HIAT2015 - List of Authors (Liu, X.)

Paper	Title	Page
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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MOPA21	Particle Tracking Simulation With Space Charge Effects for an Induction Synchrotron and Preliminary Application to the Kek Digital Accelerator	89
	X. Liu Department of Energy Sciences, Tokyo Institute of Technology, Yokohama, Japan
	In order to study the beam behaviour of the induction synchrotron which features low energy injection, a dedicated particle tracking simulation code with a 2.5D space charge field solver, which takes into account of the boundary condition, has been developed. The beam dynamics included in this code are discussed and simulation results assuming parameters of the KEK Digital Accelerator are presented. This code will help to understand the various features of the beam behaviour in the present beam commissioning and serve as a tool for the design of the future induction synchrotrons.
	Poster MOPA21 [0.631 MB]
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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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MOPA26	SI-Thyristor Matrix Array Driven Electrostatic Injection Kicker for the KEK Digital Accelerator and Beam Dynamics Analysis of Injection	101
	H. Kobayashi Tokyo City University, Tokyo, Japan T. Adachi, T. Kawakubo KEK, Ibaraki, Japan X. Liu TIT, Yokohama, Japan
	For heavy ion beam injection into the KEK-DA ring [], the electrostatic (ES) kicker is used []. A voltage of 20 kV is put across the electrostatic electrodes before injection so as to deflect the injected beam on the ring orbit. The ES-Kicker excitation circuit where a coaxial cable is charged to the required voltage by a resonant charging power supply and discharged just after beam injection. The SI-Thyristor Matrix Array (SI-Thy MA) as a discharging device has been developed to replace the conventional thyratron. The developed SI-Thy MA has proved to be quite useful in getting rid of inherent issues associated with thyratron's use. Recently it has turned out that ringing in a voltage pulse of 3.5 μs, which is originated from its longer switching time than that of the thyratron, affects on beam injection dynamics, resulting inμbunch formation. In order to understand this phenomenon, a computer simulation code including the longitudinal space-charge effects has been developed. Comparisons of the experimental results obtained for various parameters with the computer simulation will be discussed. [] T.Iwashita et al.,"KEK Digital Accelerator",Phys. Rev.ST-AB 14,071301(2011). [**] T.Adachi and T.Kawakubo,"Electrostatic Injection Kicker for KEK-DA",Phys. Rev.ST-AB 16, 053501 (2013).
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Paper

Title

Page

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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MOPA21

Particle Tracking Simulation With Space Charge Effects for an Induction Synchrotron and Preliminary Application to the Kek Digital Accelerator

89

X. Liu
Department of Energy Sciences, Tokyo Institute of Technology, Yokohama, Japan

In order to study the beam behaviour of the induction synchrotron which features low energy injection, a dedicated particle tracking simulation code with a 2.5D space charge field solver, which takes into account of the boundary condition, has been developed. The beam dynamics included in this code are discussed and simulation results assuming parameters of the KEK Digital Accelerator are presented. This code will help to understand the various features of the beam behaviour in the present beam commissioning and serve as a tool for the design of the future induction synchrotrons.

Poster MOPA21 [0.631 MB]

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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)

MOPA26

SI-Thyristor Matrix Array Driven Electrostatic Injection Kicker for the KEK Digital Accelerator and Beam Dynamics Analysis of Injection

101

H. Kobayashi
Tokyo City University, Tokyo, Japan
T. Adachi, T. Kawakubo
KEK, Ibaraki, Japan
X. Liu
TIT, Yokohama, Japan

For heavy ion beam injection into the KEK-DA ring [*], the electrostatic (ES) kicker is used [**]. A voltage of 20 kV is put across the electrostatic electrodes before injection so as to deflect the injected beam on the ring orbit. The ES-Kicker excitation circuit where a coaxial cable is charged to the required voltage by a resonant charging power supply and discharged just after beam injection. The SI-Thyristor Matrix Array (SI-Thy MA) as a discharging device has been developed to replace the conventional thyratron. The developed SI-Thy MA has proved to be quite useful in getting rid of inherent issues associated with thyratron's use. Recently it has turned out that ringing in a voltage pulse of 3.5 μs, which is originated from its longer switching time than that of the thyratron, affects on beam injection dynamics, resulting inμbunch formation. In order to understand this phenomenon, a computer simulation code including the longitudinal space-charge effects has been developed. Comparisons of the experimental results obtained for various parameters with the computer simulation will be discussed.
[*] T.Iwashita et al.,"KEK Digital Accelerator",Phys. Rev.ST-AB 14,071301(2011).
[**] T.Adachi and T.Kawakubo,"Electrostatic Injection Kicker for KEK-DA",Phys. Rev.ST-AB 16, 053501 (2013).

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