Hi Allan. Many of the sources are in German, or obscure previously classified WW2 archives. I uploaded the two page NARA report G-344 by Dr. Jessie Beams of the Manhattan project to Flickr for you.
(Page #1): https://flic.kr/p/MgFfmF
(Page #2): https://flic.kr/p/N6TCgP
If you read these you will learn that Nazi Germany developed three successful different centrifuge designs during WW2.
Bagge’s Isotope Sluice which literally spun four buckets filled with Uranium hexafluoride and sluiced off the top. This could enrich 250 grams of Uranium 235 by 7% per day/per machine.
The Anschutz Mark IIIA / Hellage Mark IIIB which is analogous to Uranium centrifuges we know today. These were arranged in cascades and I know of two underground Uranium enrichment plants operating in Nazi Germany during 1944 under the direction of Dr Paul Harteck.
The Krupp thermal centrifuge, copied by the Soviets and today known as the Zippe Centrifuge, using heat and centrifugal force to “boil” U235 to the top.
Secret recordings of Nazi nuclear scientists held at Farm Hall Cambridgeshire in August 1945 revealed they mentioned some of these efforts. The Nazis also had developed four 18 MeV particle accelerators and were building another 32 MeV particle accelerator.
A “MAGIC” intercept of a signal from the Japanese Embassy, which can be found in US archives as “RG0457 National Security Agency / Central Security Service, Entry #A1- 9004 Japanese Army Attache Translations SRA 14,200 thru 15,000 Aug 25 1941 — Aug 1945 Stockholm to Tokyo, №232.9 December 1944,” which the NSA declassified in October 1978. The signal referred to the Atomic bomb as Genshi Hakai Dan,” with a warhead weighing 5 kilograms stating:
“The German atom-splitting device is the Neuman disintegrator. Enormous energy is directed into the central part of the atom and this generates an atomic pressure of several tens of thousands of tons per square inch. This device can split the relatively unstable atoms of such elements as Uranium. Moreover, it brings into being a store of explosive atomic energy…. That is, a bomb deriving its force from the release of atomic energy."
Hitler himself was noted in the so called table talks referring to a Uranium bomb with to Romania’s wartime leader Marshal Antonescu on 5th August 1944. By September 1944, Antonescu had been toppled by a coup, was under arrest and was being interrogated by Soviet Military Intelligence before his execution. The Table Talks report what Hitler said. Ribbentrop, Hitler and Keitel met with Antonescu at the Wolf’s Lair HQ in Poland 5th August 1944. Antonescu quoted Hitler. He said Hitler described Germany’s latest work on
“…new explosives, whose development was already advanced to the experimental stage. Hitler confided his view that the jump from modern explosives to this one was the biggest since gunpowder.”
Hitler was aware Antonescu was in talks with Opposition forces in Romania who also had direct contact with London. Hitler’s aim was to convey a threat to London of his nuclear capability. By this date the V-2 still had not seen its operational debut against London. Hitler however expressed caution about deployment of the Atomic bomb until Germany could protect itself from counter attack with similar weapons.
“Then Hitler explained the difficulty with all new weapons was the same. He had ordered therefore that no new weapon was to be employed until Germany had herself developed measures counter to it. For this reason Hitler explained, a new type of mine they had developed could still not be employed. The Fuhrer added Germany had four secret weapons. Of these the V-1 flying bomb and the V-2 rocket were only two. He said another of these weapons for example, has such colossal force that all human life is destroyed within three to four kilometres of the point of impact.”
The Anthrax threat by Churchill was referred to in the secret Farm Hall recordings and later after the war confirmed in letters by Dr Paul Harteck
The history of the Heinkel He277 is well known but ask me if you need elaboration?
The He-277 was developed in response to a demand by Hitler at a 1943 conference of aircraft designers where he demanded a bomber capable of bombing London by day and night. Hienkel responded with an ultra high altitude design developed from the He-177 with new wings and a pressurized cockpit.