
D
Based on our feedback from two Single-Spoke Conical shape

F
R resonators and a Triple-Spoke resonator fabrication
(EURISOL)
Racetrackshape
Achievement of an acceptable solution
P. 8
RF RESULTS
 Last modifications (included in the prototypes)
 Technical issues for manufacturing
Minor parameters changes
 New ESS requirements
Hexahedral Tetrahedral
Mesh type
(2.2 millions meshcells) (600000 tetra.) E field
Beta optimal 0.50 0.50
R
O
Epk/Eacc 4.51 4.33
T
A
N Bpk/Eacc [mT/MV/m] 6.99 6.89
O
S G [Ohm] 131 130
E
R
r/Q [Ohm] 425 426
E H field
H
•Epk/Eacc> 4.38: compromise between the cavity length, end cap shape feasibility and tuning sensitivity.
T
•Lacc= 3 / 2 x beta optimal x lambda
F
O
⋅
 Coupling calculations: Qext = 1.5 105 (with the parameters 50mA and 8MV/m)
N
G
∅
I  Coupler port location ( =100mm):
S 100 to 170mm
E ↔
Variation of the coupler port center from 100 to 170mm ( distance to the origin)
D

F
R
 Penetration of the antenna: Variation from +5 to -15 mm
+5
Qext = 1.5 ⋅105 for:
 5mm of tip penetration -15
 coupler port location: 120mm
MWS model of the cavity with antenna –G. Olry
P. 9
CONTENTS
 CONTEXT
 RF DESIGN OF THE RESONATOR
 MECHANICAL DESIGN OF THE RESONATOR
 INTEGRATION IN THE CRYOMODULE
 STATUS OF THE PROTOTYPES
P. 10