Study of the frequency multiplication process in a multistage HGHG FEL

Brefeld, W.; Faatz, B.; Feldhaus, J.; Körfer, M.; Krzywiński, J.; Möller, Thomas; Pflueger, J.; Roßbach, J.; Saldin, E.L.; Schneidmiller, Evgeni; Schreiber, S.; Yurkov, M.V.

doi:10.1016/s0168-9002(02)00290-5

Cited by 13 publications

(4 citation statements)

References 16 publications

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“…These theoretical predictions have been demonstrated in the HGHG experiments [8][9][10]. However, significant bunching at higher harmonics would degrade the quality of the electron beam by increasing the beam energy spread in the modulator, which would result in a degradation of the amplification process in the radiator [11]. The need to limit the growth of the energy spread prevents the possibility of reaching short wavelength in a single stage HGHG.…”

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confidence: 87%

Design study for the cascaded HGHG experiment based on the SDUV-FEL

et al. 2012

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Cascading stages of high-gain harmonic generation (HGHG) free electron laser (FEL) is a promising way to produce fully coherent X-ray radiation. As a test facility for modern FEL R&D, the Shanghai deep ultraviolet FEL (SDUV-FEL) is now under upgrading for the cascading two stages of HGHG experiment. Since the energy of the electron beam is as low as about 185 MeV after upgrade, the total harmonic number of this two stages HGHG is only 2×2, and the wavelength of the final radiation is 196.5 nm which is the 4th harmonic of the 786 nm seed laser. With help of three-dimensional simulation codes, design studies on the FEL physics for the cascaded HGHG experiment are present based on the parameters of the upgraded SDUV-FEL facility. It is found from the simulation results that the part of the electron beam which has been used in the first stage can still generate powerful radiation in the radiator of the second stage, and this radiation will be difficult to be separated from the radiation generated by the fresh part of the electron beam. To overcome this problem, a novel method based on the energy spectrum of the electron beam is proposed in this paper to demonstrate the "fresh bunch" technique. Free electron lasers (FELs) hold great promise to produce coherent short wavelength radiation with high brightness and ultra-fast time structures which will enable scientists in physics, chemistry, biology and medicine to study nature down to the molecular and atomic level at a time-scale that fits this resolution. Because of its unique performance, FEL is complement to the 3rd generation light source like the Shanghai Synchrotron Radiation Facility (SSRF) [1]. Selfamplified spontaneous emission (SASE) [2,3] and seeded harmonic generation schemes [4][5][6][7] are two leading candidates for approaching deep ultraviolet (DUV) to X-ray region. The SASE process produces short wavelength radiation with high peak power and an excellent spatial mode. As the SASE FEL starts from electron beam shot noise, the output radiation typically has poor temporal coherence and large power fluctuations. An alternative way for generation of fully coherent short wavelength radiation is using the high-gain harmonic generation (HGHG) scheme [4,5]. HGHG consists of two undulators separated by a chicane. The electron beam is first energy modulated by a seed laser in the first short undulator (modulator) and then sent through a chicane (dispersion section) which converts the energy modulation into a density modulation. The density modulated beam is then sent through the second long undulator (radiator) to generate powerful radiation at the high harmonic of the seed frequency. The output property of the HGHG is a direct map of the seed laser's attributes which can have a high degree of temporal coherence and much smaller energy fluctuations than SASE. These theoretical predictions have been demonstrated in the HGHG experiments [8][9][10]. However, significant bunching at higher harmonics would degrade the quality of the electron beam

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confidence: 87%

Design study for the cascaded HGHG experiment based on the SDUV-FEL

et al. 2012

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“…In recent years, the available microwave spectrum becomes increasingly scarce [3][4], which means that we need to exploit spectrum resources at higher frequencies. Ordinary electronic oscillators generate high-frequency signals by frequency multiplication process, which degrades the phase noise performance [5][6]. On the other hand, by incorporating ultra-low loss delay, optoelectronic oscillators (OEO) have unique advantages in generating highfrequency signal with ultra-low noise [7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Hybrid-integrated optoelectronic oscillator with wideband tunability and low phase noise

Zhang,

Hao,

et al. 2023

Real-Time Photonic Measurements, Data Management, and Processing VII

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With the development of the economy and the society, spectrum resources of higher frequencies are becoming increasingly scarce. Beneficial from the photonic technology, optoelectronic oscillators (OEOs) have the advantages in generating microwave signal with high center frequency and low phase noise. However, applications of OEO systems are limited by its bulky size. In this work, a hybrid integrated OEO is proposed and experimentally demonstrated. A high integration level is achieved by assembling all the optical and electrical chips. A compact fiber ring and a YIG filter are also well packaged. At the oscillation frequency of 10 GHz, phase noise of the proposed OEO is -115.83 dBc/Hz@10 kHz. Wideband frequency tuning from 3 GHz to 18 GHz is also realized, the phase noise is better than -110 dBc/Hz @10 kHz at the entire tuning range. This work shows the great potential of integrated OEO in a wide range of applications such as wireless communications and satellite communications.

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“…For example, the third one is typically at the level of a percent of the fundamental intensity, 1,[3][4][5]7 and the higher harmonics are much weaker. To amplify the harmonics, various seeded FEL schemes [8][9][10][11][12][13][14][15][16][17][18] were proposed and intensively studied around the world. High-gain harmonic generation (HGHG) [8][9][10][11][12] is one of the harmonic amplification FEL schemes, where the seed in a first undulator (modulator) is used to induce an energy modulation in the electron beam, and convert the energy modulation into density modulation using a magnetic chicane.…”

Section: Introductionmentioning

confidence: 99%

Efficiency enhancement of a harmonic lasing free-electron laser

2015

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The harmonic lasing free-electron laser amplifier, in which two wigglers is employed in order for the fundamental resonance of the second wiggler to coincide with the third harmonic of the first wiggler to generate ultraviolet radiation, is studied. A set of coupled nonlinear first-order differential equations describing the nonlinear evolution of the system, for a long electron bunch, is solved numerically by CYRUS code. Solutions for the non-averaged and averaged equations are compared. Remarkable agreement is found between the averaged and non-averaged simulation for the evolution of the third harmonic. Thermal effects in the form of longitudinal velocity spread are also investigated. For efficiency enhancement, the second wiggler field is set to decrease linearly and nonlinearly at the point where the radiation of the third harmonic saturates. The optimum starting point and the slope of the tapering of the amplitude of the wiggler are found by a successive run of the code. It is found that tapering can increase the saturated power of the third harmonic considerably. In order to reduce the length of the wiggler, the prebunched electron beam is considered.Comment: 29 pages, 12 figure

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Study of the frequency multiplication process in a multistage HGHG FEL

Cited by 13 publications

References 16 publications

Design study for the cascaded HGHG experiment based on the SDUV-FEL

Design study for the cascaded HGHG experiment based on the SDUV-FEL

Hybrid-integrated optoelectronic oscillator with wideband tunability and low phase noise

Efficiency enhancement of a harmonic lasing free-electron laser

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