semicircular vacuum chamber: 26 7/16 in x 14 in; 67.15125 cm x 35.56 cm
ion source: 12 1/4 in x 1 5/8 in; 31.115 cm x 4.1275 cm
ion collector: 7 1/4 in x 1 1/8 in; 18.415 cm x 2.8575 cm
United States: Minnesota, Minneapolis
Background on Nier Mass Spectrograph; object id no. 1990.0446.01; catalog no. N-09567
This object consists of the following three components: ion source with oven and acceleration electrode; semicircular glass vacuum chamber; ion collector with two plates. The original device included an electromagnet, which is not part of this accession.
In 1939, as political tensions in Europe increased, American physicists learned of an astonishing discovery: the nucleus of the uranium atom can be split, causing the release of an immense amount of energy. Given the prospects of war, the discovery was just as worrying as it was intellectually exciting. Could the Germans use it to develop an atomic bomb?
The Americans realized that they had to determine whether a bomb was physically possible. Uranium consists mostly of the isotope U-238, with less than 1% of U-235. Theoreticians predicted that it was the nuclei of the rare U-235 isotope that undergo fission, the U-238 being inactive. To test this prediction, it was necessary to separate the two isotopes, but it would be difficult to do this since they are chemically identical.
Alfred Nier, a young physicist at the University of Minnesota, was one of the few people in the world with the expertise to carry out the separation. He used a physical technique that took advantage of the small difference in mass of the two isotopes. To separate and collect small quantities of them, he employed a mass spectrometer technique that he first developed starting in about 1937 for measurement of relative abundance of isotopes throughout the periodic table. (The basic principles of the mass spectrometer are described below.)
As a measure of the great importance of his work, in October 1939, Nier received a letter from eminent physicist Enrico Fermi, then at Columbia University, expressing great interest in whether, and how, the separation was progressing. Motivated by such urging, by late February 1940, Nier was able to produce two tiny samples of separated U-235 and U-238, which he provided to his collaborators at Columbia University, a team headed by John R. Dunning of Columbia. The Dunning team was using the cyclotron at the University in numerous studies to follow up on the news from Europe the year before on the fission of the uranium atom. In March 1940, with the samples provided by Nier, the team used neutrons produced by a proton beam from the cyclotron to show that it was the comparatively rare uranium-235 isotope that was the most readily fissile component, and not the abundant uranium-238.
The fission prediction was verified. The Nier-Dunning group remarked, "These experiments emphasize the importance of uranium isotope separation on a larger scale for the investigation of chain reaction possibilities in uranium" (reference: A.O. Nier et. al., Phys. Rev. 57, 546 (1940)). This proof that U-235 was the fissile uranium isotope opened the way to the intense U.S. efforts under the Manhattan Project to develop an atomic bomb. (For details, see Nier’s reminiscences of mass spectrometry and The Manhattan Project at: http://pubs.acs.org/doi/pdf/10.1021/ed066p385).
The Dunning cyclotron is also in the Modern Physics Collection (object id no. 1978.1074.01; catalog no. N-09130), and it will be presented on the SI collections website in 2015. (Search for “Dunning Cyclotron” at http://collections.si.edu/search/)
The Nier mass spectrometer used to collect samples of U-235 and U-238 (object id no. 1990.0446.01)
Nier designed an apparatus based on the principle of the mass spectrometer, an instrument that he had been using to measure isotopic abundance ratios throughout the entire periodic table. As in most mass spectrometers of the time, his apparatus produced positive ions by the controlled bombardment of a gas (UBr˅4, generated in a tiny oven) by an electron beam. The ions were drawn from the ionizing region and moved into an analyzer, which used an electromagnet for the separation of the various masses. Usually, the ion currents of the separated masses were measured by means of an electrometer tube amplifier, but in this case the ions simply accumulated on two small metal plates set at the appropriate positions. Nier’s mass spectrometer required that the ions move in a semicircular path in a uniform magnetic field. The mass analyzer tube was accordingly mounted between the poles of an electromagnet that weighed two tons, and required a 5 kW generator with a stabilized output voltage to power it. (The magnet and generator were not collected by the Smithsonian.) The ion source oven, 180-degree analyzer tube, and isotope collection plates are seen in the photos of the Nier apparatus (see accompanying media file images for this object).
Basic principles of the mass spectrometer
When a charged particle, such as an ion, moves in a plane perpendicular to a magnetic field, it follows a circular path. The radius of the particle’s path is proportional to the product of its mass and velocity, and is inversely proportional to the product of its electrical charge and the magnetic field strength. A mass spectrometer consists of three components: an ion source, a mass analyzer, and a detector. The ion source converts a portion of the sample into ions. There is a wide variety of ionization techniques, depending on the phase (solid, liquid, gas) of the sample and the efficiency of various ionization mechanisms for the unknown species. An extraction system removes ions from the sample and gives them a selected velocity. They then pass through the magnetic field (created by an electromagnet) of the mass analyzer. For a given magnetic field strength, the differences in mass-to-charge ratio of the ions result in corresponding differences in the curvature of their circular paths through the mass analyzer. This results in a spatial sorting of the ions exiting the analyzer. The detector records either the charge induced or the current produced when an ion passes by or hits a surface, thus providing data for calculating the abundance and mass of each isotope present in the sample. For a full description with a schematic diagram of a typical mass spectrometer, go to: http://www.chemguide.co.uk/analysis/masspec/howitworks.html
The Nier sector magnet mass spectrometer (not in Smithsonian Modern Physics Collection)
In 1940, during the time that Nier separated the uranium isotopes, he developed a mass spectrometer for routine isotope and gas analysis. An instrument was needed that did not use a 2-ton magnet, or required a 5 kW voltage-stabilized generator for providing the current in the magnet coils. Nier therefore developed the sector magnet spectrometer, in which a 60-degree sector magnet took the place of the much larger one needed to give a 180-degree deflection. The result was that a magnet weighing a few hundred pounds, and powered by several automobile storage batteries, took the place of the significantly larger and heavier magnet which required a multi-kW generator. Quoting Nier, “The analyzer makes use of the well-known theorem that if ions are sent into a homogeneous magnetic field between two V-shaped poles there is a focusing action, provided the source, apex of the V, and the collector lie along a straight line” (reference: A.O. Nier, Rev. Sci. Instr., 11, 212, (1940)). This design was to become the prototype for all subsequent magnetic deflection instruments, including hundreds used in the Manhattan Project.
overall: 13 cm x 13 cm x 53 cm; 5 1/8 in x 5 1/8 in x 20 7/8 in
Lasers have served as teaching tools in more ways than one. This ruby laser, made by General Electric (GE), inspired teenager Ebe Helm from New Jersey to learn more about lasers.
Mr. Helm wrote: "this laser head was originally on display in the Franklin Institute in Philadelphia as part of an electromagnetic spectrum exhibit from GE. It was a working unit that would fire downward on a spool of typewriter ribbon when a button was pushed. The hole it burned could be observed from several angles around its display and through large magnifying lenses arranged over it. ... I first saw this laser on display during a class trip in 1972. The laser had been on display for some years, possibly since the 1960's, and was not working. After it had been removed to a basement store room I managed to talk the Franklin Institute into giving it to me in 1976. I used the components to make an operational ruby laser in 1977 at age 17."
Mr. Helm donated this laser, and several others, to the Smithsonian in 2005.
Invention rarely stops when the inventor introduces a new device. Thomas A. Edison and his team worked to improve his electric lighting system for some years after the initial introduction in 1880. This lamp shows the changes made after six years of labor aimed at lowering costs and increasing production. The simplified base required little material; the diameter and thread-pitch are still used today. The filament was changed from bamboo to a treated cellulose invented by English chemist Joseph Swan. The bulbs were made by semi-skilled laborers blowing glass into iron molds. The cost had dropped from about $1.00 per lamp to less than 30¢.
from Princeton University, Dept. of Electrical Engineering, thru Dean Howard Menand
overall: 10 1/2 in x 10 1/2 in; x 26.67 cm x 26.67 cm
United States: Pennsylvania, Philadelphia
This model of a direct-current generator was designed by Elihu Thomson to produce a constant voltage. It could also be used as a motor that would maintain a constant speed. It came to the Smithsonian from the U. S. Patent Office, representing patent number 333,573, issued to Thomson on January 5, 1886. The patent itself indicates that no model was submitted (which is not surprising since by that time models were not required), and this example was probably given to the Patent Office at a slightly later date for display purposes.
Thomson and Edwin Houston were school teachers in Philadelphia in the 1870s when they formed a partnership (the Thomson-Houston Company) to enter the new and competitive arc-lighting field. They produced a number of successful generators, motors, meters, and lighting devices. Most of their system employed alternating current, which was as good as direct current for lighting. With the development of the transformer in the mid-1880s, AC systems assumed added importance because electricity generated at a low voltage could now be converted to high voltage for more efficient transmission and then converted back to safer low voltage for use by consumers. But electro-chemical applications (like plating) required DC generators, and, until the invention of a practical AC motor by Nikola Tesla at the end of the 1880s, street railways depended on DC.
Thomson-Houston merged with Edison's company in 1892 to form General Electric.
open: 18 in x 10 1/4 in x 10 1/2 in; 45.72 cm x 26.035 cm x 26.67 cm
Lasers have proven very useful in the construction industry. One example is this Spectra-Physics model 910 "LaserLevel" made in the early 1980s. In use, a construction worker attached the unit to a tripod and adjusted it so that it was nearly parallel to the ground. The level automatically completed the adjustment process when activated, and then emitted a beam of infrared light from a rotating head. The worker then moved to where-ever a measurement was needed and used a special laser detector to complete the task.
The "LaserLevel" self-adjusted if bumped slightly and completely shut off if bumped too much. The level operated automatically so it allowed one person to do work of two, resulting in cost savings since fewer assistants were needed.
Metal Disintegration Machining System for Three Mile Island Nuclear Reactor Vessel
PCI Energy Services, Inc.
metal (overall material)
graphite (electrodes in cutting head material)
plastic (overall material)
upper shaft of arm, diam.: 4 7/16 in; 11.27125 cm
top of middle tube clamp to axis of pivot arm: 13 3/4 in; 34.925 cm
top of cutting head box to axis of pivot arm: 55 7/8 in; 141.9225 cm
total radius of swinging arm: 79 5/8 in; 202.2475 cm
power cable conductor diam.: 9/16 in; 1.42875 cm
overall height: 108 in; 274.32 cm
cutting head box height: 23 3/4 in; 60.325 cm
top of cutting head box to top of middle tube clamp: 42 1/2 in; 107.95 cm
top of middle tube clamp to top of tubes: 42 in; 106.68 cm
cutting head box: 23 3/4 in x 13 1/8 in x 11 5/8 in; 60.325 cm x 33.3375 cm x 29.5275 cm
cutting head jaws (electrodes) (outside length): 7 in; 17.78 cm
cutting head jaws opening (retracted): 3 3/8 in; 8.5725 cm
cutting head jaw plate thickness: 1/4 in; .635 cm
metal disintegration machining (MDM) system
The metal disintegration machining (MDM) system consists of a box enclosing a cutting head assembly and an attached articulating arm assembly. The lower end of the arm is attached to the top of the cutting head assembly. The MDM system is the principal object of accession no. 2012.0171 in the NMAH Modern Physics Collection.
Background on Metal Disintegration Machining (MDM) System
Edited excerpts from "Phase 4 Status Report, Removal of Test Specimens from the TMI-2 Reactor Vessel Bottom Head, Project Summary, MPR-1195", October 1, 1990, prepared for U.S. Nuclear Regulatory Commission (NRC) Office of Nuclear Regulatory Research (RES). [Copy of Report in NMAH Curator's file for this accession.]
Following the accident in March of 1979, the Three Mile Island Unit 2 (TMI-2) [nuclear] reactor vessel sustained significant internal damage. The resulting damage to the lower head and the margin to failure have been of interest to the nuclear industry. In early 1988, GPU Nuclear, the owner/operator of the TMI facility, had completed a large portion of the disassembly and defueling work inside the reactor and was preparing to remove the lower structural internals and defuel the lower head. At that point, NRC-RES initiated a project with MPR Associates to remove metallurgical specimens of the lower head and adjacent areas to determine the extent of damage to the vessel and to gain insight into the events that took place inside the vessel during the accident. The project was set up such that sampling work in the vessel would be performed by MPR after GPU Nuclear had completed defueling. Defueling ended on Jan. 30, 1990, at which time GPU Nuclear turned control of the reactor vessel over to MPR.
Techniques and Special Tooling
[In order to satisfy NRC-RES, GPUN and MPR project objectives], electrical discharge machining was selected for vessel sampling. The cutting technique used is referred to as metal disintegration machining (MDM). Both the MDM process and the more commonly used electric discharge machining (EDM) remove conductive material by melting away small bits of material using an electric arc between an electrode and the work piece. EDM makes and breaks electrical arcs by switching the electrical current on and off using transistors. MDM makes and breaks electrical arcs by moving the electrode into and away from the work material. MDM was used in the project due to the high conductivity of the reactor vessel water. The MDM cutting head has two U-shaped graphite electrodes to cut the triangular [boat-shaped] samples. The electrodes are attached to hydraulic cylinders and slide on tracks mounted at angles to provide a sample with an included angle of about 60 degrees. The electrodes are consumable and were designed to be replaced after each sample cut. PCI Energy Services, under contract to MPR, developed and tested the MDM cutting equipment. The MDM head was positioned at the vessel sample locations with a delivery system consisting of several long pipe sections and a hinged arm which articulated the MDM cutting head to the desired angle for sampling the vessel head. The MDM cutting system was used to cut samples both in open areas of the vessel and at incore penetrations.
For details on the MDM cutting system and associated equipment, and for a full description of the development and qualification program, refer to the above Report document in the Curator's file for this acquisition.
Most incandescent lamps were designed for general use in homes and businesses. However, some required special features for use in particular locations. Westinghouse engineers designed this so-called mill lamp for use in factories and other areas subject to high levels of vibration. An intricate internal support structure absorbed vibrations and kept the filament intact for the life of the lamp. Lamps of this type were later sold as rough-service lamps. The filament itself is made from the element tantalum. Invented in 1902, tantalum filament lamps sold in the U.S. until about 1910 when tungsten lamps were introduced.
The abundance of timber along the shores of the Great Lakes gave steamboats a ready supply of fuel. Partly burned logs from Indiana's boiler grate indicate that the boiler had been stoked just before the steamboat sank.
Pound for pound, coal provides more energy than wood. Coal was found in the vicinity of the boiler in the hold, and historical sources indicate that it was a common fuel on upbound (northerly) voyages, while wood was the principal downbound fuel.
Expansion and Reform
On the Water online exhibition
Related Web Publication:
Gift of Michigan Department of State, Michigan History Division (through Bruce J. Andrews)