\section{Accelerator development for nuclear physics}

The TRIUMF Accelerator Division has plans for projects in several areas of
interest to nuclear physicists. Short and intermediate-term projects are
primarily in support of enhanced beam properties for ISAC/ARIEL, but
longer-term projects include research into new accelerator concepts, such as
those discussed in Secs.~\ref{sec:isacupgrade} and \ref{sec:eic4}.  Those projects are directed to beam or accelerator development for a specific goal which would more likely be supported by TRIUMF or CFI funds, while the most fundamental accelerator physics questions might fall within the purview of
NSERC SAPES funding.

%GH: the rest of the text is from Accelerator_brief.docx
\subsection{ISAC/ARIEL High-power target development}

To fully exploit the future increase of beam power provided by the driver accelerators, new high-power target technologies are required. Target development addresses material development and new target station technologies including remote handling. Commissioning of ARIEL target stations and ramping the driver beam power to unprecedented levels is an important objective of this LRP period and will require development projects. The electron-to-gamma converter target concept that involves a two-stage process where electrons bombard a sophisticated material composite converter positioned in front of the target container to create bremsstrahlung photons need to demonstrate 100~kW capabilities. In the long term, a concept will be required to go beyond this power stage, which is a huge challenge.

The TRIUMF targets and Ion Sources Department is embedded in a framework of international collaborations. TRIUMF is leading in the application of high-power targets for radioisotope beam production and handling of target components. New technologies are developed for and with international partners. TRIUMF has an existing strength in the engineering of efficient high-power target material structures. Building on this leading position and within the RADIATE collaboration, TRIUMF is developing the infrastructure and methodology to test materials in extreme GGy/h-level radiation fields and analyze microscopic and mechanical degradation.

RIB ion source and transfer line development capability will be required to provide new, purer, and more intense isotope beams to the NP community. The ARIEL target assembly concept will allow for more versatile and capable ion sources and selective transfer lines. An ARIEL laser ion source will initially be installed in the east station only and will be the element selective work-horse for RIB delivery. In the long term, laser-ionized radioisotopes need to be available from both ARIEL target stations, requiring additional investments. 

The development of new targets requires detailed understanding of materials and chemistry at high temperatures. The R\&D on new target compositions and materials requires according laboratory infrastructure at TRUMF, which goes beyond the present stage. Conventional chemistry lab, specialized target assembly and test areas as well as an Actinide target laboratory are mandatory for the long-term future of target R\&D for secondary particle production.

\subsection{ISAC accelerator development} \label{sec:AccDev:isac}
%GH: linkage to ring discussion earlier in this chapter needs to be made, and overlap removed

Another focus in terms of beam delivery of rare isotopes to experiments is on the beam preparation and the post acceleration capabilities. In the period of the LRP, TRIUMF accelerator division will exploit the full potential of CANREB and the ISAC beam preparation addressing charge state breeders, beam cooler, yield stations and mass separators. In the long term a multi reflection time-of-flight (MR-TOF) analyser will complement the high-resolution separator and the yield stations.

On the ISAC post accelerator side, long term developments even beyond the period of the LRP, are envisaged to boost the final energy of ISAC-II and to add a low energy storage ring for nuclear astrophysics investigations. To boost the ISAC-II energy a stripping foil would be employed at beam energies beyond 6 MeV/u to increase the charge state before a new high performance (high gradient) cryomodule give a boost to $>$20~MeV/u for $A/q=2$ ions.

A low-energy heavy ion storage ring connected to an ISOL facility (see Secs.~\ref{sec:NA:TRISR} and \ref{sec:isacupgrade}) provides a unique environment to carry out nuclear physics experiments with stored radioactive beams due to the up to six orders of magnitude increased luminosity compared to ``one-time-pass'' experiments. The installation of a low-energy storage ring at ISAC-I would create a worldwide unique facility and provide a valuable extension of TRIUMF's physics program by attracting new users. The design of a storage ring and neutron source to generate a neutron target which will allow neutron transfer measurements, is a challenging task, which will provide unique training of young researchers in a new field of Accelerator Science for Canada.

A neutron generator based on $(d,d)$ or $(d,t)$ reactions, the moderation technology and required shielding will lead neutron science and in health physics into a new territory. A suitable storage ring should cover an energy range of about 0.1-10~MeV/u, has approx. 50 m circumference providing a maximum beam rigidity of about 1.5~Tm. A design study will aim for a TDR within the period of the LRP so construction could potentially start thereafter.

\subsection{Electron-Ion Collider related accelerator technologies}

The Electron-Ion Collider (EIC) at Brookhaven National Lab
is the first major collider to be built in North America in the 21st century, and a challenging accelerator project with the most demanding operational parameters in terms of intensity and luminosity for the electron and ion beams. The EIC will require high polarization, sophisticated SRF cavities, hadron beam cooling with intense electron beams that require Energy Recovery Linac (ERL) technologies. The beam dynamics design for the different machines is challenging in particular the spin dynamics and keeping a high degree of polarization of the beams. 

TRIUMF’s accelerator physicists and engineers could support the construction as a Canadian in-kind contribution. Contributions could be systems like crab cavity cryomodules, high brightness electron gun, beam physics models as well as ERL studies for hadron cooling. The beam physics of the EIC collider accelerators requires handling of high degrees of polarization (up to 85\%). The spin dynamics has to be treated within a highly symmetric ring lattice and residual depolarization effects will need correction with partial Siberian snakes. The TRIUMF beam physics group wants to embark on spin dynamics in rings via an involvement in SUPER KEKB led UVic. The treatment of spin dynamics in SUPER KEKB and according spin-optics devices will prepare the group for an engagement at the EIC. The goal is to give Canadian scientists a place at the table while engaging senior and junior accelerator scientist in a cutting-edge accelerator project.

\subsection{General Accelerator R\&D}

\subsubsection{Model-based and model-coupled beam tuning}

New accelerator facilities or upgrades of existing accelerators aim for unprecedented beam
properties that do not allow for beam losses and may require smart machine control and
protection systems. For beam production and delivery, sophisticated numerical codes are
used to determine operation parameters, and to predict beam parameters at locations of beam
diagnostics elements. This model coupled beam tuning also provides opportunities to introduce
model-based beam tuning and Machine Learning (ML) for particle accelerators.

TRIUMF Accelerator R\&D is working on full end-to-end accelerator beam simulation models of
accelerators, like the linacs of the ISAC facility. Usually, multiparticle tracking codes are
employed, ray tracing thousands to millions of particles through the system, depending on the
desired accuracy of the calculation. While these provide the advantage of illustrating individual
particle evolution throughout the accelerator, they are generally computationally intensive and
slow. The TRIUMF developed envelope code TRANSOPTR, a second order beam transport
code that is based on the Hamiltonian formalism of relativistic charged particle beams, is
capable of a fast output in real time comparable to beam measurement periods. This allows the
implementation of the code TRANSOPTR as part of an accelerator tuning tool at TRIUMF as a
first step towards model coupled accelerator beam tuning and machine learning. High level
applications (HLA) will play a major role in this R\&D, on one hand using HLAs such as beam phase
space tomography, while on the other hand allowing the development of new application that will
allow tests of a model coupled beam tuning procedures.

The objective of this R\&D is the training of a tailored NN with a benchmarked TRANSOPTR model to
prepare a first test by using a virtual accelerator testbed platform allowing for off-line testing and
analysis of tuning algorithms on the ISAC accelerators. This testbed is under development in the
framework of a Ph.D. thesis. The final long-term goal is the automatic beam tuning of the TRIUMF
ISAC linacs and the compensation of drifts of RF-phases of cavities that deteriorate the transmission
of beam towards the many experiments served. The transfer of the beam tuning technology to driver
beam accelerators like the TRIUMF e-linac will be possible.

\subsubsection{High intensity proton driver accelerators (medical purpose or neutron production)}

TRIUMF’s expertise in high power accelerators has been requested by the community to support the
development of a Canadian Compact Accelerator-driven Neutron Source (CANS) and a high
gradient high intensity driver accelerator for tumor therapy. CANS technology is modular, highly
tuneable, and dramatically less expensive than other methods of neutron production. The R\&D
for CANS and medical accelerators comprises high current ion sources, high intensity Radio
Frequency Quadrupole (RFQ) accelerators and modern high gradient H-type structures and RF-
systems. For the neutron production, high power target-moderator systems are a new field of
R\&D TRUMF’s Accelerator division will address in the period of the LRP.