The 184-inch Commissioning Papers, 1946–47
Six technical memoranda from the University of California Radiation Laboratory, written during the Berkeley 184-inch synchrocyclotron’s first year of operation (first beam November 1946; manuscripts February–June 1947) and published by the AEC in the Manhattan District Declassified (MDDC) series. Hosted here as six separate PDFs, cited and downloadable below.
Scans: Internet Archive (University of Florida library copies), e.g. MDDC-1092 (archive.org)
Why these documents can be hosted
All six are MDDC-series documents: each title page carries “United States Atomic Energy Commission,” the AEC’s reproduction-inquiries text, and printed manuscript and declassification dates (May–July 1947). Manhattan District declassified documents are US Government works, which carry no copyright; pre-1978 distribution without notice stands as an independent public-domain basis. Verified against each title page; determination made August 2026.
Reading guide — one problem, six memos
Commissioning logs are the rarest survivors of the construction era: final reports get archived, but the week-by-week record of a machine not yet working usually dies in a filing cabinet. These memos are that record for the first synchrocyclotron, and five of the six orbit a single problem. The 184-inch was designed to accelerate to the 85-inch radius, where the field index n reaches 1. The beam vanished at 82 inches.
Read MDDC-984 first. The theory group had predicted that at n = 0.2 the coupling between radial and vertical oscillations would dump radial amplitude into vertical motion and throw the beam into the dee; the memo tests this with U-shaped copper targets of varying slot width, bombarded one at a time and radioautographed. The films show the beam spreading vertically at 81½ inches — “this agrees quite closely with the point at which n = 0.2 from magnetic measurements” — and the autograph prints are reproduced in the memo. MDDC-1092 is the synthesis, written four months later: the resonance mechanism with the energy-transfer arithmetic (vertical amplitude can reach double the radial), plus a second discovery — synchroscope traces of the circulating beam showed each FM pulse built of minor pulses, explained quantitatively as precession of the orbit centers and phase oscillation. MDDC-987 supplies the confirming experiment for that explanation: a second probe 155° around the tank, with the pip pattern handing off from one probe to the other as the auxiliary probe moves inward — camera failures noted as candidly as results. MDDC-1051 records an attempted cure, a 60 kV DC vertical deflector at the 81-inch radius meant to push the spreading beam into a deflection channel: it held voltage, probably moved the beam once, sparked to its 0.002-inch copper foil, and warped it — “not suitable for this job.” MDDC-982 measures what bombardment did to the probe hardware, mapping 13–21 mR/hr peaks across the probe head with a collimated counter behind lead bricks: early operational health physics on paper. MDDC-964, the outlier, is a one-page capacitance measurement of the oscillator plate circuit — recorded partly because Harvard’s cyclotron engineer asked, and partly “for the records.”
For a builder, the cluster models the commissioning craft itself: instrument the machine (probes, synchroscope, film), trust theory enough to design the decisive experiment, write down the failures, and measure the activation before handling the hardware. Each memo is two to eight pages; the scans carry rough archive.org OCR layers, and page counts below include the AEC covers.
The six memoranda
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184-inch Cyclotron Vertical Beam Oscillations in the Region of 82-inch Radius
The C-target radioautograph experiment that located the beam loss at the n = 0.2 resonance.
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184 Cyclotron: Synchroscope Beam Pictures on Two Probes
Two-probe synchroscope photographs proving the beam-current "pips" are precession.
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184" Cyclotron: Vertical D.C. Electrostatic Deflector
A 60 kV vertical deflector trial at the 81-inch radius, reported failures included.
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184" Cyclotron: Oscillator Capacitance Measurements
Bridge measurements of the oscillator plate-to-ground capacitance, taken for the record.
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184" Cyclotron: Radiation Measurement of Breech Load Probe Head
Collimated-counter scan of activation across a bombarded probe head.
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Some Operating Phenomena Associated with the 184-inch Cyclotron
The synthesis memo: the n = 0.2 loss mechanism and the beam fine structure, with the theory.
Design rules extracted from these documents
13 Design Guide rules cite the six memos — commissioning diagnostics, the n = 0.2 lesson, and extraction-trial hardware limits. Per memo: MDDC-984 2, MDDC-987 2, MDDC-1051 3, MDDC-964 1, MDDC-982 1, MDDC-1092 4. Representative examples:
- dg-686 — if the beam dies short of design radius, check the n = 0.2 radius first (MDDC-984)
- dg-687 — measure the vertical beam envelope with slotted targets and film — zero electronics (MDDC-984)
- dg-688 — multiple pips per beam pulse are precession, proven with a second probe (MDDC-987)
- dg-692 — ~60 kV is a realistic ceiling for an in-tank DC deflector electrode (MDDC-1051)
- dg-694 — the n = 0.2 coupling resonance is deadliest on low-dee-voltage, many-turn machines (MDDC-1092)
Filter the guide by memo: MDDC-984 · MDDC-987 · MDDC-1051 · MDDC-964 · MDDC-982 · MDDC-1092
Used by the beam measurement, beam dynamics, beam extraction, and beam quality deep dives.