Download 229 N S G

identify the source of a nuclear device and its fuel will deter advocates of such unthinkable acts.
Figurefrompage229ofExploringtheHeartofMa2er
fission
238
Pu
(n,γ)
(n,2n)
239
Pu
fission
(n,γ)
(n,2n)
240
Pu
(n,γ)
(n,2n)
241
Pu
fission
(n,γ)
(n,2n)
242
Pu
(n,γ)
243
(n,2n) Pu
β-decay
240
Am
fission
(n,γ)
(n,2n)
241
Am
(n,γ)
(n,2n)
242
Am
β-decay
242
Cm
Forensics Figure 2_FS-2_forensics-Pu-Am.eps
FIGURE FOR 2 Plutonium (Pu) and americium (Am) reaction chains. One of the pieces in a
nuclear forensics puzzle is the amount of plutonium-241 in a nuclear device, which can be
determined after an explosion. The figure illustrates all of the neutron-induced reactions that
need to be understood to deduce the original amount of plutonium-241 in the device and the
fluence of high-energy neutrons in the subsequent explosion. These include reactions on americium-241, the daughter from radioactive decay of plutonium-241. The relative abundance of
americium-240 in the explosion debris would provide key information for forensic analyses,
because americium-240 can only be produced by high-energy (En > 6.67 MeV) neutrons.
SOURCE: Courtesy of A. Haynes, Los Alamos National Laboratory.
•  Nuclearforensics:analysis/evalua2onofpostdetona2ondebrisorunexplodeddevices.
•  Basicidealikeanalysisofstellarnucleosynthesis:inferfromreac2onproducts.
•  Usehalf-lifeandabundancetodetermineage,cf.carbonda2ng.E.g.,plutonium-240and
241fromreactor;Pu-241àAm-241with14.4yearhalf-lifegives2meelapsed.
Copyright © National Academy of Sciences. All rights reserved.
•  Designofdetonateddevicefromshapeofneutronfluxspectrum.E.g.,Am-240canonly
bemadefrom(n,2n)reac2onwith6.7MeVneutronsàinfoonhigh-energycomponent.
Figure3.3frompage160ofExploringtheHeartofMa2er
FIGURE 3.3 Muons passing through high-Z materials (like uranium and plutonium) are scattered more
than those passing through other materials (such as steel or water). Cosmic ray muons can therefore
be used as an active interrogation probe of nuclear materials by detecting muons above and below a
truck. SOURCE: Courtesy of C.L. Morris, Los Alamos National Laboratory (LANL).
•  Borderdetec2onofnuclearcontrabandwithnoveldetec2onschemes(because
conven2onalgammarayandneutrondetec2oncanbeevadedbyshielding).
•  UsescaTeringofcosmicraymuonstoscanforhigh-Zmaterials,detectedaboveand
belowthevehicle.Muonsinteractwithatomicelectronsandnucleiandthisprovides
Copyright © National Academy of Sciences. All rights reserved.
radiographicsignals;e.g.,large-anglescaTeringcanindicateuraniumorplutonium.
Figure3.4frompage162ofExploringtheHeartofMa2er
Measureneutroninducedcrosssec2ons
onfissionableac2nides
(Z=90-103).Needto
reduce2-3%uncertainty
to1%forstockpile
stewardshipandreactor
design.
3Deventreconstruc2on
withhighbackground
rejec2onusing2me
projec2onchamber(TPC)
FIGURE 3.4 TPCs are sensitive instruments in basic research in high-energy and nuclear physics used,
for example, in the solenoidal tracker at RHIC (STAR). A new application of a TPC is being developed
to enable measurements of neutron-induced fission probabilities of actinides with unprecedented
accuracies. The TPC will measure the energy, mass, and direction of fission fragments. Upgrades
to the baseline TPC, including additional detectors, would also measure the energy, direction, and
multiplicities of fission neutrons and will be able to correlate gamma-radiation with fission events.
Such measurements of fission probabilities and properties are important in a wide range of disciplines
including nuclear energy, nuclear forensics, national security, and basic nuclear science. SOURCE:
Courtesy of M. Heffner, LLNL.
Figure3.9frompage174ofExploringtheHeartofMa2er
Electron source
and accelerator
Magnetic structure
(undulator)
Electron Beam
Light beam
FIGURE 3.9 FELs are a powerful source of coherent electromagnetic radiation that is produced by
a relativistic electron beam propagating through a magnetic field. They are used in numerous basic
and applied science applications, including 3-09.eps
probing materials, biological systems, and nuclei. Shown
is a schematic diagram ofbitmap
the basic with
layout vector
of an FEL.masks
The electron
beam is transported through the
& type
periodically varying magnet field of an undulator magnet. Microbunching inside the electron beam at
a spacing equal to that of the light’s wavelength enables electrons to radiate coherently in order to
establish lasing. An FEL can be operated with either an optical resonator or in a single-pass configuration with a long undulator section. SOURCE: Image courtesy of Deutsches Elektronen-Synchrotron
(DESY) in Hamburg, Germany. Copyright: DESY 2006.
Figures3.12,3.13frompages180-181ofExploringtheHeartofMa2er
FIGURE 3.13 Thermohaline circulation, commonly referred to as the ocean “conveyor belt,” is made
up of ocean currents that transport heat from the tropics to the polar regions. AMS of the radioactive isotope argon-39 will be used to explore this conveyor belt and its impact on climate. SOURCE:
National Oceanic and Atmospheric Administration.
Measureisotopesofinertnoblegases(nonis comparable
to the amount transported by the atmosphere. Therefore, it is very
important to understand this system. With a half-life of 269 years, argon-39 is
reac2ve,easiertorecoversmallquan22es).
particularly well suited to study questions related to ocean circulation. However,
its extremely low concentration (argon-39/Ar = 8.1 × 10–16), coupled to its long
Understandgroundwaterflowfromkrypton-81,
half-life,
makes it impossible to measure the argon-39 decay in any sample of
reasonable
size.4
producedbycosmicrays.Usefullife2mebut
AMS using the ATLAS heavy ion accelerator at Argonne National Laboratory
hardtomeasureabundance.Uselaser-based
has been
successful in separating argon-39 from its ubiquitous potassium-39 isobaric background, the latter being 6-7 orders of magnitude more intense. Measureatomtraptraceanalysisàgroundwaterage.
ment of isotopic ratios as small as argon-39/Ar = 4 × 10–17 have been achieved.
This program is now poised to measure argon-39 concentrations in ocean water
samples in order to explore the oceanic “conveyor belt.”
FIGURE 3.12 Understanding the flow of groundwater that circulates through Earth’s crust is an open
question in geology. In a collaboration of nuclear scientists and geoscientists, the precision technique
of atom-trap analysis was used to measure the radioactive isotope krypton-81 in deep wells of the
Nubian Aquifer in Egypt. The map shows sample locations and their krypton-81 ages (in 100,000
years) in relation to oasis areas (shaded green). Groundwater flow in the Nubian Aquifer is toward
the northeast. SOURCE: Adapted from N.C. Sturchio et al., 2004, One million year old groundwater in
the Sahara revealed by krypton-81 and chlorine-36, Geophysical Research Letters 31. Copyright 2004
American Geophysical Union. Reproduced/modified by permission of American Geophysical Union.
Understandoceancurrentsbyaccelerator
massspectroscopyofargon-239,with
half-lifeof269years,eveninverylow
concentra2ons.Isotopicra2oassmallas
4x10-17isnowpossible.