--- title: "MDDC-1045 — R.F. System for Frequency Modulated Cyclotron · Cyclotron Info" canonical: https://cyclotroninfo.com/library/classics/mddc-1045/ description: "Hosted public-domain copy of the 1946 MDDC-1045 report on the Berkeley 37-inch FM conversion — the RF system of the first synchrocyclotron — with a reading guide." 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/) # R.F. System for Frequency Modulated Cyclotron MacKenzie, K. R., and V. B. Waithman. *R.F. System for Frequency Modulated Cyclotron*, MDDC-1045. University of California Radiation Laboratory. Manuscript August 1, 1946; declassified June 16, 1947; printed by the AEC, Oak Ridge. Record: [DTIC AD-A319179 (archive.org)](https://archive.org/details/DTIC_ADA319179) [Download PDF — 1.1 MB, 12 pages](https://cyclotroninfo.com/classics/mddc-1045.pdf) ## Why this document can be hosted MDDC-1045 belongs to the Manhattan District Declassified series — AEC-published, declassified June 16, 1947, printed and priced (10 cents) at Oak Ridge — and such documents are US Government works, which carry no copyright. Pre-1978 distribution without notice is an independent public-domain basis. The title page states the copy “is reproduced as a project report” whose manuscript was submitted to the Review of Scientific Instruments: what is hosted here is the AEC report, not the 1947 journal article. Verified against the title page; determination made August 2026. The DTIC scan had no text layer; this copy was OCR’d in August 2026 and is searchable. ## Reading guide This eight-page report documents the RF system of the machine that proved synchrocyclotrons work: the Berkeley 37-inch, shimmed in 1946 so its field fell 13% from center to the 18-inch radius to imitate the planned 184-inch, then driven with a frequency-modulated oscillator. Deuterons reached 7.5 MeV on 15 kV of dee voltage — after which “the successful acceleration of deuterons to 7.5 Mev was sufficient basis for converting the 184-inch” (p. 3). Everything in it happens at a scale an amateur recognizes: a one-dee system, 5–6 kW of RF, and commercial triodes. The introduction (pp. 1–2) records a decision worth knowing: electronic frequency modulation was tried first and produced 10% frequency swings — but only at 500 V of dee voltage per kilovolt of modulator, so mechanical modulation by rotary capacitor won. The rotary-capacitor arrangement (pp. 2–3) sits outside the magnetic field on its own vacuum system, coupled through a 14-foot transmission line operating in the half-wave mode; minimum capacitor capacity is matched to the 300 µµf dee capacity so the capacitor never sees more voltage than the dee. The oscillator section (pp. 3–5) compares three grounded-grid builds on the same circuit — four 304TL triodes in parallel, an 889, and the 3X2500A3 that the authors say would have made the others unnecessary — with the practical details: zircon replacing a heat-cracked porcelain dee insulator, a housing of copper sheet nailed to a wood frame, sponge-rubber-backed joints, a tuning vane giving ±6% of frequency trim, and the finding that all-steel rotary condenser surfaces were tolerable at 10 Mc but had to be copper-plated at 20 Mc. The phase-correction analysis (pp. 7–8) is the report’s most transferable engineering: a grounded-grid oscillator picks up 20° or more of plate-to-filament phase shift, worked here as a vector diagram and corrected by choosing the filament bypass capacitor — the same 220 µµf capacitor doubles as the correction element. The closing pages cover amplitude modulation over the FM cycle and the discharge phenomena that appear when an RF cavity, a magnetic field, and 10⁻⁵ mm of gas share a volume. Page references are the report’s printed numbers; the hosted PDF carries two DTIC cover pages in front. ## Design rules extracted from this document [13 Design Guide rules](https://cyclotroninfo.com/design-guide/?q=MDDC-1045) cite MDDC-1045 — a remarkable yield for twelve pages, nearly all of it oscillator and discharge practice at small-machine scale. Representative examples: - [dg-671](https://cyclotroninfo.com/design-guide/#dg-671) — dee-voltage-per-watt benchmark: 15 kV at 10 Mc from 6 kW input - [dg-676](https://cyclotroninfo.com/design-guide/#dg-676) — keep the grid-leak RC below a tenth of the resonant system’s time constant - [dg-679](https://cyclotroninfo.com/design-guide/#dg-679) — a series emission limiter in the oscillator HV lead - [dg-680](https://cyclotroninfo.com/design-guide/#dg-680) — the sub-500 V electron-oscillation discharge and its bias cure - [dg-682](https://cyclotroninfo.com/design-guide/#dg-682) — a tickler oscillator to drive the dee through the low-voltage region Used by the [dee RF coupling](https://cyclotroninfo.com/learn/dee-coupling/) deep dive. > **Page provenance.** Last reviewed: 12 August 2026 · Hosted copy verified against the archive.org DTIC scan; rights review August 2026 · [Methodology](https://cyclotroninfo.com/about/methodology/) · [Report a correction](mailto:info@cyclotroninfo.com?subject=Correction%3A%20MDDC-1045%20%E2%80%94%20R.F.%20System%20for%20Frequency%20Modulated%20Cyclotron) · [Changelog](https://cyclotroninfo.com/changelog/)