Journal of Nuclear Science, Engineering and Technology (JONSAT)
In cooperation with the Iranian Nuclear Society

Design of high gradient S-band cavity and coupler

Document Type : Research Paper

Authors

S.M. Aghayan 1
S.F. Masoudi 1
S.H. Shaker 2
F. Ghasemi 3

1 Department of Physics, K.N Toosi University of Technology, P.O.Box: , Tehran – Iran

2 Canadian Light Source Inc. (CLS), Saskatoon - Canada

3 Physics and Accelerator Research School, Nuclear Sciences and Technology Research Institute, AEOI, P.O.Box: 14155-1339, Tehran – Iran

https://doi.org/10.24200/nst.2022.1351
Abstract
Studies on high gradient linear accelerators are among the new areas in the field of accelerators. The most important factor that limits the electric field gradient in linear accelerators is the radio frequency breakdown. Many studies have been conducted on the effect of the material and manufacturing method of cavities on the achievable gradient, which shows that rigid structures fabricated without high-temperature processes achieve a better high gradient performance. Employing the brazing method, as the most common method for construction of cavities, requires the use of high-temperature furnaces, which causes softening of the copper. Therefore, using non-brazing methods to construct high gradient cavities has been considered. Based on the experiences gained in the national electron linear accelerator project at the institute for research in fundamental science (IPM) and the shrinking fit method used to fabricate and assemble its acceleration cavities, the design and construction of high gradient S-band cavities are in progress with international cooperation. Radiofrequency design of cavity with vacuum breakdown consideration and coupler design are discussed. Achieving the appropriate shape and dimensions of the cavity and coupler for maximizing the axial electric field (134 MV/m) with a breakdown rate of less than  at 8 MW input power and S11 parameter -60 dB for the coupler are the results of this article.

Highlights

1.             E.I. Simakov, V.A. Dolgashev, S.G. Tantawi, Advances in high gradient normal conducting accelerator structures, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 907, 221-230 (2018).

 

2.             A. Vnuchenko, et al., High-gradient testing of an S-band, normal-conducting low phase velocity accelerating structure, Physical Review Accelerators and Beams, 23(8), 084801 (2020).

 

3. N. Shafqat, C. Serpico, T. Lucas, Design and high-power test of a short prototype of high gradient S-band accelerating structure for the FERMI free electron laser linac upgrade, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 979, 164473 (2020).

 

4.             M. Diomede, High-gradient structures and rf systems for high-brightness electron linacs (Phd thesis),  Università degli studi di Roma-La Sapienza (2020).

 

5. D. Angal-Kalinin, et al., Design, specifications, and first beam measurements of the compact linear accelerator for research and applications front end, Physical Review Accelerators and Beams, 23(4), 044801 (2020).

 

6. A. Korsbäck, et al., Vacuum electrical breakdown conditioning study in a parallel plate electrode pulsed dc system, Physical Review Accelerators and Beams, 23(3), 033102 (2020).

 

7. V. Dolgashev, et al., Materials and technological processes for High-Gradient accelerating structures: new results from mechanical tests of an innovative braze-free cavity, Journal of Instrumentation,  15(01), P01029 (2020).

 

8. V. Dolgashev, et al., Innovative compact braze-free accelerating cavity, Journal of Instrumentation,  13(09), P09017 (2018).

 

9. D. Alesini, et al., Design, realization, and high power test of high gradient, high repetition rate brazing-free S-band photogun, Physical Review Accelerators and Beams, 21(11), 112001 (2018).

 

10. D. Alesini, et al., New technology based on clamping for high gradient radio frequency photogun, Physical Review Special Topics-Accelerators and Beams, 18(9), 092001 (2015).

 

11. V.A. Dolgashev, et al., RF breakdown in normal conducting single-cell structures. in Particle Accelerator Conference, Knoxville, Tennessee. (2005).

 

12. V. Dolgashev, et al., Status of high power tests of normal conducting single-cell structures, In Conf. Proc, (2008).

 

13.          V. Dolgashev, Building and High Power Testing Welded Accelerating Structures. in 12th International Workshop on Breakdown Science and High-Gradient Technology, HG2019, from 10 to 14 June 2019, Chamonix, France. (2019).

 

14. M. Aicheler, et al., A Multi-TeV linear collider based on CLIC technology: CLIC Conceptual Design Report, SLAC National Accelerator Lab., Menlo Park, CA (United States) (2014).

 

15. F. Ghasemi, et al., Design, construction and tuning of S-band coupler for electron linear accelerator of institute for research in fundamental sciences (IPM E-linac), Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 772, 52-62 (2015).

 

16. S.S. Hajari, et al., RF emittance in a low energy electron linear accelerator, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 888, 250-256 (2018).

 

17. H. Shaker, F. Ghasemi, Design of a Pi/2 Mode S-Band Low Energy TW Electron Linear Accelerator, In Conf. Proc. (2011).

 

18. M. Aghayan, F.M., H. Shaker, F. Ghasemi, Plans for constructing high-gradient S-band cavities using non-brazing method in Iran, International Workshop on Breakdown Science and High Gradient Technology (HG2018), (2018).

 

19. H. Shaker, Electron linac in Iran, International Workshop on Breakdown Science and High Gradient Technology (HG2017), (2017).

 

20. C. Nantista, S. Tantawi, V. Dolgashev, Low-field accelerator structure couplers and design techniques, Physical Review Special Topics-Accelerators and Beams, 7(7), 072001 (2004).

 

21. T.P. Wangler, RF Linear accelerators, John Wiley & Sons (2008).

 

22. C. Karzmark, C.S. Nunan, E. Tanabe, Medical electron accelerators, McGraw-Hill (1993).

 

23. A. Grudiev, S. Calatroni, W. Wuensch, New local field quantity describing the high gradient limit of accelerating structures, Physical Review Special Topics-Accelerators and Beams, 12(10), 102001 (2009).

 

24. G. Castorina, et al., A TM01 mode launcher with quadrupole field components cancellation for high brightness applications, In Journal of Physics: Conference Series, IOP Publishing (2018).

 

25.          A. Cahill, et al., RF design for the TOPGUN photogun: A cryogenic normal conducting copper electron gun, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment,  865, 105-108 (2017).

Keywords

Linear accelerator
High gradient
Breakdown rate
Surface field
S11 parameter
1.             E.I. Simakov, V.A. Dolgashev, S.G. Tantawi, Advances in high gradient normal conducting accelerator structures, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 907, 221-230 (2018).
 
2.             A. Vnuchenko, et al., High-gradient testing of an S-band, normal-conducting low phase velocity accelerating structure, Physical Review Accelerators and Beams, 23(8), 084801 (2020).
 
3. N. Shafqat, C. Serpico, T. Lucas, Design and high-power test of a short prototype of high gradient S-band accelerating structure for the FERMI free electron laser linac upgrade, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 979, 164473 (2020).
 
4.             M. Diomede, High-gradient structures and rf systems for high-brightness electron linacs (Phd thesis),  Università degli studi di Roma-La Sapienza (2020).
 
5. D. Angal-Kalinin, et al., Design, specifications, and first beam measurements of the compact linear accelerator for research and applications front end, Physical Review Accelerators and Beams, 23(4), 044801 (2020).
 
6. A. Korsbäck, et al., Vacuum electrical breakdown conditioning study in a parallel plate electrode pulsed dc system, Physical Review Accelerators and Beams, 23(3), 033102 (2020).
 
7. V. Dolgashev, et al., Materials and technological processes for High-Gradient accelerating structures: new results from mechanical tests of an innovative braze-free cavity, Journal of Instrumentation,  15(01), P01029 (2020).
 
8. V. Dolgashev, et al., Innovative compact braze-free accelerating cavity, Journal of Instrumentation,  13(09), P09017 (2018).
 
9. D. Alesini, et al., Design, realization, and high power test of high gradient, high repetition rate brazing-free S-band photogun, Physical Review Accelerators and Beams, 21(11), 112001 (2018).
 
10. D. Alesini, et al., New technology based on clamping for high gradient radio frequency photogun, Physical Review Special Topics-Accelerators and Beams, 18(9), 092001 (2015).
 
11. V.A. Dolgashev, et al., RF breakdown in normal conducting single-cell structures. in Particle Accelerator Conference, Knoxville, Tennessee. (2005).
 
12. V. Dolgashev, et al., Status of high power tests of normal conducting single-cell structures, In Conf. Proc, (2008).
 
13.          V. Dolgashev, Building and High Power Testing Welded Accelerating Structures. in 12th International Workshop on Breakdown Science and High-Gradient Technology, HG2019, from 10 to 14 June 2019, Chamonix, France. (2019).
 
14. M. Aicheler, et al., A Multi-TeV linear collider based on CLIC technology: CLIC Conceptual Design Report, SLAC National Accelerator Lab., Menlo Park, CA (United States) (2014).
 
15. F. Ghasemi, et al., Design, construction and tuning of S-band coupler for electron linear accelerator of institute for research in fundamental sciences (IPM E-linac), Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 772, 52-62 (2015).
 
16. S.S. Hajari, et al., RF emittance in a low energy electron linear accelerator, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 888, 250-256 (2018).
 
17. H. Shaker, F. Ghasemi, Design of a Pi/2 Mode S-Band Low Energy TW Electron Linear Accelerator, In Conf. Proc. (2011).
 
18. M. Aghayan, F.M., H. Shaker, F. Ghasemi, Plans for constructing high-gradient S-band cavities using non-brazing method in Iran, International Workshop on Breakdown Science and High Gradient Technology (HG2018), (2018).
 
19. H. Shaker, Electron linac in Iran, International Workshop on Breakdown Science and High Gradient Technology (HG2017), (2017).
 
20. C. Nantista, S. Tantawi, V. Dolgashev, Low-field accelerator structure couplers and design techniques, Physical Review Special Topics-Accelerators and Beams, 7(7), 072001 (2004).
 
21. T.P. Wangler, RF Linear accelerators, John Wiley & Sons (2008).
 
22. C. Karzmark, C.S. Nunan, E. Tanabe, Medical electron accelerators, McGraw-Hill (1993).
 
23. A. Grudiev, S. Calatroni, W. Wuensch, New local field quantity describing the high gradient limit of accelerating structures, Physical Review Special Topics-Accelerators and Beams, 12(10), 102001 (2009).
 
24. G. Castorina, et al., A TM01 mode launcher with quadrupole field components cancellation for high brightness applications, In Journal of Physics: Conference Series, IOP Publishing (2018).
 
25.          A. Cahill, et al., RF design for the TOPGUN photogun: A cryogenic normal conducting copper electron gun, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment,  865, 105-108 (2017).

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