# Publications by Suzie Sheehy

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

Journal of Physics: Conference Series **1067** (2018)

© Published under licence by IOP Publishing Ltd. 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 alternating gradient lattice configuration. Recently a similar apparatus, the Intense Beam Experiment (IBEX), has been constructed at the Rutherford Appleton Lab in the UK. To use either of these experiments to study beam dynamics in more complex lattice configurations in the future, further diagnostic techniques must be developed for Paul traps. Here we describe a new method to measure the beta function and emittance in a Paul trap.

## Commissioning and first results of the Intense Beam EXperiment (IBEX) linear Paul trap

8TH INTERNATIONAL PARTICLE ACCELERATOR CONFERENCE (IPAC 2017) **874** (2017)

## Characterization techniques for fixed-field alternating gradient accelerators and beam studies using the KURRI 150 MeV proton FFAG

PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS (2016) ARTN 073G01

## Studies of ultimate intensity limits for high power proton linacs

IPAC 2016 - Proceedings of the 7th International Particle Accelerator Conference (2016) 951-954

Copyright © 2016 CC-BY-3.0 and by the respective authors. Although modern high power proton machines can now routinely deliver MW level operating powers, the next generation accelerators will be required to reach powers orders of magnitude higher [1,2]. Significant developments will be needed both in technology and in understanding the limits of high intensity operation. The present study investigates the beam dynamics in three experimental linac designs when the beam intensity is increased above current levels such that for CW regimes, beam powers of up to 400 MW can be attained. In the first, a 1 A proton beam is accelerated to 400 MeV using normal conducting structures. In the second, a comparison is made when two front ends accelerate 0.5 A beams to ∼20 MeV where they are funnelled to 1 A and accelerated to 400 MeV. Similarly, in the third, two 0.25 A beams are funnelled to 0.5 A and then accelerated in superconducting structures to 800 MeV. In addition, alternative unconventional methods of generating high current beams are also discussed. The further studies that are needed to be undertaken in the future are outlined, but it is considered that the three linac configurations found are sufficiently promising for detailed technical designs to follow.

## Overview of the design of the IBEX linear Paul trap

IPAC 2016 - Proceedings of the 7th International Particle Accelerator Conference (2016) 3104-3106

Copyright © 2016 CC-BY-3.0 and by the respective authors. We report on the status and design of the Intense Beam Experiment (IBEX) at RAL. This small experiment consists of a linear Paul trap apparatus similar to the S-POD system at Hiroshima University, confining non-neutral Argon plasma in an rf quadrupole field. The physical equivalence between this device and a beam in a linear focusing channel makes it suitable for accelerator physics studies including resonances and high intensity effects. We give an overview of the design and construction of IBEX and outline plans for commissioning and the future experimental programme.

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

PHYSICAL REVIEW SPECIAL TOPICS-ACCELERATORS AND BEAMS **18** (2015) ARTN 034001

## The PyZgoubi framework and the simulation of dynamic aperture in fixed-field alternating-gradient accelerators

NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT **775** (2015) 15-26

## Progress on simulation of fixed field alternating gradient accelerators

6th International Particle Accelerator Conference, IPAC 2015 (2015) 495-498

Copyright © 2015 CC-BY-3.0 and by the respective authors. Fixed Field Alternating Gradient accelerators have been realised in recent decades thanks partly to computational power, enabling detailed design and simulation prior to construction. We review the specific challenges of these machines and the range of different codes used to model them including ZGOUBI, OPAL, SCODE and a number of inhouse codes from different institutes. The current status of benchmarking between codes is presented and compared to the results of recent characterisation experiments with a 150 MeV FFAG at KURRI in Japan. Finally, we outline plans toward ever more realistic simulations including space charge, material interactions and more detailed models of various components.

## Fixed points in presence of space charge in circular particle accelerators

6th International Particle Accelerator Conference, IPAC 2015 (2015) 389-391

Copyright © 2015 CC-BY-3.0 and by the respective authors. Recent measurements performed in the framework of the multi-turn extraction (MTE) studies at the CERN Proton Synchrotron showed a dependence of the position of beamlets obtained by crossing a stable transverse resonance on the total beam intensity. This novel observation has triggered a number of studies aiming at understanding the source of the observed effect. In this paper the results of numerical simulations performed in different conditions are discussed in detail.

## Plans for a Linear Paul Trap at Rutherford Appleton Laboratory

6th International Particle Accelerator Conference, IPAC 2015 (2015) 2590-2593

Copyright © 2015 CC-BY-3.0 and by the respective authors. For over a decade, Linear Paul Traps (LPT) have been used in the study of accelerator beam dynamics. LPT studies exploit the similarity of the Hamiltonian with that of a beam in a quadrupole channel while having advantages in the flexibility of parameter choice, compactness and low cost. In collaboration with Hiroshima University, LPT research planned at STFC Rutherford Appleton Laboratory (RAL) in the UK aims to investigate a range of topics including resonance crossing, halo formation, long-term stability studies and space charge effects. Initially, a conventional quadrupole-based LPT will be built at RAL and used for a variety of experiments. In parallel, a design for a more advanced LPT that incorporates higher order multipoles will be pursued and later constructed. This multipole trap will allow non-linear lattice elements to be simulated and so broaden considerably the range of experiments that can be conducted. These will include the investigation of resonance crossing in non-linear lattices, a more detailed study of halo formation and the effect of detuning with amplitude. In this paper we report on progress made in the project to date and future plans.

## Study of resonance crossing in non-scaling FFAGS using the S-POD linear Paul trap

IPAC 2014: Proceedings of the 5th International Particle Accelerator Conference (2014) 1571-1573

Copyright © 2014 CC-BY-3.0 and by the respective authors. Experiments on EMMA have shown that with rapid acceleration a linear non-scaling FFAG can accelerate through several integer tunes without detrimental effects on the beam [1]. Proton and ion applications such as hadron therapy will necessarily have a slower acceleration rate, so their feasibility depends on how harmful resonance crossing is in this regime. A simple and useful tool to answer such fundamental questions is the Simulator of Particle Orbit Dynamics (S-POD) linear Paul trap (LPT) at Hiroshima University, which can be set up to simulate the dynamics of a beam in an FFAG. We report here results of experiments to explore different resonance crossing speeds, quantify beam loss and study nonlinear effects. We also discuss the implications of these experimental results in terms of limits on acceptable acceleration rates and alignment errors.

## Conceptual design of a nonscaling fixed field alternating gradient accelerator for protons and carbon ions for charged particle therapy

PHYSICAL REVIEW SPECIAL TOPICS-ACCELERATORS AND BEAMS **16** (2013) ARTN 030101

## The potential for a high power FFAG proton driver for ADS

11th International Topical Meeting on Nuclear Applications of Accelerators, AccApp 2013 (2013) 261-265

Fixed-field alternating gradient accelerators are promising candidates for next-generation 10 MW-class high power proton drivers. Recent advances in lattice design of non-scaling FFAGs have progressed toward both isochronicity and chromatic correction. The resulting 1 GeV non-scaling FFAG design may be able to support a continuous (CW) beam with far lower peak current than the pulsed alternative. A 6-cell non-scaling FFAG design is described and recent work in modeling 3D space charge using the OPAL framework is presented, including fixed energy studies and beam dynamics with fast acceleration in the so-called serpentine channel.

## PIP: A low energy recycling non-scaling ffag for security and medicine

IPAC 2013: Proceedings of the 4th International Particle Accelerator Conference (2013) 3711-3713

PIP, the Proton Isotope Production accelerator, is a low energy (6-10 MeV) proton nsFFAG design that uses a simple 4-cell lattice. Low energy reactions involving the creation of specific nuclear states can be used for neutron production and for the manufacture of various medical isotopes. Unfortunately a beam rapidly loses energy in a target and falls below the resonant energy. A recycling ring with a thin internal target enables the particles that did not interact to be re-accelerated and used for subsequent cycles. The increase in emittance due to scattering in the target is partially countered by the re-acceleration, and accommodated by the large acceptance of the nsFFAG. The ring is essentially isochronous, the fields provide strong focussing so that losses are small, the components are simple, and it could be built at low cost with existing technology.

## Experimental studies of resonance crossing in linear non-scaling ffags with the S-POD plasma trap

IPAC 2013: Proceedings of the 4th International Particle Accelerator Conference (2013) 2675-2677

In a linear non-scaling FFAG the betatron tunes vary over a wide range during acceleration. This naturally leads to multiple resonance crossing including first order integer resonances. The S-POD (Simulator for Particle Orbit Dynamics) plasma trap apparatus at Hiroshima University represents a physically equivalent system to a charged particle beam travelling in a strong focusing accelerator lattice. The S-POD system can be used as an experimental simulation to investigate the effects of resonance crossing and its dependence on dipole errors, tune crossing speed and other factors. Recent developments and experiments are discussed. Copyright © 2013 by JACoW- cc Creative Commons Attribution 3.0 (CC-BY-3.0).

## The effect of beam interruptions on the integrity of ADSR fuel pin cladding: A thermo-mechanical analysis

ANNALS OF NUCLEAR ENERGY **46** (2012) 97-105

## The Advantages and Challenges of Helical Coils for Small Accelerators-A Case Study

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY **22** (2012) ARTN 4100110

## Acceleration in the linear non-scaling fixed-field alternating-gradient accelerator EMMA

Nature Physics **8** (2012) 243-247

In a fixed-field alternating-gradient (FFAG) accelerator, eliminating pulsed magnet operation permits rapid acceleration to synchrotron energies, but with a much higher beam-pulse repetition rate. Conceived in the 1950s, FFAGs are enjoying renewed interest, fuelled by the need to rapidly accelerate unstable muons for future high-energy physics colliders. Until now a 'scaling' principle has been applied to avoid beam blow-up and loss. Removing this restriction produces a new breed of FFAG, a non-scaling variant, allowing powerful advances in machine characteristics. We report on the first non-scaling FFAG, in which orbits are compacted to within 10 mm in radius over an electron momentum range of 12-18 MeV/c. In this strictly linear-gradient FFAG, unstable beam regions are crossed, but acceleration via a novel serpentine channel is so rapid that no significant beam disruption is observed. This result has significant implications for future particle accelerators, particularly muon and high-intensity proton accelerators. © 2012 Macmillan Publishers Limited. All rights reserved.

## Acceleration in the linear non-scaling fixed-field alternating-gradient accelerator EMMA

NATURE PHYSICS **8** (2012) 243-247