--- title: "The Rochester 27-inch — five hosted reports · Cyclotron Info" canonical: https://cyclotroninfo.com/library/classics/rochester-27-inch/ description: "Five hosted public-domain reports from one 27-inch university cyclotron: starting the oscillator past its multipactor band, a hooded arc ion source, an external beam focusing and analyzing system, a broad-range spectrograph, and a fast-neutron time-of-flight system." generated: 2026-11-12 note: "Markdown rendering of the canonical HTML page, generated at build for AI assistants and text tools. Figures and interactive elements are described, not reproduced. On Design Guide rules the source quote, this site's paraphrase and this site's editorial note are labelled separately and must not be conflated." licence: "Datasets CC BY 4.0, census snapshot CC BY-NC 4.0 (https://cyclotroninfo.com/data/); cite as Cyclotron Info, cyclotroninfo.com" --- [Construction Classics](https://cyclotroninfo.com/library/classics/) # The Rochester 27-inch Most of this site about building a cyclotron ends at first beam. These five come from **one 27-inch machine in a university physics department** across eight years, and between them they cover both halves of its life: getting the thing to run, and then getting work out of it. Two are machine reports — starting an oscillator that will not start, and making more ions from less filament. Three are what came after — getting the beam out and analysed, building a spectrograph around it, timing neutrons with it. The pairing is the point. The same laboratory that published a broad-range spectrograph also had to publish a note about a spark gap, because the machine would not come up to voltage. Very few institutions wrote the second kind down. ## The documents - **The Sparker, a Device to Overcome the Multipactor Difficulty in Starting the Oscillator of a Cyclotron** Fulbright, H. W. The Sparker, a Device to Overcome the Multipactor Difficulty in Starting the Oscillator of a Cyclotron, NYO-9359. Department of Physics and Astronomy, University of Rochester, under AEC contract AT(30-1)-875, 3 January 1961. Record: [UNT Digital Library](https://digital.library.unt.edu/ark:/67531/metadc1463590/) · [Download PDF — 1.6 MB, 8 pages](https://cyclotroninfo.com/classics/nyo-9359.pdf) - **A Hooded Arc Ion Source with a Magnetic Mirror Feature** Fulbright, H. W. A Hooded Arc Ion Source with a Magnetic Mirror Feature, NYO-9358. Department of Physics and Astronomy, University of Rochester, under AEC contract AT(30-1)-875, 1 January 1962. Record: [UNT Digital Library](https://digital.library.unt.edu/ark:/67531/metadc1463589/) · [Download PDF — 1.3 MB, 5 pages](https://cyclotroninfo.com/classics/nyo-9358.pdf) - **The Design of a Focusing and Analyzing System for the 27" Cyclotron Beam** Bromley, D. A., and J. A. Bruner. The Design of a Focusing and Analyzing System for the 27" Cyclotron Beam, NYO-3823. Physics Department, University of Rochester, under AEC contract AT(30-1)-875, 1954. Record: [OSTI 4405665](https://www.osti.gov/biblio/4405665) · [Download PDF — 3.3 MB, 53 pages](https://cyclotroninfo.com/classics/nyo-3823.pdf) - **Broad Range Spectrograph for Use with the Rochester 27" Cyclotron** Alford, W. Parker, O. M. Bilaniuk, and R. A. Hawrylak. Broad Range Spectrograph for Use with the Rochester 27" Cyclotron, NYO-9683. Department of Physics and Astronomy, University of Rochester, 1961. Record: [OSTI 4821529](https://www.osti.gov/biblio/4821529) · [Download PDF — 3.6 MB, 27 pages](https://cyclotroninfo.com/classics/nyo-9683.pdf) - **A Fast Neutron Time of Flight System for Use with Cyclotrons** Fulbright, H. W., J. W. Verba, V. K. Deshpande, and A. K. Hamann. A Fast Neutron Time of Flight System for Use with Cyclotrons, NYO-9360. Department of Physics and Astronomy, University of Rochester, 1962. Record: [OSTI 4795540](https://www.osti.gov/biblio/4795540) · [Download PDF — 1.2 MB, 35 pages](https://cyclotroninfo.com/classics/nyo-9360.pdf) ## Why these documents can be hosted All three are University of Rochester reports in the AEC’s **NYO-** series (New York Operations Office), NYO-3823 under contract AT(30-1)-875, each carrying the standard US Government sponsorship disclaimer. AEC contractor reports are treated as US Government works and carry no copyright, and pre-1978 distribution without a copyright notice is an independent basis. Two of the three carry something better than inference. NYO-3823 and NYO-9360 are stamped **“This document is PUBLICLY RELEASABLE”** with an authorizing officer — an explicit release determination on the document itself rather than a rights argument built from its series and date. Checks recorded: the “IEEE” strings a text search finds in NYO-3823 are OCR garbage from its figure regions, not a publisher marking; the “thesis” and “Proceedings of” hits in NYO-3823 and NYO-9683 are reference-list entries; and NYO-9360’s “to be published in Nuclear Instruments and Methods” describes a privately circulated monograph it cites, not this report. Verified by reading the scans; determinations made August 2026. ## A small machine is a beamline problem The Rochester 27-inch is the size class this site is about, and these reports show what a department does with one over a decade. That trajectory is worth seeing whole, because the [builds census](https://cyclotroninfo.com/builds/) records no amateur machine with a documented external beam (its one extraction claim, Seoul National University's 1959 graduate build, left no technical record) — so the amateur record stops precisely where this one starts. **NYO-3823 (1954)** is 53 pages on getting the beam out and making it useful: a focusing and analyzing system for the extracted beam. It is the longest of the three and the most directly relevant to a builder who has beam inside a chamber and wants it somewhere else. Pair it with the [extraction hardware](https://cyclotroninfo.com/library/classics/extraction-hardware/) cluster, which covers getting the beam past the septum; this covers what happens after. **NYO-9683 (1961)** is a broad-range spectrograph designed around the machine — an instrument sized to a specific small cyclotron rather than a general design. Instrument papers rarely state the constraints their host machine imposed; this one has to. **NYO-9360 (1962)** is a fast-neutron time-of-flight system, and it is the most transferable of the three in one specific way: *timing*. A time-of-flight measurement needs a start signal referenced to the accelerating RF, which makes it a diagnostic of the machine as much as of the reaction. Its title says “for use with cyclotrons” in general, not just this one. ## What these are not None of the three is a construction report. They will not tell you how the 27-inch was built, and the machine itself is documented elsewhere — Rochester’s 8 MeV variable-energy cyclotron report NYO-6541 remains in the [queue](https://cyclotroninfo.com/library/classics/#queue). Read these for the layer above the machine: what external beams, spectrographs and timing systems demand of a small cyclotron, which is often how a builder discovers a requirement they should have designed for. ## Design rules extracted from these documents **53 Design Guide rules** come from these reports. Representative examples: - [dg-965](https://cyclotroninfo.com/design-guide/#dg-965) — architect an external beamline as condenser → shielded slit → analyzer - [dg-966](https://cyclotroninfo.com/design-guide/#dg-966) — put the beam-defining slit inside the shield wall — the slits intercept most of the beam - [dg-967](https://cyclotroninfo.com/design-guide/#dg-967) — prefer a strong-focusing quadrupole pair over a sector magnet: about ten times less space - [dg-970](https://cyclotroninfo.com/design-guide/#dg-970) — hyperbolic quadrupole pole profiles are not worth precision machining at this scale - [dg-988](https://cyclotroninfo.com/design-guide/#dg-988) — a cyclotron needs no beam sweeper for time-of-flight — the beam is already RF-bunched - [dg-989](https://cyclotroninfo.com/design-guide/#dg-989) — derive the timing reference from the oscillator, not from a beam-intercepting pickup - [dg-993](https://cyclotroninfo.com/design-guide/#dg-993) — time-resolution budget honesty: 2 ns FWHM at best, 2–3.5 ns typically - [dg-1276](https://cyclotroninfo.com/design-guide/#dg-1276) — a third multipactor cure: shock-excite the dee past the top of the loading band - [dg-1280](https://cyclotroninfo.com/design-guide/#dg-1280) — the decay envelope of a ringing dee maps the multipactor band edges - [dg-1284](https://cyclotroninfo.com/design-guide/#dg-1284) — a passive magnetic mirror from a 1/8-inch steel bearing ball at the top of the arc - [dg-1287](https://cyclotroninfo.com/design-guide/#dg-1287) — filament life scales strongly with the emission the arc demands of it Used by the [beam measurement](https://cyclotroninfo.com/learn/beam-measurement/) and [beam extraction](https://cyclotroninfo.com/learn/beam-extraction/) deep dives. > **Page provenance.** Last reviewed: 17 August 2026 · Hosted copies verified against the OSTI originals; rights review August 2026 · [Methodology](https://cyclotroninfo.com/about/methodology/) · [Report a correction](mailto:info@cyclotroninfo.com?subject=Correction%3A%20The%20Rochester%2027-inch%20%E2%80%94%20five%20hosted%20reports) · [Changelog](https://cyclotroninfo.com/changelog/)