CLIC Drive Beam Linac Rolf Wegner. Outline Introduction: CLIC Drive Beam Concept Drive Beam Modules...
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Transcript of CLIC Drive Beam Linac Rolf Wegner. Outline Introduction: CLIC Drive Beam Concept Drive Beam Modules...
CLIC Drive Beam Linac
Rolf Wegner
Outline
• Introduction: CLIC Drive Beam Concept
• Drive Beam Modules (modulator, klystron, accelerating structure)
• Optimisation of accelerating structure
• Conclusions
2CLIC Drive Beam Linac Rolf Wegner25-Oct-2012
Introduction: CLIC Drive BeamThe CLIC Drive Beams are powerful energy sources from which the Power Extraction and Transfer Structures (PETS) extract a total peak power of 9.2 TW at X-band (3 TeV CLIC)•Specs: 2.4 GV, 100 A, 24 x 240 ns long bunch trains, bunch spacing <=> 12 GHz, 50 Hz rep. rate
•2 x 24 x 240 GW peak, 140 MW avg beam power60 kJ / bunch train, 1.4 MJ / pulse
Reason: efficient X-band power production (alternative: 35’000 x 50 MW X-band klystrons + pulse compr.)
3CLIC Drive Beam Linac Rolf Wegner25-Oct-2012
Introduction: CLIC Drive Beam
4CLIC Drive Beam Linac Rolf Wegner25-Oct-2012
DB source
SH bunchers
DB acceleration
beam gymnastics
PETS
main beam acc. structures
fbunch facc Ibeam, train avg Vbeam Ttrain
500 MHz
1 GHz 4.2 A 2.4 GV 140 μs
12 GHz 100 A 2.4 GV 24 x 240 ns
12 GHz
Introduction: 3 TeV CLIC scheme
5CLIC Drive Beam Linac Rolf Wegner25-Oct-2012
Introduction: CLIC Drive Beam Complexfacc= 0.99952 GHz
Ipulse= 4.2 A
Vacc= 2.37 GV
ηRF->beam≥ 95%Ppeak,RF ≈ 12 GW
Pavg,RF ≈ 90 MW
fbunch= ½ facc
Qbunch= 8.4 nC
φs= 19⁰
6CLIC Drive Beam Linac Rolf Wegner25-Oct-2012
Drive Beam Accelerator
7CLIC Drive Beam Linac Rolf Wegner25-Oct-2012
present baseline:• modules composed of
modulator (24 MW), klystron (1 GHz, 18 MW), Erk Jensen: cost optimum 15-20 MW including lifetime + future R&Daccelerating structure (15 MW)
• ~ 1’600 modules for 2 DB-Linacs for a 3 TeV CLICVacc, module= 3.2 MV (φs=-19°)
Modulator
8CLIC Drive Beam Linac Rolf Wegner25-Oct-2012Steffen Döbert: “Plans for the drive beam front-end and CLIC zero outlook”, LCWS 2012
avg. power per modulator ~ 180 kWavg. power of 1’600 modulators ~ 300 MW
Modulator challenges
9CLIC Drive Beam Linac Rolf Wegner25-Oct-2012Steffen Döbert: “Plans for the drive beam front-end and CLIC zero outlook”, LCWS 2012
Klystron
10CLIC Drive Beam Linac Rolf Wegner25-Oct-2012Steffen Döbert: “Plans for the drive beam front-end and CLIC zero outlook”, LCWS 2012
Klystron
11CLIC Drive Beam Linac Rolf Wegner25-Oct-2012Steffen Döbert: “Plans for the drive beam front-end and CLIC zero outlook”, LCWS 2012
Accelerating structure
12CLIC Drive Beam Linac Rolf Wegner25-Oct-2012
Fundamental principles:• full beam loading (RF to beam efficiency ≥ 95%)• TWS - SICA (Slotted Iris – Constant Aperture)
(+ short range wakefields, efficient HOM damping)
• filtering of frequencies ~ 4.1 MHz (<=> Tcombination)(+ noise reduction <=> combination scheme)
• reduction of wakefields by damping and detuning
Principle: full beam loading
13CLIC Drive Beam Linac Rolf Wegner25-Oct-2012
input power at acc. structure: 15 MW (peak)dissipated power: 330 kW (peak)lost power at output: 10 kW (peak)power transferred to beam: 14.66 MW => η~ 97.7%
unloaded (no beam)loaded
Principle: SICASICA = Slotted Iris – Constant Aperture
3 GHz SICA structures built and operated in CTF
14CLIC Drive Beam Linac Rolf Wegner25-Oct-2012
Principle: filtering
15CLIC Drive Beam Linac Rolf Wegner25-Oct-2012
noise at multiples of ~ 4.1 MHz (<=> 240..250 ns) adds up coherently due to combination scheme
tDL~ 240..250 ns
tfill [ns]
da
mp
ing
fa
cto
r D
245 nsD ≈ 1/18
368 nsD ≈ 1/4
124 nsD ≈ 1/4
245 ± 8.5 ns D ≈ 1/17
Erk Jensen
=> using fill time of acc. structure to filter 4.1 MHz signals before combination
Tfill= 245 ± 8.5 ns => damping factor 1/17 ~ 6%
Principle: wakefield reduction
reduction of wakefields by damping and detuning16CLIC Drive Beam Linac Rolf Wegner25-Oct-2012
…
Structure optimisation
5 10 15 20 25 30 35 400
5
10
15Pin= 10.00 MW, Ib= 4.21 A
cell no
vgr/
c0 [
%]
N= 7, RB=33.0mm
N=10, RB=39.0mmN=13, RB=45.0mm
N=16, RB=53.0mm
N=19, RB=55.0mm
N=22, RB=59.0mmN=25, RB=63.0mm
N=28, RB=65.0mm
N=31, RB=71.0mm
N=34, RB=73.0mmN=37, RB=77.0mm
N=40, RB=79.0mm
235 240 245 250 2550
1
2
3
4
5
filling time [ns]
1-et
a [%
]
17CLIC Drive Beam Linac Rolf Wegner25-Oct-2012
Variables:1. input power [Pin]2. structure length = no of cells [N]3. beam pipe aperture [radius RB]4. group velocity profile along structure [vgr(n)]
Results:1. RF to beam efficiency [eta], here “1-eta” used2. fill time
Structure optimisation
ηRF ≥ 97.5 %
|tfill – 245 ns| ≤ 5 ns
0 10 20 30 40 50 60 70 80 900
10
20
30
40
50
60
70
RB [mm]
cell
no
no of cells <-> BP radius, eta >= 97.5%, |tfill-t0| <= 5.00 ns, Ib= 4.21 A
Pin= 5.00 MWPin= 10.00 MW
Pin= 15.00 MW
Pin= 20.00 MW
Pin= 30.00 MWPin= 40.00 MW
Pin = 15 MW
Beam dynamic (Avni Aksoy): RB = 49 mm,N = 19 cells
18CLIC Drive Beam Linac Rolf Wegner25-Oct-2012
Baseline DB accelerating structure
19CLIC Drive Beam Linac Rolf Wegner25-Oct-2012
Pin = 15 MWN = 19 normal cellsbeam aperture ø = 2*49 = 98 mm
unloaded (no beam)loaded
group velocity profile
acc. gradient
avg. dissipated power
Baseline DB accelerating structure
20CLIC Drive Beam Linac Rolf Wegner25-Oct-2012
input reflection
operating freq. 999.5 MHz
Pin = 15 MWN = 19 normal cells + 2 couplersstructure length = 2.4 mbeam aperture ø = 98 mm
Baseline structure, detuning curves
21CLIC Drive Beam Linac Rolf Wegner25-Oct-2012
monopole modes
dipole modes
Baseline structure, wakefields
22CLIC Drive Beam Linac Rolf Wegner25-Oct-2012
longitudinal wakefield
transverse wakefields
ConclusionsModulator and klystron:
• challenging specifications
• R & D has been started, further collaborations are welcome
Baseline accelerating structure has been designed• input power 15 MW, 19+2 cells, beam aperture ø 98 mm
• efficiency ≥ 97.5% (fully beam-loaded), filling time 245 ns ± 5 ns
• wakefields efficiently reduced by damping and detuning
Further research on Drive Beam Modules:• reduction of total number (combination of klystron power)
• structure re-optimisation, including fabrication cost
23CLIC Drive Beam Linac Rolf Wegner25-Oct-2012
Thank you for your attention
24CLIC Drive Beam Linac Rolf Wegner25-Oct-2012
25CLIC Drive Beam Linac Rolf Wegner25-Oct-2012
Introduction: CLIC Drive Beam front-end
26CLIC Drive Beam Linac Rolf Wegner25-Oct-2012Steffen Döbert: “Plans for the drive beam front-end and CLIC zero outlook”, LCWS 2012
3 GHz DBA structure – Erk Jensen
facc= 3 GHz
Pin= 33 MW
ncell= 33
Length= 1.22 m
Øoutside= 17.4 cm
weight ≈ 200 kg
17.4 cm
fully beam-loaded, Pbeam / PRF = 94%
Corsini, R et al.: First Full Beam Loading Operation with the CTF3 LinacCERN-AB-2004-057 ; SLAC-PUB-10762 ; CTF-3-NOTE-066 ; CLIC-Note-604
27CLIC Drive Beam Linac Rolf Wegner25-Oct-2012
design of TWS
gapn
RBPE0T(n)
Vacc
Ncells
PoutPin
Pb Pb
constant aperture
η= ΔPb/Pin
tfill
mode spectrum
constantfree parameter
vgr,n
tapering
Ra,n
φn=120⁰
28CLIC Drive Beam Linac Rolf Wegner25-Oct-2012
basic cell geometry
gapa
La
RBP
Ra
110
60
11
18R 6
R 6
R 9
R 9
99.979
typical dimensions
49
29CLIC Drive Beam Linac Rolf Wegner25-Oct-2012
30CLIC Drive Beam Linac Rolf Wegner25-Oct-2012