FEL2012 - List of Authors (Maesaka, H.)

Paper	Title	Page
MOPD51	Developing S-band Accelerating Structures	153
	S. Miura MHI, Hiroshima, Japan T. Inagaki, H. Maesaka RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan H.-S. Lee PAL, Pohang, Kyungbuk, Republic of Korea H. Matsumoto KEK, Ibaraki, Japan T. Shintake OIST, Onna-son, Okinawa, Japan
	We have supplied more than fifty high gradient S-band accelerating structures to KEK/ATF, SPring-8, PAL/Korea and INFN/Italy. Maximum accelerating garinent of these structures reaches in 30MV/m. Now we are developing new S-band accelerating structures. This time we report manufacturing of these structures.

TUPD36	Variation of Beam Arrival Timing at SACLA	317
	T. Ohshima, S. Matsubara JASRI/SPring-8, Hyogo, Japan H. Maesaka, Y. Otake RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
	The user operation of SACLA was started on March 2012. In this machine, it is a key issue to deliver stable timing signals (better than 30 fs) to the beam monitor units and apparatus of XFEL users. Since the arrival timing change of the X-ray at an experimental station depends on that of the electron beam, we measured the arrival timing of the electron beam by comparing an rf reference signal and a beam induced signal from an rf beam position monitor (rf bpm). A standard deviation of the arrival timing of the bpm was around 70 fs averaged in 100 beam-shots. The timing signal also changes by a drift of the rf reference signal, and this change leads to the measurement error. To evaluate this contribution, we measured difference of the arrival timings between two bpms located at the entrance and the exit of a beamline which has 18 ID units having the rf bpm, each. The difference corresponding to the reference time drift was less than 100 fs p-p in a day. We can measure the arrival timing of the X-ray with a resolution of less than 100 fs which is acceptable level in the current stage.

TUPD37	Upgrade of a Precise Temperature Regulation System for the Injector at SACLA	321
	T. Hasegawa, T. Asaka, T. Inagaki, H. Maesaka, Y. Otake, K. Togawa RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan T. Fukui, S. Takahashi JASRI/SPring-8, Hyogo, Japan
	A precise temperature regulation system for the injector at SACLA is being upgraded. To make stable operation of the SACLA, it is indispensable to achieve extremely high stability of the accelerator's components. At the beam commissioning, it has become clear that even a tiny fluctuation in the cooling water temperature, such as 0.1 K, for RF cavities of the injector can significantly influence on lasing stability. Although the existing temperature control system has been able to keep temperature stability of the cavity less than 0.08 K by using an ON-OFF alternatively heating method with a pulse width modulation, a laser power fluctuation has been observed, which has a strong correlation with the cavity temperature. An improvement in temperature stability for this system is expected by replacing a PLC module to a temperature controller with an extremely high temperature resolution of 0.001 K. We will be applying continuous level control of a heater with the DC power supply. This system will dramatically improve our lasing stability. This paper describes the temperature control scheme and its performance in detail.

TUPD38	Stability Improvements of SACLA	325
	H. Maesaka, T. Asaka, T. Hara, T. Hasegawa, T. Inagaki, T. Ohshima, Y. Otake, H. Tanaka, K. Togawa RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan T. Hasegawa, Y. Kano, T. Morinaga, Y. Tajiri, S. Tanaka, R. Yamamoto SES, Hyogo-pref., Japan S. Matsubara JASRI/SPring-8, Hyogo, Japan
	The XFEL facility, SACLA, achieved first x-ray lasing in June 2011 and started public user operation in March 2012. In the early days after the first x-ray lasing, large drift of FEL intensity was observed and the period of FEL lasing condition to keep within acceptable intensity variation was only about an hour. We found that this short period mainly came from drifts of the rf phases and amplitudes of sub-harmonic buncher cavities and accelerator cavities in an injector section (238, 476, 1428, 5712 MHz). These rf drifts caused drifts of a peak current, a beam energy and a beam trajectory. As a result, the FEL gain was significantly degraded. Since the rf field in the cavity had a strong correlation with the cavity temperature, we improved a cavity temperature regulation system by a factor of 2 or 3 and the temperature stability was reduced to be 0.08 K peak-to-peak. In addition, we introduced an energy feedback loop for a C-band main accelerator and an orbit feedback loop for an undulator beamline. After these improvements, the FEL intensity was maintained within 10% for longer than a day.

Paper

Title

Page

Developing S-band Accelerating Structures

153

S. Miura
MHI, Hiroshima, Japan
T. Inagaki, H. Maesaka
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
H.-S. Lee
PAL, Pohang, Kyungbuk, Republic of Korea
H. Matsumoto
KEK, Ibaraki, Japan
T. Shintake
OIST, Onna-son, Okinawa, Japan

We have supplied more than fifty high gradient S-band accelerating structures to KEK/ATF, SPring-8, PAL/Korea and INFN/Italy. Maximum accelerating garinent of these structures reaches in 30MV/m. Now we are developing new S-band accelerating structures. This time we report manufacturing of these structures.

TUPD36

Variation of Beam Arrival Timing at SACLA

317

T. Ohshima, S. Matsubara
JASRI/SPring-8, Hyogo, Japan
H. Maesaka, Y. Otake
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan

The user operation of SACLA was started on March 2012. In this machine, it is a key issue to deliver stable timing signals (better than 30 fs) to the beam monitor units and apparatus of XFEL users. Since the arrival timing change of the X-ray at an experimental station depends on that of the electron beam, we measured the arrival timing of the electron beam by comparing an rf reference signal and a beam induced signal from an rf beam position monitor (rf bpm). A standard deviation of the arrival timing of the bpm was around 70 fs averaged in 100 beam-shots. The timing signal also changes by a drift of the rf reference signal, and this change leads to the measurement error. To evaluate this contribution, we measured difference of the arrival timings between two bpms located at the entrance and the exit of a beamline which has 18 ID units having the rf bpm, each. The difference corresponding to the reference time drift was less than 100 fs p-p in a day. We can measure the arrival timing of the X-ray with a resolution of less than 100 fs which is acceptable level in the current stage.

TUPD37

Upgrade of a Precise Temperature Regulation System for the Injector at SACLA

321

T. Hasegawa, T. Asaka, T. Inagaki, H. Maesaka, Y. Otake, K. Togawa
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
T. Fukui, S. Takahashi
JASRI/SPring-8, Hyogo, Japan

A precise temperature regulation system for the injector at SACLA is being upgraded. To make stable operation of the SACLA, it is indispensable to achieve extremely high stability of the accelerator's components. At the beam commissioning, it has become clear that even a tiny fluctuation in the cooling water temperature, such as 0.1 K, for RF cavities of the injector can significantly influence on lasing stability. Although the existing temperature control system has been able to keep temperature stability of the cavity less than 0.08 K by using an ON-OFF alternatively heating method with a pulse width modulation, a laser power fluctuation has been observed, which has a strong correlation with the cavity temperature. An improvement in temperature stability for this system is expected by replacing a PLC module to a temperature controller with an extremely high temperature resolution of 0.001 K. We will be applying continuous level control of a heater with the DC power supply. This system will dramatically improve our lasing stability. This paper describes the temperature control scheme and its performance in detail.

TUPD38

Stability Improvements of SACLA

325

H. Maesaka, T. Asaka, T. Hara, T. Hasegawa, T. Inagaki, T. Ohshima, Y. Otake, H. Tanaka, K. Togawa
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
T. Hasegawa, Y. Kano, T. Morinaga, Y. Tajiri, S. Tanaka, R. Yamamoto
SES, Hyogo-pref., Japan
S. Matsubara
JASRI/SPring-8, Hyogo, Japan

The XFEL facility, SACLA, achieved first x-ray lasing in June 2011 and started public user operation in March 2012. In the early days after the first x-ray lasing, large drift of FEL intensity was observed and the period of FEL lasing condition to keep within acceptable intensity variation was only about an hour. We found that this short period mainly came from drifts of the rf phases and amplitudes of sub-harmonic buncher cavities and accelerator cavities in an injector section (238, 476, 1428, 5712 MHz). These rf drifts caused drifts of a peak current, a beam energy and a beam trajectory. As a result, the FEL gain was significantly degraded. Since the rf field in the cavity had a strong correlation with the cavity temperature, we improved a cavity temperature regulation system by a factor of 2 or 3 and the temperature stability was reduced to be 0.08 K peak-to-peak. In addition, we introduced an energy feedback loop for a C-band main accelerator and an orbit feedback loop for an undulator beamline. After these improvements, the FEL intensity was maintained within 10% for longer than a day.