This is a census of documented amateur cyclotrons: machines designed and built by
individuals, high-school teams, or small undergraduate groups outside professional
accelerator programs. An entry qualifies if the build itself is documented — a project
site, thesis, conference paper, or credible press account — not merely rumored. Design
studies count when they left a public record; unverifiable claims are noted as such.
Few of these projects reach beam, and the reasons repeat across seven decades: a
cyclotron demands a ton-scale homogeneous magnet, high vacuum, a kilovolt-level RF
resonator, a working ion source, and diagnostics — every subsystem at near-professional
standard before anything at all happens. Builders at the 2010 amateur cyclotron
conference estimated two to three years of work and roughly $125,000 in parts if bought
new (Symmetry, Aug 2010), which is why nearly every successful machine leans on donated
magnets, surplus hardware, and patient scrounging. The entries below are presented in a
uniform format, in rough chronological order, with each machine's claims traceable to
the linked sources.
Plotted as a timeline, the census tells its story at a glance: a cluster of school
builds in the postwar decades, then a silence of more than twenty years before the
renaissance that began in the 1990s and has not slowed since.
17 documented projects · 8 with a demonstrated or routinely
operated beam.
operated beam demonstrated in progress stalled outcome unknown
Documented amateur and school cyclotron projects, from start year to first beam or last
documented activity (dot = single documented year; arrow = ongoing). Bar shading ranks
each project's documented outcome in the legend's order, from routinely operated to
outcome unknown; spans for entries the census dates with “c.” are approximate. Hover a
row for details, or select it to jump to the full entry below.
El Cerrito High School Cyclotron
Four students with physics teacher Ben Siegel, El Cerrito High School, California1947
operatedUSA
Magnet
≈1 t (one-ton) welded soft-steel yoke
RF frequency
20 MHz (reported), ≈1.5 kW
Particle
protons
Energy
“million-electron-volt” claimed in period press; unverified
The earliest well-documented school-built cyclotron, constructed in about three months for roughly $500 and featured in Physics Today and Popular Science in 1947. The students operated the one-ton machine by remote control from a plywood panel in a closet-sized room, and the Research Corporation waived royalties on the Lawrence cyclotron patents it infringed. Contemporary press reported the machine running at 20 MHz, but no beam measurements survive, so the million-electron-volt figure should be read as a period claim.
Three high-school students, Fort Wayne, Indiana1951
outcome unknownUSA
In 1951 three students remodeled their high-school basement into a cyclotron laboratory and were already at work on the accelerator by the time the principal found out. The group kept careful engineering notes that later amateur builders cite as an early blueprint, and two of the students went on to work at Fermilab. No surviving documentation confirms whether the machine ultimately accelerated ions.
Successive student teams (L. Zuckerman, N. Ostroff, J. Horowitz and others; later S. Goldwasser and others), Central High School, Philadelphia1958 – c. 1970
outcome unknownUSA
Pole diameter
178 mm (7 in)
Field
≈2 T (20 kG) reported at full excitation
RF frequency
≈7 MHz initially, later ≈20 MHz
Particle
protons (intended)
Energy
≈1 MeV theoretical; no measured beam
A cyclotron built and rebuilt by roughly three generations of Philadelphia high-school students between 1958 and about 1970, documented in a detailed retrospective by one of the later participants. The 7-inch machine was theoretically capable of about 1 MeV, but the account itself doubts a real proton beam was ever achieved; the best evidence of operation was a marginal exposure of dental X-ray film.
Student Cyclotron Committee, Stuyvesant High School, New York Cityearly 1960s
outcome unknownUSA
Stuyvesant students organized a Cyclotron Committee with specialized teams for the electromagnet, vacuum chamber, and RF system, collecting donations that included a half-ton of steel and five miles of copper wire at a project cost of roughly $10,000. A 1962 school publication suggested the machine was completed, but a retrospective in the school's own newspaper found no evidence the project actually reached completion.
Fred Niell (high-school student, home-built)c. 1993–1994
beam demonstratedUSA
RF frequency
resonance observed at 2.2–2.3 MHz
Particle
residual-air ions (mostly nitrogen)
Vacuum
small diffusion pump backed by a rotary pump
A cyclotron designed and built at home by a high-school student, set up in the room next to his bedroom, with every component — magnet, RF amplifier, vacuum gauges — of his own construction. Running on residual air rather than an isolated gas species, it demonstrated cyclotron mass resonance with a clear output peak at 2.2–2.3 MHz consistent with nitrogen ions and their harmonics. The associated science-fair project won the grand prize at the 1994 International Science and Engineering Fair.
Fred Niell (high-school student, home-built)1994–1995
beam demonstratedUSA≈70 keV
Field
≈0.67 T (6.7 kG, measured)
RF frequency
0.5–16 MHz variable; H⁺ resonance observed at 10 MHz
Particle
protons, helium ions
Energy
≈70 keV (H⁺ at measured resonance, r = 5.7 cm)
Vacuum
diffusion pump with molecular-sieve trap
A second, more research-oriented machine built the following school year, fixing the shortcomings of the first: a variable-frequency RF system (0.5–16 MHz) driven by a tube push-pull amplifier allowed resonance mapping of more than one ion species. Measured resonance peaks for hydrogen and helium matched prediction within about 2% once the magnet coil count was corrected, corresponding to roughly 70 keV protons. The machine was left at the school when the builder went to college and was later dismantled for parts.
Tim Koeth and Stu Hanebuth, undergraduates at Rutgers University1995–1999
beam demonstratedUSA
Pole diameter
229 mm (9 in), Varian V-3400 NMR magnet
Field
0.889 T (8.89 kG) operating; 1.2 T maximum
RF frequency
13.56 MHz
Particle
protons
Energy
up to ≈50 nA proton current at the chamber periphery
The feasibility prototype for the later 12-inch machine, built around a repurposed Varian NMR magnet turned on its side, with a fixed 13.56 MHz industrial-band RF system setting the 0.889 T operating field. Successful resonance runs in 1999 showed a strong proton current at the predicted field, with beam detected at up to about 50 nA at the periphery. Its results justified moving to a 12-inch magnet with a 1 MeV design goal.
Tim Koeth, Stu Hanebuth, and successive Rutgers undergraduates1995–present
operatedUSA800 keV
Pole diameter
305 mm (12 in)
Field
1.2 T (12 kG) design
RF frequency
≈18 MHz (design)
Particle
protons
Energy
800 keV, 200 nA demonstrated by 2006; 1 MeV capability; tens of µA after 2012 PIG source upgrade
The best-documented amateur-origin cyclotron: begun as a personal project by two undergraduates in 1995, it became the centerpiece of the Rutgers modern physics teaching lab from 2001, reliably producing 800 keV proton beams by 2006 and, after a PIG ion source upgrade in 2012, tens of microamperes over 30-hour runs. Nineteen undergraduates gained hands-on accelerator experience on the machine, several going on to accelerator-physics careers. In 2016 it moved to the University of Maryland, where it anchors a capstone design class.
Jeff Smith, undergraduate at Knox College, Illinoisc. 1999–2001
outcome unknownUSA
A fixed-frequency cyclotron built as an honors senior thesis in physics, completed in 2001 with assistance from Fermilab cyclotron builder Chris Olsen after the builder encountered cyclotrons at a Fermilab public lecture. The builder went on to accelerator physics at Cornell and SLAC; the machine itself remains in the basement of Knox College, and no documentation of a demonstrated beam has been published.
Mark Yuly and successive undergraduate students, Houghton College, New York2003–present
beam demonstratedUSA
Chamber
170 mm (6.7 in) inner-diameter aluminum chamber
Field
≈1.1 T (11 kG)
Particle
protons, deuterons, helium ions
Energy
design energies of tens to hundreds of keV; picoampere-scale internal beams measured
Vacuum
diffusion-pumped high-vacuum system
A deliberately small cyclotron developed as a continuing undergraduate research program, with each student generation documenting improvements in theses and conference talks since 2003. The machine has accelerated ions — beam-current-versus-radius measurements at the helium resonance and at least one proton run are documented — though hardware failures have repeatedly interrupted operation. It hosted the first amateur cyclotron conference in 2010 and remains a teaching and research tool.
An undergraduate thesis project documenting the design and construction of a cyclotron intended to accelerate protons to 2 MeV for low-energy beam experiments in MIT's nuclear engineering department. The thesis and two videos are the surviving public record; no demonstrated beam is documented, and the project appears not to have been completed.
Heidi Baumgartner and Peter Heuer (high-school students), with German Diagama; built at Jefferson Labc. 2008–2013
stalledUSA
Dee diameter
305 mm (12 in) single dee with grounded dummy dee
Field
1.6 T (16 kG)
RF frequency
24 MHz, 3 kW tube amplifier
Particle
protons
Energy
2 MeV (design)
Vacuum
10⁻⁷ torr (design)
Two high-school students designed a 2 MeV proton cyclotron and, after a funding email reached the associate director of Jefferson Lab, were invited to build it at the national lab over several summers. All components — a 1.6 T H-magnet, welded stainless chamber, 24 MHz RF system, and thermionic ion source — were completed, but lab safety rules for minors prevented power testing, and no beam was ever run. The machine was transferred to Old Dominion University to await further student work; both builders went on to physics careers.
Ch. Wolf, M. Frank, E. Held and students, Gymnasium Ernestinum, Coburgc. 2010–2016
beam demonstratedGermany24–48 keV
Pole diameter
150 mm (6 in), Bruker BE-15 laboratory magnet
Field
0.38 T (3.8 kG) operating; up to 0.7 T available
RF frequency
5.63 MHz, 2–3 kV dee voltage
Particle
protons
Energy
24–48 keV design; no extraction, by design, so no radiation escapes
Vacuum
10⁻⁵ mbar (10⁻⁴ mbar with hydrogen flowing)
A teaching cyclotron built at a German Gymnasium expressly so that students could see and operate a real accelerator, using standard components and donated hardware including a Jülich laboratory magnet and an industrially fabricated chamber. The design keeps final energy low enough that no harmful radiation leaves the chamber, and the machine registered its first proton beam in April 2014, with continued improvements in following years. It was presented at the Cyclotrons 2013 conference.
Undergraduate design classes led by Timothy Koeth, University of Marylandc. 2016–present
in progressUSA
Pole diameter
483 mm (19 in), restored historic magnet
Particle
protons (planned)
A successor machine under construction by successive undergraduate cohorts at the University of Maryland, built around a restored 19-inch magnet alongside the relocated Rutgers 12-inch cyclotron. Unlike the 12-inch machine, whose beam stays inside the chamber, the 19-inch design is intended to extract beam for experiments; on completion it would be the largest cyclotron built by undergraduates.
Simon and Chris Mullins (father and son, home-built)2017–2019
beam demonstratedUSA≈164 keV
Field
582 mT (5.82 kG)
RF frequency
8.87 MHz
Particle
protons
Energy
≈164 keV demonstrated
A father-and-son garage build documented on a dedicated project site, carried from magnet design through working machine between 2017 and 2019. Operating at 582 mT with an 8.87 MHz RF system, it demonstrated acceleration of protons to approximately 164 keV. The build log covers the magnet, vacuum system, RF chain, and beam measurements.
Reed Michael Upson and Ray Anchordoquy (backyard workshop build)2018–present
in progressUSA
Dee diameter
356 mm (14 in)
Field
≈0.3 T (3 kG) median-plane
Particle
protons
Energy
60 keV target (revised down from 1.1 MeV over incidental-radiation concerns)
Vacuum
10⁻⁵ torr target
A two-person build housed in a purpose-built, Faraday-caged garden shed, under way since 2018 and documented on a project site. The original 1.1 MeV goal was deliberately reduced to about 60 keV to avoid incidental radiation hazards. As of the site's last update in late 2024, subsystems including vacuum and the ion source were being validated individually and no beam had yet been produced.
Student-led “Engineering a Mini Cyclotron Crew”, Dawson College, Montreal2020s
in progressCanada
A student-led initiative at a Montreal CEGEP with the stated goal of constructing a compact cyclotron as a hands-on learning project, with leadership rotating to new students each fall. The college foundation page describes the program but publishes no specifications or construction milestones, so the project may still be at the design stage.