Canadian High-Energy Neutron Spectrometry and

Mixed-Radiation Field Studies

B.J. Lewis and L.G.I. Bennett B.J. Lewis and L.G.I. Bennett Royal Military College of CanadaRoyal Military College of Canada

M. Smith, M. Zhang and H. M. Smith, M. Zhang and H. IngIngBubble Technology IndustriesBubble Technology Industries

JSC Radiation Detection WorkshopJSC Radiation Detection WorkshopHouston, Texas Houston, Texas April 6April 6--7, 20067, 2006

Outline

Canadian High-Energy Neutron Spectrometry System (CHENSS)Mixed-Field Measurement

• NFSE (bubble technology)• Tissue Equivalent Proportional Counter (TEPC)• Ionization chamber and SWENDI neutron remmeter • LIULIN (Si-based LET Spectrometer)• New technology: “DNA” dosimeter

Neutron Dosimetry in Space

Complex mixed charged particle and neutron environment exists in low Earth orbit (difficult to apply ground approaches)

Secondary neutrons (albedo neutrons from Earth’s atmosphere and production from spacecraft shielding) contributes to 10-30% of total dose equivalent

•TEPC gives reliable doses <20 MeV (response to higher energies?)•CR-39 passive dosimeters used to complement TEPC (and TLDs)

Improve radiation dosimetry in space by accurately measuring the neutron fluence and neutron energy distribution

Measure/predict radiation dose to astronauts and optimize shielding scenarios

Neutron Energy Distributions

Neutron Energy (MeV)

10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1 100 101 102 103

E φE (c

m-2

s-1)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Airline (Goldhagen)Accelerator (*0.0547) MIR Station (Lyagushin)

.

CHENSS:Canadian High-Energy Neutron Spectrometry System

20 cm

• Three gain settings provide desired dynamic range (1 – 100 MeV scale)• Internal 22Na (200 Bq) γ-ray source and two green LED’s provide energy calibration and gain stability checks• Amplitude and shape signals, hit patterns, scalersand diagnostics recorded on two hard drives• 50 W power from alkaline batteries• Designed for autonomous operation in NASA GAS can on space shuttle

G. Jonkmans et. al., Acta Astronautica 56, 975 (2005)

CHENSS: Principle of Operation -Distinguishing Space Radiation

Types of Space Radiation

• cosmic rays (vetoed by outer plastic scintillator)

• neutrons (detected by primary scintillator)

• electrons and γ rays (short pulses)

scattered neutron

neutron

cosmic ray

hydrogenous scintillating material(xylene + naphthalene)good n-γ discriminationisotropic responsereliable cross-sections

recoil proton

Constraints Imposed by Space

• Self-contained experiment with minimal human involvement• Scintillator is considered a hazardous payload by NASA• Significant temperature variations• Weight and power limitations• Physical size limitation• Data to be retrieved and examined after mission is completed

Demands a conservative, reliable and rugged design

Performance of Gelled Xylene ScintillatorNeutron – Gamma Discrimination

20 0 20 40 600.1

1

10

100

1 10 3

1 10 4C

ount

s pe

r Cha

nnel

Time (ns)

gamma neutron

gelled

liquid

contaminated

Total weight = 84.5 kg = 185 lbs

Batteries20 kg

Base20 kg

Top18 kg

Pressurevessel10kg

Cylindricalsupport4 kg

Electronics + wiring10 kg

Experimentalmounting plate

Visco-elasticscintillator

Phototubes

Scintillatingsidepanels2.5 kg

CHENSS Design

CHENSS Calibration at PTB

CHENSS Calibration at PTB

CHENSS irradiated by 2.5-, 5-, 14.8- and 19-MeV neutronsShadow-cone and blank-target backgrounds subtractedγ-ray events removed using pulse-shape analysisSpectra unfolded using (5-inch cylindrical) BC-501A response matrix*Fluence compared to independent PTB measurements

*N. Nakao et. al., Nucl. Instrum. Meth. Phys. Res. Sect. A 362, 454 (1995)

PTB Irradiation Spectra

Shape (channels)

En

erg

y (c

han

nel

s)

5 MeV

0 10 20 30 40 50 600

50

100

150

200

250

0

1

2

3

4

Shape (channels)

En

erg

y (c

han

nel

s)

2.5 MeV

0 10 20 30 40 50 600

50

100

150

200

250

-1

0

1

2

3

4

5

Shape (channels)

En

erg

y (c

han

nel

s)

14.8 MeV

0 10 20 30 40 50 600

50

100

150

200

250

0

1

2

3

4

5

6

Shape (channels)

En

erg

y (c

han

nel

s)

19 MeV

0 10 20 30 40 50 600

50

100

150

200

250

-2

-1

0

1

2

3

4

5

n

γ

3H(p,n)3He 2H(d,n)3He

3H(d,n)4He 3H(d,n)4He

Spectral Unfolding and Fluence Analysis

0 5 10 15 20 25-4

-2

0

2

4

6x 106

Energy (MeV)

Co

un

ts/M

eV

19 MeV

0 5 10 15 20 25-4

-2

0

2

4

6

8

10

12x 106

Energy (MeV)

Co

un

ts/M

eV

14.8 MeV

PTB and CHENSS (peak) fluences normalized to CHENSS live-time

Accelerator Facilities for High-Energy Neutron Calibration

• PTB neutron beams up to 19 MeV

• Higher energy beams at Louvain-la-Neuve, Belgium and iThemba, South Africa7Li(p,n)

Louvain

iThemba

Further Measurements for CHENSS

•If possible, higher-energy (30 – 100 MeV) tests at Louvain-la-Neuve and iThemba (2006 +)

• Airborne measurements at RMC, Kingston• Space mission(s) in the future

Neutron Bubble Technology: Ground-Based Calibration at CERF

TEPCTEPC

SWENDISWENDI

IonizationIonizationChamberChamber

Bubble Bubble DetectorsDetectors

NFSENFSE

Nuclear Fragmentation Separation Experiment

• Charged particle signature accompanies ~ 10% of events registered in BD- Agreement with FLUKA: charged hadron (p, π) fluence rate one order of

magnitude less than neutrons• BD-PND (260±50 pSv/PIC) vs CERF reference value (265±5 pSv/PIC)

Mixed-Field Measurement: Aircrew Radiation Studies

~>200 Flights (Portable Instruments) • Ionization Counter/Al2O3 TLDs (low-LET)• SWENDI Remmeter/Bubble Detectors (high-LET)• Liulin-4N & 4SN (Si-based) LET Spectrometers • 2 Tissue Equivalent Proportional Counters (TEPC)

Ionization Chamber (IC)

Extended Range Neutron Detector (SWENDI)

He-3 Detector

Tungsten Shell

PolyethyleneModerator

Handle

Meter Connection

Neutron Energy (MeV)0.1 1 10 100 1000 10000

Rel

ativ

e R

espo

nse

0.1

1

10WENDI-II (Side)Eberline Hankins-NRDAndersson-Braun (Side)

LIULIN-4N and 4SN (GPS) LET Spectrometer

(100 x 64 x 24 mm, 0.23 kg)

Tissue Equivalent Proportional Counter

Neutron Energy (MeV)

0.1 1 10

Dos

e Eq

uiva

lent

-to-F

luen

ce[p

Sv c

m2 ]

0

200

400

600

800

ICRP74 PTB 2000NPL 2002 PTB 2002 PTB 2005

BDsBDs & & TLDTLD’’ss (under foam)(under foam)

TEPC & IC + SWENDI: Pacific Routes

YY

Z - H

NL

HN

L - S

YD

Ant

arct

ic (1

)

Ant

arct

ic (2

)

Ant

arct

ic (3

)

SY

D -

LAX

YV

R -

PE

K

PEK

- YVR

YYZ

- HKG

HKG

- YY

Z

H*(

10) (

µ Sv)

0

10

20

30

40

50

60

70

% D

iffer

ence

200

-20TEPC SWENDI + IC

TEPC & IC + SWENDI World-wide Dose Rate at 10.7 km

0 2 4 6 8 10 12 14 16 180

2

4

6

8

10

1999 RMC data2001-02 RMC dataBest fit f1 (Climax = 4004 counts/h/100, Φ = 616MV)Best fit f2 (Climax = 3745 counts/h/100, Φ = 1007 MV)

Am

bien

t Dos

e E

quiv

alen

t Rat

e (µ

Svh

-1)

Nor

mal

ized

at 1

0.67

km

Vertical Cutoff Rigidity Rc (GV)

f1

f2

SOLAR MAXIMUM REGION

SOLAR MINIMUM REGION

Vertical cutoff rigidity Rc (MV)0 2 4 6 8 10 12 14 16 18

Am

bien

t dos

e eq

uiva

lent

rate

(µS

v/h)

norm

aliz

ed to

10.

6 km

0

2

4

6

8

RMC IC+SWENDI (Climax = 3744 counts/h/100, Φ = 984 MV)ACREM IC+NMX (Climax = 4277 counts/h/100, Φ = 498 MV) Best Fit ACREM IC+NMXBest Fit RMC IC+SWENDI

TEPC

Ionization Chamber + Neutron Remmeter

Poles Equator

Upgraded to HAWK

TEPC Limitations for Low-LET Analysis (in Mixed-Field)

TEPC unable to provide measurement below ~0.6 keV/µm due to electronic noise (S. Rollet et al., Rad. Prot. Dos 110 (2004) 833).

•Fluka simulation to determine missing low-LET dose•Correction applied by manufacturer (60Co calibration)

Missing dose

60Co: Low-LET (y < 10µm) Neutrons (0.5 MeV) : High-LET (y > 10µm)

LIULIN-4N Detector

• Portable instrument needed (periodic checking of PCAIRE code)• Absorbed route dose (46 flights)

• LIULIN vs TEPC (Reference Instrument)

DLIULIN (µGy)

0 5 10 15 20 25

DTE

PC ( µ

Gy)

0

5

10

15

20

25

Elapsed Flight Time (min)0 200 400 600 800

Abs

orbe

d D

ose

per I

nter

val (

µGy/

20 m

in)

0.0

0.2

0.4

0.6

0.8

Alti

tude

(ft)

0

10000

20000

30000

40000

LIULINTEPCAltitude

H*(10) Analysis for Liulin

• Methodology (H=QD):(i) Q as a function of cutoff rigidity(ii) LIULIN LET spectral analysis (ICRP-60 Q(L))

Quality Factor vs Cutoff Rigidity

Cutoff Rigidity, RC (GV)0 2 4 6 8 10 12 14 16 18

Qua

lity

Fact

or, Q

HA

WK

0

1

2

3

03 Nov 0311 Nov 0321 Nov 0302 Dec 0309 Jan 0331 Oct 0301 Dec 0308 Dec 0301 Oct 0322 Sep 0329 Sep 0304 Oct 03Linear Reg'n

Geographic Longitude (degrees)-180-160-140-120-100 -80 -60 -40 -20 0 20 40 60 80 100 120 140 160 180

Geo

grap

hic

Latit

ude

(deg

rees

)

-80-70-60-50-40-30-20-10

0102030405060708090

2.22.22.22.2

2.12.12.12.1

1.9 1.91.9

1.91.81.8

1.81.81.7

1.71.8

1.81.81.8 1.9

1.6

2.12.1 2.1

2.12.2

1.9 1.9

1.9

1.72.2

2.2

1.7

1.71.7

1.7 1.71.7

1.6 1.6

1.6

1.6 1.6

2.32.3

2.3

2.3

1.4

1.4

2.32.3

2.02.0

2.02.0

2.02.0 2.0

2.0

1.5 1.5

1.51.5

CCHAWK RRQ 06.036.2)( −=

LIULIN Spectral Analysis (ICRP-60 Q(LET))

Channel LET Counts Quality Factor (ICRP60) H*(10)I (keV/um) n(i) in(i) Q(L) (uSv)

0 0.25 0 0 1.000 0.001 0.75 5643 5643 1.000 1.582 1.25 7642 15284 1.000 4.283 1.75 4190 12570 1.000 3.524 2.25 2816 11264 1.000 3.155 2.75 1657 8285 1.000 2.326 3.25 1200 7200 1.000 2.017 3.75 842 5894 1.000 1.65

18 9.25 68 1224 1.000 0.3419 9.75 43 817 1.000 0.2320 10.25 44 880 1.000 0.2521 10.75 48 1008 1.080 0.3022 11.25 30 660 1.240 0.2323 11.75 30 690 1.400 0.27

196 98.25 0 0 29.080 0.00197 98.75 0 0 29.240 0.00198 99.25 0 0 29.400 0.00199 99.75 0 0 29.560 0.00200 100.25 0 0 29.963 0.00201 100.75 0 0 29.888 0.00202 101.25 0 0 29.814 0.00203 101.75 0 0 29.741 0.00253 126.75 0 0 26.647 0.00254 127.25 0 0 26.595 0.00255 127.75 0 0 26.542 0.00

Count Sum 27061 116243 24.50

)(1033.9)( 5 iniGyDi ⋅⋅×= −µ

∑=

=255

0

)())(10(*i

ii DLQSvH µ

mkeVLi µ/5.0=∆

H*(10) with LIULIN vs TEPC

Flight Date

28-M

ay-0

3 am

28-M

ay-0

3 pm

29-M

ay-0

316

-Jun

-03

18-J

un-0

3 am

18-J

un-0

3 pm

19-J

un-0

315

-Jul

-03

22-J

ul-0

331

-Jul

-03

2-A

ug-0

3 am

2-A

ug-0

3 pm

5-A

ug-0

36-

Aug

-03

am6-

Aug

-03

pm8-

Aug

-03

am8-

Aug

-03

pm9-

Aug

-03

10-A

ug-0

3 am

10-A

ug-0

3 pm

12-A

ug-0

3 am

12-A

ug-0

3 pm

13-A

ug-0

314

-Aug

-03

22-S

ep-0

327

-Sep

-03

29-S

ep-0

31-

Oct

-03

4-O

ct-0

326

-Oct

-03

27-O

ct-0

3 (1

)27

-Oct

-03

(2)

27-O

ct-0

3 (3

)1-

Nov

-03

3-N

ov-0

310

-Nov

-03

21-N

ov-0

323

-Nov

-03

1-D

ec-0

32-

Dec

-03

5-D

ec-0

38-

Dec

-03

3-Ja

n-04

5-Ja

n-03

9-Ja

n-03

H*(

10) (

µ Sv)

0

10

20

30

40

50

60

70

% D

iff (T

EP

C) (

%)

-380-360-340-320

-280-260-240-220

-180-160-140-120

-80-60-40-20

20406080

-400

-300

-200

-100

0

100

H*(10) TEPCH*(10) Liulin

0

10

20

30

40

50

60

70

YY

Z - Y

VR

YV

R -

ICN

ICN

- Y

VR

YV

R -

YY

Z

YY

Z - L

AX

LAX

- S

YD

SY

D -

LAX

LAX

- A

KL

SY

D -

JBG

JBG

- S

YD

JBG

- S

YD

YK

G -

YY

Z

YY

Z - Y

VR

YV

R -

PE

K

YY

Z - H

KG

(P)

HK

G -

YY

Z

YY

Z - Y

GK

YY

Z - Y

VR

YV

R -

ICN

ICN

- S

IN

SIN

- IC

N

YY

Z- L

HR

LHR

- Y

YZ

YY

Z - Y

GK

YG

K -

YY

Z

YY

Z - M

UC

MU

C -

HA

J

HA

J - M

UC

MU

C -

YY

Z

YY

Z - Y

GK

Flights

Tota

l Am

bien

t Dos

e Eq

uiva

lent

(µSv

)

H*(10)TEPC (µSv) H*(10) Liulin 4N (µSv) H*(10) Liulin 4SN (µSv)

Novel New Technology: DNA Dosimeter

Polymeric biosensor to detect double strand DNA (dsDNA) breaks induced by radiation (biologically-relevant dosimeter for mixed-field measurement)

• Captor (nanotechnology) of known amounts of target dsDNA (predefined length with specific terminal sequence tag)

• Detector (optically-clear hybridization chamber) to read fluorescent signal of cleaved-target dsDNA

• Correlated against biological dosimetry and compared to physical dosimetry for mixed fields

Tag sequence

Tag complementaryprobe

Wash

Captor Captor exposedto radioactivity

Detector

----------------

+++++++++++++++

--------------------

+++++++++++++++

420 nm 572 nm

----------------

+++++++++++++++

----------------

+++++++++++++++

+

420 nm

----------------

+++++++++++++++

----------------

+++++++++++++++

----------------

+++++++++++++++

----------------

+++++++++++++++

----------------

+++++++++++++++

++

+

+

----------------

+++++++++++++++

--------------------

+++++++++++++++

420 nm 572 nm

----------------

+++++++++++++++

----------------

+++++++++++++++

+

420 nm

----------------

+++++++++++++++

----------------

+++++++++++++++

----------------

+++++++++++++++

----------------

+++++++++++++++

----------------

+++++++++++++++

++

+

+

----------------

+++++++++++++++

--------------------

+++++++++++++++

420 nm 572 nm

----------------

+++++++++++++++

----------------

+++++++++++++++

+++

420 nm

----------------

+++++++++++++++

----------------

+++++++++++++++

----------------

+++++++++++++++

----------------

+++++++++++++++

----------------

+++++++++++++++

++++++

+++

++

Conclusions

CHENSS can be used for high-energy neutron spectral measurement• Currently being calibrated at accelerator facilities

NFSE shows promise for n measurement with bubble technology in mixed-field Mixed-field measurements made at jet altitudes

• Good comparison of H*(10) by summing low (IC) and high (SWENDI) LET components with TEPC measurement

• Good comparison of H*(10) between TEPC and LIULIN

Novel technology: biologically-relevant “DNA” dosimeter

Acknowledgements

Funding support from the Life and Physical Sciences Directorate of the Canadian Space Agency (CSA) and Transport CanadaR. Nolte and S. Rottger of the Physikalisch Technische Bundesanstalt(PTB) Thanks are also due to: H.R. Andrews, E.T.H. Clifford, V.T. Koslowsky and R. Noulty (BTI), M. Boudreau (RMC), C. Vachon(NRC) and L. Tomi (CSA)

Cosmic-Ray Detector(anti-coincident shield, 100% efficient)

Plastic scintillating panel• 1cm thick, creates strong signal• 8 panels provide full coverage• openings for cables and

mechanical fasteners• cushioned with VITON gaskets

and caulking from metalsurfaces

• no fasteners or tapped holes(no dead areas)

Phototubes• one per panel• cement to plastic• withstand 20g

Cross-sectional A-A

A A