longitudinal hom power estimations for pulsed beams.rev w. weingarten 31 may 20101spl cavity wg...
DESCRIPTION
On longitudinal HOM excitation for pulsed beams (as in high intensity proton drivers) 2/4 31 May 2010SPL Cavity WG Meeting3TRANSCRIPT
Longitudinal HOM power estimations for pulsed beams.rev
W. Weingarten
31 May 20101 SPL Cavity WG Meeting
On longitudinal HOM excitation for pulsed beams (as in high intensity proton drivers) 1/4
31 May 2010SPL Cavity WG Meeting2
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On longitudinal HOM excitation for pulsed beams (as in high intensity proton drivers) 2/4
31 May 2010SPL Cavity WG Meeting3
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On longitudinal HOM excitation for pulsed beams (as in high intensity proton drivers) 3/4
31 May 2010SPL Cavity WG Meeting4
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31 May 2010SPL Cavity WG Meeting5
I = 40 mA; pulse length 1 ms, R/Q = 100 W ;Rep. rate 50 Hz; fHOM = 2.1 GHz; Q0 = 1010
On longitudinal HOM excitation for pulsed beams (as in high intensity proton drivers) 4/4
0 .0 20 0 0 .0 2 02 0 .02 04 0 .02 0 6 0 .02 0 8 0 .02 1 00
5 0 0 0 0
10 0 0 0 0
15 0 0 0 0
ts
PW
5 .0 10 8 1 .0 10 9 1 .5 10 9 2 .0 10 9 2.5 10910 6
10 4
0.01
1
10 0
f H z
PmaxW
Power built-up/decay during pulse of 1 msMaximum power vs. frequency showing principal Fourier components of beam
Power dumped by beam into a HOM 1/4f (HOM) precisely on beam spectral line
31 May 2010SPL Cavity WG Meeting6
I = 40 mA; pulse length 1 ms, R/Q = 100 W ;Rep. rate 50 Hz; fHOM = 2.1 GHz; Q0 = 1010
10 00 104 105 10 6 10 7 10 8 10 910
10 0
10 00
10 4
10 5
Q ex
PradW
1000 104 10 5 10 6 10 7 10 8 1 0910 6
10 4
0 .01
1
100
10 4
Q ex
PcW
Power dumped by beam into a HOM 2/4comparison between CW and pulsed beam
7 SPL Cavity WG Meeting 31 May 2010
-4
-3
-2
-1
0
1
2
3
1 2 3 4 5 6 7 8 9 10
log
P [W
]
log Qext
Dissipated power in HOM absorber for SPL with R/Q = 100 Ω and Δf = 1 MHz Q0 = 1·1010
-4
-3
-2
-1
0
1
2
3
1 2 3 4 5 6 7 8 9 10
log
P [W
]
log Qext
Dissipated power in HOM absorber for SPL with R/Q = 100 Ω and Δf = 0.1 MHz Q0 = 1·1010
CW CW
1 00 10 4 10 6 1 08
1 0 5
0 .0 0 1
0 .1
Q ex
PWpulsed 5%
100 104 10 6 10 8
0 .001
0 .1
10
Q ex
PW
pulsed 5%
from presentation “Beam tube damping estimations for SPL cavity “ of 8 March 2010
Power dumped by beam into a HOM 3/4beam spectral line Df away from resonant frequency of HOM
8 SPL Cavity WG Meeting 31 May 2010
1 00 1 04 10 6 1 08
0 .0 01
0 .1
1 0
Q ex
PradW
1 00 10 4 1 0 6 1 0810 8
10 7
10 6
10 5
10 4
Q ex
PcW
Df= 0.1 MHzDf= 0.1 MHz
10 0 10 4 10 6 10 8
0 .01
0 .1
1
10
10 0
Q ex
PradW
1 0 0 10 4 10 6 1 081 0 8
1 0 7
1 0 6
1 0 5
1 0 4
0 .0 0 1
0 .0 1
Q ex
PcW
Df= 0.01 MHzDf= 0.01 MHz
I = 40 mA; pulse length 1 ms, R/Q = 100 W ;Rep. rate 50 Hz; fHOM = 2.1 GHz; Q0 = 1010
Power dumped by beam into a HOM 4/4Courtesy M. Schuh
31 May 2010SPL Cavity WG Meeting9
Preliminary conclusion concerning HOM power dumped into the pulsed cavity
The main beam Fourier components (n·352 MHz) contribute significantly to the HOM power, the 50 Hz Fourier component, however, only marginally; to reduce the HOM power below 100 W, the Q-value of the HOM must be < 104
Avoiding the main beam Fourier components by the HOM frequencies within 10 kHz reduces the HOM power significantly, with a tendency to become even smaller for larger Q-values (P < 1 W @ Q > 107)
→ The HOM power could possibly be reduced by inelastic detuning or an appropriate design of the cavity (though without changing the fundamental mode frequency) with the aim to keep sufficiently off ALL HOM frequencies from the main Fourier components
31 May 2010SPL Cavity WG Meeting10
I = 40 mA; pulse length 1 ms, R/Q = 100 W ;Rep. rate 50 Hz; fHOM = 2.1 GHz; Q0 = 1010