FEL2012 - List of Authors (Tanaka, T.)

Paper

Title

Page

X-ray Based Undulator Commissioning in SACLA

543

T. Tanaka, T. Hara, T. Hatsui, H. Tanaka, K. Togawa
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
M. Yabashi
RIKEN/SPring-8, Hyogo, Japan

SACLA, the SPring-8 Angstrom Compact free electron LAser, achieved first lasing in June 2011 at the wavelength of 0.12 nm, which soon got down to 0.08 nm. After further beam tuning aiming at higher laser power and more stable operation, the user operation started in March 2012. In SACLA, 18 segments of in-vacuum undulator have been installed to achieve FEL saturation in an x-ray region. Each segment is 5-m long and placed with a 1.15-m long interval for installation of diagnostics and magnetic components. Because of such a segmented structure, we have many error sources that can lead to gain reduction. For example, the undulator K value can fluctuate from segment to segment, the electron beam can be kicked by the misalignment of quadrupole magnets, and so on. In order to eliminate all these errors, we have to optimize many parameters related to undulator operation. Such an optimization process is referred to as undulator commissioning. In SACLA, the undulator commissioning has been carried out based on the characterization of x rays both in spontaneous radiation and FEL radiation. In this paper, the details of the commissioning procedure and the achieved results are reported.

Slides THOCI01 [1.637 MB]

THPD38

Laser Wavelength Tuning by Variable-gap Undulators in SACLA

618

K. Togawa, T. Hara, H. Tanaka, T. Tanaka
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan

Wavelength tunability by variable-gap in-vacuum undulators is one of the features of SACLA. To fully utilize this advantage, it is important to suppress gap-dependent field errors down to the tolerance level, sub-microradian per undulator segment, which assures high SASE amplification gain enabling XFEL power saturation. For this purpose, we introduced a 'feed-forward correction' scheme, which is well-known technique in third-generation light sources. However, in linac-based XFELs, it was not easy to make a sufficiently accurate correction table to cancel out error fields due to shot-by-shot beam orbit and energy fluctuation propagating from the accelerator. By using cross-correlation technique based on the accelerator model, we so far succeeded in suppressing the gap-dependent orbit distortion down to a 10-micron level over the undulator section. Owing to this effort, experimental users at SACLA can quickly change the laser wavelength in a few seconds according to their demands by setting only the undulator K-value. In this conference, we will report the present status of wavelength tuning by the undulator gap in SACLA and problems to be solved towards the perfect control.

Paper	Title	Page
THOCI01	X-ray Based Undulator Commissioning in SACLA	543
	T. Tanaka, T. Hara, T. Hatsui, H. Tanaka, K. Togawa RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan M. Yabashi RIKEN/SPring-8, Hyogo, Japan
	SACLA, the SPring-8 Angstrom Compact free electron LAser, achieved first lasing in June 2011 at the wavelength of 0.12 nm, which soon got down to 0.08 nm. After further beam tuning aiming at higher laser power and more stable operation, the user operation started in March 2012. In SACLA, 18 segments of in-vacuum undulator have been installed to achieve FEL saturation in an x-ray region. Each segment is 5-m long and placed with a 1.15-m long interval for installation of diagnostics and magnetic components. Because of such a segmented structure, we have many error sources that can lead to gain reduction. For example, the undulator K value can fluctuate from segment to segment, the electron beam can be kicked by the misalignment of quadrupole magnets, and so on. In order to eliminate all these errors, we have to optimize many parameters related to undulator operation. Such an optimization process is referred to as undulator commissioning. In SACLA, the undulator commissioning has been carried out based on the characterization of x rays both in spontaneous radiation and FEL radiation. In this paper, the details of the commissioning procedure and the achieved results are reported.
	Slides THOCI01 [1.637 MB]

THPD38	Laser Wavelength Tuning by Variable-gap Undulators in SACLA	618
	K. Togawa, T. Hara, H. Tanaka, T. Tanaka RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
	Wavelength tunability by variable-gap in-vacuum undulators is one of the features of SACLA. To fully utilize this advantage, it is important to suppress gap-dependent field errors down to the tolerance level, sub-microradian per undulator segment, which assures high SASE amplification gain enabling XFEL power saturation. For this purpose, we introduced a 'feed-forward correction' scheme, which is well-known technique in third-generation light sources. However, in linac-based XFELs, it was not easy to make a sufficiently accurate correction table to cancel out error fields due to shot-by-shot beam orbit and energy fluctuation propagating from the accelerator. By using cross-correlation technique based on the accelerator model, we so far succeeded in suppressing the gap-dependent orbit distortion down to a 10-micron level over the undulator section. Owing to this effort, experimental users at SACLA can quickly change the laser wavelength in a few seconds according to their demands by setting only the undulator K-value. In this conference, we will report the present status of wavelength tuning by the undulator gap in SACLA and problems to be solved towards the perfect control.