| Paper | Title | Page |
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| TUPSO46 | Analysis and Measurement of Focusing Effects in a Traveling Wave Linear Accelerator | 329 |
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We propose a further precise model of the transverse dynamics in a traveling wave linear accelerator (TWA) and report experimental results to demonstrate the validity of the model. In SACLA, the beam orbit is calculated by using a transfer matrix based on the transverse dynamics model of each component and the matrix is utilized for orbit stabilization, beam envelop matching etc. For the TWA part, a transfer matrix including an emittance damping effect and an edge focusing effect [*] is employed. However, the beam orbit measured by rf cavity beam position monitors (RF-BPM) [**] did not agree with the calculated orbit, especially for the off-crest acceleration part. Therefore, focusing effects in a TWA structure were analyzed by using a 3-dimensional rf simulation code. The analysis indicated that the transverse dynamics model of the TWA should include an additional quadrupole edge focusing effect. The amount of the additional focusing effect of the TWA was measured in SACLA and the rf simulation result was confirmed to be consistent with the measurement. After the modification of the transverse dynamics model, the beam orbit measured by RF-BPM agrees with the calculation.
* T. Hara et al., Nucl. Instrum. Methods A 624, 65 (2010). ** H. Maesaka et al., Nucl. Instrum. Methods A 696, 66 (2012). |
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| THOANO01 | Stable Operation of HHG-Seeded EUV-FEL at the SCSS Test Accelerator | 728 |
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| We performed the higher-order harmonic (HH) seeded FEL operation at a 61.2 nm fundamental wavelength, using a seeding source of HH pulses from a Ti:sapphire laser at the SCSS (EUV-FEL) accelerator. It is important for the HH seeded FEL scheme to synchronize the seeding laser pulses to the electron bunches. We constructed the relative arrival timing monitor based on Electro-Optic sampling (EOS). Since the EOS-probe laser pulses were optically split from HH-driving laser pulses, the arrival time difference of the seeding laser pulses, with respect to the electron bunches, were measured bunch-by-bunch. This non-invasive EOS monitor made uninterrupted, real-time monitoring possible even during the seeded FEL operation. The EOS system was used for the arrival timing feedback with a few-hundred-femtosecond adjustability for continual operation of the HH-seeded FEL. By using the EOS-locking system, the HH seeded FEL was operated over half a day with a 20-30% hit rate. The output pulse energy reached 20uJ at the 61.2 nm wavelength. A user experiment was performed by using the seeded EUV-EL and a clear difference between the SASE-FEL and the seeded FEL was observed. | ||
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Slides THOANO01 [11.493 MB] | |
THIBNO02 |
Demonstration Of Two-color XFEL Operation and Autocorrelation Measurement at SACLA | |
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| Recently two-color XFEL operation with a relative wavelength separation of 30 % has been achieved at SACLA in hard x-rays. In the two-color operation at SACLA, a simple and lucid scheme is employed, namely the first and second halves of the undulators are set at different K values. To make a time delay between the two-color photon pulses, a magnetic chicane is installed between the two undulator sections to detour the electron beam. Since the two-color pulses are emitted from the same electron bunch, there is no time jitter and the delay can be finely adjusted up to 40 fs. Two wavelengths can be freely selected in hard x-rays. The photon pulse length of the single-color operation measured by an autocorrelation technique is less than 10 fs (FWHM). The two-color operation of SACLA, which provides femtoseconds-short pulses with a GW-level peak power, is an ideal light source for x-ray pump x-ray probe experiments. | ||
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Slides THIBNO02 [1.988 MB] | |