A centrifuge is not a cyclotron and as far as I know from reading quite a lot about the Manhattan Project, neither of these was involved in obtaining the U235 for the Hiroshima bomb. The Manhattan Project used gaseous diffusion and calutrons (large mass spectrometers).
Thanks for your feedback wideminded.
The author is supposed to be an expert on the subject whereas I am a housewife. You may wish to provide the author feedback which is located in the comments section at the end of the article here:
http://www.longwarjournal.org/threat-matrix/archives/2009/11/uranium_centrifuges_and_uraniu.php
A cyclotron is used for radiation therapy.