Landscape of Modern and Future Acceleratorsand the Snowmass'21 Planning Process
Steve Gourlay*, Vladimir Shiltsev** and Tor Raubenheimer***Snowmass21 Accelerator Frontier Co-Conveners*LBNL (Retired), PNTZ Consulting Group, LLC**Fermi National Accelerator Laboratory***SLAC National Accelerator Laboratory

Strategic Planning Process for US HEP• Brief look at current US landscape of Projects and Programs• Snowmass – the beginning of the process• Organization:• Committees, Frontiers and Topical Groups• Timeline• Accelerator Frontier• Topical Groups and Initiatives:• Implementation Task Force• Muon Collider Forum• Physics Limits of Ultimate Beams
2

Large US Accelerator Construction Projects• Many large accelerator projects across the United States:• High Energy Physics:••

High Luminosity LHC upgrade (~0.5B, ~2026)
Long-Baseline Neutrino Facility / PIP-II (~4B, 2030)• Nuclear Physics:••

Facility for Rare Ion Beams (~0.6B, 2022)
Electron-Ion Collider (~2B, 2031)• Basic Energy Sciences:••••

Argonne Photon Source Upgrade (~1B, 2026)
Advanced Light Source Upgrade (~0.5B, 2026)
LCLS-II / LCLS-II High Energy (~2B, 2030)
SNS Power Upgrade and Second Target Station (~0.3B, 2027 / ~1B, 2030+)

US High Energy Physics Accelerator R&D Subpanel•

Guided by 2015 Accelerator R&D Subpanel Report:•Near-term goals:••••

Mid-term goals:••••

PIP-II à LBNF / DUNE
HL-LHCILC e+/e- collider

Multi MW proton accelerator
Very high energy proton-proton collider
TeV-scale upgrade of ILC

Long-term goals:••

Multi-TeV e+/e- collider
Neutrino factoryUS HEP Accelerator Mid- and Long-term R&D Focus• US largely focused on accelerator technology R&D• High Field magnet and High Gradient RF development as well as other technology
development has been ongoing in part to support ILC and a high energy pp collider• US was heavily engaged in Linear Collider R&D from 1980 à 2008
• Refocused on SRF technology for cost reduction• Strong advanced acceleration programs•

No concept for a collider at this time but focused on fundamental demonstrations• Muon Accelerator Program (MAP) from 2011 to 2015
• Examined feasibility of MC subsystems but redirected before looking at integration

What is “Snowmass?”• “Snowmass is a particle physics
community study”• https://www.snowmass21.org/• Provides input to P5(Particle Physics Project
Prioritization Panel) whichdevelops a strategy for
the US HEP program
No prioritizations from Snowmass

Snowmass

1.5-2 yrs

P5Strategy~5-7 yrs ofhard work

DOE/NSFprogram~ 1 yrSnowmass Timelines
Fall
2021

01/22

02/22

03/22

04/22

5/22

06/22

07/22

CSS

08/22

09/22

10/22
Snowmass
Book& arXiv

July 17-27, 2022
Community Summer Study
UW - Seattle

White paper submission
Preliminary TG reports

Preliminary Frontier reports
Frontier Executive summariesFinal TG/Frontier reports
Snowmass Book (SG) & on-line arXiv docs

Snowmass Organization
Advisory Group
Steering Committee

Snowmass Frontiers (10)Liaisons + Early Career

Topical Groups (80)CommunitySnowmass’21 Frontier Conveners
EnergyFrontier

Accelerator
Frontier
Meenakshi Narain(Brown U)

Laura Reina(FSU)

Alessandro Tricoli(BNL)

Steve Gourlay(LBNL)Tor Raubenheimer(SLAC)

Vladimir Shiltsev(FNAL)

Phil Barbeau(Duke)

Petra Merkel(FNAL)

Jinlong Zhang(ANL)

Steven Gottlieb(Indiana U.)

Ben Nachman(LBNL)

Oliver Gutsche(FNAL)

Instrumentation
FrontierFrontiers inNeutrinos
Patrick Huber(Virginia Tech)

Kate Scholberg(Duke U.)

Elizabeth Worcester(BNL)

Frontiersin Rare &Precision

Computational
Frontier
Marina Artuso(Syracuse U.)

Alexey Petrov(Wayne State U.)

Bob Bernstein(FNAL)

CosmicFrontier
Aaron Chou(Fermilab)

Marcelle Soares-Santos(U.Michigan)

Tim Tait(UC Irvine)

Underground
Facilities andInfrastructure
Frontier

Laura Baudis(U. Zurich)Jeter Hall(SNOLAB)

Kevin Lesko(LBNL)

John Orrell(PNNL)

Community
Engagement
Frontier

TheoryFrontier
Nathaniel Craig(UCSB)

Csaba Csaki(Cornell)

Aida El-Khadra(UIUC)

Shiltsev | Snowmass AF

Kétévi Assamagan(BNL)

Breese Quinn(Mississippi)

9Snowmass’21: Frontiers and Topical Groups
10 Frontiers

80 Topical Groups

Energy Frontier

Higgs Boson properties and couplings, Higgs Boson as a portal to new physics, Heavy flavor and top quark physics, EW
Precision Phys. & constraining new phys., Precision QCD, Hadronic structure and forward QCD, Heavy Ions, Modelspecific explorations, More general explorations, Dark Matter at colliders

Frontiers in Neutrino Physics

Neutrino Oscillations, Sterile Neutrinos, Beyond the SM, Neutrinos from Natural Sources, Neutrino Properties, Neutrino
Cross Sections, Nuclear Safeguards and Other Applications, Theory of Neutrino Physics, Artificial Neutrino Sources,
Neutrino Detectors

Frontiers in Rare Processes &Precision Measurements

Weak Decays of b and c, Strange and Light Quarks, Fundamental Physics and Small Experiments. Baryon and Lepton
Number Violation, Charged Lepton Flavor Violation, Dark Sector at Low Energies, Hadron spectroscopy

Cosmic Frontier
Theory Frontier
Accelerator Frontier
Instrumentation Frontier

rs,enDark Matter: Particle-like, Dark Matter: Wave-like, Dark Matter: Cosmicve Probes,sDark Energy & Cosmic Acceleration: Thennoo
Modern Universe, Dark Energy & Cosmic Acceleration: CosmiccDawn & Before,si Dark Energy & Cosmic Acceleration:
paiu
LComplementarity of Probes and New Facilitieso
Gr areerlacString theory, quantum gravity, black holes,
C theory techniques, CFT and formal QFT, Scattering amplitudes,piEffective
yfieldolrT
Lattice gauge theory, Theory techniques
forprecision
physics,phenomenology, BSM model building, Astroa
0 information
E science,Collider
552particle physics and cosmology,
Quantum
Theoryof Neutrino Physics
2~~,s,
rs
Beam Physics andAccelerator
ne aisEducation,on Accelerators for Neutrinos, Accelerators for Electroweak and Higgs Physics,
evinMulti-TeV Colliders,Accelerators
Physics Beyond Colliders & Rare Processes, Advanced Accelerator Concepts,
coTechnologyr LR&D: RF, foreriAccelerator
Magnets, Targets/Sources
etint -FronoQuantumrFr Sensors, Photon Detectors, Solid State Detectors & Tracking, Trigger and DAQ, Micro Pattern Gas Detectors,et30 0 Calorimetry,nElectronics/ASICS, Noble Elements, Cross Cutting and System Integration, Radio Detection
I4>

Computational Frontier

Experimental Algorithm Parallelization, Theoretical Calculations and Simulation, Machine Learning, Storage andprocessing resource access (Facility and Infrastructure R&D), End user analysis

Underground Facilities andInfrastructure Frontier

Underground Facilities for Neutrinos, Underground Facilities for Cosmic Frontier, Underground Detectors

Community Engagement Frontier

Applications & Industry, Career Pipeline & Development, Diversity & Inclusion, Physics Education, Public Education &Outreach, Public Policy & Government Engagement

10Snowmass Community Planning Meeting: Oct 5-8, 2020
~3,000 participants~650 outside the North America Time Zone
(Note that 11am-4pm U.S. Central time was inconvenient – very inconvenient for many countries)

Letters of Interest

Accelerator Frontier• Co-Conveners• Steve Gourlay (LBNL, Retired)• Tor Raubenheimer (SLAC)• Vladimir Shiltsev (FNAL)
Description

The Accelerator Frontier activities include discussions on high-energy hadron and lepton colliders,high-intensity beams for neutrino research and for the “Physics Beyond Colliders”, accelerator
technologies, science, education and outreach as well as the progress of core accelerator technology,including RF, magnets, targets and sources. Participants will submit Letters of Intent, contributed
papers, take part in corresponding workshops and events, contribute to writing summaries and takepart in the general Snowmass'21 events

Accelerator Frontier – Key Questions
1. What is needed to advance the physics?
2. What is currently available (state of the art) around the world?
3. What new accelerator facilities could be available in the next decade (ornext next decade)?
4. What R&D would enable these future opportunities?
5. What are the time and cost scales of the R&D and associated test facilities
as well as the time and cost scale of the facilities?

Accelerator Frontier Topical Groups and Conveners
Topical Group

Topical Group co-Conveners

AF1

Beam Phys & Accel. Education

Z. Huang (Stanford)

M. Bei (GSI)

S. Lund (MSU)

AF2

Accelerators for Neutrinos

J. Galambos (ORNL)

B. Zwaska (FNAL)

G. Arduini (CERN)

AF3

Accelerators for EW/Higgs

M. Ross (SLAC)

Q. Qin (IHEP, Beijing)

G.Hoffstaetter (Cornell)

AF4Multi-TeV Colliders

M. Palmer (BNL)

A. Valishev (FNAL)N Pastrone (INFN,Torino)

AF5

Accelerators for PBC and Rare
Processes

E. Prebys (UC Davis)

M. Lamont (CERN)

R.Milner (MIT)AF6

Advanced Accelerator Concepts

C. Geddes (LBNL)

M. Hogan (SLAC)

P. Musumeci (UCLA)

AF7

Accelerator Technology R&D
Sub-group RF

E. Nanni (SLAC)

S. Belomestnykh (FNAL)

H. Weise (DESY)

Sub-Group Magnets

G. Sabbi (LBNL)

S. Zlobin (FNAL)

S. Izquierdo Bermudez (CERN)

Sub-Group Targets & Sources

C. Barbier (ORNL)

Y. Sun (ANL)F. Pellemoine (FNAL)

J.Tang (IHEP,Beijing)

R. Assmann(DESY)

Plus, the Accelerator Implementation Task Force (ITF) to evaluate and compare various options

9 out of 29 are representatives of Asia and Europe; 5 womenAgenda – Joint AF/EF Workshop on Future Colliders
Day 1: https://indico.fnal.gov/event/43871/

Day 2: https://indico.fnal.gov/event/43872/

Some Working Group Activities• AF1 – has been running a series on physics of Ultimate Beams and examining thefundamental limits of accelerator technology• AF3 – looking broadly at Higgs factories from e+/e-, g/g, µ+/µ• AF4 – considering multiple paths to high energy including e+/e-, g/g, µ+/µ- and p/p;
lots of enthusiasm for µ+/µ- in part because of potential to fill in the gap from 3-14
TeV with US MC Forum and Int. MC Collab.
• AF5 – working on many small or moderate scale proposals• AF6 – working to understand options to upgrade a more conventional linear collider
as well as limits of plasma acceleration (Multi-TeV)• AF7 – 3 subgroups exploring limits of accelerator technology (many efforts
supported in part by US-Japan)

AF Implementation Task Force (ITF)• Key question for Snowmass’21 Accelerator Frontier to address: “…What are
the time and cost scales of the R&D and associated test facilities as well as thetime and cost scale of the facility?”• A large number of possible accelerator projects: ILC, Muon Collider, gammagamma and ERL options, a large circumference electron ring, and a large
circumference hadron ring amongst others.
• Comparison of the expected costs (using different accounting rules), schedule,and R&D status for the projects.
• The Accelerator Implementation Task Force is comprised of 9 worldrenowned accelerator experts from Asia, Europe and US and two
representatives of the Snowmass Young; it is chaired by Thomas Roser(BNL) and charged with developing metrics and processes to facilitate acomparison between projects• Focused on HEP Colliders

Jim Strait(FNAL)

Marlene Turner(LBNL)

Spencer Gessner(SLAC)

Thomas Roser(BNL, Chair)

Philippe Lebrun(CERN)

Steve Gourlay(LBNL)Tor Raubenheimer(SLAC)

Katsunobu
Oide (KEK)Sarah Cousineau(ORNL)

Vladimir Shiltsev(FNAL)

ReinhardBrinkmann(DESY)John Seeman(SLAC)

Charge to the ITF
1. Develop the metrics to compare projects’ cost, schedule/timeline, technical
2.
3.
4.
5.
6.
7.

risks (readiness), operating cost and environmental impact, and R&D status
and plans;
Select the accelerator projects to be evaluated (provided by the AF topicalgroups);
Work with the proponents of the selected accelerator projects to evaluate
them against the metrics from item 1;
Consider the ultimate limits of various types of colliders: e+/e-, p/p, mu+/mu-;
Consider limits and timescales due to accelerator technology for varioustypes of colliders: e+/e-, p/p, mu+/mu-;Lead the evaluation of the different HEP accelerator proposals and informand communicate with the Snowmass’21 AF, EF, NF and TF;
Document the metrics, processes, and conclusions for the Snowmass'21
meeting in the Summer 2022; write and submit a corresponding White Paper.

ITF: Higgs Factory Concepts/Proposals (8)Name

Details

POC

AFGroup

CepC

e+e-, 𝑠 = 0.24 TeV, L= 3.0 ×10!"

Jie Gao (gaoj@ihep.ac.cn)

AF3

CLIC (Higgs factory)

e+e-, 𝑠 = 0.38 TeV, L= 1.5 ×10!"

Steinar Stapnes (Steinar.Stapnes@cern.ch)

AF3

ERL ee collider

e+e-, 𝑠 = 0.24 TeV, L= 73 ×10!"

Thomas Roser (roser@bnl.gov)

AF3

FCC-eee+e-, 𝑠 = 0.24 TeV, L= 17 ×10!"

Katsunobu Oide (katsunobu.oide@ern.ch)

AF3gamma gamma

X-ray FEL-based 𝛾𝛾 collider

Tim Barklow (timb@slac.stanford.edu)

AF3

ILC (Higgs factory)

e+e-, 𝑠 = 0.25 TeV, L= 1.4 ×10!"

Shin-ichi Michizono(shinichiro.michizono@kek.jp

AF3

LHeC

𝑒𝑝, 𝑠 = 1.3 TeV, L= 0.1 ×10!"

Oliver Bruening (oliver.bruening@cern.ch)

AF3

MC (Higgs factory)

𝜇𝜇, 𝑠 = 0.13 TeV, L= 0.01 ×10!"

Mark Palmer (mpalmer@bnl.gov)

AF3

ITF :18 (!) high energy collider concepts/proposals
NameDetails

POC

AF Group

Cryo-Cooled Copper linac

e+e-, 𝑠 = 2 TeV, L= 4.5 ×10!"

Emilio Nanni (nanni@slac.Stanford.edu)

AF3High Energy CLIC

e+e-, 𝑠 = 1.5 −3 TeV, L= 5.9 ×10!"

S.Stapnes (steinar.stapnes@cern.ch)

AF4High Energy ILC

e+e-, 𝑠 = 1 −3 TeV

Hassan Padamsee (hsp3@cornell.edu)

AF4

FCC-hhpp, 𝑠 = 100 TeV, L= 30 ×10!"

M.Benedikt(Michael.Benedikt@cern.ch)

AF4

SPPC

pp, 𝑠 = 75/150 TeV, L= 10 ×10!"

J.Tang (tangjy@ihep.ac.cn)

AF4Collider-in-Sea

pp, 𝑠 = 500 TeV, L= 50 ×10!"

P.McIntyre mcintyre@physics.tamu.edu

AF4

LHeC

𝑒𝑝, 𝑠 = 1.3 TeV, L= 1 ×10!"

Y.Zhang (yzhang@jlab.org)

AF4

FCC-eh𝑒𝑝, 𝑠 = 3.5 TeV, L= 1 ×10!"

Y.Zhang (yzhang@jlab.org)

AF4

CEPC-SPPpC-eh

𝑒𝑝, 𝑠 = 6 TeV, L= 4.5 ×10!!

Y.Zhang (yzhang@jlab.org)

AF4

VHE-ep𝑒𝑝, 𝑠 = 9 TeV

Y.Zhang (yzhang@jlab.org)

AF4

MC – Proton Driver 1𝜇𝜇, 𝑠 = 1.5 TeV, L= 1 ×10!"

D.Schulte (daniel.schulte@cern.ch)

AF4MC – Proton Driver 2𝜇𝜇, 𝑠 = 3 TeV, L= 2 ×10!"

D.Schulte (daniel.schulte@cern.ch)

AF4MC – Proton Driver 3𝜇𝜇, 𝑠 = 10 − 14 TeV, L= 20 ×10!"

D.Schulte (daniel.schulte@cern.ch)

AF4MC – Positron Driver

𝜇𝜇, 𝑠 = 10 − 14 TeV, L= 20 ×10!"

D.Schulte (daniel.schulte@cern.ch)

AF4LWFA-LC (e+e- and 𝛾𝛾)Laser driven; e+e-, 𝑠 = 1 − 30 TeV

Carl Schroeder (CBSchroeder@lbl.gov)

AF6

PWFA-LC (e+e- and 𝛾𝛾)

Beam driven; e+e-, 𝑠 = 1 − 30 TeV

Gessner, Spencer J. (sgess@slac.edu)

AF6

SWFA-LC

Structure wakefields; e+e-, 𝑠 = 1 − 30TeV

Chunguang Jing (jingchg@anl.gov)

AF6

Muon Collider Forum• Joint EF-AF-TF-IF Initiative• Aspirations for energy frontier facility in the US• Based on results of successful US-Muon Accelerator
Program (MAP) that ended in 2016 and bold CERN-led
initiative in Europe
21European Planning Influences Snowmass Topics••

European Strategy for Particle Physics (ESPP) describes strategy for particle
physics in Europe and their contributions world-wide (June 19, 2020)
European National Laboratories Directors Group (LDG) – July 2 (Chaired byLenny Rivkin)••

Immediate outcome à Accelerator R&D Task Forces reporting to Lab Directors Group(LDG) and CERN Council

Address the question of what are the most promising Accelerator R&D activities
for HEP

Snowmass AF participants areactive on all the LDG panels

Steps Toward a Muon Collider in Europe• EU Strategy –International Design Study• High-priority future initiatives . . . In addition to the high field magnets theaccelerator R&D Roadmap could contain:• . . . An international design study for a muon collider, as it represents a unique
opportunity to achieve a multi-TeV energy domain beyond the reach of e+ecolliders, and potentially within a more compact circular tunnel than for a hadroncollider. The biggest challenge remains to produce an intense beam of cooledmuons, but novel ideas are being explored;• LDG agrees to start building the collaboration for an international muon collider design study• Daniel Schulte as interim project leader – with N. Pastrone and L. Rivkin• Kick-off meeting held – July 3• > 250 participants – https://indico.cern.ch/event/930508/

Physics Limits of Ultimate Beams
As part of the Snowmass2021 community discussion, AF1 (AcceleratorScience, Education, Outreach), AF4 (Multi-TeV Colliders) and AF6(Advanced Accelerator Concepts) launched a joint workshop on the topicof Physics Limits of Ultimate Beams. The main scope of this workshop
was to engage the community to explore:• Fundamental ultimate beams for various physics goals. In
particular, for colliders, we would like to understand the required
luminosity scaling with energy• Potential and feasibility of advanced concepts towards theultimate physics limits, such as PeV beams yet low luminosity, etc.
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Snowmass’21 Accelerator Frontier: Summary• Times have been difficult• Impact of COVID-19 on particle physics and accelerator research – delays in projects andprograms• All of the Snowmass meetings and workshops so far have been virtual.
• We have challenges to deal with uncertainty in 2021-22.

• In spite of this, there has been tremendous effort and major progress by thecommunity:• Huge thanks to the AF community, Topical Groups’ and ITF leaders!!

• Snowmass is a community-driven process:• We appreciate the community’s continued strong participation in the process• We very much welcome the international accelerator community -please, join us!!

• Visit the Snowmass AF wiki page (https://www.snowmass21.org/accelerator/ ) to findout the best way to contribute• We very much look forward to a productive Snowmass study25