Intense Pulsed Neutron Generation to Detect Illicit

Materials.

Chris FranklynP-LABSRadiation Science Dept.Necsa

Task:Develop an intense pulsed neutron generator that is cost effective for implementing in the identification of illicit material and explosives.

Task circa 2006:Develop a D-D/ D-T pulsed neutron generator based on the principle of the plasma immersion ion implantation (PI3) technique.

PI3NG

Produce an intense burst of mono-energetic neutrons for use in neutron detection techniques, such as neutron back-scattering, radiography, as well as time-of-flight activation analysis.

Mode of operationRF plasma: 18 MHz 2kW D2 gas pressure: 1 – 10 mTorr

Resonant pulse power supplyUtilizing amorphous toroidal inductor cores for magnetic pulse compression

>10A 4.5 J / pulse1A 25 mJ/ pulseAv. Current

10 kHzup to 400 HzPulse rep. rateup to 40 msup to 40 msPulse width

~100 ns<800 nsPulse rise time-100 kV-20 - 40 kVHVFuturePresent

D-D fusion

dNdt = n0 . Iion . ∫ s(E).dE

(dE/dx)

Simplify:

N = 2 . E1/2 . n0 . σ(E) . Iion . ∆r . t / (45 . e)

n0 ~ 4 . 1022 cm-3

E ~ 20 keV

∆r ~ 10-5 cm

σ ~ 3.5 . 10-28 cm2

For 1 A and pulse width ~ 10 µsWe have 1740 fusions

Or 870 neutrons

Extending to 100 kV, 10 A, pulse width 40 µs at 10 kHz

4.5 x 1010 neutrons per second

Important factor is the target material.Pd ideal, but will outgas too rapidly if not kept cool

Resorting to the D-T reaction would result in at least 2 orders of magnitude increase in yield.

Task circa 2008:

Implement RFQ accelerator systems for the generation of quasi-monoenergetic neutrons between 4 and 8 MeV through the d(d,n)3He reaction.

Use fast neutron resonance radiography technique to detect explosives.

Resonance features of fast neutron interaction cross-sections.

1 2 3 4 5 6 7 8 En (MeV)

mbH C N O

0

2

4

6

8

Actual buildingat DebTech

Radiationshield

Accelerationof deuteron ions

Neutron production&

detection

ADM RFQ accelerator facilityADM RFQ accelerator facility

D-100 facility at P1900

Chillers

Level-2: RF Transmitter

Level-1: RFQ Linac, Detector, Conveyor

Level-0: Electricals, chillers

RFAmp-1

RFQ linac-1

RFAmp-2

RFQ linac-2

Injectorelectronics& gas supply

IonSource

ADM RFQ linac

D2

D+

25 keV

200 kW RF425 MHz

4 MeV

160 kW RF425 MHz

4 / 5 MeV

HEBTmagnetic field

Steered and focusedhigh energy beam

To gas target

BEAM ENERGY

RFQ 1

AMP 1

3.43.63.84

4.24.44.64.85

5.2

-200 -150 -100 -50 0 50 100 150 200 250Relative rf Phase [Deg]

Deute

ron E

nerg

y [Me

V]

360o

0.6% duty cycle0.32% duty cycle

RFQ 1 only

RFQ 2

AMP 2

RFQ1 & RFQ2 in phase

RFQ1 & RFQ2 in phase

Varying phase shift

3.43.63.84

4.24.44.64.85

5.2

-200 -150 -100 -50 0 50 100 150 200 250Relative rf Phase [Deg]

Deute

ron E

nerg

y [Me

V]

360o

0.6% duty cycle0.32% duty cycle

Gas target

Accelerator 10-6 mbar

D+ beamGas Cell3 bar

DeuteriumGas

Vacuum Pumps

Differentially PumpedChambers

5.1 x 10-3m

bar

6.3 mbar

6.5 x 10-6m

bar

Rotating seals with 3 slots

0 2 4 6 8 10 12 14 16 18 20Angle from beam axis (Deg.)

Neutr

on flu

x (10

4n.m

m-2 )

46

8

10

4 MeV

5 MeV

Neutron yield for 3 cm, 3 bar D2 gas target at 100 µA

En=8.2 MeV

En=7.2 MeV

3 cm 3 bar D2 gas Target

35 keV D+ ion source

Main RFQ accelerator- Accelerate ions to 4 MeV

High Energy Beam Transport tofocus and steer ions into gas target

Booster for extra 1 MeV ion acceleration

Spinning disc beam dump

Beam direction

D-100 RFQ accelerator system

Gas Target HEBT Ion SourceRFQ Linac

RF Amplifier

Detector

Booster

Schematic layout of the D-100 RFQ accelerator facility at Necsa

0 60 120 180 240 300 360

2.62.42.22.01.81.61.4

Relative RF phase to booster (Deg.)

Proto

n ene

rgy (

MeV) 35 kW

10 kW

Extracted proton beam at 180 kW in first cavity

10 20 30 40

400

300

500

Energ

y gain

(keV

)

Booster power (kW)

At 120o

50 mA , 20% duty cycle 10 mA , 2.5% duty cycle

3 bar deuterium gas cell 1 bar1012 n.s-1 1010 n.s-1

DESIGN CURRENT

10101012Neutron flux (n.s-1)4.4 4.5 linac length (m)

280/1601000/200pulsed RF power requirement (kW)1.2 %20 %maximum RF duty factor20-20020-100repetition rate (Hz)

0.12maximum beam pulse width (ms)850booster output current (pulsed)(mA)1255injector output current (pulsed)(mA)

3.6 - 4.93.7 - 5.1output energy (MeV)25.035.0injection energy (keV)425200operating frequency (MHz)ADMD-100Features

Operating specifications for the two accelerator systems.

Conventional radiography configuration - ADM

Detectors

Gas Target

D-100 detection system

Scintillator

Image intensifierMirrors

Beam splitter

Hi-energy CCDLow-energy CCD

Neutron efficiency: 70%Light conversion: at least 1 photon / neutronImage intensifier size: 150 mmDrift scanning: Yes

H/C scintillating fibre plastic array400 mm

60 mm

37

37

19 x 20 fibres0.5 mm thick

> 31 km of fibres

neutrons

289 fibres in 10mm x 10mm block

41 x 41 blocks

Amorphous Si array, pixel size 400 µm

D-100 ADM

D-100 dose at 1012

ADM dose at 1010

Fast Neutron Radiography for DWIK Detection

Diamond ImageKimberlite

run-of-mine

NeutronsNeutrons

00.10.20.30.40.50.60.70.80.91

1.1

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14Neutron Energy [MeV]

Linea

r Atte

nuati

on [c

m-1

]

Diamond

Kimberlite

GRANULATEEXPLOSIVE

PLASTIC

COPPERGELEXPLOSIVEGRAPHITE

O and Nsignal

The future

� Operation of D-100 and ADMDemonstrating� intense neutron production� explosives detection sensitivity� illicit material detection sensitivity

PTB collaboration:Implementation of short beam pulse system to enable TOF techniques

Thank You