HIAT2015 - List of Authors (Yoshimoto, T.)

Paper	Title	Page
MOPA16	Coherent Synchro-Beta Coupling in the KEK Digital Accelerator	77
	T. Monma, K. Takayama, T. Yoshimoto KEK, Ibaraki, Japan K. Takayama, T. Yoshimoto TIT, Yokohama, Japan K. Takayama Sokendai, Ibaraki, Japan
	The required acceleration voltage per turn in any circular accelerator is written by Vacc=ρC0dB/dt, where ρ, C0, and B are the bending radius, circumference of the orbit, and magnetic flux density, respectively. Since the guiding magnetic fields of the KEK Digital Accelerator, which is a fast cycling induction synchrotron, are excited sinusoidally, an ideal profile of Vacc is of half sine. From the engineering constraint of the current induction acceleration system, however, the output voltage is always constant between 1.5 kV and 2.0 kV. Thus the induction acceleration voltage pulse is discretely generated based on the specific pulse density program so as to satisfy a size of the required voltage integrated for a short time period. The induction acceleration cells are placed at the region where the magnitude of the momentum dispersion function is not zero but 1.4 m. It has been reported that the coherent motion of the beam centroid is strongly excited at the early stage of acceleration cycle . Discrete acceleration at the finite momentum dispersion function region is suspected to cause such a coherent motion. K.Takayama et al., "Induction acceleration of heavy ions in the KEK digital accelerator: Demonstration of a fast-cycling induction synchrotron", Phys. Rev. ST-AB 17, 010101(2014)
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MOPA22	Beam Confinement Dynmics in a Barrier Bucket	92
	M. Hirose Tokyo City University, Tokyo, Japan X. Liu, K. Takayama, T. Yoshimoto TIT, Yokohama, Japan X. Liu, K. Takayama, T. Yoshimoto KEK, Ibaraki, Japan K. Takayama Sokendai, Ibaraki, Japan
	Barrier bucket beam trapping has some history. For the first time Griffin proposed this method and demonstrated in Tevatron project in 1983. There the barrier voltage has been generated in the way that higher harmonic components of RF voltage are superimposed. Since then several groups tried this method and it has been utilized in a routine operation of Fermilab Antiproton Recycler . The induction synchrotron concept was proposed in 2000. Barrier bucket created by the pulse voltages has been assumed for beam confinement in this accelerator. Its concept was confirmed in the experiment using the 12 GeV PS in 2006. From the early days of barrier bucket development chaotic-like motions of trapped particles in the phase space have attracted our concerns . However there are no systematic studies focusing on this point. The paper will discuss what causes such chaotic motions and how it is sensitive to barrier bucket parameters such as the voltage pulse profile with a finite rising/falling time and its amplitude. We will propose what counter measures are effective in order to mitigate increasing of the longitudinal emittance caused by this instability. J. Griffin et al., IEEE Trans. Nucl. Sci. NS-30, 3502, 21-23 Mar. 1983. ** Ken Takayamaet et al. , "Induction Synchrotron" (Springer, Heidelberg, 2011).
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MOPA17	Super-Bunch Induction Acceleration Scheme in the KEK Digital Accelerator	80
	T. Yoshimoto, K. Takayama TIT, Yokohama, Japan T. Adachi, E. Kadokura, T. Kawakubo, X. Liu, K. Okamura, S. Takano, K. Takayama KEK, Ibaraki, Japan T. Adachi, K. Takayama Sokendai, Ibaraki, Japan H. Kobayashi Tokyo City University, Tokyo, Japan X. Liu Department of Energy Sciences, Tokyo Institute of Technology, Yokohama, Japan
	One of our next missions for the KEK digital accelerator,* is to demonstrate super-bunch (very long beam) acceleration technique in which a beam length occupies over half of the ring at injection**. This machine uses an induction cell driven by a switching power supply (SPS) which can generate rectangular pulses with their timings precisely controlled by a field-programmable gate array (FPGA). A power supply for the SPS is planned to be upgraded from present DC setup to a time-varying type generating a beam-required acceleration voltage per turn. This suppresses an emittance blow-up longitudinally and allows the super-bunch acceleration stably. In this presentation, we discuss concrete super-bunch acceleration scheme with simulation results and its hardware developments. T. Iwashita et al, Phys. Rev. ST-AB 14, 071301 (2011). K. Takayama, T. Yoshimoto et al, Phys. Rev. ST-AB 17, 010101 (2014). * K. Takayama et al, Phys. Rev. Lett. 88, 144801 (2002).
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Paper

Title

Page

Coherent Synchro-Beta Coupling in the KEK Digital Accelerator

77

T. Monma, K. Takayama, T. Yoshimoto
KEK, Ibaraki, Japan
K. Takayama, T. Yoshimoto
TIT, Yokohama, Japan
K. Takayama
Sokendai, Ibaraki, Japan

The required acceleration voltage per turn in any circular accelerator is written by Vacc=ρC0dB/dt, where ρ, C0, and B are the bending radius, circumference of the orbit, and magnetic flux density, respectively. Since the guiding magnetic fields of the KEK Digital Accelerator, which is a fast cycling induction synchrotron, are excited sinusoidally, an ideal profile of Vacc is of half sine. From the engineering constraint of the current induction acceleration system, however, the output voltage is always constant between 1.5 kV and 2.0 kV. Thus the induction acceleration voltage pulse is discretely generated based on the specific pulse density program so as to satisfy a size of the required voltage integrated for a short time period. The induction acceleration cells are placed at the region where the magnitude of the momentum dispersion function is not zero but 1.4 m. It has been reported that the coherent motion of the beam centroid is strongly excited at the early stage of acceleration cycle *. Discrete acceleration at the finite momentum dispersion function region is suspected to cause such a coherent motion.
* K.Takayama et al., "Induction acceleration of heavy ions in the KEK digital accelerator: Demonstration of a fast-cycling induction synchrotron", Phys. Rev. ST-AB 17, 010101(2014)

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MOPA22

Beam Confinement Dynmics in a Barrier Bucket

92

M. Hirose
Tokyo City University, Tokyo, Japan
X. Liu, K. Takayama, T. Yoshimoto
TIT, Yokohama, Japan
X. Liu, K. Takayama, T. Yoshimoto
KEK, Ibaraki, Japan
K. Takayama
Sokendai, Ibaraki, Japan

Barrier bucket beam trapping has some history. For the first time Griffin proposed this method and demonstrated in Tevatron project in 1983*. There the barrier voltage has been generated in the way that higher harmonic components of RF voltage are superimposed. Since then several groups tried this method and it has been utilized in a routine operation of Fermilab Antiproton Recycler . The induction synchrotron concept was proposed in 2000. Barrier bucket created by the pulse voltages has been assumed for beam confinement in this accelerator. Its concept was confirmed in the experiment using the 12 GeV PS in 2006**. From the early days of barrier bucket development chaotic-like motions of trapped particles in the phase space have attracted our concerns . However there are no systematic studies focusing on this point. The paper will discuss what causes such chaotic motions and how it is sensitive to barrier bucket parameters such as the voltage pulse profile with a finite rising/falling time and its amplitude. We will propose what counter measures are effective in order to mitigate increasing of the longitudinal emittance caused by this instability.
* J. Griffin et al., IEEE Trans. Nucl. Sci. NS-30, 3502, 21-23 Mar. 1983.
** Ken Takayamaet et al. , "Induction Synchrotron" (Springer, Heidelberg, 2011).

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reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

MOPA17

Super-Bunch Induction Acceleration Scheme in the KEK Digital Accelerator

80

T. Yoshimoto, K. Takayama
TIT, Yokohama, Japan
T. Adachi, E. Kadokura, T. Kawakubo, X. Liu, K. Okamura, S. Takano, K. Takayama
KEK, Ibaraki, Japan
T. Adachi, K. Takayama
Sokendai, Ibaraki, Japan
H. Kobayashi
Tokyo City University, Tokyo, Japan
X. Liu
Department of Energy Sciences, Tokyo Institute of Technology, Yokohama, Japan

One of our next missions for the KEK digital accelerator*,** is to demonstrate super-bunch (very long beam) acceleration technique in which a beam length occupies over half of the ring at injection***. This machine uses an induction cell driven by a switching power supply (SPS) which can generate rectangular pulses with their timings precisely controlled by a field-programmable gate array (FPGA). A power supply for the SPS is planned to be upgraded from present DC setup to a time-varying type generating a beam-required acceleration voltage per turn. This suppresses an emittance blow-up longitudinally and allows the super-bunch acceleration stably. In this presentation, we discuss concrete super-bunch acceleration scheme with simulation results and its hardware developments.
* T. Iwashita et al, Phys. Rev. ST-AB 14, 071301 (2011).
** K. Takayama, T. Yoshimoto et al, Phys. Rev. ST-AB 17, 010101 (2014).
*** K. Takayama et al, Phys. Rev. Lett. 88, 144801 (2002).

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reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)