Oral Presentation Schedule

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Oral Presentation Schedule
April 7 Adam Bryant Quark-Gluon Plasma April
14 Erik Swanberg s-Process David
Murer r-Process April 16 Raluca Scarlat
April 23 Chit Hlaing Half-life
Variations April 28 Michelle Galloway Big
Bang/Dark Matter Manuel Aldan
Cerenkov/Transition Radiation April 30 Sven
Chilton Tritium breeding Brien Ninemire
K-Isomers May 5 - Amy Coffer Barbara
Wang NMR
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Oral presentations Prepare roughly 20 minute
presentation on topic youve chosen Assume
audience knows little about your topic Explain
basic ideas Dont worry too much about
details Powerpoint Cite references Be
prepared for questions !
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Guest Lectures
Wednesday April 9 Dr. Kenneth Gregorich,
LBNL Heavy Element Physics and
Chemistry Monday April 21 Dr. Augusto
Macchiavelli, LBNL Gamma-ray Tracking with
GRETINA
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Fate of Stars

• ? White Dwarf (maximum mass 1.4 MSun)
• Chandrasekhar Mass limit
• Supported by electron degeneracy pressure

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Supernova Explosion

• Temperature goes up
• Density goes up
• p e- ? n ne
• e e- ? n n
• 99 of SN energy comes off in neutrinos

SN 1987a
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Supernova Remnants

• Neutron star supported by neutron degeneracy
  pressure
• Upper limit on neutron star mass 2.5 MSun
• Oppenheimer-Volkoff limit
• Higher masses ? black hole
• RSchwarzschild 2GM/c2
• For 1 MSun, Rs 3 km

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Particle Data Group
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Particle Data Group
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Ziegler
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Clock isotopes in cosmic rays
Advanced Composition Explorer
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3/2-
0
7Be t1/2 53.3 days
10
478
1/2-
QEC 862 keV
90
3/2-
0
7Li stable
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Half life of bare 54Mn nucleus 106 years
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Detecting hidden fissile material
Time between generations is measured in shakes
(10 ns)
2 3 neutrons and
10 g rays emitted per fission
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Detectors For Time Correlation Experiments

• 96 Xylene Liquid Scintillators
• 4x3
• Fast Neutron / Gamma Separation
• 1 ns Timing
• 24 Plastic Scintillator Blocks
• 4 x 8 x 40
• Gammas and Cosmic Muons
• 1 ns Timing
• 18 Plastic Scintillator Paddles
• 2x 20 x 40
• 40 He3 Detectors
• 2 x 40
• 4 atmospheres pressure
• Thermal Neutron Detection

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Demonstration of technique using neutrons
106 measurements
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1
2
3
4
106 measurements
0
1
5
2
3
4
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Sensitivity from Detecting the Correlation
Between Neutrons and Photons from 235U Fission
Chains

• Measured data from 22 kg bare HEU shell

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Particle Number Since First in Burst
10
n Detector x Photon Detector
Photons from individual fissions in the chain
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?t Interval Between Counts
1 ?s
1 ns
120
0
20
40
60
80
100
Time Since Start of Burst (?s)
Fission photons have short characteristic time
scale, which enables detection of SNM even in the
presence of high background rates.
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Fast neutron counting time intervals between
adjacent counts for HEU in polyethylene inside a
lead pile.
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Fast neutron counting data from HEU run

Time interval distribution from fast neutron
counting for HEU shell in polyethylene and Pb.
The time intervals between about 10 and 100 ns
are enhanced relative to that observed with
un-moderated HEU.
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Detecting nuclear weapons in cargo containers
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Potential danger at the worlds sea ports

• 90 of the worlds trade moves via sea-going
  containers
• Cargo is attractive for smuggling illicit
  material
• Large volume and mass of material in each
  container
• Cargo is non-homogeneous
• Volume of traffic is enormous
• More than 6,000,000 containers enter the U.S.
  annually
• U.S. west coast ports are processing
  11,000/day An average of 8/min on a 24/7 basis
• Successful delivery of one weapon of mass
  destruction in a container can be catastrophic

San Francisco
Oakland Bay Bridge

2 mi
The Port of OaklandSan Francisco Bay, California
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The cargo is the challenge
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Scope of the project

• Concentrate on the threat with the gravest
  consequences nuclear explosives
• Uranium and plutonium with very high isotopic
  content of the nuclides 235U and 239Pu
• Heavily shielded material
• Develop a prototype detection system for use at
  sea ports
• Functions for a range of material density 0 lt
  rL lt 150 g/cm2
• Is reliable False positive and false negative
  rates lt 10-3
• Preserves the flow of commerce through the port
  tscan lt 1 min / container

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We need a useful signature unique to fissionable
material

• Radiation must penetrate from deep within a
  cargo container to reach a detector outside and
  must be intense enough to be discriminated from
  background
• 235U and 239Pu are both radioactive and have
  unique gamma radiation signatures. Can we exploit
  these passive emissions?
• 239Pu (t1/2 2.4x104 yr) emits weak gamma rays
  and neutrons
• 235U (t1/2 7.0 x108 yr) emits weak, low-energy
  gamma rays
• Active methods inject particles into container to
  produce fission reactions in fissile material and
  provide unique return signals
• We dont expect to rely exclusively on active
  approaches
• Passive radiation detection
• Radiography to locate high-density components
  buried within an otherwise low-density cargo

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Active interrogation
Prompt 235U(n,g)236U Detect capture
g-rays Problem mass(U or Pu) lt 10 kg mass
(other cargo) 10,000 kg S/N is very
small and need high energy resolution
detectors to identify U or Pu
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A word about the fission reaction andb-delayed
gamma rays and neutrons

• Thermal-neutron induced fission reaction produces
  two fission fragments and zero to many neutrons.
  For example
• n 235U ? 236U ? 90Kr 143Ba 3n
• b-decay of the fission fragments frequently
  leaves the
• daughter nucleus in an excited state
• Sometimes above the binding energy of the last
  neutron gt neutron emission
• More often to a high-energy state that
  de-excites by high-energy g-ray emission
• - g-ray emission is 10 times more likely
• Both processes are fission signatures

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High-energy gamma-ray yields in 235U thermal
neutron fission
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High-energy gamma-ray yields in 239Pu thermal
fission
gt4 MeV gammas/fission
gt3 MeV gammas/fission
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Delayed n or g?
Attenuation 3
Delayed neutrons are highly attenuated in
hydrogenous material (estimate includes yield /
fission)
Flux
Thickness of Al or wood (g/cm2)
The high energy g-ray signal leaving thick
hydrogenous cargo may be as much as 102 to 104
larger than the delayed-n flux.
1 LLNL Nuclear Data Group, 2003,
http//nuclear.llnl.gov/CNP/nads/ 2 LBNL
Isotope Explorer, 2003, http//ie.lbl.gov/ensdf/

3 T. Rockwell III, Reactor Shielding Design
Manual, D. Van Nostrand Co., New York (1956).
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High-energy ?-rays detected between neutron
pulses are used to identify fissile material

• Fission product ?-rays integrated from 3 to 7 MeV
  between interrogation beam pulses are used to
  identify the presence of fissionable material
• Distinguished from activation and background
  sources by their high energies (E? gt 3 MeV)
• And their characteristic decay times
• There is expected to be some ?-radiation between
  beam pulses due to activation of cargo
• That radiation is expected to be low energy
  (lt 2.5 MeV)
• And mostly characterized by longer half-lives
  (typically gtgt 1 min)
• Detailed experimental evaluation of these
  assumptions and interferences is being conducted
  with real cargos to qualify this methodology

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We made use of two majorexperimental facilities
LLNL Cargo Scanning Laboratory Full-scale
evaluation and testing
LBNL 88? Cyclotron Proof of principle and
benchmark experiments
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b-delayed g-rays above 3 MeV attributable to U, Pu

• Experiment by Norman et al. 2004 1

• En thermal
• Separate neutron irradiations of 235U (93),
  239Pu (95), wood, polyethylene, aluminum,
  sandstone, and steel.
• Cycles of 30 s irradiation and 30 s counting.
• 10 sequential 3-second g-ray spectra were
  acquired with a single coaxial 80 HPGe detector.

235U(nth,f) and 239Pu(nth,f) Significant g-ray
intensity above 3 MeV. Short effective half-life
(approximately 25 s).
1 E. B. Norman et al., NIMA 521 (2004)
608-610. 2 E. B. Norman et al., NIMA 534 (2004)
577.
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The LLNL cargo screening laboratory
15.2 cm
25.4 cm
PMT
Mock Cargo 0.6 g / cm3
HEU samples U3O8 469.7 g (376.5 g 235U) 280.4
g (221.1 g 235U)
61 cm
HEU U3O8
g
Decay curve cycle 30 s n-irradiation 100 s
count delayed g and n
61 cm
61 cm
15.2 cm
Passive Background no neutron irradiation
61 cm
basement
n
61 cm
25.4 cm
Active Background regular irradiation cycle no
HEU
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Plywood and steel pipes are representative
cargoes
Plywood
Steel
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A pallet of plywood was installed over the
neutron source and 380 g HEU lowered into a hole
near center
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The signal is evident in the raw g-ray energy
spectrum
There are a significant number of g-rays with
energies above 3 MeV
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Decay times coincide with fission products
235U Products with most intense activity at Eg gt
3 MeV and with t1/2 lt 10 min
t1/2 (s)
Product
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Delayed g-ray signal stands out in 0.55 g/cm3
wood at low beam current for a lt 0.4 kg HEU sample

• Single cycle decay curves are shown for Rf
  30, 61, 91 and 122 cm plywood.
• Normalized to 25 mA (100 W) into the D2
  gas target.
• Passive background has been subtracted.
• 2s Poisson uncertainties.
• Integrating to 30 s shows a signal 5 s
  (actual) above the active background for Rf
  122 cm.

1 30-s irradiation, 25 mA
Rf 30 cm
Rf 61 cm
Rf 91 cm
Rf 122 cm
15.2 cm
25.4 cm
Active background
1 min since start of scan
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Delayed g-ray signal is significant through 0.6
g/cm3 steel pipe cargo at low beam current for a
lt 0.4 kg HEU sample

• Single cycle decay curves are shown for Rf
  46 and 76 cm steel pipe cargo.
• Normalized to 25 mA into the D2 gas target.
• Passive background has been subtracted.
• 2s Poisson uncertainties.
• Integrating to 30 s shows a signal 4s (actual)
  above the active background at Rf 122 cm.

1 30-s irradiation, 25 mA
Rf 46 cm
Rf 76 cm
3He tubes
15.2 cm
Active background
25.4 cm
1 min since start of scan
Rf
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Experiments have been performed to analyze
fission 16N signals together

• Rf 91 cm.
• HEU placed on top of Teflon in plywood.
• Specific time-energy combinations can be
  considered.

1
Energy projections
1 T. Luu, private communication
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• Active neutron interrogation

Hidden WMD
Cargo
Detector arrays (hidden)
Neutrons
Neutron generator
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A combined solution
Document screening
Arrival at port
Passive screening
Radiography screening
Active interrogation
Unload container
Response
Cleared for delivery
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Active Interrogation Group at LLNL Experiments
Steve AsztalosAdam BernsteinPeter
BiltoftJennifer ChurchAlexander LoshakDouglas
ManattJoe MaugerThomas MooreRick Norman
David
Petersen (UCB)Dennis SlaughterWarren Tenbrook
ModellingMarie-Anne DescalleJim HallJason
PruetStan Prussin (UCB)FacilityOwen
AlfordMark AccatinoDione Anceta