SAP2023 - Classification: Advanced acceleration concept

Paper	Title	Page
MOCYA01	Study of the Key Physics Problems in 10mA-class High Current Cyclotron	9
	T.J. Bian, S. An, F.P. Guan, L.Y. Ji, S.M. Wei CIAE, Beijing, People’s Republic of China
	Funding: National Natural Science Foundation of China (Grant No. 12105370) and the Scientific Research Program for Young Talent Elite Project of China National Nuclear Corporation (Grant No. FY212406000404). Proton beam with an average current of 10mA has many important applications in particle physics towards the intensity frontier, as well as in the advanced energy and material science. At present, superconducting linac is the mainstream of high current accelerator. As cyclotron has advantages of continuous beam structure, high beam/grid efficiency(60%~65% can be expected in superconducting ring cyclotron) and lower cost, cyclotron is also a potential candidate for future accelerator scheme with beam current of 10mA-class. Firstly, we will discuss the application prospect and motivation of 10mA-class high power cyclotron(10mA-HPC). Secondly, the key physics problems of 10mA-HPC are summarized, which includes strong space charge problems in low energy region, integer resonance crossing problems in high energy region and beam losses problems in extraction region. Thirdly, possible solutions for key physics problems and preliminary design of 10mA-HPC are proposed.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOCYA01
About •	Received ※ 30 June 2023 — Revised ※ 08 July 2023 — Accepted ※ 12 July 2023 — Issued ※ 30 May 2024
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MOPB001	Terahertz-Driven MeV Electron Bunch Compression and Streaking	14
	Y. Xu, K. Fan, Z. Liu, Y. Song, C.-Y. Tsai, J. Wang HUST, Wuhan, People’s Republic of China
	Electron bunches with ultra-short bunch length and ultra-high timing stability are crucial for various applications. To achieve these desired characteristics, there is a growing interest in employing Terahertz-driven techniques to manipulate and diagnose electron bunches. This paper presents a method capable of compressing and measuring electron bunch lengths. Theoretical and simulation results demonstrate that the bunch length of 54 is reduced to 4 fs by utilizing THz-driven resonant cavity compression, achieving a compression ratio of 13. Furthermore, we also verify the bunch compression using a terahertz-driven streak camera.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB001
About •	Received ※ 28 June 2023 — Revised ※ 09 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 26 February 2024
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MOPB002	Preliminary Research of Laser-Beam Interaction in Dielectric Structure
	S.J. Fan TUB, Beijing, People’s Republic of China
	The acceleration gradient of traditional accelerator has met the threshold due to the RF breakdown effect. Then the concept of DLA (dielectric laser accelerator) was proposed. As a kind of DLA structure, dual-pillar structure was studied in the field of theory, simulation and experiment. Based on CST with PIC simulation in dual-drive acceleration mode, dual-drive deflection mode and single-drive acceleration mode, the results of the distribution of EM field, damage threshold assessment and size of beam bunch are simulated. For dual-drive acceleration mode, the effect of different input phase of bunch on 3D bunch size is discussed. For deflection mode, the effect from EM field and self-interaction force on the transverse velocity is discussed with the variation of the transverse size of the beam observed in simulation. For single-drive acceleration mode, the effect of distribution Bragg reflector on the energy gain of beam and acceleration gradient is discussed based on the comparison of different drive modes. Based on theory and simulation result, possible experiment scheme is preliminary designed, including hundred-micron acceleration experiment based on dual-drive mode.
	Poster MOPB002 [0.525 MB]
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MOPB029	Multi-bunch Operation Mode for Simultaneously Serving SASE and Seeding FEL Beamlines	66
	X.F. Wang Institute of Advanced Science Facilities, Shenzhen, People’s Republic of China X.M. Li, J.T. Sun, X.M. Yang, Y. Yu, W.Q. Zhang DICP, Dalian, Liaoning, People’s Republic of China Y.F. Liang, X.M. Yang, H. Yi, L. Zeng, W.Q. Zhang IASF, Shenzhen, Guangdong, People’s Republic of China
	Modern free-electron laser (FEL) facilities are de-signed to simultaneously serve multiple undulator lines to provide x-ray pulses with high peak power and tunable wavelengths. To satisfy different scientific demands, it is preferred to make the separate undulator lines work under different FEL schemes, such as the self-amplified spontaneous emission (SASE) scheme and the echo-enabled harmonic generation (EEHG) scheme. However, different FEL schemes have differ-ent requirements on the beam longitudinal distribu-tion. Here, we propose to use multiple bunches to sim-ultaneously serve the undulator lines and put the bunches at different acceleration phase to change the bunch length with two compressor chicanes. The ac-celeration phase for each bunch is varied by adjusting the time delays of the photocathode drive laser pulses with the accelerator settings unchanged. The start-to-end simulation demonstrates that a fs bunch with high peak current can be produced to serve the SASE line while a bunch with hundred-of-fs length and uniform current distribution can be produced to serve the EEHG line. The FEL performances are simulated and discussed.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB029
About •	Received ※ 25 June 2023 — Revised ※ 10 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 07 September 2024
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MOPB038	Achromatic Beam Design for a Laser-Driven Proton Therapy Accelerator
	K.D. Wang PKU, Beijing, People’s Republic of China
	Laser-driven ion acceleration is one of the research hotspots in the field of accelerator in recent years. The high energy ion beam accelerated by laser has the characteristics of small size, narrow pulse width and good directivity, so it has many potential applications. This work will introduce the beam line dynamics design of a laser driven proton radiotherapy planned to be completed by Peking University. The beam line will be used as the key system of the laser proton radiotherapy application demonstration device, and the beam transport system will complete the follow-up operation. The whole beam design can provide horizontal and vertical irradiation modes respectively. It can efficiently collect the large divergence beam generated by the laser. It also contains a complete energy selection system, which can effectively select the energy dispersion of the laser accelerated beam to meet the application requirements. Finally, the beam accelerated by laser passes through the beam transport system to provide a proton beam with a diameter of less than 5 mm and an energy propagation of less than 5% at the horizontal and vertical irradiation targets.
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MOPB039	Low-Alpha Storage Ring Design for Steady-State Microbunching to Generate EUV Radiation	88
	Z. Pan, A. Chao, X.J. Deng, W.-H. Huang, Z.Z. Li, C.-X. Tang TUB, Beijing, People’s Republic of China
	A new concept is proposed for minimizing the longitudinal emittance of a low momentum compaction factor (low-alpha) storage ring which has the capability to stably store sub-femtosecond electron bunches for the first time. This storage ring is designed for Steady-State microbunching (SSMB) to generate kW level average power EUV radiation. The proposed design approach can be applied to any quasi-isochronous storage rings to yield very high radiation power due to longitudinal coherence of the radiation. We obtain an optimal lattice design by minimizing global and local momentum compaction factors simultaneously and the result of single-particle tracking shows that the electron beam with equilibrium rms bunch length of about 40 nm can be stored in this ring. Nonlinear dynamics is studied for this lattice.
DOI •	reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB039
About •	Received ※ 03 July 2023 — Revised ※ 08 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 31 December 2023
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TUAA01	Recent progresses of laser plasma based electron acceleration at Shanghai Jiao Tong university
	M. Chen Shanghai Jiao Tong University, Shanghai, People’s Republic of China
	Funding: National Natural Science Foundation of China (Grants No. 11991074, 12225505) and the Strategic Priority Research Program of the Chinese Academy of Sciences (Grants No. XDA25010500, XDA25050000). Laser plasma based electron acceleration has many applications. Aiming to the high energy electron acceleration, we have performed both theoretical and experimental studies. A curved plasma channel has been proposed to guide intense lasers for multistage laser wakefield acceleration. In our recent experiment we found that when the channel curvature radius is gradually increased and the laser incidence offset is optimized, the stable laser guiding is possible and wakefields can be excited in the curved channel. Electrons with maximum energy of 0.7GeV have been observed. Our results show that such a channel exhibits good potential for seamless multi-stage laser wakefield acceleration. A 200+300TW two-laser system platform will be installed in SJTU. The research plans, such as staged wakefield acceleration, Thomson scattering and plasma optics studies on this platform, will be introduced.
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TUAA02	Acceleration and Transport of Protons in a PW Laser Accelerator
	C. Lin, W.J. Ma, K.D. Wang, Q. Wang, X.Q. Yan, J.R. Zhao, Y.Y. Zhao, K. Zhu PKU, Beijing, People’s Republic of China
	Laser plasma accelerator has been considered as a promising candidate for future compact accelerator and radiation source. Laser ion acceleration is an extremely high gradient transient process: the established field can exceed TV/m, accelerating ions to high energy within tens of micron distance. Such pulsed high-current proton sources enable significant advances in many fields, such as FLASH tumor therapy, proton radiograph, and irradiation in extreme condition. With the support of the Ministry of Science and Technology of China, a prototype of proton radiotherapy system based on PW (10 15 W) laser accelerator is under construction by Peking University at Beijing Laser Innovation Center. In this presentation, we will introduce the latest progress of the laser proton accelerator, as well as the key technologies related to the project, such as improvement to the acceleration mechanism, transport of the broad energy spread beams, and the proton irradiation applications.
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TUXA01	Studies of Injection Mechanism Optimization and Radiation Reaction in Plasma Wakefield Accelerators
	M. Zeng IHEP, Beijing, People’s Republic of China
	Laser or charged beam driven plasma wakefield accelerators (PWAs) are considered as the accelerators of the next generation. Before the actual applications of PWAs in a wide range of disciplines, the output beam quality parameters require further improvements. Especially, the output beam charge and energy spread are contradictory parameters for optimization. This talk will present the recent works on the simultaneous optimization of the output beam charge and energy spread at Institute of High Energy Physics (IHEP), Chinese Academy of Sciences. In addition, this talk will present the work of modeling the betatron oscillation in long-distance PWAs by considering the higher-order electromagnetic field structure and the radiation reaction effect, and show new phenomena based on this model. This model is useful for the beam optimization in future long-distance and high-energy PWAs.
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TUXA02	High-energy laser wakefield electron acceleration and its feasibility as a synchrotron radiation injection source
	X.Z. Chen Rejected, Tanzania
	The development of high-energy collider requires the development of new high-gradient particle acceleration technologies. In order to achieve this grand scientific goal, laboratories around the world are currently focused on the application and development of novel acceleration technologies at the energy level of several GeV. With the advancements in ultra-intense and ultra-short laser technology, laser plasma acceleration has the potential to further advance accelerator technology, owing to its ultra-high acceleration gradients, short pulse duration and high current density. In this report, we will mainly introduce the current research progress of our team in high-energy laser wakefield electron acceleration. We will discuss the common technical research conducted in combining laser wakefield electron acceleration with traditional accelerator technology. Additionally, we will discuss the challenging issues faced by laser wakefield electron acceleration technology as an injection source technology for synchrotron radiation facilities. These discussions aim to offer some considerations for the further development of compact injection sources and high-energy colliders.
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TUBA01	High-quality electron beams and free-electron lasing based on laser wakefield accelerator
	W. Wang Shanghai Institute of Optics and Fine Mechanics, Shanghai, People’s Republic of China
	X-ray free-electron lasers can generate intense and coherent radiation at wavelengths down to the sub-ångström region, and have become indispensable tools for applications in structural biology and chemistry, among other disciplines. Laser wakefield accelerators can sustain accelerating gradients more than three orders of magnitude higher than those of radio-frequency accelerators, and are regarded as an attractive option for driving compact X-ray free-electron lasers[1]. After ten years of efforts, we present an experimental demonstration of undulator radiation amplification in the exponential-gain regime by using electron beams based on a laser wakefield accelerator[2-4]. The amplified undulator radiation, which is typically centred at 27 nanometres and has a maximum photon number of around 10¹⁰ per shot, yields a maximum radiation energy of about 150 nanojoules. The results constitute a proof-of-principle demonstration of free-electron lasing using a laser wakefield accelerator, and pave the way towards the development of compact X-ray free-electron lasers based on this technology with broad applications. 1. K. Nakajima, Nat. Phys. 4, 92-93 (2008). 2. Wentao Wang, et al., Nature 595, 516 (2021). 3. Wentao Wang, et al., PRL 117, 124801 (2016). 4. Lingtong Ke, et al., PRL 126, 214801 (2021).
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TUYA01	Attosecond X-ray free-electron lasers utilizing an optical undulator in a self-selection regime
	X. Xu SLAC, Menlo Park, California, USA
	Accelerator-based X-ray free-electron lasers (XFELs) are the latest addition to the revolutionary tools of discovery for the 21st century. The two major components of an XFEL are an accelerator-produced electron beam and a magnetic undulator which tend to be kilometer-scale long and expensive. Here, we present an ultra-compact scheme to produce 10s of attosecond X-ray pulses with several GW peak power utilizing a novel aspect of the FEL instability using a highly chirped, pre-bunched and ultra-bright electron beam from a plasma-based accelerator interacting with an optical undulator. The self-selection of electrons from the combination of a highly chirped and pre-bunched beam leads to the stable generation of attosecond X-ray pulses. Furthermore, two-color attosecond pulses with sub-femtosecond separation can be produced by adjusting the energy distribution of the electron beam so that multiple FEL resonances occur at different locations within the beam. Such a tunable coherent attosecond X-ray sources may open up a new area of attosecond science enabled by X-ray attosecond pump/probe techniques.
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TUYA02	Ultra-high Harmonic Conversion of a Seeded Free-electron Laser via Harmonic Optical Klystron
	X.F. Wang Institute of Advanced Science Facilities, Shenzhen, People’s Republic of China
	External seeded free-electron lasers (FELs) have proven to be compelling tools for generating fully coherent EUV and soft X-ray radiations. Echo-enabled harmonic generation (EEHG), as the most typical representative of external seeded FELs, has unparalleled harmonic conversion efficiency. However, due to the limitations of various collective effects, the harmonic conversion of a high-gain EEHG that has been proved in experiments does not exceed 50 times. This paper proposes a new EEHG technology with the help of harmonic optical klystron technology, which can effectively increase the number of harmonic conversion to about 100 times. Theoretical analysis and numerical simulations show that intense and almost fully coherent FEL pulses with a radiation wavelength of 3 nm can be generated. At the same time, the seed laser intensity required by this scheme is lower, compared to nominal EEHG, thus facilitating the generation of high repetition rate seeded FELs.
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TUPB036	Optimisation of RFQ Transmission Efficiency Based on Reinforcement Learning Control Policy
	C.G. Su, Z.J. Wang IMP/CAS, Lanzhou, People’s Republic of China
	The reinforcement learning (RL) algorithm is utilized to control the low-energy beam transport (LEBT) and radiofrequency quadrupole (RFQ) in linear accelerators, with the aim of improving RFQ transmission efficiency, achieving high beam intensity, reducing debugging time, and improving operational efficiency. A neural network model is established as part of the Interaction environment to partially replace the Tracewin software for RL training proceess. The SAC algorithm is a reinforcement learning algorithm used to optimize control policies for continuous action spaces. By using the SAC algorithm and interacting with the neural network model, a policy was trained to control the LEBT solenoids, optimizing the RFQ transmission efficiency to above 95% on the simulation software Tracewin. To test the generalization ability of the strategy, we applied it to a real accelerator and successfully validated its ability to optimize the RFQ transmission efficiency. The results demonstrate that RL policy trained in simulation-based environments can be applied on real accelerator control.
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TUPB037	RF Design and Cold Test of SCDTL Structure for Proton Therapy
	X.X. Li IMP/CAS, Lanzhou, People’s Republic of China
	Side coupled drift tube linac (SCDTL) was selected in the middle energy accelerator of the cancer treatment device, which works at 3 GHz. The periodic structure of six accelerator cavities has been completed, and it can accelerate proton from 10 to 20 MeV. Besides, the electromagnetic design and preliminary cold measurement of a single accelerator cavities (b= 0.15) have been finished. The frequency of single-cavity electromagnetic design is 2.961 GHz, the Q₀ value is 12498, Kp is 2.19. The initial measurement frequency is 2.9579 GHz, the Q₀ value is 6927, which is 55% of the design value, but the Q₀ value can be improved by electrochemical polishing, so the experiment of increasing the value of Q₀ is being carried out.
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Paper

Title

Page

Study of the Key Physics Problems in 10mA-class High Current Cyclotron

9

T.J. Bian, S. An, F.P. Guan, L.Y. Ji, S.M. Wei
CIAE, Beijing, People’s Republic of China

Funding: National Natural Science Foundation of China (Grant No. 12105370) and the Scientific Research Program for Young Talent Elite Project of China National Nuclear Corporation (Grant No. FY212406000404).
Proton beam with an average current of 10mA has many important applications in particle physics towards the intensity frontier, as well as in the advanced energy and material science. At present, superconducting linac is the mainstream of high current accelerator. As cyclotron has advantages of continuous beam structure, high beam/grid efficiency(60%~65% can be expected in superconducting ring cyclotron) and lower cost, cyclotron is also a potential candidate for future accelerator scheme with beam current of 10mA-class. Firstly, we will discuss the application prospect and motivation of 10mA-class high power cyclotron(10mA-HPC). Secondly, the key physics problems of 10mA-HPC are summarized, which includes strong space charge problems in low energy region, integer resonance crossing problems in high energy region and beam losses problems in extraction region. Thirdly, possible solutions for key physics problems and preliminary design of 10mA-HPC are proposed.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOCYA01

About •

Received ※ 30 June 2023 — Revised ※ 08 July 2023 — Accepted ※ 12 July 2023 — Issued ※ 30 May 2024

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MOPB001

Terahertz-Driven MeV Electron Bunch Compression and Streaking

14

Y. Xu, K. Fan, Z. Liu, Y. Song, C.-Y. Tsai, J. Wang
HUST, Wuhan, People’s Republic of China

Electron bunches with ultra-short bunch length and ultra-high timing stability are crucial for various applications. To achieve these desired characteristics, there is a growing interest in employing Terahertz-driven techniques to manipulate and diagnose electron bunches. This paper presents a method capable of compressing and measuring electron bunch lengths. Theoretical and simulation results demonstrate that the bunch length of 54 is reduced to 4 fs by utilizing THz-driven resonant cavity compression, achieving a compression ratio of 13. Furthermore, we also verify the bunch compression using a terahertz-driven streak camera.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB001

About •

Received ※ 28 June 2023 — Revised ※ 09 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 26 February 2024

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reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPB002

Preliminary Research of Laser-Beam Interaction in Dielectric Structure

S.J. Fan
TUB, Beijing, People’s Republic of China

The acceleration gradient of traditional accelerator has met the threshold due to the RF breakdown effect. Then the concept of DLA (dielectric laser accelerator) was proposed. As a kind of DLA structure, dual-pillar structure was studied in the field of theory, simulation and experiment. Based on CST with PIC simulation in dual-drive acceleration mode, dual-drive deflection mode and single-drive acceleration mode, the results of the distribution of EM field, damage threshold assessment and size of beam bunch are simulated. For dual-drive acceleration mode, the effect of different input phase of bunch on 3D bunch size is discussed. For deflection mode, the effect from EM field and self-interaction force on the transverse velocity is discussed with the variation of the transverse size of the beam observed in simulation. For single-drive acceleration mode, the effect of distribution Bragg reflector on the energy gain of beam and acceleration gradient is discussed based on the comparison of different drive modes. Based on theory and simulation result, possible experiment scheme is preliminary designed, including hundred-micron acceleration experiment based on dual-drive mode.

Poster MOPB002 [0.525 MB]

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MOPB029

Multi-bunch Operation Mode for Simultaneously Serving SASE and Seeding FEL Beamlines

66

X.F. Wang
Institute of Advanced Science Facilities, Shenzhen, People’s Republic of China
X.M. Li, J.T. Sun, X.M. Yang, Y. Yu, W.Q. Zhang
DICP, Dalian, Liaoning, People’s Republic of China
Y.F. Liang, X.M. Yang, H. Yi, L. Zeng, W.Q. Zhang
IASF, Shenzhen, Guangdong, People’s Republic of China

Modern free-electron laser (FEL) facilities are de-signed to simultaneously serve multiple undulator lines to provide x-ray pulses with high peak power and tunable wavelengths. To satisfy different scientific demands, it is preferred to make the separate undulator lines work under different FEL schemes, such as the self-amplified spontaneous emission (SASE) scheme and the echo-enabled harmonic generation (EEHG) scheme. However, different FEL schemes have differ-ent requirements on the beam longitudinal distribu-tion. Here, we propose to use multiple bunches to sim-ultaneously serve the undulator lines and put the bunches at different acceleration phase to change the bunch length with two compressor chicanes. The ac-celeration phase for each bunch is varied by adjusting the time delays of the photocathode drive laser pulses with the accelerator settings unchanged. The start-to-end simulation demonstrates that a fs bunch with high peak current can be produced to serve the SASE line while a bunch with hundred-of-fs length and uniform current distribution can be produced to serve the EEHG line. The FEL performances are simulated and discussed.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB029

About •

Received ※ 25 June 2023 — Revised ※ 10 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 07 September 2024

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MOPB038

Achromatic Beam Design for a Laser-Driven Proton Therapy Accelerator

K.D. Wang
PKU, Beijing, People’s Republic of China

Laser-driven ion acceleration is one of the research hotspots in the field of accelerator in recent years. The high energy ion beam accelerated by laser has the characteristics of small size, narrow pulse width and good directivity, so it has many potential applications. This work will introduce the beam line dynamics design of a laser driven proton radiotherapy planned to be completed by Peking University. The beam line will be used as the key system of the laser proton radiotherapy application demonstration device, and the beam transport system will complete the follow-up operation. The whole beam design can provide horizontal and vertical irradiation modes respectively. It can efficiently collect the large divergence beam generated by the laser. It also contains a complete energy selection system, which can effectively select the energy dispersion of the laser accelerated beam to meet the application requirements. Finally, the beam accelerated by laser passes through the beam transport system to provide a proton beam with a diameter of less than 5 mm and an energy propagation of less than 5% at the horizontal and vertical irradiation targets.

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MOPB039

Low-Alpha Storage Ring Design for Steady-State Microbunching to Generate EUV Radiation

88

Z. Pan, A. Chao, X.J. Deng, W.-H. Huang, Z.Z. Li, C.-X. Tang
TUB, Beijing, People’s Republic of China

A new concept is proposed for minimizing the longitudinal emittance of a low momentum compaction factor (low-alpha) storage ring which has the capability to stably store sub-femtosecond electron bunches for the first time. This storage ring is designed for Steady-State microbunching (SSMB) to generate kW level average power EUV radiation. The proposed design approach can be applied to any quasi-isochronous storage rings to yield very high radiation power due to longitudinal coherence of the radiation. We obtain an optimal lattice design by minimizing global and local momentum compaction factors simultaneously and the result of single-particle tracking shows that the electron beam with equilibrium rms bunch length of about 40 nm can be stored in this ring. Nonlinear dynamics is studied for this lattice.

DOI •

reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB039

About •

Received ※ 03 July 2023 — Revised ※ 08 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 31 December 2023

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TUAA01

Recent progresses of laser plasma based electron acceleration at Shanghai Jiao Tong university

M. Chen
Shanghai Jiao Tong University, Shanghai, People’s Republic of China

Funding: National Natural Science Foundation of China (Grants No. 11991074, 12225505) and the Strategic Priority Research Program of the Chinese Academy of Sciences (Grants No. XDA25010500, XDA25050000).
Laser plasma based electron acceleration has many applications. Aiming to the high energy electron acceleration, we have performed both theoretical and experimental studies. A curved plasma channel has been proposed to guide intense lasers for multistage laser wakefield acceleration. In our recent experiment we found that when the channel curvature radius is gradually increased and the laser incidence offset is optimized, the stable laser guiding is possible and wakefields can be excited in the curved channel. Electrons with maximum energy of 0.7GeV have been observed. Our results show that such a channel exhibits good potential for seamless multi-stage laser wakefield acceleration. A 200+300TW two-laser system platform will be installed in SJTU. The research plans, such as staged wakefield acceleration, Thomson scattering and plasma optics studies on this platform, will be introduced.

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TUAA02

Acceleration and Transport of Protons in a PW Laser Accelerator

C. Lin, W.J. Ma, K.D. Wang, Q. Wang, X.Q. Yan, J.R. Zhao, Y.Y. Zhao, K. Zhu
PKU, Beijing, People’s Republic of China

Laser plasma accelerator has been considered as a promising candidate for future compact accelerator and radiation source. Laser ion acceleration is an extremely high gradient transient process: the established field can exceed TV/m, accelerating ions to high energy within tens of micron distance. Such pulsed high-current proton sources enable significant advances in many fields, such as FLASH tumor therapy, proton radiograph, and irradiation in extreme condition. With the support of the Ministry of Science and Technology of China, a prototype of proton radiotherapy system based on PW (10 15 W) laser accelerator is under construction by Peking University at Beijing Laser Innovation Center. In this presentation, we will introduce the latest progress of the laser proton accelerator, as well as the key technologies related to the project, such as improvement to the acceleration mechanism, transport of the broad energy spread beams, and the proton irradiation applications.

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reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUXA01

Studies of Injection Mechanism Optimization and Radiation Reaction in Plasma Wakefield Accelerators

M. Zeng
IHEP, Beijing, People’s Republic of China

Laser or charged beam driven plasma wakefield accelerators (PWAs) are considered as the accelerators of the next generation. Before the actual applications of PWAs in a wide range of disciplines, the output beam quality parameters require further improvements. Especially, the output beam charge and energy spread are contradictory parameters for optimization. This talk will present the recent works on the simultaneous optimization of the output beam charge and energy spread at Institute of High Energy Physics (IHEP), Chinese Academy of Sciences. In addition, this talk will present the work of modeling the betatron oscillation in long-distance PWAs by considering the higher-order electromagnetic field structure and the radiation reaction effect, and show new phenomena based on this model. This model is useful for the beam optimization in future long-distance and high-energy PWAs.

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reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUXA02

High-energy laser wakefield electron acceleration and its feasibility as a synchrotron radiation injection source

X.Z. Chen
Rejected, Tanzania

The development of high-energy collider requires the development of new high-gradient particle acceleration technologies. In order to achieve this grand scientific goal, laboratories around the world are currently focused on the application and development of novel acceleration technologies at the energy level of several GeV. With the advancements in ultra-intense and ultra-short laser technology, laser plasma acceleration has the potential to further advance accelerator technology, owing to its ultra-high acceleration gradients, short pulse duration and high current density. In this report, we will mainly introduce the current research progress of our team in high-energy laser wakefield electron acceleration. We will discuss the common technical research conducted in combining laser wakefield electron acceleration with traditional accelerator technology. Additionally, we will discuss the challenging issues faced by laser wakefield electron acceleration technology as an injection source technology for synchrotron radiation facilities. These discussions aim to offer some considerations for the further development of compact injection sources and high-energy colliders.

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TUBA01

High-quality electron beams and free-electron lasing based on laser wakefield accelerator

W. Wang
Shanghai Institute of Optics and Fine Mechanics, Shanghai, People’s Republic of China

X-ray free-electron lasers can generate intense and coherent radiation at wavelengths down to the sub-ångström region, and have become indispensable tools for applications in structural biology and chemistry, among other disciplines. Laser wakefield accelerators can sustain accelerating gradients more than three orders of magnitude higher than those of radio-frequency accelerators, and are regarded as an attractive option for driving compact X-ray free-electron lasers[1]. After ten years of efforts, we present an experimental demonstration of undulator radiation amplification in the exponential-gain regime by using electron beams based on a laser wakefield accelerator[2-4]. The amplified undulator radiation, which is typically centred at 27 nanometres and has a maximum photon number of around 10¹⁰ per shot, yields a maximum radiation energy of about 150 nanojoules. The results constitute a proof-of-principle demonstration of free-electron lasing using a laser wakefield accelerator, and pave the way towards the development of compact X-ray free-electron lasers based on this technology with broad applications.
1. K. Nakajima, Nat. Phys. 4, 92-93 (2008).
2. Wentao Wang, et al., Nature 595, 516 (2021).
3. Wentao Wang, et al., PRL 117, 124801 (2016).
4. Lingtong Ke, et al., PRL 126, 214801 (2021).

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TUYA01

Attosecond X-ray free-electron lasers utilizing an optical undulator in a self-selection regime

X. Xu
SLAC, Menlo Park, California, USA

Accelerator-based X-ray free-electron lasers (XFELs) are the latest addition to the revolutionary tools of discovery for the 21st century. The two major components of an XFEL are an accelerator-produced electron beam and a magnetic undulator which tend to be kilometer-scale long and expensive. Here, we present an ultra-compact scheme to produce 10s of attosecond X-ray pulses with several GW peak power utilizing a novel aspect of the FEL instability using a highly chirped, pre-bunched and ultra-bright electron beam from a plasma-based accelerator interacting with an optical undulator. The self-selection of electrons from the combination of a highly chirped and pre-bunched beam leads to the stable generation of attosecond X-ray pulses. Furthermore, two-color attosecond pulses with sub-femtosecond separation can be produced by adjusting the energy distribution of the electron beam so that multiple FEL resonances occur at different locations within the beam. Such a tunable coherent attosecond X-ray sources may open up a new area of attosecond science enabled by X-ray attosecond pump/probe techniques.

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TUYA02

Ultra-high Harmonic Conversion of a Seeded Free-electron Laser via Harmonic Optical Klystron

X.F. Wang
Institute of Advanced Science Facilities, Shenzhen, People’s Republic of China

External seeded free-electron lasers (FELs) have proven to be compelling tools for generating fully coherent EUV and soft X-ray radiations. Echo-enabled harmonic generation (EEHG), as the most typical representative of external seeded FELs, has unparalleled harmonic conversion efficiency. However, due to the limitations of various collective effects, the harmonic conversion of a high-gain EEHG that has been proved in experiments does not exceed 50 times. This paper proposes a new EEHG technology with the help of harmonic optical klystron technology, which can effectively increase the number of harmonic conversion to about 100 times. Theoretical analysis and numerical simulations show that intense and almost fully coherent FEL pulses with a radiation wavelength of 3 nm can be generated. At the same time, the seed laser intensity required by this scheme is lower, compared to nominal EEHG, thus facilitating the generation of high repetition rate seeded FELs.

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TUPB036

Optimisation of RFQ Transmission Efficiency Based on Reinforcement Learning Control Policy

C.G. Su, Z.J. Wang
IMP/CAS, Lanzhou, People’s Republic of China

The reinforcement learning (RL) algorithm is utilized to control the low-energy beam transport (LEBT) and radiofrequency quadrupole (RFQ) in linear accelerators, with the aim of improving RFQ transmission efficiency, achieving high beam intensity, reducing debugging time, and improving operational efficiency. A neural network model is established as part of the Interaction environment to partially replace the Tracewin software for RL training proceess. The SAC algorithm is a reinforcement learning algorithm used to optimize control policies for continuous action spaces. By using the SAC algorithm and interacting with the neural network model, a policy was trained to control the LEBT solenoids, optimizing the RFQ transmission efficiency to above 95% on the simulation software Tracewin. To test the generalization ability of the strategy, we applied it to a real accelerator and successfully validated its ability to optimize the RFQ transmission efficiency. The results demonstrate that RL policy trained in simulation-based environments can be applied on real accelerator control.

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TUPB037

RF Design and Cold Test of SCDTL Structure for Proton Therapy

X.X. Li
IMP/CAS, Lanzhou, People’s Republic of China

Side coupled drift tube linac (SCDTL) was selected in the middle energy accelerator of the cancer treatment device, which works at 3 GHz. The periodic structure of six accelerator cavities has been completed, and it can accelerate proton from 10 to 20 MeV. Besides, the electromagnetic design and preliminary cold measurement of a single accelerator cavities (b= 0.15) have been finished. The frequency of single-cavity electromagnetic design is 2.961 GHz, the Q₀ value is 12498, Kp is 2.19. The initial measurement frequency is 2.9579 GHz, the Q₀ value is 6927, which is 55% of the design value, but the Q₀ value can be improved by electrochemical polishing, so the experiment of increasing the value of Q₀ is being carried out.

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