Compact single-pass X-ray FEL with harmonic multiplication cascades

Zhukovsky, K. V.

doi:10.1016/j.optcom.2018.02.039

Cited by 23 publications

(10 citation statements)

References 34 publications

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“…Наряду с этим в ЛСЭ также используют эхо нескольких затравочных лазеров, которые последовательно модулируют энергию электронного банча [15]; этот принцип реализован, например, в [16,17]. Возможен случай, когда гармоника в ондуляторе не излучается, но группировка электронов на ее длине волны создает эквивалентную мощность для усиления в следующем ондуляторе, настроенном в резонанс [18,19]; возможно также использование нескольких каскадов для умножения гармоник [20][21][22]. Применение монохроматоров или иная фильтрация излучения между каскадами ЛСЭ, настроенных на гармоники друг друга, позволяет получить от первых ондуляторов в режиме SASE затравочное лазерное излучение для последующих каскадов ЛСЭ (harmonic lasing selfseed, HLSS); этот принцип реализован, например, в ЛСЭ FLASH2 с изменяемым параметром дипольности k ондуляторов [23,24].…”

Section: к жуковскийunclassified

Об Излучении Гармоник В Рентгеновских Лазерах На Свободных Электронах С Изменяемым Параметром Дипольности Ондуляторов

Жуковский¹

2021

Журнал Технической Физики

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X-ray free electron lasers (FELs) produce ultra short bursts of coherent radiation at the wavelengths ~1–100 . In the absence of ready seed in this range, the fundamental tone is usually radiated in self-amplified spontaneous emission (SASE) FELs. With the goal to achieve maximum performance in minimum size and cost of a FEL, we study the harmonic multiplication in resonating undulator cascades as viable alternative to the SASE fundamental radiation. The harmonic power evolution along FELs is analyzed for the SASE and the harmonic self-seed. The analytical results are compared with available data for soft X-rays FLASH2. The possibility of harmonic radiation is studied for FELs with variable deflection parameter k: FLASH2, SwissFEL and currently built LCLS-II. We demonstrate earlier growth of the harmonic power in a buncher as compared with the SASE regime at the same wavelength. The difference is explained theoretically by the harmonic bunching growth in the buncher, as compared with that in the SASE FEL at the same wavelength. Excellent characteristics of the SwissFEL allow amplification of its third harmonic. We propose the harmonic self-seed, which would allow 10 m shorter undulator length for saturation at the same power, and up to 30% shorter radiation wavelength with the existing electron beam. At the LCLS-II, good bunching at the third harmonic wavelength in a dedicated buncher allows early and strong third harmonic growth. However, further resonating amplifier requires small value of k in LCLS-II undulators, which makes the amplification slow. We propose using the full amplification of the third FEL harmonic in LCLS-II undulators with bunching disruption between them at the wavelength of the fundamental. We show that this scheme allows >1 GW FEL power at λ=0.25 nm wavelength achievable already at ~40 m of the undulators with the electron beam energy E=4 GeV.

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Section: к жуковскийunclassified

Об Излучении Гармоник В Рентгеновских Лазерах На Свободных Электронах С Изменяемым Параметром Дипольности Ондуляторов

Жуковский¹

2021

Журнал Технической Физики

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“…The latter is based on the Pierce parameter ρ [45][46][47][48][49][50], and it significantly develops the first approach in [51][52][53], applied with some modifications in [54][55][56][57][58][59][60]. The present formulation in contrast with [51][52][53] describes all losses separately for each FEL harmonic; it also includes the gradual dual-stage saturation and reproduces the oscillations of the saturated power, differently from that in [54][55][56][57][58][59][60]. Moreover, formulae (4)-( 7), ( 22), ( 23) above in Section 2 in the limiting cases of the planar 2-frequency undulator correct the misprinted results in [54][55][56][57][58][59][60].…”

Section: Analysis Of the Harmonic Generation In Some Fel Experimentsmentioning

confidence: 99%

Synchrotron Radiation in Periodic Magnetic Fields of FEL Undulators—Theoretical Analysis for Experiments

Zhukovsky

2020

Symmetry

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A theoretical study of the synchrotron radiation (SR) from electrons in periodic magnetic fields with non-periodic magnetic components is presented. It is applied to several free electron lasers (FELs) accounting for the real characteristics of their electron beams: finite sizes, energy spread, divergence etc. All the losses and off-axis effects are accounted analytically. Exact expressions for the harmonic radiation in multiperiodic magnetic fields with non-periodic components and off-axis effects are given in terms of the generalized Bessel and Airy-type functions. Their analytical forms clearly distinguish all contributions in each polarization of the undulator radiation (UR). The application to FELs is demonstrated with the help of the analytical model for FEL harmonic power evolution, which accounts for all major losses and has been verified with the results of well documented FEL experiments. The analysis of the off-axis effects for the odd and even harmonics is performed for SPRING8 Angstrom Compact free-electron LAser (SACLA) and Pohang Accelerator Laboratory (PAL-XFEL). The modelling describes theoretically the power levels of odd and even harmonics and the spectral line width and shape. The obtained theoretical results agree well with the available data for FEL experiments; where no data exist, we predict and explain the FEL radiation properties. The proposed theoretical approach is applicable to practically any FEL.

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“…Формулы (4) и (5) исправляют опечатки в [45,49,57,58,62,65,66] и добавляют важную аналитическую зависимость f n,x ,y от угла отклонения от оси ондулятора.…”

Section: использование гармоник поля ондулятора для усиления гармоник оиunclassified

“…С целью уменьшения размеров и стоимости рентгеновских ЛСЭ можно использовать генерацию гармоник [24][25][26][27][28][29][30][31][32][33][34]. Плоские и эллиптические двухчастотные ондуляторы генерируют гармоники ОИ в линейном режиме с большим коэффициентом усиления, чем обычные плоские ондуляторы ; это делает предпочтительным их использование в ЛСЭ в каскадах группирователей электронов [53][54][55][56][57][58].…”

Section: Introductionunclassified

Генерация Когерентного Рентгеновского Излучения Гармоник В Однопроходном Лазере На Свободных Электронах Со Сдвигом Фаз Электронов Относительно Фотонов

Жуковский¹,

Калитенко²

2020

Журнал Технической Физики

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Theoretical study of the radiated FEL power and bunching is conducted in single-pass free electron laser (FEL) with repetitive shift of the photon pulse with respect to the electron bunch in between the sections of the undulator with field harmonics. Using the analytical calculations, the asymmetric elliptic and planar undulator fields are identified for the undulators to be able to reduce the fundamental tone and enhance the harmonic radiation. This effect is amplified by the phase shift kπ/n, k=2,4,6… of the electrons and photons between the undulator sections. This allows n-th FEL harmonic reach its peak power beyond the fundamental saturation FEL length. It is not possible to achieve in a common FEL due to fast increase of the energy spread, induced by the fundamental tone along FEL and its early saturation. The phenomenological model of the FEL is used for the analysis of the bunching coefficients and harmonic powers evolution in the FEL. The model describes the debunching between the undulator sections, where the phase shift is imposed, and accounts for the higher sensitivity to losses of the electron-photon interaction at high harmonic wavelengths. The losses are due to the beam energy spread and emittance, deviation off the axis, diffraction etc. Explicit expressions for the Bessel coefficients of the planar and elliptic undulators with field harmonics are obtained and analyzed. The combination of the undulator field harmonics is identified, which reduces the fundamental tone and enhances the 3rd and 5th UR harmonics as compared with the radiation from a planar undulator. We propose the use of these undulators in a FEL with the electron-photon phase shift, which increases high harmonic powers in X-ray band by ~100 times with respect to common FELs.

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Compact single-pass X-ray FEL with harmonic multiplication cascades

Cited by 23 publications

References 34 publications

Об Излучении Гармоник В Рентгеновских Лазерах На Свободных Электронах С Изменяемым Параметром Дипольности Ондуляторов

Об Излучении Гармоник В Рентгеновских Лазерах На Свободных Электронах С Изменяемым Параметром Дипольности Ондуляторов

Synchrotron Radiation in Periodic Magnetic Fields of FEL Undulators—Theoretical Analysis for Experiments

Генерация Когерентного Рентгеновского Излучения Гармоник В Однопроходном Лазере На Свободных Электронах Со Сдвигом Фаз Электронов Относительно Фотонов

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