Explanipedia

Theoretical Study of Mismatch-Induced Halo Formation from an Intense Hadron Bunch in a Uniform Focusing Channel Open

Koichi Kato, H. Okamoto · 2025

A basic mechanism of halo formation in high-intensity hadron accelerators is explored theoretically. As a possible origin of halos, we focus on the deviation of an initial bunch size from its ideal dimensions, in other words, spatial misma…

Investigating Ultralow-Emittance Nanobeam Formation Using a Coulomb Crystal Open

Yosuke Yuri, Nobumasa Miyawaki, K. Hosaka, Yasuyuki Ishii, Seiji Hosoya , et al. · 2025

Ultraprecise single-ion irradiation is of practical interest for the application of research and development of quantum materials and devices. To achieve this, a single-ion irradiation system, consisting of a linear Paul trap (LPT) and ele…

Simple Design Criterion for High-Intensity Hadron Linacs Open

Asuto Kasagaki, H. Okamoto · 2024

A simple procedure is established to optimize fundamental design parameters of a high-intensity hadron linac where interparticle Coulomb interaction plays a crucial role. Based on the recently proposed semi-empirical resonance condition, a…

Table-top ion-trap experiment on the stability of intense short bunches in linear hadron accelerators Open

Masahiko Kuroda, Asuto Kasagaki, H. Okamoto, K. Ito · 2024

The novel experimental system “S-POD” (Simulator of Particle Orbit Dynamics) is employed to explore the stability of short hadron bunches in high-intensity linacs. In a previous study with the S-POD [M. Goto et al., ], a static potential w…

Simulation study of ultrahigh-precision single-ion extraction from a linear Paul trap Open

K. Muroo, H. Okamoto, Nobumasa Miyawaki, Yosuke Yuri · 2023

A detailed simulation study is conducted to explore the possibility of transporting a single ion precisely along a particular design orbit. As a practically useful example, we consider nitrogen ions sympathetically cooled with ultracold ca…

Stability study of intense hadron bunches in linear accelerators using a Paul ion trap Open

Masato GOTO, C. Ichikawa, K. Ito, Kazunobu Kojima, H. Okamoto · 2022

The collective behavior of an ion cloud confined in a linear Paul trap is physically almost equivalent to that of a relativistic beam traveling in a particle accelerator. This fact provides a new possibility for experimental beam-dynamics …

Characterization of overlapping betatron resonances above the phase advance of 90° per cell Open

Kazunobu Kojima, H. Okamoto · 2022

The space-charge-induced resonance band just above the betatron phase advance of 90° per cell is of great practical importance. The instability is closely related to the linear collective mode and can thus give rise to severe emittance gro…

A Linear Paul Trap without the use of the Transverse Quadrupole Field Open

Kunihiro Kojima, Masato GOTO, H. Higaki, K. Ito, H. Okamoto · 2022

A detailed experimental study has been conducted to demonstrate the efficient confinement of ions in the popular four-rod configuration of a linear Paul trap without exciting the transverse radio-frequency (rf) quadrupole field. The three-…

Excitation and suppression of synchrobetatron resonances in high-intensity hadron linacs Open

Yu Yamane, H. Okamoto, Kazunobu Kojima · 2021

The space-charge potential can be a source of various resonances in high-intensity hadron bunches traveling in linear accelerators at relatively low energy. Those natural resonances, which may occur even without external driving fields, ha…

Application of a Compact Ion Trap to Fundamental Beam-Dynamics Studies Open

H. Okamoto, H. Higaki, K. Ito, Kunihiro Kojima, Masanori Matsuba , et al. · 2021

Coherent and incoherent space-charge effects in high-intensity hadron rings Open

H. Okamoto, M. Aoki, C. Ichikawa, Kazunobu Kojima, T. Kurauchi , et al. · 2020

A brief overview is given of the recent work done by the beam-physics group of Hiroshima University on resonant beam instabilities in high-intensity hadron rings. Emphasis is placed upon two essentially different instability mechanisms, na…

Reply to “Comment on ‘Empirical condition of betatron resonances with space charge”’ Open

Kazunobu Kojima, H. Okamoto, Y. Tokashiki · 2020

In the Comment on our paper [Phys. Rev. Accel. Beams 22, 074201 (2019)PRABCJ2469-988810.1103/PhysRevAccelBeams.22.074201], Hofmann claims that our conclusions are based on a questionable interpretation of Vlasov’s equation and an over-inte…

Experimental observation of low-order collective oscillation modes in a strong-focusing lattice Open

K. Ito, T. Kurauchi, H. Higaki, H. Okamoto · 2019

In a conventional linear Paul trap (LPT), four electrode rods are placed symmetrically around the trap axis to generate a radio-frequency (rf) quadrupole field for transverse ion confinement. The periodic nature of the external focusing po…

Accumulating laser-coolable ions in a linear Paul trap for ultrahigh-density beam dynamics experiment Open

K. Ito, Toshio MASUDA, H. Higaki, H. Okamoto · 2019

An ion plasma confined in a linear Paul trap (LPT) exhibits the dynamic behavior physically equivalent to that of a charged-particle beam in an alternating-gradient (AG) transport channel. The Simulator of Particle Orbit Dynamics (S-POD) i…

A compact Paul ion trap for the study of space-charge effects in drift-tube linear accelerators Open

H. Okamoto, Kunihiro Kojima, K. Ito · 2019

Starting from the principle of least action, we derive a general Hamiltonian that describes the collective motion of an intense charged-particle bunch in a drift-tube linear accelerator. The Alvarez-type structure is assumed as an example,…

Empirical condition of betatron resonances with space charge Open

Kazunobu Kojima, H. Okamoto, Y. Tokashiki · 2019

This paper addresses the generalization of the single-particle betatron resonance condition derived by Courant and Snyder more than a half century ago. A two-dimensional resonance condition including the effect of space-charge interaction …

Hamiltonian Formalism of Intense Beams in Drift-Tube Linear Accelerators Open

H. Okamoto · 2019

Starting from the principle of least action, we construct a general Hamiltonian formalism for beam dynamics in drift-tube linear accelerators (DTLs). The Alvarez-type structure is considered here as an example, but the present theory can r…

Stability Tune Diagram of a High-Intensity Hadron Ring Open

H. Okamoto, Kunihiro Kojima, Y. Tokashiki · 2019

To date, the optimum operating point of a high-intensity hadron ring has been determined on the basis of the conventional incoherent picture. It is generally chosen on the tune diagram such that the so-called "incoherent tune spread" of a …

A new method to measure the beta function in a Paul trap Open

Lucy Martin, K. Ito, David Kelliher, S. Machida, H. Okamoto , et al. · 2018

The Simulator of Particle Orbit Dynamics (S-POD) is a linear Paul trap at Hiroshima University, Japan, used to study beam physics. S-POD has so far been used to study resonances in high intensity beams, predominantly using a simple alterna…

Effect of quadrupole focusing-field fluctuation on the transverse stability of intense hadron beams in storage rings Open

K. Ito, Masanori Matsuba, H. Okamoto · 2018

A systematic experimental study is performed to clarify the parameter dependence of the noise-induced beam instability previously demonstrated by a Princeton group [M. Chung et al., Phys. Rev. Lett. 102, 145003 (2009)]. Because of the weak…

A new method to measure the Beta function in a Paul trap Open

Lucy Martin, K. Ito, David Kelliher, S. Machida, H. Okamoto , et al. · 2018

The Simulator of Particle Orbit Dynamics (S-POD) is a linear Paul trap at Hiroshima University, Japan, used to study beam physics. S-POD has so far been used to study resonances in high intensity beams, predominantly using a simple alterna…

Simulations on Mixing Charged Particles in a Nested Penning Trap Open

C. Kaga, H. Higaki, Kei Fukushima, Kazuya Osaki, Kiyokazu Ito , et al. · 2017

Coherent resonance stop bands in alternating gradient beam transport Open

K. Ito, H. Okamoto, Y. Tokashiki, K. Fukushima · 2017

An extensive experimental study is performed to confirm fundamental resonance bands of an intense hadron beam propagating through an alternating gradient linear transport channel. The present work focuses on the most common lattice geometr…

Simultaneous confinement of low-energy electrons and positrons in a compact magnetic mirror trap Open

H. Higaki, C. Kaga, K. Fukushima, H. Okamoto, Y. Nagata , et al. · 2017

More than 10 ^7 electrons and 10 ^5 positrons with energy less than a few eV were confined simultaneously for the first time in a compact magnetic mirror trap with plugging potentials. The exponential decay time constant of the confined po…

Double stop-band structure near half-integer tunes in high-intensity rings Open

K. Moriya, Masato Ota, K. Fukushima, M. Yamaguchi, K. Ito , et al. · 2016

This paper addresses a detailed experimental study of collective instability bands generated near every half-integer tune per lattice period by coherent dipole and quadrupole resonances. Both instabilities appear side by side or overlap ea…

Crystalline Beam Studies with Andy Sessler Open

Jie Wei, Xiaoping Li, H. Okamoto · 2016

For over two decades since 1992, Andy Sessler worked with us as a hobby on the topic of crystallization of charged ion beams and cooling methods. In this paper, we review the studies jointly performed with Andy highlighting major findings …

Free-energy formula for emittance-growth estimation in intense mismatched beams Open

Kazuya Osaki, H. Okamoto · 2015

We construct a theoretical model that allows a quick estimate of emittance growth in an intense charged-particle beam initially mismatched to an external linear focusing potential. The present theory is a natural generalization of Reiser's…

Experimental study of integer resonance crossing in a nonscaling fixed field alternating gradient accelerator with a Paul ion trap Open

K. Moriya, K. Fukushima, K. Ito, T. Okano, H. Okamoto , et al. · 2015

We present an experimental study aimed at exploring integer resonance crossing with a focus on nonscaling fixed field alternating gradient accelerators. The method uses the Simulator of Particle Orbit Dynamics system at Hiroshima Universit…

Phase Space Volumes of Non-Neutral Electron Plasmas during Vortex Merging Processes Open

C. Kaga, Y. Soga, K. Ito, H. Higaki, H. Okamoto · 2015

Non-neutral electron plasmas in a uniform magnetic field are investigated experimentally as a two dimensional fluid. It is confirmed that the phase space volume increases during a vortex merging process, which is consistent with the presen…

Design Study of a Multipole Ion Trap for Beam Physics Applications Open

Kei Fukushima, H. Okamoto · 2015

A unique linear Paul trap is designed for a systematic experimental study of nonlinear beam dynamics with the tabletop apparatus "S-POD" at Hiroshima University. S-POD is the abbreviation of "Simulator of Particle Orbit Dynamics" where we …

H. Okamoto YOU? Author Swipe