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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)
TERA Foundation
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
7
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
9
separate Emax and Sc,max
TERA Foundation
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
10
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
11
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
TERA Foundation
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
TERA Foundation
Frequency [GHz] 5.712
ZTT [MOhm/m] 116
df/dR [MHz/mm] -140
Coupling coefficient b
1.5 ±0.05
field asymmetry15
TERA Foundation
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
17
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
TERA Foundation
18
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
TERA Foundation
Tuning done through 3 tuners diametrically inserted in cavity.Øtuners ~ 2 - 3 - 4 mm
19
Struct. design: halfcells’ brazing
Enlarged flanges (CF 34/16) for structural resistance during brazing (Øext= 39mm)
TERA Foundation
20
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:
TERA Foundation
21
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
TERA Foundation
Es (MV/m)
Hmax (kA/m)
Ppeak (kW)
ΔT (K)
260 210 700 ~ 20
400 330 1700 ~ 50
Pulsed Surface Heating
22
Struct. design: cooling plate
C10100 CopperTuners covering plate
316L stainless steel with Ni+Cu coating
TERA Foundation
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
TERA Foundation
tuning sensitivity25
TERA Foundation
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
27
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