Tim Koeth’s three-decade cyclotron project
Tim Koeth’s cyclotron project began in 1995, when he was a sophomore physics student at Rutgers University. During a modern physics lecture by Professor Tom Devlin, Tim learned how a cyclotron uses a magnetic field and radio-frequency electric fields to repeatedly accelerate charged particles. The combination immediately appealed to interests he already had: electronics, high voltage, vacuum technology, radio-frequency systems, radiation and nuclear physics. As a longtime amateur radio operator, RF technology in particular was already familiar territory. Tim’s reaction was essentially: the individual technologies were difficult, but none seemed fundamentally inaccessible—so why not build one?
What followed was an unusually ambitious undergraduate project. Tim began constructing a 12-inch cyclotron in his parents’ basement in New Jersey, largely from surplus, salvaged and donated equipment. Building it required far more than assembling an existing design: the project brought together magnet design and measurement, RF engineering, high voltage, high-vacuum technology, machining, electronics, controls, computer programming and accelerator physics. After several years of development, the machine achieved operation in 1999.
From basement experiment to Rutgers teaching accelerator
In 2000 the cyclotron moved to Rutgers, where the personal project began its transformation into something considerably more significant: a dedicated instructional particle accelerator. By 2001 it was being incorporated into senior-level undergraduate laboratory instruction. The machine eventually became known as the Rutgers 12-Inch Cyclotron and was specifically developed so that students could manipulate the accelerator rather than simply observe a professionally operated machine.
That distinction became central to Tim’s philosophy of accelerator education. Because the cyclotron is small, accessible and deliberately reconfigurable, students can change operating parameters and hardware, diagnose problems and observe accelerator phenomena directly. The program emphasizes experiments involving beam focusing, betatron motion, resonances, magnetic-field configurations, RF and dee voltage, beam diagnostics and other aspects of accelerator operation. In other words, the cyclotron became something of a working laboratory textbook in accelerator physics.
Over the years, more than 100 undergraduate students, along with high-school students and other learners, have participated in the program. Tim’s detailed documentation of the machine also had an impact outside Rutgers: students elsewhere used his work as a model for their own accelerator projects.
The unusual project attracted national attention. Physics Today profiled it in 2004 as “Building a Cyclotron on a Shoestring,” and Make magazine followed with coverage in 2005.
From Rutgers to the national accelerator-education community
The project eventually became intertwined with the United States Particle Accelerator School (USPAS), where Tim has taught accelerator and cyclotron courses.
His USPAS teaching has included Fundamentals of Accelerator Physics at Stony Brook in 2011, Cyclotron Design at Duke in 2013, Cyclotron Design, Operation, and Measurement at Rutgers in 2015, Cyclotron Design at UC Davis in 2017, Radiation & Matter in Accelerator Environments in 2019, and a later online course on practical cyclotron design and construction.
The 2015 USPAS session was particularly important to the project’s evolution: Tim’s own 12-inch machine became the centerpiece of the two-week cyclotron course at Rutgers. Thus, an accelerator that had begun twenty years earlier in his parents’ basement had become laboratory equipment for a national graduate-level accelerator school.
The University of Maryland chapter
Tim came to the University of Maryland in 2009, initially as a postdoctoral researcher. The cyclotron remained in New Jersey for several more years before finally being relocated to UMD in 2016.
At Maryland, the original machine became the nucleus of an even more ambitious educational program. Tim developed a multidisciplinary Accelerator Physics Capstone Design Project, involving students from physics, electrical engineering and materials science. Rather than merely operating the existing accelerator, students began working toward the design and construction of a larger 5-MeV, 19-inch cyclotron. The course deliberately recreates something increasingly uncommon in modern experimental science: students actually design, machine, assemble, troubleshoot and operate major pieces of experimental apparatus themselves.
The original 12-inch machine consequently acquired a second role. It remained a functional accelerator and experimental platform while also becoming a reference machine on which successive generations of students could understand the systems they were designing for the larger cyclotron.
Cyclotrons! and education beyond the laboratory
COVID-19 presented an obvious problem for a curriculum whose entire premise was hands-on laboratory work. Tim responded by attempting to capture the accumulated cyclotron curriculum on video.
The resulting Cyclotrons! series consists initially of nine detailed instructional episodes, each using the 12-inch accelerator to explain a major subsystem and the physics underlying beam production. Rather than being simply popular-science videos, they were conceived as an extension of the actual accelerator curriculum. USPAS subsequently partnered with the Koeth group and UMD on the material, and the videos became part of USPAS’s online educational resources.
A planned second phase moves beyond simply making and controlling a charged-particle beam toward neutron production and the nuclear experiments that a cyclotron beam can enable.
Research as well as education
Although education has become the defining feature of the machine, it is not merely a demonstration accelerator. Tim has deliberately maintained it as a research-grade, experimentally reconfigurable machine. That makes it particularly useful for experiments where access and flexibility can matter more than beam energy.
The broader Koeth research program now intersects accelerator science with materials under extreme conditions, radiation science, nuclear instrumentation and detector development. His current research interests include the behavior of materials under intense electric fields, radiation and charged-particle bombardment, environments directly relevant to accelerators, nuclear and energy systems and radiation detectors.
That provides a natural future for the cyclotron. Rather than competing with large research accelerators, which would make little sense for a 12-inch machine, its value lies in being small enough to modify and accessible enough to experiment with.
Where the project is going next
Tim plans to push the machine further into the territory where education and useful experimental research overlap. Neutron production is an especially natural direction. A cyclotron-produced charged-particle beam can strike suitable targets to generate neutrons, turning the accelerator into the front end of a much broader nuclear-physics and materials-testing laboratory. Tim’s group already identifies neutron production and nuclear experiments as the subject of the next Cyclotrons! educational series.
That opens possibilities for neutron detection and spectroscopy, detector development, neutron-transport experiments, materials characterization, radiation-effects studies and experiments relevant to nuclear energy, fusion systems and radiation environments. It also preserves what has made the project unusual from the beginning: students can participate in the entire experimental chain: accelerator physics, vacuum and RF systems, beam production, target interactions, radiation detection, data acquisition and interpretation.
And the larger student-built cyclotron potentially carries that philosophy forward into another generation of hardware.
The significance of the project
Seen across its full history, Tim’s cyclotron is therefore not simply a machine he built as a student.
It began in 1995 as an audacious undergraduate experiment in his parents’ basement, produced an operating accelerator by 1999, became a Rutgers instructional accelerator around 2000, evolved into a nationally recognized model for hands-on accelerator education, served as the laboratory centerpiece of a USPAS graduate course, moved to Maryland in 2016, became the foundation of a multidisciplinary accelerator capstone program, and ultimately became the physical centerpiece of an online accelerator curriculum available far beyond UMD.
Thirty-one years after that Rutgers lecture, the most remarkable aspect may be its continuity. The same basic machine that Tim conceived as a twenty-year-old undergraduate has followed him through his development from student and amateur accelerator builder to accelerator physicist, researcher and professor…and along the way has become a vehicle for successive generations of students to learn accelerator science by actually building and operating an accelerator.
The Cyclotron in the Press
Over more than two decades, Tim’s cyclotron has received coverage ranging from Rutgers publications to Physics Today, Make, Symmetry, The Washington Post, and most recently IITM Shaastra. Taken together, these articles document the project’s evolution from an unusual undergraduate experiment into an influential model for hands-on accelerator education.
Rutgers Focus — “By undergraduates, for undergraduates” (2003)
The earliest substantial coverage appeared in Rutgers Focus on April 28, 2003. The article described how Tim Koeth and Stuart Hanebuth began building a cyclotron as Rutgers physics sophomores in 1995, intending from the outset to create an accelerator that students could use for research.
Built largely from surplus, donated, and scavenged equipment, the machine entered Rutgers’ Modern Physics Laboratory in 2001. Subsequent undergraduates didn’t merely operate it—they modeled particle trajectories, redesigned magnet pole pieces, installed components, and continued improving the accelerator. It was also used through QuarkNet to introduce New Jersey high-school physics teachers to accelerator science.
A second Rutgers Focus article covered Tim’s selection as one of 50 U.S. students to attend the Lindau Nobel Laureate Meeting in Germany. While there, Tim met Physics Today‘s Stephen Benka and discussed the cyclotron with him. That encounter ultimately helped bring the project to the attention of the national physics press.
Physics Today — “Building a Cyclotron on a Shoestring” (2004)
Building a Cyclotron on a Shoestring
Physics Today provided the first major national account of the project. It recounted the cyclotron’s origins, the achievement of the first proton beam in 1999, and the subsequent construction of the more capable 12-inch machine using a massive surplus magnet obtained from Argonne National Laboratory.
The article emphasized both the ingenuity involved in constructing an accelerator inexpensively and the extraordinary breadth of knowledge required—RF electronics, high voltage, vacuum systems, machining, controls, and accelerator physics. It also documented the machine’s transition from Tim and Stuart’s project into an established Rutgers teaching accelerator.
Make Magazine — “Smashing Success” (2005)
Make introduced the cyclotron to the emerging maker community. Its “Smashing Success” feature presented Tim and Stuart’s work as an unusually ambitious example of DIY experimental science: a genuine particle accelerator constructed through surplus equipment, custom fabrication, technical knowledge, and persistence.
The article also emphasized an important distinction: the cyclotron wasn’t simply built to demonstrate that it could be done. It became permanent Rutgers physics equipment used by students for accelerator experiments and research.
Symmetry — “The Do-It-Yourself Cyclotron” (2010)
By 2010, Symmetry placed Tim’s machine within the remarkably small international community of people who had built their own cyclotrons. The article grew out of the first Small Cyclotron Conference, for which Tim served as lead organizer.
The story showed that the Rutgers accelerator had developed a life beyond its original builders. Successive students were working with the machine, and some were being drawn into accelerator physics as a career. Tim had progressed from being someone who built a cyclotron to becoming an organizer, mentor, and resource within the small-cyclotron community.
The Washington Post Magazine — UMD’s next generation (2016)
The Washington Post cyclotron feature
The Washington Post shifted the focus from the accelerator Tim built to the students Tim was teaching to build accelerators themselves.
At the University of Maryland, Tim was mentoring students undertaking the construction of a larger cyclotron. The article highlighted his philosophy that some students learn science most effectively by designing, machining, assembling, troubleshooting, and ultimately operating real experimental equipment. In effect, Tim was recreating for another generation the experience that had shaped his own education at Rutgers.
Terp Magazine — “Beam Team” (2017)
UMD’s Terp magazine continued this theme with “Beam Team.” By then, Tim’s original cyclotron had moved to Maryland and become part of a broader accelerator-education program.
The machine’s modest size was actually an educational advantage: unlike a major research accelerator, students could work directly on its subsystems, change its configuration, diagnose problems, and understand how an accelerator functions as a complete physical system. The cyclotron had effectively become a platform for Tim’s broader philosophy of learning experimental science by building and doing.
IITM Shaastra — “When Small Is Big” (2026)
The most recent chapter comes from India. In July 2026, IITM Shaastra, published by IIT Madras, explicitly traced the origins of an Indian tabletop-cyclotron effort back to Tim’s Rutgers project.
Former IIT Madras Physics Department head Pranawachandra Deshmukh became interested in small cyclotrons after the Cancer Institute in Chennai approached IIT Madras for help in 2007. While researching the subject, Deshmukh encountered the story of Tim’s student-built Rutgers cyclotron. The article states directly that Tim’s machine demonstrated an inexpensive way to teach accelerator physics and that Deshmukh subsequently “set himself on the path of building a tabletop cyclotron.”
The connection went considerably beyond inspiration from an article. Deshmukh visited Tim and the Rutgers cyclotron during 2008–2010, visits that he says solidified his belief that a student-built cyclotron was feasible.
Nearly two decades after Deshmukh first conceived the project, researchers at India’s Inter-University Accelerator Centre (IUAC) began constructing a prototype in 2024. Tim participated directly: the team arranged its twice-weekly online meetings late enough for him to join from Maryland, and Tim supplied drawings and design details from which the Indian group developed its own 2D and 3D models.
By 2026, the IUAC group had produced a prototype suitable for college experiments and was developing a subsequent version, with longer-term ambitions extending to isotope production for cancer diagnostics and therapy and potentially proton-beam applications.
This latest article therefore provides a particularly significant endpoint to the press history. A cyclotron conceived as a Rutgers student project three decades earlier became an explicit inspiration—and a source of technical knowledge—for a new cyclotron program on the other side of the world.
The larger story
The press coverage documents a clear progression:
Rutgers Focus (2003) introduced a cyclotron built by undergraduates, for undergraduates. Physics Today (2004) recognized the technical achievement of building a serious accelerator “on a shoestring.” Make (2005) presented it as advanced DIY science. Symmetry (2010) showed Tim becoming a leader within the small-cyclotron community. The Washington Post (2016) and Terp (2017) documented his transformation of that experience into an educational program at Maryland. Finally, IITM Shaastra (2026) demonstrated the project’s international influence, tracing India’s tabletop-cyclotron effort directly back to Tim’s Rutgers machine and documenting his continuing technical involvement.
Scholarship with the Cyclotron
“The Construction and Operation of a Nine Inch Cyclotron” (1999) is essentially the original technical account of the project. Tim describes the construction of the precursor to the later 12-inch machine, including magnet considerations, RF acceleration and the practical engineering required to produce beam. The nine-inch version successfully produced roughly 500-keV protons and served as the proof-of-concept for scaling the system to the 12-inch magnet and approximately 1-MeV regime.
“Rutgers 12 Inch Cyclotron Ion Source Studies: Part I” (2006) addresses one of the practical limitations encountered as the accelerator matured: the internal ion source. Tim analyzed the source geometry and electric fields using the Los Alamos Poisson/Superfish finite-element codes, connecting empirical operating behavior with accelerator modeling. This is characteristic of the project’s evolution—the machine was no longer merely being made to operate; individual subsystems were being quantitatively studied and optimized.
“Observation of Betatron Motion in the Rutgers 12-Inch Cyclotron” (2006), with Stuart Hanebuth, William Schneider and Daniel Hoffman, documents an important accelerator-physics milestone. After improvements including weak-focusing pole tips, an upgraded ion source, increased RF capability and beam diagnostics, the group observed vertical oscillations of the proton beam as a function of radius. Those oscillations were direct evidence of betatron motion and experimentally demonstrated that the magnetic-field shaping was providing the expected vertical focusing.
“Report on the 12-Inch Cyclotron Magnet Study: Measurements, Modeling, and Future Plans” (2010) is a more systematic engineering study of the cyclotron magnet. Tim describes efforts by himself, staff and students to measure and model the magnetic field and improve beam intensity. The work included detailed field measurements, magnetic modeling and investigation of pole-tip configurations. It also illustrates the educational model that developed around the machine: students were assigned genuine accelerator R&D problems whose solutions were subsequently incorporated into the operating cyclotron.
“Field Mapping in Cyclotron Magnets” (2015), by Tim Koeth and James Krutzler, is a practical technical study of methods for measuring and analyzing cyclotron magnetic fields. Drawing on experience with the Rutgers 12-Inch Cyclotron, the paper describes a computer-controlled two-dimensional field-mapping system and its application to four interchangeable pole-tip configurations, including weak-focusing, radial-sector, and spiral-sector fields. The authors show how field maps can be used to characterize average field, field errors, magnetic flutter, and focusing properties, providing both a tool for understanding the Rutgers cyclotron and a practical methodology applicable to other accelerator magnets.
The 2013 International Cyclotron Conference papers
The project’s scholarly visibility increased considerably at the 20th International Conference on Cyclotrons and Their Applications in Vancouver in 2013. Tim and his collaborators presented several papers on the Rutgers machine.
“The Rutgers 12-Inch Cyclotron: Dedicated to Training Through Research and Development” explains the overall philosophy of the facility. The 1.2-MeV proton cyclotron had evolved from the personal project begun by Rutgers undergraduates in 1995 into an accelerator incorporated into the Rutgers teaching laboratory. Rather than treating the machine as a sealed instructional apparatus, students designed and constructed accelerator components themselves. The paper therefore presents the cyclotron simultaneously as an accelerator and as an R&D training environment.
“Beam Physics Demonstrations with the Rutgers 12-Inch Cyclotron” focuses more heavily on the actual accelerator physics that can be demonstrated with the machine. Tim describes experiments involving axial and radial betatron motion, destructive resonances, weak focusing, azimuthally varying field (AVF) focusing, RF/DEE-voltage effects and beam diagnostics. An important feature is the machine’s reconfigurability: experiments can be conceived, implemented and measured on a timescale appropriate to an academic semester.
Two additional 2013 proceedings papers involved Tim as a coauthor: “The Rutgers Cyclotron: Placing Students’ Careers on Target”, led by Kiersten Ruisard, examined the educational and career impact of the program, while “A Novel Optical Method for Measuring Beam Phase and Width in the Rutgers 12-Inch Cyclotron,” led by Julia Gonski, described student-developed beam diagnostics.
“Betatron Tune Characterization of the Rutgers 12-Inch Cyclotron for Different Magnetic Poles Configurations,” by Cédric Hernalsteens, Brian Beaudoin, Timothy W. Koeth, Michelle Miller, Timothy Ponter, Kiersten Ruisard, and Robin Tesse. It was presented at the 13th International Particle Accelerator Conference (IPAC 2022) and published in the JACoW proceedings, pp. 136–139, DOI 10.18429/JACoW-IPAC2022-MOPOST033.
The major scholarly synthesis
The most complete scholarly treatment is Tim’s invited paper “Undergraduate Education with the Rutgers 12-Inch Cyclotron,” presented at CAARI 2014 and published in Physics Procedia 66 (2015), pp. 622–631.
This paper effectively synthesizes the preceding decade of work. It presents the cyclotron as a research-grade accelerator deliberately optimized for undergraduate education rather than simply as a small demonstration machine. Students can operate an actual accelerator, modify it, perform measurements and investigate accelerator phenomena including betatron oscillations, resonances, weak and AVF focusing, RF effects, beam diagnostics and low-energy nuclear reactions.
That distinction is important to understanding Tim’s scholarly contribution. The central idea wasn’t merely “an undergraduate built a cyclotron.” It became an argument that a small, accessible, reconfigurable accelerator can provide meaningful experimental accelerator-physics training that normally requires access to a major accelerator facility.