Nuclear Diagnostics at the National Ignition Facilitytid.uio.no/workshop2011/talks/t_Bleuel.pdf ·...

Nuclear Diagnostics

at the National Ignition Facility

Nuclear Diagnostics

at the National Ignition Facility

Presentation to

Third Workshop on Nuclear Level Density and Gamma StrengthThird Workshop on Nuclear Level Density and Gamma Strength

Univeristy of Oslo, May 23, 2011

Darren Bleuel

(et. a lot of al.)

NIF is the culmination of a

decade long effort to

demonstrate fusion in the labdemonstrate fusion in the lab

NIF-0211-20965.ppt Moses - Presentation to Science Councel of Japan 2

NIF concentrates all 192 beam

energy in a football stadium-sized

fac.fac.


Target Chamber Dedication June

1999


Laser bay

NIF-0509-16325.pptNIF-0211-20965.ppt Moses - Presentation to Science Councel of Japan 55

In the target chamber


How NIF/ICF worksHow NIF/ICF Works

Sh

ock/c

om

pre

ssio

n “Ignition”: this is the goal

This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under ContrThis work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contractact DEDE--AC52AC52--07NA2734407NA27344

Sh

ock/c

om

pre

ssio

n

time

La

se

r p

ow

er

time

Laser pulse

7

~20ns

“Layered-cryo” w/ hohlraum (indirect drive) vs.

“Exploding pusher” (direct drive)

“Layered-Cryo” “Exploding Pusher”

• Laser energy produces ~ 10 keV

• Laser energy produces ~300 eV x-rays in hohlraum

Simple direct

drive targets

Wall

explodes

driving

shock

into DTLaser

beams

produces ~ 10 keV electrons: heats thin Si capsule wall

• Low ρρρρR (no n scatter)

• Isotropic

• Yield up to 5x1015 n

produces ~300 eV x-rays in hohlraum “can,” heating CH or Be capsule wall

• Cryogenic DT “layered” fuel shell with gas interior

• “Hot spot” ignites high ρρρρR layer burn

• Yield up to 1019 n

Cryogenic, x-ray

driven, layered

targets

DT

Ga

s

beams

Hot core,

‘point’ source

of neutrons +

soft x-rays

n14MeV

• Yield up to 1019 n

CH or Be

ablator shells

solid cryo

DT layer

DT gas

Lofty goal of the National Ignition Campaign (NIC):

“Ignition”

Need to compress capsule adiabatically

(isentropically) to 1/30th the size (ρ x1000)

2mm

60µm

Pitfalls to achieving ignition

Asymmetric implosion

Diagnose with:

Yield, ρR,

temperature,

Ablator/Fuel mix

Diagnose with:

radchem?

Goal!

temperature,

imaging (n, x-ray)

Shock TimingIgnition: Hotspot

Shock Timing

Diagnose with:

γ-ray reaction

history (Etc>)

Ignition: Hotspot

initiates outward

“burn” into

dense outer

layer

Neutron Spectra

Diagnostics must span 9 orders of magnitudeN

eu

tro

n Y

ield

(n

/Me

V)

ρR

Yield

Tion

(ρR)2

ρR

Neutron Energy (MeV)

Ne

utr

on

Yie

ld (

n/M

eV

)

(ρR)

Atypical measurement challenge:

All neutrons born within <100 ps.

Activation: Zr Neutron activation (NAD) measures

yield for DT shots to absolute accuracy of ±±±± 7%

0.8

1

1.2In-115(n,n')In-115m

Nb-93(n,2n)Nb-92m

Zr-90(n,2n)Zr -89

C-12(n,2n)C -11

Cu-63(n,2n)Cu-62

Cro

ss

se

cti

on

(b

) Activation Foil cross sections

14 MeV n

10 MeV n

Exp.Pusher: Raw Data, 8.7mm sample

24 hours counting3 samples with

different thickness

Neutron energy (MeV)

0

0.2

0.4

0.6

0 5 10 15 20 25 30

90Zr(n,2n) ⇒ 89Zr (t1/2=3.3 d)

63Cu(n,2n) ⇒ 62Cu (t1/2=9.74 m)

Cro

ss

se

cti

on

(

MacKinnon—NIC Technical Review, February 23-25, 2011 12NIF-0211-21072s2.ppt

Co

un

ts

89Zr

1.03.5

8.7

Placed in a well 4.5m

from TCC

Y = 2.3 x 1014±±±± 7 %

Shot N

101030

Neutron

Activation

Detectors

13

MRS: The MRS has been designed and implemented

for simultaneous measurements of ρρρρR, Y1n and Tion

Low-Res

tf = 275 µµµµm

Med-Res

tf = 125 µµµµm

Aa = 20 cm2

MRS Spectrum THD-3

Yield

n

N11

02

01

Rf = 26 cm

Ra = 570 cm

Aa = 20 cm2

Downscatter from

10-12MeV neutrons

Deconvolved

width = Tion

n

d+

N11

02

01


CR-39

Accuracy requirement for the MRS absolute

yield measurement < 10% for Y1n > 1014

GRH: Gamma Reaction History (GRH) measures

Bang Time (w/in 30 ps) and Burn Width (w/in 15 ps)

with Gas Cherenkov Detectors

GRH-6m at (64,20) DT exploding pusher Data

Exploding Pusher (N101212)MZPMT

DTγγγγ

No CO

De

co

nvo

lve

d G

au

ss

ian

Tim

ing

Sh

ot

Fit

(N

101029)

Bang time

+/- 30 ps

Burn width

+/- 15 ps

DTγγγγ

0

Yie

ld R

ate

n/n

s)

0

5 1014

1 2 3-1

Time (ns)

• 4 Gas Cherenkov cells

• Detectors installed with Ultra-fast

MCP PMTs and optical Mach


No CO2Time (ns)

• Bangtime agrees with Ntof_BT data to within 100 ps

• Energy threshold of each cell set by gas pressure /composition

• 3-10MeV GRH will be fielded on DT implosions for yield and

4.4MeV carbon γγγγ (ablator density measurement)

MCP PMTs and optical Mach

Zehnders

nToF: Ion temperatures, yields, and ρρρρR from ~6 nToF

detectors are calculated by an iterative process

• Neutron energy determined by

time to reach detector

• To measure downscattered

Convolve Brysk dtBrysk= c x distance x T1/2 with IRF

• To measure downscattered

neutrons after 100x primary

14MeV signal, must choose

detector with fast recovery time

(p-xylene, CVD diamond>)

IRF∆t Fold

dtBrysk

Neutron Imaging system has begun performance

qualification process using exploding pusher shots

NIS Pinhole

arrayExploding pusher DATA

Yield = 2e14

Reconstructed Neutron

Image Raw Image

Yield = 2e14

Compare to

gated x-ray

Image


Signal: 7500

counts

pusher

150 µm 150 µm

First radiochemistry (RAGS) diagnostic utilizes 124Xe(n,γγγγ) and 124Xe(n,2n) to measure average ρρρρR

Outer Ablator

(>95% normally

ablated)

DT Ice

NIF capsule w/124Xe implanted

Normalized

0,012

0,013

Ratio of Activities:

ablated)

Inner ablator

(doped w/1015

Atoms 124Xe)

DT Gas

Pre-cleaner

NIF

Target

Turb

os

Neutron downscatter ≈ρρρρRfuel making

124Xe(n,γγγγ)125Xe

Normalized by Primaryneutrons:

124Xe(n,2n)123Xe

Cryos

(closed

during

shot)

F = 0.00642ρR + 0.00305R² = 0.96581

0,006

0,007

0,008

0,009

0,010

0,011

0,012

0,60 0,70 0,80 0,90 1,00 1,10 1,20 1,30 1,40

Ratio of Activities:

(125Xe/123Xe)

Collector

system

γ-detector

Pre-cleaner

systemTarget

Chamber

(600 m3)

Turb

os

Fuel ρρρρR (mg/cm2)

125X

e/1

23X

e

Radioactive 123,125Xe

Collected/counted post-shot

RAGS

Precleaner

(SNL)

Where we are now

and where we’re going

• Primary purpose of these first two diagnostics

phases are to achieve ignition

• We are now (≈3 weeks ago) beginning to think • We are now (≈3 weeks ago) beginning to think

about science-enabling diagnostics, including:

1. Solid-debris collection (fast and slow)

2. Energy resolving γ-ray detectors (bent crystal)

3. Fission-based low-energy neutron spectrometers

(Supplements what Lee talked about)

Coming up with an idea for a new diagnostic

is a great way to get involved

…

Nuclear Physics AT NIF (thanks Lee!)

Nuclear Physics FOR NIF

• D-T fusion 16.7 MeV γ-ray branching ratio

• T-T neutron spectrum (6He breakup)

• Sequential, di-neutron, or two-body?

• Nuclear-plasma interactions/rates/thermal population

• NEEC, NEET, etc.

• Reactions on highly-excited states

• Cross sections: (n,x) for radchem

NIF is providing opportunities to explore new areas

of nuclear physics

D + T→ 5He*

DT produces n and fusion γγγγ Neutron spectrum inferred from MRS

He5*

16.7 MeV

γγγγ1

4.5 MeV

γγγγ0

Isotropic

ρρρρr insensitive

2.5x previous

measurements

TT-n

MacKinnon—NIC Technical Review, February 23-25, 2011NIF-0211-21072s2.ppt

OMEGA measure γγγγ1/γγγγ01.35 ±±±± 0.35THD suggest HTγγγγ about 5x weaker than estimates –> more accurate average yield measurement from GRH

0 MeV He5

Confirms recent OMEGA data in TT cross section region – This information helps reduce uncertainties for RAGS

Nuclear physics needs

T-T neutron spectrum at NIF-relevant energies (~10keV)

3 body reaction

T+T αααα+n + n (0-9.5 MeV)

2 body reaction

T+T 5He+ n (8.7 MeV) αααα+n T+T 5He+ n (8.7 MeV) αααα+n

Could investigate by creating 6He at

relevant energies via 6Li(d,3He), tag

on 3He,α coincidences

• Lee Bernstein (LLNL)

• Jac Caggiano (LLNL)

• Dan Casey (MIT)

• Johan Frenje (MIT)

ThanksT

• Johan Frenje (MIT)

• Stephan Friedrich (LLNL)

• Vladimir Glebov (LLE)

• Hans Hermann (LANL)

• Joe Kilkenny (General Atomics)

• Andy MacKinnon (LLNL)

• Craig Sangster (LLE)

• Dieter Schneider (LLNL)

• Dawn Shaughnessy (LLNL)

• Wolfgang Stoeffl (LLNL)

• lots and lots of others>

Nuclear Cross Sections for Charged Particles at Energies

Relevant to Astrophysics are Difficult to Measure

Rate =<σ >S(E )

Ee−2πξv

σσσσ = < 300pb @ 20keV

0

4

8

12

16

Gamow peak

S-F

acto

r (M

eV

. barn

)

Resonance

3He(3He, 2p)4He 1030

1010

1020

Den

sit

y (

ato

ms/c

m3)

Author—NIC Review, December 2009 28NIF-0000-00000s2.ppt NIF-0000-12345.ppt Talk or Conference Name, Date

By measuring reaction products at NIF the relevant cross sections are

inferred

E (keV)

010 102

103

1010

10-1 100 101 102

103 E (keV)

The achievement of ignition will provide unique research opportunities

in astrophysics, stewardship physics, and inertial fusion energy studies

Screened reactions in dense plasma

b)

12

16Screened

Bare

Previous data

3He(3He, 2p)4He

Multi-hit reactions from 1033 n/(cm2 . s) flux

(vs 1032 n/(cm2 . s) for SNe)

S-Factor (M

eV. b)

4

8

12 Previous data

Present data (LUNA)

Solar Gamow peak

Resonance?

n produces

excited state

σσσσ for 2nd reaction

from this excited state?

Author—NIC Review, December 2009 29NIF-0000-00000s2.ppt

• Strongly screened reactions are

relevant to stellar evolution

M. Junker et al., PRC 57, 2700 (1998)

E (keV)

010 102 103

S. Libby, IFSA proceedings (2004)

• First hit gives excited nuclear state

• Second hit reaction cross section uncertain

• Reactions from excited states, relevant to

r-process nucleosynthesis of heavy elements

Nuclear Diagnostics at the National Ignition Facilitytid.uio.no/workshop2011/talks/t_Bleuel.pdf ·...

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