LINAC2014 - List of Authors (Suzuki, S.)

Paper	Title	Page
MOPP092	Compact Timing System with FPGA for SPring-8 Linac	270
	H. Dewa, H. Hanaki, S. Suzuki JASRI/SPring-8, Hyogo-ken, Japan
	Funding: This reserch was supported by TAKUMI project. A new timing system for SPring-8 linac was developed. It is a test system to confirm the possibility of replacing the current NIM module-based system. Although fast logic circuits can be made easily with NIM modules, they become complicated when they are used in a large system. The timing system for SPring-8 linac has been getting larger and larger after several improvements for injection to New SUBARU (NS), top-up injection for storage ring, low repetition operation for saving energy, fast alternative injection and so on. In order to simplify the system, we adopted FPGA technology that can run at a clock over 500 MHz. The new system has 50 NIM inputs and outputs on the front panel, which is installed in an 8U rack-mount box. It only has gun trigger parts of current system, but includes all of the circuit components used in the current system such as and/or logics, counter delay, fan in/out etc. Three clock sources for Synchrotron injection, NS injection, and linac solo use are available in the FPGA, and they can be changed rapidly according to the trigger sources. We describe here the details of test timing system, the results of timing jitter measurements.

MOPP093	Evaluation of Beam Energy Fluctuations Caused by Phase Noises	273
	H. Hanaki, H. Dewa, S. Suzuki, K. Yanagida JASRI/SPring-8, Hyogo-ken, Japan T. Asaka, T. Ohshima RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
	The SSB noises of the RF reference signal dominate the short-term instabilities of the RF phase of the carrier RF. This phase modulation finally results in beam energy fluctuation. This presentation gives a quantitative evaluation of the beam energy fluctuations in an electron linear accelerator caused by phase noises, comparing a theoretical analysis and experimental results. A simple model was introduced to understand how phase noises result in the relative phase difference between a beam bunch and accelerating RF fields. In the experiments, we measured the enhanced beam energy fluctuations by modulating the phase of the reference RF signals with an external signal. The interference between the accelerating RF phase modulation and the timing modulation of a beam bunch was found in the model analysis and also in the experimental results.

MOPP094	Latest Improvements of the SPring-8 Linac for High Reliability	276
	S. Suzuki, H. Dewa, H. Hanaki, T. Kobayashi, T. Magome, A. Mizuno, T. Taniuchi, K. Yanagida JASRI/SPring-8, Hyogo-ken, Japan T. Asaka RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
	In order to perform stable injection to the 8GeV SPring-8 storage ring, which is performing the top-up operation, the high reliability of the linac has been advanced as follows: For reduction of phase variations caused by the waveguide deformation due to the variations of temperature or atmospheric pressure, the waveguide circuit of SF6 enclosure type, which fed RF powers to the bunching section, was replaced with that of vacuum type. And S-band 10MW circulators and isolators of vacuum type were adopted for the first time in the world. The timing system was improved so that the interval time of the beam injection into the 8GeV booster synchrotron and the 1.5 GeV NewSUBARU storage ring has been reduced to 1 sec from 15 seconds, respectively, even in the top-up operation of both storage rings. As a result, the stored current by the top-up operation were further stabilized. The stored current of the NewSUBARU storage ring was stabilized to 0.18% from 0.31%. The electron gun cathode assembly has been developed to reduce the dark emission from a grid plate by the double grid method and the electrolytic polishing.

MOPP095	Emittance Measurement for SPring-8 Linac Using Four Six-Electrode BPMs	279
MOPOL09	use link to see paper's listing under its alternate paper code
	K. Yanagida, H. Hanaki, S. Suzuki JASRI/SPring-8, Hyogo-ken, Japan
	In the SPring-8 linear accelerator (linac) six-electrode beam position monitors (BPMs) have been installed to measure second-order moments. At the end of the linac where the electron beam energy is 1 GeV four quadrupole magnets are utilized for twiss parameter matching toward the following beam transport line. Last year four six-electrode BPMs were installed at the locations of these four quadrupole magnets for an emittance measurement. The relative second-order moments were obtained changing the magnetic field strength of the quadrupole magnets, then beam sizes, emittances and twiss parameters were deduced or calculated. At this time we applied one pair of beam sizes measured by the screen monitor for a precise determination of emittances but we try to implement non-destructive measurement with no screen monitor. Before the emittance measurement a calibration with fifth-order moment correction was carried out changing beam positions at the BPM locations using upstream steering magnets (the entire calibration).
	Slides MOPP095 [0.984 MB]

TUPP105	Storage Ring as a Linac Beam Monitor – Its Operation and Contribution to the Stable Top-up Injection	668
	Y. Shoji LASTI, Hyogo, Japan T. Asaka, H. Dewa, H. Hanaki, T. Kobayashi, Y. Minagawa, A. Mizuno, T. Shinomoto, S. Suzuki, Y. Takemura, T. Taniuchi, K. Yanagida JASRI/SPring-8, Hyogo-ken, Japan
	We have used the electron storage ring, NewSUBARU, as a beam monitor of the SPring-8 linac. The time and transverse profiles of the injected linac beam are recorded in a frame of a dual-sweep streak camera. A measurements through synchrotron or betatron oscillation in the ring gives multi-dimensional beam structure. The system functions as a final check of the linac beam. It gives the time profile and energy profile or transverse emittance, which includes Twiss parameters. It measures parameters of one linac bunch in a long macro pulse. A shot-by-shot measurement gives beam fluctuations. We report how we use the system and its contribution to the stable top-up operation. The beam loading effect on the bunch energy was obtained by bunch-by-bunch energy profile measurements. It confirmed the optimization of the ECS (Energy Compression System) parameters. The single shot bunch-by-bunch vertical emittance measurement proved the difference between the front bunch and the following bunches. The same measurement showed a timing jitter of the electron gun pulse although the rf synchronization was perfect. This jittering had made the injection efficiency unstable.

Paper

Title

Page

Compact Timing System with FPGA for SPring-8 Linac

270

H. Dewa, H. Hanaki, S. Suzuki
JASRI/SPring-8, Hyogo-ken, Japan

Funding: This reserch was supported by TAKUMI project.
A new timing system for SPring-8 linac was developed. It is a test system to confirm the possibility of replacing the current NIM module-based system. Although fast logic circuits can be made easily with NIM modules, they become complicated when they are used in a large system. The timing system for SPring-8 linac has been getting larger and larger after several improvements for injection to New SUBARU (NS), top-up injection for storage ring, low repetition operation for saving energy, fast alternative injection and so on. In order to simplify the system, we adopted FPGA technology that can run at a clock over 500 MHz. The new system has 50 NIM inputs and outputs on the front panel, which is installed in an 8U rack-mount box. It only has gun trigger parts of current system, but includes all of the circuit components used in the current system such as and/or logics, counter delay, fan in/out etc. Three clock sources for Synchrotron injection, NS injection, and linac solo use are available in the FPGA, and they can be changed rapidly according to the trigger sources. We describe here the details of test timing system, the results of timing jitter measurements.

MOPP093

Evaluation of Beam Energy Fluctuations Caused by Phase Noises

273

H. Hanaki, H. Dewa, S. Suzuki, K. Yanagida
JASRI/SPring-8, Hyogo-ken, Japan
T. Asaka, T. Ohshima
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan

The SSB noises of the RF reference signal dominate the short-term instabilities of the RF phase of the carrier RF. This phase modulation finally results in beam energy fluctuation. This presentation gives a quantitative evaluation of the beam energy fluctuations in an electron linear accelerator caused by phase noises, comparing a theoretical analysis and experimental results. A simple model was introduced to understand how phase noises result in the relative phase difference between a beam bunch and accelerating RF fields. In the experiments, we measured the enhanced beam energy fluctuations by modulating the phase of the reference RF signals with an external signal. The interference between the accelerating RF phase modulation and the timing modulation of a beam bunch was found in the model analysis and also in the experimental results.

MOPP094

Latest Improvements of the SPring-8 Linac for High Reliability

276

S. Suzuki, H. Dewa, H. Hanaki, T. Kobayashi, T. Magome, A. Mizuno, T. Taniuchi, K. Yanagida
JASRI/SPring-8, Hyogo-ken, Japan
T. Asaka
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan

In order to perform stable injection to the 8GeV SPring-8 storage ring, which is performing the top-up operation, the high reliability of the linac has been advanced as follows: For reduction of phase variations caused by the waveguide deformation due to the variations of temperature or atmospheric pressure, the waveguide circuit of SF6 enclosure type, which fed RF powers to the bunching section, was replaced with that of vacuum type. And S-band 10MW circulators and isolators of vacuum type were adopted for the first time in the world. The timing system was improved so that the interval time of the beam injection into the 8GeV booster synchrotron and the 1.5 GeV NewSUBARU storage ring has been reduced to 1 sec from 15 seconds, respectively, even in the top-up operation of both storage rings. As a result, the stored current by the top-up operation were further stabilized. The stored current of the NewSUBARU storage ring was stabilized to 0.18% from 0.31%. The electron gun cathode assembly has been developed to reduce the dark emission from a grid plate by the double grid method and the electrolytic polishing.

MOPP095

Emittance Measurement for SPring-8 Linac Using Four Six-Electrode BPMs

279

MOPOL09

use link to see paper's listing under its alternate paper code

K. Yanagida, H. Hanaki, S. Suzuki
JASRI/SPring-8, Hyogo-ken, Japan

In the SPring-8 linear accelerator (linac) six-electrode beam position monitors (BPMs) have been installed to measure second-order moments. At the end of the linac where the electron beam energy is 1 GeV four quadrupole magnets are utilized for twiss parameter matching toward the following beam transport line. Last year four six-electrode BPMs were installed at the locations of these four quadrupole magnets for an emittance measurement. The relative second-order moments were obtained changing the magnetic field strength of the quadrupole magnets, then beam sizes, emittances and twiss parameters were deduced or calculated. At this time we applied one pair of beam sizes measured by the screen monitor for a precise determination of emittances but we try to implement non-destructive measurement with no screen monitor. Before the emittance measurement a calibration with fifth-order moment correction was carried out changing beam positions at the BPM locations using upstream steering magnets (the entire calibration).

Slides MOPP095 [0.984 MB]

TUPP105

Storage Ring as a Linac Beam Monitor – Its Operation and Contribution to the Stable Top-up Injection

668

Y. Shoji
LASTI, Hyogo, Japan
T. Asaka, H. Dewa, H. Hanaki, T. Kobayashi, Y. Minagawa, A. Mizuno, T. Shinomoto, S. Suzuki, Y. Takemura, T. Taniuchi, K. Yanagida
JASRI/SPring-8, Hyogo-ken, Japan

We have used the electron storage ring, NewSUBARU, as a beam monitor of the SPring-8 linac. The time and transverse profiles of the injected linac beam are recorded in a frame of a dual-sweep streak camera. A measurements through synchrotron or betatron oscillation in the ring gives multi-dimensional beam structure. The system functions as a final check of the linac beam. It gives the time profile and energy profile or transverse emittance, which includes Twiss parameters. It measures parameters of one linac bunch in a long macro pulse. A shot-by-shot measurement gives beam fluctuations. We report how we use the system and its contribution to the stable top-up operation. The beam loading effect on the bunch energy was obtained by bunch-by-bunch energy profile measurements. It confirmed the optimization of the ECS (Energy Compression System) parameters. The single shot bunch-by-bunch vertical emittance measurement proved the difference between the front bunch and the following bunches. The same measurement showed a timing jitter of the electron gun pulse although the rf synchronization was perfect. This jittering had made the injection efficiency unstable.