6 Investing
in the Future
of Science
and Technology

Flagship projects often start as ideas on a blackboard. Future innovations require that the entire lifecycle of scientific discovery be supported, from initial concept to construction, operations and data analysis. R&D plays critical roles at multiple stages along the way.

To promote robust R&D efforts across a range of enabling technologies, we recommend sustained investments in key areas essential to the future of particle physics: theory, an agile project program, detector instrumentation, particle accelerators, collider R&D, facilities and infrastructure, software and computing, and data science. We also discuss the ways that particle physics leads to technology innovations for society. Note that collider R&D includes both accelerator & detector R&D targeting specific future colliders.

6.1Theory

Particle physics theory lies at the heart of our understanding of the universe at both the smallest and largest scales. Theory plays an essential role in guiding which new experiments should be pursued, informing their design, interpreting experimental measurements and observations, and exploring uncharted regimes.

Theoretical developments have far-reaching impacts and connect particle physics to other areas of science, including nuclear physics, astrophysics, atomic, molecular, and optical physics. In addition, theoretical work closely connects physicists with mathematics and computer science. Theoretical insights also incorporate new perspectives, from quantum information to artificial intelligence and machine learning, that propel innovative experimental techniques.

Theorists have opened new avenues of research and proposed new experiments; for example, theoretical investigations into possible hidden sectors led directly to the portfolio of Dark Matter New Initiatives projects. Theorists support the experimental portfolio of particle physics, providing the predictions necessary to analyze, interpret and understand experimental results. Examples of theoretical calculations underpinning the extraction of physical quantities from experimental data are neutrino-nucleus interactions for DUNE, particle collisions at the LHC, and the detailed structure of the cosmic microwave background power spectra for CMB-S4.

Theorists uncover the mathematical patterns that describe the universe and explore alternate mathematical universes to deepen our understanding of nature. Theoretical investigations into quantum gravity have unlocked connections between extreme space-time geometries and information theory. The perspectives theorists bring to particle physics play an important role in inspiring young scientists.

Computational physics is a vital component of particle theory. Powerful computers simulate the behavior of fundamental particles of the Standard Model, enabling meaningful comparisons between theoretical expectations and experimental measurements. For example, computational simulations of the strong nuclear force have been critical to precision tests of the Standard Model at the LHC and other colliders, providing new insight into the origin of matter in the early universe. Theoretical techniques are also used to create “digital twins” of the universe to test different scenarios for cosmic evolution.

Maximizing the physics reach of experiments relies on the collective effort of the particle physics community, encompassing theoretical and computational research. Maintaining a balanced program, with healthy support for theoretical research, will magnify the impact of the entire field and enable future discoveries.

Universities are home to the vast majority of theoretical research and nearly all student training, so it is critical that university support be strengthened to ensure equitable access to particle physics. The level of support for theoretical research has eroded over the last decade. These cuts were primarily absorbed by universities, to the detriment of the field. In order to catalyze tomorrow’s theoretical breakthroughs and to retain the best talent, this trend needs to be reversed. Increasing support (Recommendation 4b) will enable particle physics to thrive in a robust manner, bring diverse perspectives, strengthen talent identification, and create a more inclusive and effective workforce.

Area Recommendation 1: Increase DOE HEP-funded university-based theory research by $15 million per year in 2023 dollars (or about 30% of the theory program), to propel innovation and ensure international competitiveness. Such an increase would bring theory support back to 2010 levels. Maintain DOE lab-based theory groups as an essential component of the theory community.

6.2Advancing Science and Technology through Agile Experiments (ASTAE)

Experiments at multiple scales in both cost, size, and duration are critical to unlocking the mysteries of the universe. We recommend DOE create a portfolio of experiments that are small in scale and quick to execute, yet significant in their impact. This complements the Mid-scale Research Infrastructure program, both within the Division of Physics and across NSF. It enables DOE to strategically target emerging opportunities within its program while supporting the overall DOE mission. The program for these agile DOE experiments is (Advancing Science and Technology through Agile Experiment) ASTAE, which is Latin for “javelins”, reflecting their focused nature. Across particle physics there are important experiments that meet these criteria, experiments capable of discovery science, advancing technology, developing a workforce, and advancing US leadership.

These experiments are key to paradigm shifting discoveries, both in their own right or as incubators for new technologies and physics directions. The recent DOE-HEP Dark Matter New Initiatives (DMNI) program exemplifies the opportunity for discovery small-scale experiments can provide, while incubating key quantum technologies. Similarly the recent first observation of Coherent Elastic Neutrino-Nucleus Scattering (CEvNS) demonstrates the potential for discovery science for experiments of this scale. In addition to discovery science, this proposed portfolio can enable small-scale supporting experiments that simplify the interpretation of data from flagship measurements. They can also act as critical demonstrators for innovative instrumentation that will enable the next generation of experiments.

ASTAE will provide an essential training ground for a workforce capable of innovation and leadership to sustain the vitality of the field. These experiments train the full HEP workforce (students, postdoctoral fellows, scientists, engineers, technicians, and project managers) in the complete life-cycle of an experiment, from design, construction, commissioning, operations, and the publication of the results. The ASTAE portfolio will provide the hands-on experience needed to conceive the technological breakthroughs that will enable the scientific discoveries of the future and foster scientific ingenuity among the next generation of researchers.

Over time, this portfolio should maintain a balance of experiments across the science driver focus areas. The possibility of projects that push beyond these focus areas should be left open for compelling scientific or technological cases. The projects should be reviewed for their potential for discovery, technology innovation, and ability to provide critical inputs to the success of the greater HEP mission.

Area Recommendation 2: For the ASTAE program to be agile, we recommend a broad, predictable, and recurring (preferably annual) call for proposals. This ensures the flexibility to target emerging opportunities and fields. A program on the scale of $35 million per year in 2023 dollars is needed to ensure a healthy pipeline of projects.

Area Recommendation 3: To preserve the agility of the ASTAE program, project management requirements should be outlined for the portfolio and should be adjusted to be commensurate with the scale of the experiment.

Area Recommendation 4: A successful ASTAE experiment involves 3 phases: design, construction, and operations. A design phase proposal should precede a construction proposal, and construction proposals are considered from projects within the group that have successfully completed their design phase.

Area Recommendation 5: The DMNI projects that have successfully completed their design phase and are ready to be reviewed for construction, should form the first set of construction proposals for ASTAE. The corresponding design phase call would be open to proposals from all areas of particle physics.

6.3Detector Instrumentation

The field of particle physics is at an exciting juncture where current detector instrumentation technologies have pushed the boundaries of sensitivity and scalability to their limits. While modest advancements in some cases can pave the way for the next generation of experiments, numerous research areas eagerly await new approaches, innovative materials, and cutting-edge technologies to overcome existing technological challenges. A vital particle physics program requires a balance of investments in both evolutionary and transformational “blue sky” detector development in order to achieve paradigm shifting ideas. Many of the R&D needs for the next decade and beyond are outlined in the DOE Basic Research Needs Study for Detectors (BRN). These advances can be achieved if we support careers in instrumentation, including research scientists at universities who can support local detector innovation, provide continuity, and educate the next generation of experts (Recommendation 4d, 5d).

Purely instrumentation-based and interdisciplinary graduate programs should be empowered, and the lateral move of scientists between universities and laboratories, including joint positions, should be made easier. Career paths and recognition in detector instrumentation should be extended to all scientists, including chemists, material scientists, engineers, and technicians. Cross-disciplinary opportunities of collaboration and fertilization at universities and laboratories are essential.

The particle physics community has identified the need for stronger coordination between the different groups carrying out detector R&D in the US. We strongly support the R&D Collaborations (RDCs) that are being established and will be stewarded by CPAD, the Coordinating Panel for Advanced Detectors, overseen by the APS/DPF. The RDCs are organized along specific technology directions or common challenges, and aim to define and follow roadmaps to achieve specific R&D goals. This coordination will help to achieve a more coherent detector instrumentation program in the US, and will help to avoid duplication while addressing common challenges. International collaboration is also crucial, especially in cases where we want to have technological leadership roles. Involvement in the newly established Detector R&D Groups at CERN is encouraged, as are contributions to the design and planning for the next generation of international or global projects. Targeted future collider detector R&D in particular, such as for Higgs factories or a muon collider, is covered in Section 6.5.

In order to enable groundbreaking detector innovation and US leadership in this field, we need to invest in a coherent set of modernized facilities with enhanced capabilities. These include test beam and irradiation facilities with beam properties and intensities appropriate for future experimental demands, low-background and underground facilities, cleanroom space, access to nano-fabrication facilities, and microelectronics foundries.

To stimulate transformational breakthroughs, we need to pursue synergies with other disciplines outside of particle physics, as well as close collaborations with industry. Recent examples of this are quantum sensors and microelectronics, where communication and exchange between particle physics and other communities led to enhanced funding for technology development and the addition of external experts to the particle physics community. Over the past few years this has led to the development of a new suite of detector technologies and methods that in turn have established a new set of small-scale experiments that enhance the particle physics portfolio.

The use of quantum sensors in particle physics experiments has grown extensively and the developments within particle physics have benefitted communications, computing, and many other areas. Quantum sensors have been used in searches for dark matter, fifth forces, dark photons, permanent electric dipole moment (EDM), variations in fundamental constants, and gravitational waves, among others, and they come in a wide range of technologies: atom interferometers and atomic clocks, magnetometers, quantum calorimeters and superconducting sensors. Quantum sensors are being deployed in all areas of particle physics. To advance these technologies further for the benefit of the particle physics community, we need to continue strong support for a broad range of quantum sensors.

Much of the growth in quantum sensors over the past decade has occurred in small, laboratory-based experiments. Support for such experiments should continue as a way to rapidly develop sensor technologies and help determine the areas where quantum sensors can have the greatest impact. Several recent developments have reached the point where plans for larger-scale, longer-term experiments can and should be conceptualized. These concepts can evaluate the potential reach that can be achieved in a larger effort and the scale of required technological development. Here, potential reach is meant in terms of our physics goals, enhanced sensitivities to the phenomena we are trying to measure; enhanced compared to traditional non-quantum technologies. We recommend mechanisms to support interactions outside of the particle physics program to enable collaborations with experts in other fields who have experience with quantum sensors, including QIS theory.

In microelectronics, particle physics specializes in extreme environments such as high radiation, ultra-high vacuum, and cryogenic operations. These areas have been spearheaded by the particle physics community over the past several years and show benefits to fields outside of particle physics, such as nuclear physics, space exploration, non-proliferation, and homeland security.

Related innovations and proof of concepts from within particle physics are benefitting the microelectronics industry, with specialized cryogenic and energy efficient designs and integration techniques being adopted by industry. In addition, the facilities established at the national laboratories are of growing interest to commercial partners. Close collaboration between the particle physics microelectronics experts and CAD tool companies are needed to provide feedback on novel applications of advanced tools required for particle physics. Close collaboration between microelectronics teams at the national laboratories and engineers and scientists at universities helps cultivate talent to advance the workforce for the microelectronics industry.

Particle physics benefits from developments in other fields, such as atomic clocks developed decades ago for precision timing standards and are now being proposed for the search for variations of fundamental constants and gravitational waves. We should strive to collaborate with other scientific communities to maximize mutual benefits, such as gaining access to new sensor technologies or providing access to our development of large magnets, vacuum systems, and superconducting radio frequency cavities for outside fields. In order to facilitate this exchange, we need to move beyond traditional funding boundaries and allow scientists and engineers working with quantum sensors, whatever their specific field, to tackle the most interesting and challenging problems. Focused support for the development of quantum materials, including theoretical explorations, should be provided.

Workforce development is needed to encourage workers with the needed skills to engage with particle physics and stay in the field for our long-term success in the face of increasing competition from industrial quantum computing. The particle physics community needs to invest now in order to train and retain the next generation of quantum scientists.

Area Recommendation 6: Increase the budget for generic Detector R&D by at least $20 million per year in 2023 dollars. This should be supplemented by additional funds for the collider R&D program.

Area Recommendation 7: The detector R&D program should continue to leverage national initiatives such as QIS, microelectronics, and AI/ML.

6.4Particle Accelerators and R&D

Particle accelerators play an essential role in high energy physics research. They deliver the unique beams that enable the majority of the P5 science drivers for the next decade (section 6.4.1). Physics goals beyond this decade place radical new demands on accelerator capabilities. To achieve these demanding performance requirements, while reducing costs and minimizing environmental impacts, requires focused investment in both generic R&D (section 6.4.2) and collider R&D (section 6.5) along with strategic investment in the existing accelerator complex at Fermilab (section 6.6.2). In this context, DOE-HEP, in partnership with NSF and other Offices and agencies, has the opportunity to lead accelerator development into the future while simultaneously delivering broader benefits across science and society.

Particle accelerators rely on a broad suite of technologies. This starts with the source that injects particles into the accelerator. When the particles involved are rare or unstable, or the required intensities are very high, these injector systems require significant technology development. At the highest intensities and brightness, techniques to increase the density (in energy and space) of particles in the beams, e.g., beam cooling, must often be applied. The particles must be accelerated to the required energy, typically with metallic radiofrequency structures, dielectric structures, or, most recently, plasma-based wakefields. Particle accelerators generally utilize advanced magnets to guide and focus the beams. At the highest energies manipulating particle beams often requires very high field magnets that rely on developing technologies such as high temperature superconductors. The resulting beams are directed to an experiment or brought into collisions with another beam inside a collider detector. In order to manage and understand the behavior of the beams in each of these sub-systems, sophisticated beam physics theory and computation, as well as dedicated instrumentation and control systems are required.

High energy colliders represent perhaps the most formidable and extensive integration of particle accelerator technology. The challenge comes not only in achieving the requisite beam parameters, but in managing the complex interactions between the multiple systems that make up the machine. Incorporating the results of technology R&D to meet these challenges drives the need for sustained investment in the R&D and design of future colliders. Validation of collider designs through simulations, practical tests of individual design elements, and ultimately demonstrator facilities that test integrated segments of the design are essential steps toward transforming the results of R&D into realistic prospects for the future.

It is vital to build on the investments of the past while also developing innovative solutions for the future. Fermilab, which currently supports a strong neutrino and muon flavor physics program with its proton accelerator complex, represents one of those investments. In the near term, upgrades to that complex will allow Fermilab to deliver high power, high intensity neutrino beams to DUNE. Developing a path for the evolution of the Fermilab accelerator complex beyond that goal supports a multi-decadal vision for Fermilab as a world-leading facility, laying the foundation for a 20 plus year vision for particle physics.

6.4.1  –Particle Physics Accelerator Roadmap

Major advances in accelerator design are central to realizing some of our most ambitious scientific goals. The vision laid out in this report foresees decision points on the 5-, 10- and 20-year timescales where accelerator technology choices will need to be made. Informed decisions at each of these junctures will not be possible without a robust and responsive R&D program to deliver crucial, but as yet unknown, information about the capabilities, cost, and risks of promising technologies. While it will take time to assemble the teams required to inform these decisions, it is imperative that this R&D is pursued aggressively if we hope to act on our most ambitious goal of initiating a 10 TeV pCM collider shortly after the conclusion of the HL-LHC program.

Accelerator design is strongly influenced by the type of particle being accelerated. Electron (and positron) accelerators are constrained by the fact that beams of these very light leptons quickly lose energy to synchrotron radiation, which must be accommodated in the accelerator design. This has limited the energies of practical electron-positron circular machines to a fraction of a TeV. Linear accelerator designs aim towards the TeV beam energy scale or, using wakefield acceleration methods, potentially reach beyond it. Synchrotron radiation is strongly suppressed for heavier particles such as muons and protons, so very high energies can be achieved with circular accelerators. In the case of muons, the short lifetime of the particle means that the acceleration process must occur very rapidly.

Non-collider experiments in domains such as neutrino and flavor physics also benefit from ongoing R&D to deliver beams with increased intensity and specialized beam formatting, while carefully managing the beam physics that drives the onset of instabilities and loss of performance.

We anticipate that a concrete plan to build an off-shore Higgs factory will take shape on roughly a 5-year timescale. There are reasonably mature linear collider and circular collider designs that can achieve our science goals. These designs are still utilizing R&D to further optimize and reduce risk in the designs. The US accelerator community is well-positioned to engage in this final pre-project stage of R&D to ensure a cost-effective machine that meets all performance requirements.

Beyond the Higgs factory, the physics landscape that has shaped the science drivers points to still higher energy scales, the 10 or more TeV pCM scale. Three technological approaches are under development that have the potential to enable physics exploration at this scale. They are a proton-proton collider based on very high field magnets, a muon collider, or possibly a linear collider based on advanced wakefield technology. All three of these technologies have different appealing features and must be developed further. In order to make a confident, informed decision on the path forward—a decision that we hope to make within the next 20 years—one or more of these technologies must reach technical maturity, allowing us to reliably estimate both cost and technical risk. Reaching this point is only possible with strategic, intensive, and focused development of both the foundational technologies and the resulting collider designs.

The proposal for an affordable proton-proton machine rests on a very plausible extrapolation of the parameters for the proton beams. However, that design requires magnet technology that is currently beyond the state of the art. A multi-decade, international R&D program is essential to produce magnets meeting the necessary specifications. The US is actively engaged in this effort through the US Magnet Development Program.

In the case of the muon collider, concepts and preliminary specifications exist for each of the required sub-systems of the collider complex. That complex would be most readily built on an existing proton accelerator complex. Fermilab in the US emerges as a premier candidate for such a facility (section 6.6.2). A muon collider baseline design, that will support a detailed cost estimate, is in preparation. Significant system R&D towards this design includes developing the prototype cryomodules that integrate the high field magnets and radiofrequency accelerating cavities for the muon cooling system. This R&D along with engineering design work before the end of the decade would produce a fully costed conceptual design for a demonstrator facility, which a future panel can consider for construction.

Wakefield concepts for a collider are in the early stages of development. A critical next step is the delivery of an end-to-end design concept, including cost scales, with self-consistent parameters throughout. This will provide an important yardstick against which to measure progress with this emerging technology path.

In addition to developing the technologies and expertise to build future colliders, it is crucial to maintain US expertise in their operation and optimization. Engagement with the LHC and its high-luminosity upgrade at the energy frontier, with SuperKEKB for flavor physics, and with the Relativistic Heavy Ion Collider (RHIC) along with its successor, the Electron-Ion Collider (EIC), for nuclear physics can provide key pathways to maintaining a vibrant US accelerator and collider workforce.

The US accelerator program stewards not only accelerator technology but also the workforce that adapts that technology to particle physics science goals. The R&D efforts outlined in the following sections will inform our future decisions and should not be deferred. Acting now capitalizes on the current energy and enthusiasm of the community and maintains and motivates the necessary workforce. This is essential to effective US participation in a Higgs factory and maximizes the likelihood of realizing a 10 TeV pCM collider within a realistic timeframe.

6.4.2  –Particle Accelerator R&D

Accelerator R&D drives the innovation required to meet the increasing demands of particle physics on accelerator capacity, performance, and cost. These demands span performance improvements of operating accelerators such as the Fermilab Accelerator Complex (Section 6.6.2), advancing the technologies to deliver a Higgs factory, and developing the designs and technologies needed for colliders capable of exploring the 10 TeV pCM scale (Section 6.5). Development for muon, proton, and advanced accelerators as well as superconducting magnets will support collider R&D and also drive recruiting and workforce development.

Over the last decade, sustained R&D has created capabilities that are driving this decade’s research (Recommendation 1a, 1b). The High-Luminosity LHC upgrade leveraged generic accelerator R&D to produce Nb3Sn conductor and cable, which were utilized by the targeted LHC Accelerator Research Program (LARP) to deliver high-field magnet prototypes. The Proton Improvement Plan-II (PIP-II) project is in progress to provide high intensity beams to DUNE and other experiments based on state-of-the-art superconducting radiofrequency (RF) cavities.

The US accelerator R&D program has also made substantial progress in the past decade that impacts the future design and development of a Higgs factory and of high intensity accelerators for neutrino and flavor physics. For example, in collaboration with international partners, the US program has set new records in normal and superconducting RF gradients, in the context of an International Linear Collider (ILC) module. Tests of integrable optics and stochastic cooling demonstrated key steps toward the future of intense beams. High-intensity beam experiments also validated new accelerator target materials.

At the same time, advances in R&D now allow us to consider technology paths that can enable scientific discovery at the 10 TeV pCM scale (Recommendation 4a). New magnetic field records were set toward the needs for FCC-hh and muon colliders. Tests also demonstrated muon cooling, thus enabling a new international design effort in which US participation is essential. High-gradient plasma-wakefield-based advanced accelerators demonstrated advances towards future colliders including 8 GeV energy gain over just 20 cm (approximately a thousandth of the distance conventionally required) and positron acceleration.

Advances in accelerator R&D have a profound impact on both particle physics and a range of other disciplines. Accelerator structures developed for the ILC enable a new generation of light sources important to basic energy science (BES), including the Linac Coherent Light Source-II (LCLS-II) and the high energy LCLS-II-HE. The Cryomodule Test Facility and associated test stands support both the LCLS-II (BES) and PIP-II (HEP) accelerator projects. Investments in high field magnets by the DOE Magnet Development Program and NSF’s MagLab have advanced the state of the art in conductors and magnet design to the benefit of particle physics, materials science, fusion energy research, and commercial development.

Broad generic R&D with a long term focus is critical to extending the reach of accelerators to meet future physics needs. Technical breakthroughs are required to enable accelerators to meet the field’s science drivers, to push costs lower than estimates based on current technology, and to reduce environmental impact. There are exciting opportunities in the development of (i) new high average power, efficient drivers (RF, lasers, and electron beams), (ii) accelerating structures that can sustain high average power and gradient (metallic, plasma and dielectric), (iii) high temperature superconducting magnets, and (iv) computing, instrumentation and controls. Normal conducting radio frequency (RF), superconducting RF, superconducting magnets, targets, and advanced acceleration concepts are essential to develop the next generation of accelerators for particle physics. The normal conducting RF program should incorporate innovative concepts such as cryogenic cool copper and distributed coupling. Accelerator and beam physics research is also critical, including large-scale computation as machines become more complex. Superconducting high field magnet R&D is essential to future proton (FCC-hh) and muon collider options; timely execution of magnet R&D would leverage expertise becoming available with the completion of the HL-LHC Accelerator Upgrade Project.

Stronger investment in accelerator R&D is needed across the program (Recommendation 4c). The DOE HEP GARD program sponsors crucial work at both laboratories and universities across the program areas.

Area Recommendation 8: Increase annual funding to the General Accelerator R&D program by $10M per year in 2023 dollars to ensure US leadership in key areas.

Test facilities are ever more important to develop the advanced technology for future machines (Recommendation 4a, 4c). The need is magnified by the small number of training opportunities on operating machines and the significant timescales and technical demands of the next colliders. Use of the existing test facilities should be maximized. The development of high intensity beams, supported by proton and superconducting RF accelerators, can be pursued using FAST and IOTA at Fermilab. Key acceleration and beam requirements of a stage for a future collider based on wakefield technology, including energy gain with high brightness beams at high efficiency, can be developed using FACET-II at SLAC, BELLA at LBNL, AWA at ANL, ATF at BNL, ZEUS at University of Michigan (NSF), and other facilities. In addition to demonstrating a single self-contained stage, some of these facilities, particularly BELLA and potentially ZEUS, can demonstrate the next step toward a plasma wakefield collider, operation with two linked stages.

Future test facilities would typically be mid-scale projects. Technical and scientific plans should be developed for test facility projects that could be launched within the next 5–10 years. These could include the second stage cool copper test, which could develop high gradient normal conducting RF technology. Advanced accelerator test facilities can explore technology and concepts that could significantly reduce cost and risks associated with a 10 TeV pCM collider.

An upgrade for FACET-II e⁺ is uniquely positioned to enable study of positron acceleration in high gradient plasmas. New kW-class efficient lasers, and use of their kilohertz repetition rate for active feedback at kBELLA, will advance stage performance and enable beam tests. An AWA upgrade would support GeV advanced structures. These, together with muon collider development, will advance the technology and feed into a future demonstrator facility to make possible a 10 TeV pCM collider (see Sec. 6.5). Many of these projects may be ready for scientific, technical, and cost reviews within the context of the HEP program toward the middle to end of this decade (Recommendation 6).

Area Recommendation 9: Support generic accelerator R&D with the construction of small scale test facilities. Initiate construction of larger test facilities based on project review, and informed by the collider R&D program.

Robust growth in the field requires strengthened investment in education, training, and retention to renew the workforce and develop expertise in accelerator disciplines. A strong and creative workforce is necessary to develop and build new accelerators and colliders. Creating such a workforce is driven by state-of-the-art R&D that attracts high-level talent and can execute the machine design, development, and research needed for major new accelerator projects. Such growth is seeded by development of university groups and targeted training, such as the curriculum at the US Particle Accelerator School, structured to provide opportunities to a broad base of talent (Recommendation 5).

NSF support is important to the unique role of universities, including exploration of novel ideas at the forefront of accelerator science, and educating the next generation. NSF has an effective program in plasma-wakefield accelerators, in magnet science, and in focused conventional accelerator centers. Building a general program, potentially modeled on the successful NSF-DOE partnership in plasma science, would be of strong benefit.

Investments in Accelerator Science and Technology (AS&T) drive innovation that has benefits extending well beyond particle physics. AS&T efforts that directly support particle physics goals also meet critical needs in other offices, agencies and organizations. For example, major US facilities such as LCLS-II, the future LCLS-II-HE, and the Electron-Ion Collider rely on past and ongoing AS&T investments, and provide workforce development opportunities which should be encouraged.

More broadly, these investments lead to valuable partnerships with other DOE Science offices, other US agencies such as the Defense Advanced Research Projects Agency (DARPA) and the National Nuclear Security Agency (NNSA), academia, and industry. These partnerships are dynamic drivers of innovation and progress in accelerators that benefit both particle physics and the nation. They help build a national workforce that can develop and execute major accelerator projects (Section 6.8).

In the global context, investment in accelerator-related technologies has increased dramatically over the last decade. This reflects a broad consensus about the importance of advanced technology development and scientific advances for the health of societies—from supporting a strong technology workforce to providing critical scientific and technical capabilities. Continued US investment is required to maintain leadership and a robust workforce. Sustained investment and continued development of strong AS&T partnerships are key to maintaining a US leadership role (Recommendation 4c).

6.5Collider R&D

Targeted collider R&D is required to translate advancements in detector and accelerator technology into the experimental facilities that shape our understanding of the universe. The development of these future colliders requires broad R&D programs (sections 6.3, 6.4). It also requires increased investment in promising directions for specific future colliders. In the near term an off-shore Higgs factory and the exploration of 10 TeV pCM collider technologies present exciting possibilities, each requiring further development (section 6.4.1). Involvement in these efforts will re-invigorate accelerator physics research in the US and guide the direction of future R&D.

Design choices for the detector and accelerator elements of a collider are inextricably intertwined. In this section, collider R&D therefore refers to both elements.

Targeted R&D investments are crucial for developing comprehensive designs with cost models, guiding technology advancements and collider pathways, establishing advanced performance benchmarks for detectors and accelerators, and training the next generation of experts. This increased investment complements general detector and accelerator R&D (Section 6.3, 6.4), which focuses on developing the necessary infrastructure and technologies. This synergistic approach is essential for positioning the US as a leader in projects outlined in our 20-year vision. This includes robust participation in an off-shore Higgs factory and a pivotal role in shaping the path towards a future 10 TeV pCM machine, potentially on US soil.

The decisions related to construction of an off-shore Higgs factory are anticipated to be made later this decade. The current designs of both FCC-ee and the ILC satisfy our scientific requirements. To secure a prominent role in a future Higgs factory project, the US should actively engage in feasibility and design studies (Recommendation 2c). Engagement with FCC-ee specifically should include design and modeling to advance the feasibility study, as well as R&D on superconducting radio frequency cavities designed for the ring and superconducting magnets designed for the interaction region. These efforts benefit from synergies in workforce development through participation in SuperKEKB and the Electron-Ion Collider.

Maintaining engagement with ILC accelerators through the ILC Technology Network can include design updates and cryomodule construction. These will support significant US contributions to potential projects. A global framework for future collider development, such as the ILC International Development Team as implemented by ICFA for the ILC, is relevant for all future colliders.

For Higgs factory detectors, a concerted effort of targeted R&D synchronized with the targeted accelerator R&D program is needed. The US should participate in international design efforts for specific collider detectors. To achieve the scientific goals, several common requirements apply to the detectors of the various collider options, including vertexing, tracking, timing, particle identification, calorimetry, muon detection, and triggering. Central coordination of these requirements is crucial. The US should engage in this coordination while taking leading roles in some of the design efforts.

Major international decisions on the route to a Higgs factory are anticipated later this decade. Supported by ICFA, the Japanese HEP community remains committed to hosting the ILC in Japan as a global project. The FCC-ee feasibility study is scheduled for completion by 2025, followed by an update by the European Strategy Group and a decision by the CERN Council. Once a specific project is deemed feasible and well-defined, the US should focus efforts towards that technology. A separate panel should determine the level and nature of US contribution while maintaining a healthy US on-shore program in particle physics (recommendation 6). In the scenario where a global consensus to move forward with the Higgs factory is not reached, the next P5 should reevaluate.

Parallel to the R&D for a Higgs factory, the US should pursue a 10 TeV pCM collider. Designs addressing technical and cost feasibility for the future energy frontier at the 10 TeV pCM are required and build on technical progress in accelerator and detector technologies (Recommendation 4a).

End-to-end designs are needed well before a decision can be made on a project in order to understand potential performance parameters and costs. These will guide research priorities and technology development as well as demonstrator facilities. Such early designs will also play a critical role in creating and sustaining the expertise to design such machines. Progress on these end-to-end designs should be evaluated (Recommendation 6).

The 10 TeV pCM energy scale and potential performance benefits motivate muon collider development, as well as ongoing work to advance proton and possible advanced wakefield accelerator paths (section 6.4.1). The US should pursue a leading role in the muon collider design effort, in concert with the International Muon Collider Collaboration (IMCC). This includes R&D on relevant technologies and preparations for a demonstrator facility. Delivery of a baseline design later this decade is also a crucial milestone. Development of technologies under accelerator R&D (Section 6.4) are essential to this effort, including superconducting magnets at higher field crucial to both future proton (FCC-hh) and muon colliders, and high temperature superconductors suitable for high field and temperature. Similarly, progress in advanced wakefield accelerators motivates efforts to develop a self-consistent design to understand feasibility and costs. Each of these research areas will benefit from international engagement to enable timely progress.

Targeted detector R&D for 10 TeV pCM machines is needed to address challenges specific to these high energy machines, such as ultrafast timing, radiation hardness, and high rate capabilities. In particular, detector R&D for a muon collider is needed to address challenges related to the unstable nature of muons. Beam-induced backgrounds due to the in-flight muon decays from the beam line can potentially inhibit the ability of the detectors to successfully reconstruct collision products. While many aspects of detector design and optimization are common to all future collider detectors, this unique feature requires dedicated study and R&D.

Overall, an iterative co-design process that integrates accelerator, detector, and simulation expertise is crucial for addressing challenges specific to 10 TeV pCM machines and for demonstrating their technical and costing feasibility. R&D efforts in the next five years will inform test facilities as discussed in Section 6.4 for the mid-to-late decade time period and collider design results will set the stage for initiating a demonstrator facility (Recommendation 6), that would feed into future decisions on a potential collider project.

Area Recommendation 10: To enable targeted R&D before specific collider projects are established in the US, an investment in collider detector R&D funding at the level of $20M per year and collider accelerator R&D at the level of $35M per year in 2023 dollars is warranted.

For the targeted detector R&D, we suggest initially allocating 70% of the funds for Higgs factory detector R&D, with about 30% reserved for 10 TeV pCM detector R&D. Once detector R&D for a Higgs factory is funded and coordinated as a project, targeted detector R&D for a 10 TeV pCM machine should be ramped up.

6.6Facilities and Infrastructure

Experimental particle physics in the US relies on strategic facilities and infrastructure that enable exploration of the unknown. Stewardship of these facilities through maintenance, planning, and development is central to the future efforts recommended in this report. Maintaining existing capability is specifically outside the scope of this report. The sections below describe important enhancements to enable the science in this report.

6.6.1  –Role of National Facilities

National Laboratories and facilities play central roles in the major initiatives slated for the next decade, providing scientific and technical expertise, as well as the management, support, and site infrastructure essential to successful projects. Leading these global projects requires seamless collaboration between international and domestic partners, requiring frequent access to the laboratory sites. To meet this demand, national laboratories and funding agencies should pursue streamlined access policies, enabling researchers to work both on-site and remotely. In addition, facilitating procurement processes and ensuring technical support for experimenters is essential to timely project completion and delivery of scientific results. Equally vital is the creation of a safe, inclusive, and welcoming culture within these facilities, fostering diversity and openness, which are essential for the flourishing of innovation and scientific discovery on a global scale. In this pivotal role, US national laboratories and facilities are poised to drive the future of scientific exploration and collaboration.

Area Recommendation 11: To successfully deliver major initiatives and leading global projects, we recommend that:

1. National Laboratories and facilities should work with funding agencies to establish and maintain streamlined access policies enabling efficient remote and on-site collaboration by international and domestic partners.
2. National Laboratories should prioritize the facilitation of procurement processes and ensure robust technical support for experimenters.
3. National Laboratories and facilities should prioritize the creation and maintenance of a supportive, inclusive, and welcoming culture.

6.6.2  –Fermilab Accelerator Complex

The Fermilab Accelerator Complex began operations in 1967 and has become the center of accelerator-based particle physics in the US. Over the decades Fermilab has necessarily been modernized and upgraded, and that continues today. Ongoing major upgrades of the proton complex by the PIP-II project (Recommendation 1c) will enable production of the world’s most intense high-energy beam of neutrinos for the DUNE experiment, along with providing a variety of beams to other experiments. The ACORN project is modernizing portions of the electronic controls and power systems. Planned improvements to the Main Injector Ring and Target station (ACE-MIRT) will allow timely delivery of 2.1 MW proton beams on target to ensure high impact initial data sets from the DUNE detectors (Recommendation 2b).

Beyond these upgrades, the Fermilab Accelerator Complex must continue to evolve to support the next generations of experiments based on a high-performance proton complex. Preliminary concepts for the evolution of the accelerator complex have been explored; further development of a plan that accounts for changes in the science landscape and supports a multi-decadal vision for Fermilab is needed. We recommend that Fermilab work with the US and international communities to deliver a compelling long-term plan that identifies required R&D and defines a roadmap for upgrade efforts over the next two decades (Recommendation 4f, 6; Section 6.6.2).

Area Recommendation 12: Form a dedicated task force, to be led by Fermilab with broad community membership. This task force is to be charged with defining a roadmap for upgrade efforts and delivering a strategic 20-year plan for the Fermilab accelerator complex within the next five years for consideration (Recommendation 6). Direct task force funding of up to $10M should be provided.

Optimal performance and reliability of the accelerator complex must be ensured to capitalize on the investments in the accelerators and the experiments (including DUNE). In particular, the reliability of the Booster synchrotron was identified as a central factor in maximizing the DUNE physics production, providing partial justification for a replacement. Even in the case of a rapid replacement, the DUNE experiment will operate for several years at up to 2.1 MW (with ACE-MIRT) prior to a complete Booster replacement. This period will be the most crucial for delivering the physics results. The reliability of the complex in this mode must be critically analyzed; a modest set of mid-term investments to the Booster and other existing infrastructure should be devised by Fermilab to optimize reliability.

Area Recommendation 13: Assess the Booster synchrotron and related systems for reliability risks through the first decade of DUNE operation, and take measures to preemptively address these risks.

6.6.3  –Sanford Underground Research Facility

The Sanford Underground Research Facility (SURF) is the nation’s premier site for particle physics research deep underground, enabling detection of rare interactions that would otherwise be swamped by the far more numerous interactions from particles bombarding Earth’s surface from space. Excavation for the Long Baseline Neutrino Facility will provide the shielded space for the DUNE far detectors. Additional expansion of SURF using state and private funds, at a greatly reduced cost due to the mobilization for the DUNE excavation, is currently planned. DOE support for outfitting the resulting cavern(s) into a laboratory space would provide a US home for a G3 WIMP dark matter search (as described in Section 4.1), as well as space for other future particle or nuclear physics experiments for neutrinos or dark matter.

Area Recommendation 14: To provide infrastructure for neutrino and/or dark matter experiments, we recommend DOE fund the cavern outfitting of the SURF expansion.

6.6.4  –South Pole Station

The South Pole, the site of the NSF-operated Amundsen-Scott South Pole Station, is a unique site that enables groundbreaking scientific discoveries in particle physics and astrophysics. The world-leading infrastructure and logistics capabilities of the US Antarctic Program and South Pole Station in particular are a unique national resource that enables US scientific leadership. We commend NSF Office of Polar Programs (OPP) for their leadership and vision in constructing and maintaining this facility, which is a monumental effort in such a remote location and a harsh environment. In the next decade, the South Pole can continue to be a place of US scientific leadership, pushing the boundaries of our understanding of fundamental physics in a way that can only be done at this site.

US-led experiments sited at the South Pole—the South Pole Telescope, the BICEP suite of telescopes, and the IceCube Observatory—have produced important discoveries in fundamental physics. For experiments that observe the Cosmic Microwave Background, the South Pole provides a high, dry, stable atmosphere with continuous access year round for deep observations of the same low-foreground patch of sky. These observing conditions are particularly important for measuring the signal from inflation in the early universe that is imprinted on the CMB. For IceCube, the South Pole provides an unmatched volume of deep, clear glacial ice that allows for precision observations of optical signals made by astrophysical neutrino interactions in the ice.

The significant advancements in our understanding of inflation and the early universe by CMB-S4 and the wide range of exciting science enabled by neutrino astrophysics by IceCube-Gen2 will be made possible by continued NSF investment in infrastructure at the South Pole. The NSF has begun a South Pole Master Planning Process to create a plan for maintaining critical infrastructure and capabilities with a 30–50 year horizon. Beyond maintenance, further expansion of the capacity to support projects at the South Pole would allow for more future scientific opportunities. Renewable energy infrastructure at the South Pole is an exciting opportunity to streamline and expand the capabilities for supporting science.

Area Recommendation 15: Maintaining the capabilities of NSF’s infrastructure at the South Pole, focused on enabling future world-leading scientific discoveries, is essential. We recommend continued direct coordination and planning between NSF-OPP and the CMB-S4 and IceCube-Gen2 projects, which is of critical importance to the field of particle physics.

6.7Software, Computing and Data Science

Software and computing play a critical role in maximizing the science output of particle physics experiments. It is an integral component of experimental design, trigger and data-acquisition, simulation, reconstruction, and data analysis. It also underlies simulation and design of particle accelerators. The complexity, computational needs and data volumes of particle physics experiments are expected to increase dramatically in the next decade or so. Advances in software and computing (including AI/ML) will be key for solving the challenges associated with the data deluge and also for enhancing the sensitivity of the experimental results.

6.7.1  –Software, Computing, and Cyberinfrastructure

A hallmark of particle physics is scientific instruments that produce extremely large datasets. For example, at the ATLAS and CMS experiments at the LHC, sophisticated real-time algorithms implemented in hardware and software discard all but the most interesting 0.01% of collisions, with a final recorded output that still consists of tens of petabytes of raw data per year. These datasets are then processed to translate detector signals into a coherent picture of the particles created in the collisions.

Collecting, managing, and analyzing these datasets is a key challenge and represents a significant portion of the total operations cost for many projects. At the same time, simulating the quantum mechanics of particle interactions and the corresponding detector signals at the necessary level of precision to interpret the data poses processing and storage challenges of equivalent or larger complexity to analyzing raw data. Software, computing, and the overarching cyberinfrastructure are essential parts of project portfolios.

The enormous computational demands of particle physics call for expanded investments in R&D to maximize the physics reach of the programs. These R&D efforts have been synergistic with national initiatives in artificial intelligence/machine learning (AI/ML), quantum, computing, and microprocessors. Funding agencies should continue to leverage the resources made available through those national initiatives.

Area Recommendation 16: Resources for national initiatives in AI/ML, quantum, computing, and microprocessors should be leveraged and incorporated into research and R&D efforts to maximize the physics reach of the program.

Advances in computing are constantly emerging which can reduce costs and expand capabilities that enable new science. These advances are powered by new computing architectures, software paradigms, network capabilities, and access to expanded computing resources. Leveraging these advances, however, requires significant effort.

Based on experience from the last decade, we recommend adding support for a sustained R&D effort—at the level of $9M per year in 2023 dollars—to adapt to emerging hardware and other computing technologies. This should include efforts to transition the products of software R&D into production. We also suggest that DOE’s Office of High Energy Physics and NSF’s Directorates for Mathematical and Physical Sciences and Astronomy coordinate with other programs within the Office of Science and NSF to ensure that the profile of computing resources available matches the needs of particle physics experiments.

Area Recommendation 17: Add support for a sustained R&D effort at the level of $9M per year in 2023 dollars to adapt software and computing systems to emerging hardware, incorporate other advances in computing technologies, and fund directed efforts to transition those developments into systems used for operations of experiments and facilities.

The potential of the quantum computing paradigm and quantum information science (QIS) has given rise to a National Quantum Initiative. The initiative encourages transformative scientific discoveries through investments in core QIS research programs. The national strategy includes investments that target the discovery of quantum applications and foster quantum-relevant skills in the next generation of scientists and engineers. The quantum nature of particle physics phenomena provides a rich set of problems where quantum computing is expected to have an inherent advantage over classical computing. For example, quantum computing approaches can resolve fundamental challenges to studying the structure of nuclear matter that are encountered with the classical computing approaches.

In order to adapt to the quickly changing landscape, we support the creation of a group focused on software and computing, modeled after the Coordinating Panel for Advanced Detectors (CPAD). Such a group would serve as a valuable resource for DOE and NSF to consult in order to ensure a coordinated strategy for computing that maximizes the impact of investments in computational infrastructure.

We must ensure sustained development, maintenance, and user support for key cyberinfrastructure components, including widely-used software packages, simulation tools, and information resources, such as the Particle Data Group and INSPIRE. Although most of these shared cyberinfrastructure components are not specifically tied to projects, nearly all scientists in the field rely on them. A significant investment—at the level of $4M per year in 2023 dollars—for this type of shared cyberinfrastructure with dedicated personnel is appropriate.

As the nation and the world increasingly embrace open science, now is the time for a paradigm shift in the long-term preservation, dissemination, and analysis of the unique data collected by various experiments and surveys in order to realize their full scientific impact. An investment—at the level of $4M per year in 2023 dollars—is needed to establish these new forms of shared infrastructure and the dedicated personnel. The infrastructure should support the requisite theoretical inputs and computational requirements for analysis.

Area Recommendation 18: Through targeted investments at the level of $8M per year in 2023 dollars, ensure sustained support for key cyberinfrastructure components. This includes widely-used software packages, simulation tools, information resources such as the Particle Data Group and INSPIRE, as well as the shared infrastructure for preservation, dissemination, and analysis of the unique data collected by various experiments and surveys in order to realize their full scientific impact.

Research scientists and research software engineers at universities and labs are key to realizing the vision of the field. They possess highly specialized knowledge and are critical for maintaining a technologically advanced workforce. Strong investments in career development, including recruiting, training, and retention will ensure future success.

Area Recommendation 19: Research software engineers and other professionals at universities and labs are key to realizing the vision of the field and are critical for maintaining a technologically advanced workforce. We recommend that the funding agencies embrace these roles as a critical component of the workforce when investing in software, computing, and cyberinfrastructure.

6.7.2  –Artificial Intelligence, Machine Learning, and Data Science

The particle physics community benefits from and contributes to the rapid advances in artificial intelligence (AI) and machine learning. Our field has used various forms of machine learning for decades to enhance the sensitivity of experiments through more efficient accelerator control, data collection, and data analysis. The rise of deep learning has dramatically expanded the potential for these approaches by bringing qualitatively new capabilities, including the ability to work with low-level sensor data, to generate synthetic data, and to identify anomalies in data.

These capabilities can have a comparable impact on the physics reach of experiments as do enhancements to accelerator facilities, instrumentation, and detector design. Performing AI inference in reprogrammable hardware, closer to the detectors in the readout path, will unlock new capabilities in data collection. Emerging techniques in generative artificial intelligence are leading to productivity enhancements, particularly in writing code for software; these technologies may dramatically alter the way physicists develop code to analyze data or accelerate the process of porting code to new computing architectures. Advances are also being made in formal mathematics and mathematical physics where generative AI can serve as a creative assistant or be paired with a verification system.

The transformative potential of artificial intelligence should drive a robust investment targeted at individual projects, as well as cross-cutting capacity to accelerate technology transfer. Resources for the national initiatives in artificial intelligence should be incorporated into research and R&D efforts to maximize the physics reach of the program.

Specific skills are needed to deploy artificial intelligence and advanced statistics techniques to datasets at the scale found in particle physics, both in real time during data collection and during the subsequent data analysis. Because particle physicists must understand analysis techniques, data management, and software and computing infrastructure, the field of particle physics has proven to be an excellent training ground for data scientists. By aligning the tools and techniques used within particle physics with those used in industry, the field can more quickly benefit from advances driven by industrial data science applications and ensure that the training experiences translate outside of particle physics.

6.8Technology Innovations and Impact on Society

Particle physicists have a long history of recognizing, embracing, and fostering emerging technologies. The devices and tools that particle physics develops enable applications beyond fundamental physics in fields as different as medicine and aerospace. This section outlines the different ways particle physics spurs innovation, example impacts, and recommendations for a more sustainable future for the field.

6.8.1  –Computing

Particle physicists are the stewards of some of the world’s largest datasets and therefore have a special connection to computing and data applications. Particle physicists were among the first to transition from analog to digitized data systems, were early adopters of the use of machine learning algorithms. The world wide web and the web browser were invented at CERN as an efficient information sharing system for particle physicists. To cope with enormous datasets, particle physicists played leading roles in the development of global-scale distributed computing technologies and high-performance networking. The ambitious portfolio of projects proposed for the next 10 years will drive innovation that addresses the scientific needs of the particle physics community and will broadly impact society.

6.8.2  –Artificial Intelligence & Machine Learning

The unique challenges encountered in particle physics have proven to be fertile ground for innovation of AI/ML. Importing new techniques into the particle physics context requires a process of translation, through which those techniques are stress-tested, generalized, and improved. These improvements feed back into the wider AI/ML research community, completing a cycle of use-inspired research.

For example, when particle physicists began incorporating advances in deep learning for images, it revealed these techniques were not well suited to non-uniform detector geometries or sparse data with high-dynamic range. Coping with these unique challenges led to rapid innovations in graph neural networks and geometric deep learning. These developments were effective at building cross-disciplinary collaborations including universities, national labs, and the private sector and led to innovations that have been incorporated into the mainstream of AI/ML research.

We are witnessing an unprecedented level of cross-pollination among scientific disciplines as AI/ML has become a common language and vehicle to transfer innovations. AI-enhanced statistical inference techniques developed for particle physics are now being used in fields as disparate as materials science, neuroscience, systems biology, epidemiology, and genetics. Similarly, AI-enhanced Monte Carlo sampling techniques developed for lattice quantum chromodynamics are co-evolving with the techniques used to study molecular dynamics and gravitational waves. In addition, many of the technical developments at the core of modern machine learning frameworks, such as automatic differentiation, are being incorporated into traditional scientific computing. These advances have involved partnership among scientists working closely with AI researchers and applied mathematicians. Furthermore, these advances impact a wide range of industrial applications.

6.8.3  –Quantum Information Science

Particle physics is intrinsically rooted in the realm of quantum mechanics. This unique intersection of particle physics and quantum science positions the field as a vital contributor to the National Quantum Initiative. Particle physics is deeply involved in all five National Quantum Information Science Centers and actively engages in various activities sponsored by the Department of Energy (DOE) and the National Science Foundation (NSF).

The precision and sensitivity of particle detectors directly hinge on the capabilities of the sensors and the noise levels in the associated electronics. To meet the stringent demands of the field, particle physics has long-used cutting-edge quantum sensing techniques and ultra low-noise electronics to meet the stringent requirements of the science. This makes particle physics an ideal testing ground for these technologies. Several of the DMNI experiments are perfect examples of this paradigm. They are pushing beyond the standard quantum limit for electronic noise and scale the number of channels deployed.

A strong connection exists between quantum information science and particle theory. There are a wide variety of problems in high energy physics that cannot be addressed using classical computation. There is a strong effort to explore the potential of quantum simulation to render complex and previously insurmountable problems into manageable ones. There is significant effort to use the profound connections between quantum information theory and quantum gravity to form a better understanding of these complex fundamental problems. Finally, the next generation of experiments are beginning to explore technologically and theoretically what could be measured by actively preparing entangled quantum systems.

6.8.4  –Microelectronics

The particle physics community has also developed application-specific integrated circuits (ASICs) to cope with extreme environments, such as high levels of ionizing radiation or cryogenic temperatures. These developments are benefitting areas outside of particle physics, such as space exploration and defense needs. Specialized cryogenic and energy efficient microelectronics designs and integration techniques are now adopted by the microelectronics industry. In addition, the microelectronics facilities established at the national laboratories are of growing interest to commercial partners.

6.8.5  –Detectors and Instrumentation

Detectors for particle physics have found their way into many applications that benefit society. One of the most profound impacts is in the area of medical imaging. Detectors developed for vertexing, tracking and photon detection in particle physics can also be used to minimize exposure times for patients. Over time technology advancements in particle detectors have lowered detection thresholds, which in turn allows reducing the dose needed for medical imaging applications. Single photon detectors that were developed for low-mass dark matter searches, such as Skipper-CCDs, are being used in nuclear non-proliferation applications. Silicon-based tracking detectors have also found application in muon tomography of ancient structures like pyramids, enabling scans for hidden caverns. Development in tracking detectors of cosmic-ray muons made the recent archeological discovery of hidden chambers in the Great Pyramid of Giza possible. In addition to these examples, the development and construction of these advanced detectors and instrumentation is critical for training the technical and scientific workforce. Many detector physicists move into careers that focus on the application of these technologies.

6.8.6  –Accelerators

Particle accelerators exemplify how development of frontier machines for high energy physics enables broad science and societal applications, including X-ray light sources, material science, medical therapy, and particle sources for national security and industry. As an example of such broad science, accelerator structures developed for the ILC are enabling a new generation of light sources including LCLS-II and LCLS-II-HE. Light sources and other new capabilities have been made possible through decades of development of transformational accelerator techniques by the particle physics community.

Accelerator technology development enables further applications. Magnets have benefitted applications including medicine and fusion development. Similarly, lasers have greater impacts including advanced manufacturing, medicine and security applications. Future advances, such as those needed to reach higher beam powers and energies, will inspire yet more research on very high field magnets, extraordinarily intense beams, and accelerator technologies with the potential to be radically more compact (Recommendation 4a, 4c, Sections 2.3.2, 6.3, 6.4, and 6.5). In turn, these developments may lead to improved efficacy in cancer treatment, more compact fusion devices, and compact sources of particles and radiation for industry and security, both benefiting from and reinforcing particle physics investment.

6.9Sustainability and the Environment

Commitment to sustainability is a high priority for particle physics activities. This includes energy and carbon management, energy efficiency and savings, and environmental impact. It concerns present and future accelerators as well as testing and computing facilities.

In the study of future accelerator projects, it is important to establish and launch at an early stage a full lifecycle sustainability effort. Because future accelerators, conceived for higher beam energies and intensities, will have higher energy demands, the promotion of energy efficient accelerator concepts, as well as identification and development of energy saving accelerator technology, is critical. These considerations will affect the affordability of new accelerators and demonstrate the responsible role of the HEP community in society.

Accelerator technologies play a key role in sustainability. Investments in high field magnets by the DOE Magnet Development Program and NSF’s MagLab have advanced the state of the art in conductors and magnet design to the benefit of particle physics, but also materials science, fusion energy research (FES), and commercial development. In this context, high temperature superconducting materials, operated at temperatures higher than superfluid or liquid helium, can play a key role in reducing energy consumption e.g. for future colliders including muons or FCC-hh. Accelerator structure improvements can also play an important role, including higher quality factor, and concepts like cool copper.

Other new technologies such as muon and possibly wakefield colliders have potential to improve power required for a given luminosity and reduce the size and impact of future facilities. Innovation in electric power generation, management and distribution also contribute to sustainable development and shall be encouraged.

Upgrade, construction, and operation of accelerator complex (section 4.2) and test facilities are part of the global effort to advance particle physics. Defining sustainable requirements on industrially procured technology, including construction, electrical, and cooling equipment, should be included in the project development.

To contribute to the global decarbonization effort, future projects will aim to reduce the CO₂ footprint of their civil engineering components. Research and adoption of sustainable and eco-friendly materials will be encouraged, and this applies to gasses with high global warming impact used in some types of detectors. Study of alternative solutions will be investigated and implemented, in addition to the adoption of stringent recirculation requirements when those gasses are used. Re-use of materials should be encouraged to foster sustainable development and to limit the use of natural resources and raw materials, including critical minerals that are subject to potential shortages.

The international nature of particle physics activities calls for extensive travel to participate in meetings and conferences and to carry out experiments. The dramatic increase in the use of remote conferencing mandated by the COVID-19 pandemic spurred an evolution of practices and technologies that allow researchers to increase participation and inclusivity. With this new paradigm in place, laboratories should facilitate hybrid meetings and invest in upgrades to video conferencing equipment as necessary. Meeting organizers should establish protocols that ensure people connecting from remote locations can participate fully, including in discussions. At the same time, in-person meetings remain strongly valuable and should not be discouraged because they facilitate open and effective communication and build trust in international partnership. Assessing and implementing sustainability strategies require R&D and investment of appropriate resources. The field would benefit from development of consistent metrics for sustainability of research, construction, and operations.

Area Recommendation 20: HEPAP, potentially in collaboration with international partners, should conduct a dedicated study aiming at developing a sustainability strategy for particle physics.