compact and miniature pulsed neutron generators based on … · 2005-12-11 · compact and...

Thermonuclear Plasma DepartmentChilean Nuclear Energy Commission

IAEA TM Neutron Generators for Detection ofExplosives and Illicit Materials

Compact and miniature pulsed neutron generators based on

plasma focus technology

Leopoldo Soto,José Moreno, Patricio Silva, Gustavo Sylvester, Marcelo Zambra,

Cristian Pavez+, Ariel Tarifeño+

Comisión Chilena de Energía Nuclear+ Universidad de Concepción



“Talk low, talk slow, don´t tell too much”

John Wayne



Landmines in thenorth and in thesouth of Chile

30 years



• Chile signed the Otawa agreement

• CCHEN has been developing a coordinate activity with the Chilean Army

Army provides information regarding with the mines (explosive and original location)

CCHEN: nuclear techniques



• Using the reactor RECH-1 to irradiatemines, the gamma peak of 10.8 MeV wasobtained

1.6x106 n/s cm2 6 hours

• Also soil from the zones with mines wasstudied



Thermonuclear Plasma Department

L. Soto

M. Zambra P. Silva

R. Muñoz

J. Moreno

G. Sylvester

Ph D students

A. Rozas

Dense, hot plasmas



Why dense hot plasmas are interesting?

Physics:Possibility to study:

- High energy density and high mass density state of matter- Fast plasma dynamics

Production of energy: - Nuclear Fusion

Other applications: Generation of:- particles beams and plasma jets- Radiation



Jz

Bθ

z axis

Z-pinch geometry

How to obtain a dense hot plasma – The Z-pinch.

Parameters:- Density n > 1018 cm-3

- Temperature T∼ keV- Duration ∼ns-µs

Products:- Ion and electron beams- Plasma jets- Radiation from VUV to hard X-ray- Neutrons.



Plasma focusPlasma focus + gas puff

Gas embedded compressional Z-pinch (double column)

Wire arrays X-pinch



The biggest experiment in the world (11.4MJ)

R. Leeper et al. APS Spring Meeting, Philadelphia (April 6, 2003)

K. Chang, New York Times (April 8, 2003)



PLASMA ENERGY DENSITY

~1012 J/m3

1J in a sub millimeter volume

0.1J in a sphere of 60µm of diameter

PLASMA PHYSICS IN SMALL DEVICES



Plasma Focus

PF chamber

cathode

insulator

anode

B

F

HVC

+n

+n +n+nn

++n

+n+n

He

Tr

D+

D+(deuterón)

50%

X

e

i

X



Device[reference]

Energy (kJ) Anode diameter(cm)

Operation mode

PF-1000 [6] 1000 23 Single shotSPEED 2 [3] 100 11.7 Single shotGN1 [17] 4.7 3.8 Single shotAAAPT [7] 3 1.9 Single shot

Fraunhofer InsituteILT-AachenRWTH LLT [11]

2-5 ______ Repetitive, 2Hz

Research Lab.,Alameda [12]

2 ______ Repetitive, 2Hz

NX1 [13] 3 3 Repetitive, 3HzNX2 [13] 1.9 4 Repetitive, 16HzPF-400J (CCHEN) 0.4 1.2 Single shotPF-50J (CCHEN) 0.05 0.6 Single shot

Some plasma focus devices with their characteristic energy, size anode electrode and operation mode. PF-1000: atthe Institute of Plasma Physics and Laser Microfusion, Warsaw, Poland; SPEED 2: at Heinrich-Heine-Universität, Düsseldorf, Germany (1986-2000), at present in operation at the Comisión Chilena de Energía Nuclear, Chile; GN1: at the Universidad de Buenos Aires, Argentina; AAAPT: Asian-African Association for Plasma Training Network, ILT-LLT: Fraunhofer Insititut für Lasertechnik and Lehrstuhl für Lasertechnik, Aachen, Germany; SRL: ScienceResearch Laboratory, Alameda, USA; NX1 and NX2: at Nanyang Technological University, Singapore. It can be seen that the energy of the device described in the present article is relatively very low.



-30

0

30

60

Volta

ge (k

V)

-1

0

1

dI/d

t (A

/sx1

013 )

1000 1500 2000

-1012

Time (ns)

Cur

rent

(MA

)

-30

0

30

60

-1

0

1

1500 2000 2500

-1012

Time (ns)

a) b)

September 2002

1010-1011 neutrons (measured at CCHEN)

June 2001

January 2002

SPEED2 at CCHENA donation from U. of Düsseldorf

to the CCHEN´s group

187KJ, 4MA, 400ns



Compact PF devices

SPEED 4

6kJ, 500kA, 350ns

PF-400J: 400J, 130kA, 300ns

PF-50J: 50J, 40kA, 150ns



200 300 400 500 600 700 800

ArIX

-2

ArX-

2Ar

X-2

ArIX

-3

ArIX

-2

ArVI

IAr

IX-3

ArX-

3Ar

X-3 Ar

VII

ArVI

I

ArIX

-5

ArVI

IIAr

VII12

5.9 16

5.8

170.

47

125.

9

203.

64

475.

65 163.

8216

7.83

170.

47 585.

7558

8.92 12

5.9

700.

2571

3.8

Inte

nsity

(a.u

.)

λ(Å)

0 250 500 750

0

2

4

# Cuentas en detector de plata activada : 327 equivale a una producción de 1.07*106 neutrones

Señal del detector de He3

Volta

je (v

olt)

t (µs)

Diagnostics

Our diagnostics capabilities

-505

101520

V

dI/dt

FM2

-100 0 100 200 300 400 500 600 700

1.5 m

pD2

= 7.7 mbarVoper = 25 kV

t (ns)

68 ns

SHOT 84V270603

FM1



J. Moreno, P. Silva and L. Soto, Plasma Sources Sci. and Technol. 12, 39 (2003)

PF-50J the smallest plasma focus in the world



PF-50JVisible plasma images obtained with a ICCD, 5ns exposure time

222 ns 309 ns37 ns



0

20

200ns/divSHOT 13J290802

Voltaje

-1

0

1 dI/dt

-500

50100150

I(kA)

dI/d

t (TA

/s)

V(kV

)

I

4 5 6 7 8 9 10 11 12 13240

260

280

300

320

340

360

380

400

420

t pinc

h &

t peak

cur

rent (

ns)

pressure (mbar)

6 7 8 9 10 11 12

2.0x105

4.0x105

6.0x105

8.0x105

1.0x106

1.2x106

Y

Pressure (mbar)

PF-400J

PF-400J

0

10

20

Volta

ge (k

V)

-0.4

0.0

0.4

0.8

dI/d

t (10

12A

/s)

-3

-2

-1

0

FM

2 (v

olt)

0 200 400 600

-0.8

-0.4

0.0

FM

2 (v

olt)

t (ns)

68 ns∆L = 1.5 m

SHOT84270603

PF-400J

P. Silva, J. Moreno, L. Soto, L. Birstein, R. Mayer, and W. Kies, App. Phys. Lett. 83, 3269 (2003).



0

25Voperación = 29 kV

t (ns)SHOT 37W041202

Voltaje

-1

0

1

dI/dt

0 200 400 600 800

-50

0

50

I(kA)

dI/d

t (TA

/s)

V(kV

)

I

-20

0

20Voperación = 25 kV

t (ns)SHOT 89W051202

Voltaje

-1

0

1

dI/dt

0 200 400 600 800

-50

0

50

I(kA)

dI/d

t (TA

/s)

V(kV

)

I

5 6 7 8 9140

150

160

170

180

190

200

210

220

230 tPinch v/s presión PF-50J a 25 kV

t pinc

h (ns

)

Pressure (mbar)6 7 8 9 10 11 12 13

140

150

160

170

180

190

200

210

220

230 tPinch v/s presión PF-50J a 29 kV

t pinc

h (ns

)

Pressure (mbar)

PF-50J



5 6 7 8 9 10 11 12

5.0x103

1.0x104

1.5x104

2.0x104

2.5x104

3.0x104

3.5x104

Y

Pressure (mbar)

4 5 6 7 8 9

2.0x103

4.0x103

6.0x103

8.0x103

1.0x104

1.2x104

Y

Pressure (mbar)

PF-50J 25kV, 50J

29kV, 70J

0 200 400 600

0

1

2

3

0 200 400 600

0.00

0.03

0.06

0.09

30 count/30s Area = 77.4



150 count/30s Area = 856.0

Inte

nsity

(vol

t)

t (µs)

Area = 3.5 Area = 18.0 Area = 21.7

(b)(a)

A special technique was necessary develop to detect the neutron yield

See poster SPD-11: “Proportional counter of 3He adapted to measure neutron pulses of low total yield in plasma focus devices”



Applications with small devices?Neutrography.In accordance with commercial information from internet readily available on fast neutron radiography using a CCD coupled to a Gdconverter, it may be concluded that a proposed 106 neutron per shot source as PF-400J, placing the sample 5cm from the source, a 5cm2

analysis area may be recorded with 103 to 104 shots, depending on sample nature and shape. With a 10Hz repetition rate this fluenceswill attained after 100 to 1000 seconds. The device presented here conceived for laboratory purposes, is a single shot machine which can be operated only at 0.5Hz.

Detection by transient activation analysisAccording to the same commercial information, sources providing 106

– 108 neutrons/s at 10kHz repetition rate are useful for prompt gammaneutron analysis. This translates into a 102 – 104 neutrons/shot. A plasma focus device in the tens of joules range and ∼104 neutrons/ shot as PF-50J or smallest could be useful (but with high repetition rate).



Hard X-ray nanoflash

X-ray from PF-400J

∼ 90±5 keV energy



X-ray nanoflash

Tomography

PLADEMA



It is interesting note that plasma parameters practically constant in plasma focus devices are correlated with the value of electrical and geometrical parameter of the devices, this is useful for design considerations.



va= ga( I / a p1/2) vr = gr (I / a p1/2)S. Lee et al., Amer. J. Phys. 56, 62 (1988)

Pinch radius ~ 0.13 a, a=anode radius

maximum high, z~0.8 a S. Lee and A. Serban, IEEE Trans. Plasma Sci. 24, 1101 (1996)

Thus, PF energy density can be estimated in

E/Vpinch~ 28E/a3



How low is possible to go in energy keeping the same energy density?

66.768

7.3x1010

5.2x101096

6050

0.30.3

0.070.05

PF-50J

705.2x101091270.60.4PF-400J

953.6x1091.52502.52PACO

819.5x10108.51720.952.9UNU/ICTP-PFF]

730.8x10103.73502.54.6Fuego Nuevo II

-1.9x1010--1.94.7GN1

913.7x101063901.7577kJ PF-Japan

-1.2x10102.724005.470SPEED2

751.3x10104750560PF-360

721.8x10106200011.51000PF-1000

Driven factorI0 /p1/2a

(kA/mbar1/2cm)

Energy density parameter

28 E/a3 (J/m3)

Pressure(mbar)

Peak currentI0 (kA)

Anode radiusa (cm)

Energy E (kJ)

Device



RECENT DEVELOPMENTMINIATURIZATIONNANOFOCUSE < 1J

A plasma focus driven by a capacitor bank of less than 1J

Conceptual design and electrical parameters expected:

C=5-10nF

L=5-10nH

Vo=5-15kV (E~ 0.06 - 1 J)

Ipeak= 5kA-15kA

Expected neutron yield at 10kA, Y ~ 103



RECENT DEVELOPMENTMINIATURIZATION

NANOFOCUS

E < 1JConceptual design and electrical parameters expected:C=5-10nFL=5-10nHVo=5-15kV (E~ 0.06 - 1 J) Ipeak= 3kA-15kA, T/4=8ns-16ns

Expected neutron yield at 10kAY ~ 103 neutron/shot



0500

100015002000250030003500

VoltajeI (

kA)

dI/d

t (kA

/ns)

V

(V)

-0.5

0.0

0.5 dI/dt

0 50 100 150 200-2.0-1.5-1.0-0.50.00.51.01.52.0

Shot#31; pc = 20mbar, Sept. 10, 2003

Corriente

t (ns) 77 nsICCD camera 4ns exposure timeT = 30ns

C = 4.9nF, L = 4.8nH,

3 mm

a = 0.8mm

H2 20 mbar



Nanofocus

0

2

4

6

8

10

Shot#135b; p = 3mbar, Oct. 2003

I (kA

)dI

/dt (

kA/n

s)

V (k

V)

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

-50 0 50 100 150-5-4-3-2-1012345

t (ns)

E=1/2 CV2

C~ 5 ± 1nF

V=6.5±0.3kV

E ~ 100mJ!

3mm

3mm

-26ns 30ns5ns



In deuterium similar results (preliminary) have been obtainedEnergy density parameter: E/Vpinch~ 28E/a3

~5x109J/m3

Drive parameter:

I/a(p)1/2 ~ 70 kA/cm mbar1/2

I= 4.2kA, a = 0.08cm, p = 3mbar

I/a(p)1/2 ~ 30kA/cm mbar1/2

It is necessary to increase the current (a spark gap is being designed in order to control the charging voltage)or decrease the radius



I~ 4.5kA,a = 0.021cm,

p = 3mbarI/a(p)1/2 ~ 130kA/cm mbar1/2

0

2

4

6

8

10Voltaje

I (kA

)dI

/dt (

kA/n

s)

V

(kV)

-1.0

-0.5

0.0

0.5

1.0dI/dt

-50 0 50 100 150-5-4-3-2-1012345

Shot#198b; p = 3mbar, 5 Nov. 2003

Corriente

t (ns)



-19.1 ns -11.1 ns

0.1 ns

-3.1 ns

4.9 ns 8.9 ns

30 ns

3 mma = 0.21mm

E=1/2 CV2

C~ 5 ± 1nF, V=9±0.5kV

E ~ 0.2J 200mJ~6x1011 J/m3



How to measure the neutron yield?

• In principle the adapted 3He detector can measures pulses as low as 7x102 neutrons per shot.

• The nano PF operating at 100Hz by 10 s could produce 106 neutrons, thus a silver activation counter could be used.

It could produce soft X-ray?



FUTURE• Ion beams characterization

• Enhancement of thermonuclear component of the neutron yield– Yth α I 4 v4 and Ybt α I 4.5 v1.5

– v = 10 cm/micro s in the axial phase– v = 25 cm/micro s in the radial collapse– Increasing v (or I/a), it could be possible to increase the thermonuclear

component of the neutron yield and to decrease the beam targetcomponent. In fact, in the limit keeping the anode radius constant whilstincreasing the current, Yth α I 8 and Ybt α I 3

• With this improved or enhanced yield dependence, thethermonuclear component of neutron yield will rapidly outstripthe beam target component.



FUTUREBiology

• Study of the effect of the pulsed intense irradiation on cells, and its use in biology and pulsed dossimetry.

Centro de Estudios Científicos, Valdivia

Dr. Steffen Härtel

Dr. Felipe Barros



SPEED2 SPEED4 PF-400J PF-50J

1meter

Plasma Focus Nanofoco

2004 →

“New Trends and Future Perspectives on Plasma Focus Research”, L. Soto Invited review paper ICPP 2004, published in Plasma Physics and Controlled Fusion 47, A361 (2005).



Extreme pinch devices

Z Acelerator 10MJ

Sandia National Laboratories, USA

Nano Focus 100mJ

Chilean Nuclear Energy Commission, Chile

1m

1cm

compact and miniature pulsed neutron generators based on … · 2005-12-11 · compact and...

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