Looking for info on the Betatron nuclear trigger from the early 1950s

A colleague (PhD Physics, no weapons experience) asked me (MA Physics, with DoD work experience) about the Betatron nuclear trigger in the early Fifties. I know it used a toroidal accelerator to produce an electron beam impacting a Beryllium target, but I don't remember (and cannot find) any further details. Any ideas/sources?

I found these two:​

Excitation Function for the Photodisintegration of Beryllium​

R. Nathans and J. Halpern​

Phys. Rev. 92, 940 – Published 15 November 1953​

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Detection of Fissioning Materials Using a Neutron Source Based on a Compact Betatron​

• V. M. Golovkov,
• V. L. Chakhlov &
• M. M. Shtein

Atomic Energy volume 96, pages 127–132 (2004)Cite this article

Abstract​

The possibility of using a neutron source based on a 10 MeV compact betatron and 1 kg heavy water or 3.3 kg beryllium in the betratron bremsstrahlung beam is investigated. The 235U detection limit in a 358 mm in diameter and 782 mm high container with probability 0.997 in an experimental apparatus with one epithermal-neutron detector is 40 mg with exposure 10 min. Increasing the mass of the neutron target to 10 kg heavy water and the number of neutron counters to 25 could decrease the 235U detection limit to 3 mg. A neutron detector based on a compact betatron can be expected to give 235U detection sensitivity 10–8 g/g.
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Meir Achuz said:

Detection of Fissioning Materials Using a Neutron Source Based on a Compact Betatron​

• V. M. Golovkov,
• V. L. Chakhlov &
• M. M. Shtein

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Thank you! From the cited "REFERENCES", I was able to locate the paper online:
https://www.researchgate.net/profil...eutron-source-based-on-a-compact-betatron.pdf