Minimizing reflected energy for superconducting cavity filling for pulsed accelerators y shaping of pulse profile.

1. Minimization of Reflected Energy
from ESS Medium and High beta
Cavities for Intense Neutrino
Super Beam Experiment
Anirban (Krish)na Bhattacharyya
FREIA / HIGH ENERGY PHYSICS
Uppsala University
03/11/15

2. Large accelerator projects in Sweden
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MAX IV
ESS

3. ESS
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Cavity
Type
Cavity
Length (m)
Input Energy
(MeV)
Frequency
(MHz)
Geometric β # of
Sections
Temp (K)
RFQ 4 75 Χ 10-3 352.21 -- 1 ≈ 300
DTL 8 3 352.21 -- 3 ≈ 300
Spoke 0.639 79 352.21 0.5 14(2c) ≈ 2
Low Beta 1.145 201 704.42 0.67 15(4c) ≈ 2
High Beta 1.356 623 704.42 0.9 30(4c) ≈ 2
Pulse rate of the ESS Linac is 14 Hz at 5 MW average power for 2 GeV
Neutrino beam requires higher pulse rate at 28 Hz.

4. Cavity Parameters
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PARAMETER SYMBOL VALUE
Accelerating gaps n 5
Bare cavity Quality factor Q0 6.0 Χ 109
External Quality factor Qext 6.8 Χ 105
Cavity shape constant R/Q 340
DC beam current Ib,DC 62.5 mA
PARAMETER SYMBOL VALUE
Accelerating gaps n 5
Bare cavity Quality factor Q0 6.0 Χ 109
External Quality factor Qext 7.1 Χ 105
Cavity shape constant R/Q 477
DC beam current Ib,DC 62.5 mA
Medium
Beta
High Beta

5. Cavity Parameters
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Medium
Beta
High
Beta

6. 03/11/15 Anirban Krishna Bhattacharyya 6
Cavity Parameters
Medium
Beta
High Beta

7. Step Charging
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RF
Source
Circulator
Cavity
Load
Cavity
(super - conducting)
Courtesy of P. Duthil
(T = 1)

8. Step Charging
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RF
Source
Circulator
Cavity
Load
Cavity
(super - conducting)
Courtesy of P. Duthil
(T = 1)

9. Step Charging
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RF
Source
Circulator Cavity
Load
Cavity
(super - conducting)
Courtesy of P. Duthil
(T = 1)

10. Step Charging (Frequency domain)
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(MHz)

11. Optimal Charging
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• Instantaneous cavity voltage
Ib
Ig
Ir
Filling time
(Natural time
scale)
Loaded
Quality
factor
Generator
current
Loaded
cavity
impedance
(Nominal cavity voltage)

12. Optimal Charging
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• Instantaneous cavity voltage
• Reflected current
Ib
Ig
Ir
Filling time
(Natural time
scale)
Loaded
Quality
factor
Generator
current
Loaded
cavity
impedance
External
Quality factor
Bare cavity
Quality factor

13. Optimal Charging
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• Instantaneous cavity voltage
• Reflected current
• Reflected energy
Filling time Loaded Q Generator
current
Loaded
impedance
External Q Bare cavity Q

14. Optimal Charging
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Optimal charging profile
Find optimal
and such
that is
minimum.

15. Optimal Charging
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Optimal charging profile
Free parameter

16. Effect of Optimal filling
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(T = 1)

17. Effect of Optimal filling
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18. Effect of Optimal filling
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19. Effect of charging time ( )
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Peak generator powerRelative Reflected Energy

20. Practical sources
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Gain characteristics Efficiency characteristics

21. Practical sources
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Efficiency characteristics
Klystron !!!!
W. Doherty, A new high efficiency power amplifier for modulated waves,
Radio Engineers, Proceedings of the Institute of 24 (9) (1936) 1163–1182.
doi:10.1109/JRPROC.1936.228468.
B. Kim, J. Kim, I. Kim, J. Cha, The doherty power amplifier, Microwave
Magazine, IEEE 7 (5) (2006) 42–50. doi:10.1109/MW-M.2006.247914.
R. Pengelly, N-way rf power amplifier with increased backoff power and
power added efficiency, wO Patent App. PCT/US2003/002,365 (Aug. 7
2003).
URL http://www.google.com/patents/WO2003065573A1?cl=en
P. Colantonio, F. Giannini, R. Giofr, L. Piazzon, The doherty power ampli
fier, INTERNATIONAL JOURNAL OF MICROWAVE AND OPTICAL
TECHNOLOGY 5 (6) (2010) 419–430.
G. Ahn, M. su Kim, H. chul Park, S. chan Jung, J. ho Van, H. Cho,
S. wook Kwon, J.-H. Jeong, K. hoon Lim, J. Y. Kim, S. C. Song, C.-S.
Park, Y. Yang, Design of a high-efficiency and high-power inverted doherty
amplifier, Microwave Theory and Techniques, IEEE Transactions on 55 (6)
(2007) 1105–1111. doi:10.1109/TMTT.2007.896807.
NXP Semiconductors, AN10967 BLF578 demo for 352 MHz 1kW CW
power, 2nd Edition, application note (November 2012).
D. Rees, D. Keffeler, W. Roybal, P. Tallerico, Characterization of a
Klystrode as a RF Source for High-Average-Power Accelerators, Conf.Proc.
C950501 (1995) 1521.
E. Montesinos, Tetrode power amplifiers, in: TIARA Workshop on RF
Power Generation for Accelerators, Uppsala University, A˙ ngstr¨om Laboratory,
2013.
N. Pupeter, Significant increase of efficiency of solid state amplifiers due
to improved ac/dc conversion and adaption of p1 point to actual operating
power, in: EnEfficient RF Sources, Cockcroft Institute, 2014.

22. Practical sources
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Source efficiency during filling
RF Gain Source
loss

23. Practical sources (T = 1)
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Tetrodes can be run in Doherty
architecture

24. Effect of Transit time factor
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IOT Solid State Doherty amplifier
Most gains from higher transit time factors

25. Effect of Transit time factor
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IOT
Medium beta cavities
Solid State Doherty amplifier

26. Effect of Transit time factor
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IOT
High beta cavities
Solid State Doherty amplifier

27. Effect of Transit time factor
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Operation: 14n Hz pulse rate
Total operation time: 20 years, 8000hours/year
Medium Beta Cavities High Beta Cavities
Source type IOT DSSA IOT DSSA
Energy saved/pulse (J) 27 17 47 40
Energy saved/sec (J) 380n 240n 650n 560n
Energy saved in lifetime
(MWhrs)
61n 38n 104n 90n
Number of cavities 60 120
Total savings (MWhrs) 3660n 2280n 12480n 10800n
SEK saved (Millions) 6.5n 4n 22.5n 19.4n
At an electricity price in Sweden of 1.8 SEK/kWhr

28. Minimization of power consumption during charging of superconducting
accelerating cavities, in Nuclear Instruments and Methods in Physics Research
Section A: Accelerators, Spectrometers, Detectors and Associated Equipment,
Volume 801, pages "78 – 85" 2015,
http://dx.doi.org/10.1016/j.nima.2015.07.056,
url = "http://www.sciencedirect.com/science/article/pii/S0168900215008852",
By Anirban Krishna Bhattacharyya and Volker Ziemann and Roger Ruber and
Vitaliy Goryashko

29. THANK YOU
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