Book contents
- Frontmatter
- Contents
- List of Illustrations
- Preface
- 1 Introduction
- 2 Early Research on Fission: 1933–1943
- 3 The Early Materials Program: 1933–1943
- 4 Setting Up Project Y: June 1942 to March 1943
- 5 Research in the First Months of Project Y: April to September 1943
- 6 Creating a Wartime Community: September 1943 to August 1944
- 7 The Gun Weapon: September 1943 to August 1944
- 8 The Implosion Program Accelerates: September 1943 to July 1944
- 9 New Hopes for the Implosion Weapon: September 1943 to July 1944
- 10 The Nuclear Properties of a Fission Weapon: September 1943 to July 1944
- 11 Uranium and Plutonium: Early 1943 to August 1944
- 12 The Discovery of Spontaneous Fission in Plutonium and the Reorganization of Los Alamos
- 13 Building the Uranium Bomb: August 1944 to July 1945
- 14 Exploring the Plutonium Implosion Weapon: August 1944 to February 1945
- 15 Finding the Implosion Design: August 1944 to February 1945
- 16 Building the Implosion Gadget: March 1945 to July 1945
- 17 Critical Assemblies and Nuclear Physics: August 1944 to July 1945
- 18 The Test at Trinity: January 1944 to July 1945
- 19 Delivery: June 1943 to August 1945
- Epilogue
- 20 The Legacy of Los Alamos
- Notes
- Name Index
- Subject Index
17 - Critical Assemblies and Nuclear Physics: August 1944 to July 1945
Published online by Cambridge University Press: 31 March 2010
- Frontmatter
- Contents
- List of Illustrations
- Preface
- 1 Introduction
- 2 Early Research on Fission: 1933–1943
- 3 The Early Materials Program: 1933–1943
- 4 Setting Up Project Y: June 1942 to March 1943
- 5 Research in the First Months of Project Y: April to September 1943
- 6 Creating a Wartime Community: September 1943 to August 1944
- 7 The Gun Weapon: September 1943 to August 1944
- 8 The Implosion Program Accelerates: September 1943 to July 1944
- 9 New Hopes for the Implosion Weapon: September 1943 to July 1944
- 10 The Nuclear Properties of a Fission Weapon: September 1943 to July 1944
- 11 Uranium and Plutonium: Early 1943 to August 1944
- 12 The Discovery of Spontaneous Fission in Plutonium and the Reorganization of Los Alamos
- 13 Building the Uranium Bomb: August 1944 to July 1945
- 14 Exploring the Plutonium Implosion Weapon: August 1944 to February 1945
- 15 Finding the Implosion Design: August 1944 to February 1945
- 16 Building the Implosion Gadget: March 1945 to July 1945
- 17 Critical Assemblies and Nuclear Physics: August 1944 to July 1945
- 18 The Test at Trinity: January 1944 to July 1945
- 19 Delivery: June 1943 to August 1945
- Epilogue
- 20 The Legacy of Los Alamos
- Notes
- Name Index
- Subject Index
Summary
Through mid-1945 the Los Alamos Laboratory continued to pursue a strategy of overlapping approaches in its programs to test and refine critical mass and perform other calculations affecting bomb design and deployment. These activities included work in R-, G-, and F-Divisions with critical and subcritical assemblies, nuclear constant and other measurements by R-Division, and theoretical fine-tuning by T-Division, along with a backburner effort on the Super in F-Division. In addition, new projects were begun after mid-1944, among them a series of tests on critical assembly by G-Division, work on a high-power Water Boiler (nicknamed Hypo) to be used by F-Division for critical mass measurements, and the development of a spectacular assembly suggested by Frisch, which, unlike other experimental assemblies, went critical with prompt neutrons alone.
Besides diverting resources from implosion development and preparations for the Trinity test, these projects were sometimes quite dangerous and often risked the loss of precious fissionable materials. Nonetheless, they were mounted with considerable enthusiasm, and characteristically subjected to empirical testing. As had been the case in early nuclear constant measurements by P-Division and in the metallurgy program, researchers attempted to compensate for the lack of 239Pu by working with 239U, in hopes that the results could be extrapolated to reveal the properties of the heavier element.
Continuation of the Critical Mass Studies
Short of the real explosion, there was no way to determine precisely the extent of supercriticality achieved in the gun- or implosion-assembled bomb, or to measure other chain reaction properties, such as the neutron population growth rate.
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- Information
- Critical AssemblyA Technical History of Los Alamos during the Oppenheimer Years, 1943–1945, pp. 335 - 349Publisher: Cambridge University PressPrint publication year: 1993