Beam monitor system for an x-ray free electron laser and compact laser

Otake, Yuji; Maesaka, H.; Matsubara, Shigeo; Inoue, Shiro; Yanagida, K.; Ego, H.; Kondo, Chikara; Sakurai, Takayasu; Matsumoto, Takahiro; Tomizawa, H.

doi:10.1103/physrevstab.16.042802

Cited by 22 publications

(16 citation statements)

References 10 publications

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“…Dark current from the accelerator structures was measured by current transformers [13] installed between the C-band accelerator units. The total amount of dark current was less than 5 pC per pulse per unit for an 8 GeV electron beam energy.…”

Section: B Operational Performance At Sacla and Discussionmentioning

confidence: 99%

“…The C-band linac consists of an array of "accelerator units," each including a klystron and accelerator structures as described in a later section. In addition, a quadrupole magnet, a steering magnet, electron beam monitors [13] and a gate valve were installed between every four accelerator units, which are grouped as a "section." In the SACLA linac, 12 accelerator units (section CB01-CB03) are used from BC2 to BC3, and 52 units (section CB05-CB18) are used after BC3.…”

Section: Design Of the C-band Linacmentioning

confidence: 99%

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High-gradientC-band linac for a compact x-ray free-electron laser facility

Inagaki

Kondo

Maesaka

et al. 2014

Phys. Rev. ST Accel. Beams

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An electron linac using a C-band rf frequency, 5.712 GHz, has enabled us to obtain an acceleration gradient of more than 35 MV=m reliably. A C-band accelerator system has been developed and constructed for the compact x-ray FEL facility, SACLA, in order to fit within the available site length at SPring-8, and to reduce construction costs. An accelerator unit consists of two 1.8 m-long accelerator structures, a cavitytype rf pulse compressor and a 50 MW pulsed klystron. In order to achieve a compact rf source and to obtain extremely stable rf fields in the accelerator structures, an oil-filled, high-voltage pulse modulator combined with an extremely stable, inverter-type, high voltage charger was developed. SACLA uses 64 sets of these accelerator units in order to achieve a final beam energy of 8.5 GeV. After rf conditioning for 1 700 hours, the maximum acceleration gradient achieved was 38 MV=m. The typical trip rate for each accelerator unit at 35 MV=m and 30 pps is about once per day. Dark current from the accelerator structures is less than 5 pC, which causes a negligible effect on the beam monitors. The phase and amplitude stability of the rf fields were measured to be 0.03 degree and 0.01% rms, respectively, which is sufficient for the XFEL operation of SACLA. Since the first beam commissioning in 2011, the C-band accelerator has demonstrated fairly stable performance under continuous operation for 20 000 hours.

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Section: B Operational Performance At Sacla and Discussionmentioning

confidence: 99%

Section: Design Of the C-band Linacmentioning

confidence: 99%

High-gradientC-band linac for a compact x-ray free-electron laser facility

Inagaki

Kondo

Maesaka

et al. 2014

Phys. Rev. ST Accel. Beams

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“…9, the laser pulse energies of BL2 and BL3 are plotted with respect to the CSR intensity, which relates with the longitudinal distribution of the electron bunch, measured at the final bunch compressor (BC3 in Fig. 1) [26]. From Fig.…”

Section: Multi-beam-line Operationmentioning

confidence: 99%

High peak current operation of x-ray free-electron laser multiple beam lines by suppressing coherent synchrotron radiation effects

Hara

Kondo

Inagaki

et al. 2018

Phys. Rev. Accel. Beams

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The parallel operation of multiple beam lines is an important means to expand the opportunity of user experiments at x-ray free-electron laser (XFEL) facilities. At SPring-8 Angstrom free-electron laser (SACLA), the multi-beam-line operation had been tested using two beam lines, but transverse coherent synchrotron radiation (CSR) effects at a dogleg beam transport severely limited the laser performance. To suppress the CSR effects, a new beam optics based on two double bend achromat (DBA) structures was introduced for the dogleg. After the replacement of the beam optics, high peak current bunches of more than 10 kA are now stably transported through the dogleg and the laser pulse output is increased by a factor of 2-3. In the multi-beam-line operation of SACLA, the electron beam parameters, such as the beam energy and peak current, can be adjusted independently for each beam line. Thus the laser output can be optimized and wide spectral tunability is ensured for all beam lines.

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“…The VME-ADC module [7,26], as shown in Fig. 19, was developed to digitize the signals including the rf phase and amplitude information detected with the IQ demodulator.…”

Section: -Bit 238 Mhz Vme Adc and Dac Modules For Rf Drivementioning

confidence: 99%

Timing and low-level rf system for an x-ray laser

Otake

Maesaka

Matsubara

et al. 2016

Phys. Rev. Accel. Beams

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An x-ray free-electron laser (XFEL), SACLA, designed to open up new science, was constructed for generating coherent x rays with a peak power of more than 10 GW and a very short pulse of below 30 fs. This feature demands a very highly short-term temporal stability of less than 50 fs to the acceleration rf field of SACLA. For this reason, we developed a timing and low-level rf (LLRF) system for SACLA based on that of the SPring8 compact SASE source (SCSS) test accelerator for verifying the feasibility of an XFEL. The performance of the system using the in-phase and quadrature rf manipulation method was improved from SCSS's system. Since the facility length of SACLA is 700 m, which is 10 times longer than that of the SCSS test accelerator, a phase-stabilized optical-fiber system designed to transmit time standard rf signals with low loss was also developed and deployed. This optical-fiber system equips fiber optical-length feedback control in order to mitigate environmental effects, such as temperature and humidity changes. On the other hand, the demanded maximum rf temporal stability is less than 50 fs, which is almost 10 times smaller than that of the SCSS test accelerator. Hence, reducing electric noise and increasing the temperature stability around timing and LLRF instruments were necessary and realized with a very low-noise power supply and a hemathermal 19-inch enclosure. The short-term temporal performance of the timing LLRF system finally attained a temporal stability of less than 13.6 fs in rms measured by a beam arrival-time measurement. This stability greatly helps to achieve the stable x-ray lasing of SACLA for routine operation during user experiments.

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Beam monitor system for an x-ray free electron laser and compact laser

Cited by 22 publications

References 10 publications

High-gradientC-band linac for a compact x-ray free-electron laser facility

High-gradientC-band linac for a compact x-ray free-electron laser facility

High peak current operation of x-ray free-electron laser multiple beam lines by suppressing coherent synchrotron radiation effects

Timing and low-level rf system for an x-ray laser

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