ROSSANA BONOMI, ALBERTO DEGIOVANNI,

MARCO GARLASCHÉ, SILVIA VERDÚ ANDRÉS

5.7 GHz high gradient test cavity

16 - 06 - 2010

2

Outline

- High gradient test goals and program

- RF design

- Structural design

- Tolerances and tuning

- Open issues

TERA Foundation

TERA high gradient program3

S-band single cell

C-band single cell C-band mini-tank

Why ? - find operation limit in S-band- scaling law ?

- find operation limit in C-band- scaling law ?- bd craters distribution (cut 1 cavity)

- test cyclinac structure with high gradient- feasibility of C-band modules

Where ?

- pre-test @CTF3- precise test @PSI?

-?-ADAM lab /Frascati

- ? (source availability)

When ? - end 2010 - end 2010 ? - June 2011 ?

TERA Foundation

4

Design overview

Accelerating cell @ 5.7 GHz(two unsymmetrical half cells)

RF H-coupling system(waveguide, short circuit)

Connection to data acquisition(through CF flanges)

Cooling system(3 plates, in-out pipes)

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power source5

TERA Foundation

VE2098 – Tunable C-band Magnetron

Output Power 2.5 MW

Frequency 5707-5717

MHz

Pulse duration 4.0 µs

Duty cycle 0.08% -

frequency tuning

2 MHz/turn

RF Design

TERA Foundation

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Cavities comparison

TERA Foundation

7.47

18.8

1.5

2.0

1.0

1.0

1.0

17.39

15.8

25°

All values in mm !

C-band 1 cell test:NAME NEEDED!!!

β 0.7163

Q0 9305.7

T 0.905

ZTT [MOhm/m] 128.73

E0 [MV/m] 33

Es,max [MV/m] 154

Sc,max [MW/mm2] 0.708

Hmax [kW/mm2] 0.0858

Es,max/ E0 4.656

P [kW] 130

r(Es,max)-r(Sc,max) [mm] 0.42

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separate Emax and Sc,max

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Flat Nose

InnerNose Radiu

s

Outer Nose Radiu

s

9

separate Emax and Sc,max

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Power and Surface Electric Field

scaling:

1

2

0

max 46.73/

MWP

E

E

MWE

E

EPP

norm

2*400

*)400(2

max

0

2

,0

E0,norm=33 MV/m 

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Cavities comparison

TERA Foundation

8.0

18.8

1.5

3.0

1.0

3.0

1.0

17.34

15.8

20°

All values in

mm !

C-band 1 cell test:NAME NEEDED!!!

β 0.7163

Q0 9245.93

T 0.898

ZTT [MOhm/m] 116.29

E0 [MV/m] 33

Es,max [MV/m] 115

Sc,max [MW/mm2] 0.522

Hmax [kW/mm2] 0.0888

Es,max/ E0 3.484

P [kW] 142

r(Es,max)-r(Sc,max) [mm] 1.93

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Parameter list for test

Pin

[kW]Tpulse

[μs ]Es [MV/m] Sc

[MW/mm2]lg(BDR)

242 2 150 0.89 -13.3

430 2 200 1.58 -9.5

672 2 250 2.47 -6.6

967 2 300 3.55 -4.3

1316 2 350 4.84 -2.3

1719 2 400 6.32 -0.5

TERA Foundation

mesh12

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Max. element length for:• Cell………………... 3 mm• Coupler …………. 2 mm• WG ……………….. 10 mm

Max. surf. deviation for:• Cell……………… 0.01 mm• Coupler ……… 0.01 mm

cavity parameters13

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Frequency [GHz] 5.712

ZTT [MOhm/m] 116

df/dR [MHz/mm] -140

Coupling coefficient b

1.5 ±0.05

slot dimensions14

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Coupler mm

Length SL17.65

Width SW3.80

Depth SD5

Short-circuit

field asymmetry15

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W

S

N

E

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50

-0.02

-0.01

0.00

0.01

0.02

0.03

Field asymmetry(S-N)/N

(W-N)/N

(E-N)/N

Structural Design

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Struct. design: halfcells

Øcell [mm] 34.68mm

coupling slot [mm] 17.65 x 3.8

inner cavity profile geometry tolerance = ±10 μm

roughness = 0.4 Ra

material C10100 copper

C_factor = 1.5

Tuning range ≈ 20 MHz

Two unsymmetrical halfcells: - easier brazing- no spikes in slot

Outer dimensions: 48.9 x 45.9mm

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Struct. design: halfcell #1- tuning

• Small cell diameter and brazing position do not allow controlled dimple tuning• Presence of tuners in standard linacs for med. treatment

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Tuning done through 3 tuners diametrically inserted in cavity.Øtuners ~ 2 - 3 - 4 mm

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Struct. design: halfcells’ brazing

Enlarged flanges (CF 34/16) for structural resistance during brazing (Øext= 39mm)

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Struct. design: waveguide+flanges

Waveguide: - WR 187 thickwalled(ID : 1.872 x 0.872 in – OD: 2.122 x 1.122

in) - C10100 copper

Flanges: - FDP48-FDM48 standard* - 316LN stainless steel

Brazing:

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Struct. design: cooling plate

Pp(kW)

f rep(Hz)

t pulse(us)

Duty cycle

Pav(W)

Gtot(l/min)

Nº circ Øeq

(mm)2000 <100 4 <0.4‰ 800 11 3 5.5

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Es (MV/m)

Hmax (kA/m)

Ppeak (kW)

ΔT (K)

260 210 700 ~ 20

400 330 1700 ~ 50

Pulsed Surface Heating

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Struct. design: cooling plate

C10100 CopperTuners covering plate

316L stainless steel with Ni+Cu coating

TERA Foundation

Tolerances and Tuning

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tolerances

part dz dr dfµm µm kHz

1. top straight ± 20 ± 10 -16612. OUTER_CORNer_radius ± 20 ± 10 -30893. web ± 40 ± 10 -73044. INNER_CORNer_radius ± 20 ± 10 -7275. nose angle ± 20 ± 10 -1916. OUTER_NOSE_radius ± 20 ± 10 94967. flat_top ± 20 ± 10 1288. INNER_NOSE_radius ± 20 ± 10 17939. beampipe ± 20 ± 10 4

total ± 24 MHz

12

3

456

78

9

z

r24

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tuning sensitivity25

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0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 50

2

4

6

8

10

12

14

16

18

diam 2mmdiam 3mm

penetration length [mm]

f-fr

ef

[MH

z]

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-4.0%

-3.5%

-3.0%

-2.5%

-2.0%

-1.5%

-1.0%

-0.5%

0.0%

0.5%

diam 2mm

diam 3mm

diam 4mm

penetration length [mm]

dQ

/Q0

field asymmetries26

TERA Foundation

0 0.5 1 1.5 2 2.5 3 3.5 4

-0.02

-0.01

0.00

0.01

0.02

0.03

F.A. vs distance (mm)(S-N)/N(W-N)/N(E-N)/N

3 tuners: Ø = 3-3-4 mm penetration = 3

mm Δf = + 22 MHz

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Open Issues

Prototype components:• any info on FDP-FDM standard

Test components:• advice on instrumentation needed, dimensions, weight, C to S band

transition…• Faraday cup• Optical spectrum analyzer• Thermal sensors, flowmeter, manometer..

• RF pick-up

Further tests:• Two more prototypes brazed @ 1040˚ under Nitrogen, need support

on:o geometry definition (holes, thicknesses, stresses & deformations) o production process definition (tolerances..)o brazing process definition (process sponsoring, brazing material,

logistics..)TERA Foundation

acknowledgments

Thank youfor all advice, discussions and help for our project

Thank youfor scheduling our meeting today

to be continued….

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TERA Foundation