GOBIERNO DE CHILE COMISION CHILENA DE ENERGIA …...Chilean Nuclear Energy Commission, CCHEN...

2nd Research Coordination Meeting of AIEA CRP on “Neutron Based Techniques for the Detection of Illicit Materials and Explosives”, 12 to 16 November 2007, Mumbai, India

Thermonuclear Plasma DepartmentChilean Nuclear Energy Commission, CCHEN

GOBIERNO DE CHILECOMISION CHILENA DE ENERGIA NUCLEAR

Development of portable neutron generators based on pinch and plasma

focus discharges

Leopoldo Soto1, 2, Cristian Pavez 1,2 , Miguel Cárdenas, José Moreno1,2 , and Luis Altamirano2, 3

1 Comisión Chilena de Energía Nuclear, Casilla 188-D, Santiago, Chile2 Center for Research and Applications in Plasma Physics and Pulsed

Power, Chile 3 Dicontek, Chile

[email protected]




Landmines detection based on back scattering of neutrons

TC IAEA Project




HYDAD-DHYdrogen Densisty Anomaly Detection

F. D. Brooks and M. Drosg, Applied RadiationPhysics 63, 565 (2005)

Sources of Am-Be, 252Cf: 5x104 neutrons/s scan 0.5m in 5 min




PLASMA ENERGY DENSITY

Z-machine in Sandia National Laboratory, USA

~1012 J/m3

1J in a sub millimeter volume

0.1J in a sphere of 60µm of diameter

PLASMA PHYSICS IN SMALL DEVICES

OUR APPROACH




Devices at CCHEN-Chile

SPEED2 SPEED4 PF-400J PF-50J

1meter

Plasma Foci Nanofoco

miniaturization




< 1kJ

• 1978, India: BARC, 125J, 5x105 n/shot (A. Shyam and M. Srinivasan, Applied Physics A: Material Sciece and Proccessing 17, 425, 1978)

• 2005, India: Institute for Plasma Research, 60J, 106 n/s (A. Shyamet al., Z-pinches Conference, Oxford, UK, 2005)

• 2005, India: 2005, BARC, 190J (10.6µF, 6kV) 103 n/shot (R. K. Rout et al., Sixteenth Annual Conference of Inidian Nuclear Society, 2005)

• At present, Rusia: VINIIA, 200J, 105 n/shot




-30

0

30

60

Voltage (kV

)

-1

0

1

dI/d

t (A

/sx1

013 )

1000 1500 2000

-1

0

1

2

Time (ns)

Curr

ent (M

A)

-30

0

30

60

-1

0

1

1500 2000 2500

-1

0

1

2

Time (ns)

a) b)

September 2002

1010-1011 neutrons (measured at CCHEN)

June 2001

January 2002

SPEED2 at CCHEN

A donation from U. of Düsseldorf

to the CCHEN´s group

187KJ, 4MA, 400ns



GOBIERNO DE CHILECOMISION CHILENA DE ENERGIA NUCLEAR Compact PF devices

SPEED 4

6kJ, 500kA, 350ns

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

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




Plasma Dynamics



GOBIERNO DE CHILECOMISION CHILENA DE ENERGIA NUCLEAR Electrical signals

0

20

200ns/divSHOT 13J290802

Voltaje

-1

0

1 dI/dt

-50

0

50

100

150

I(kA

)d

I/d

t (T

A/s

)V

(kV

)

I

PF-400J




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

Plasma Dynamics

PF-50J




PF-50J

Visible plasma images obtained with a ICCD, 5ns exposure time

222 ns 309 ns37 ns

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




0 50 100 150 200 250 3000

2

4

6

8

10

12

a(m

m)

time (ns)

0 100 200 300 400 500 600 7000

5

10

15

20

25

30

z 1 an

d z 2

(m

m)

time (ns)

Fig. 5. Radial plasma motion a(t) and motion of the frontal and rear axial plasma edge, z1(t) and z

2(t)




Plasma density




Interferograms

rp =7.4 mm a t=-3ns

[ ]118108.8 −⋅= mNe

TB =1.56x1011 I2/N (eV, A, m-1)

TB ~ 300 eV

LLR stabilization effects, C. Pavezet al. In preparation

t =4 ±±±±4 ns t = 12 ±±±±4 ns

12 mm

0,0 0,2 0,4 0,6 0,8 1,0

0,0

2,0x1024

4,0x1024

6,0x1024

8,0x1024

1,0x1025

z = 1.5 mm

z = 0.6 mm

p = 5 mbar (H2); t= 4 ns ; z

p= 4 mm

ne (

m-3)

r (mm)




X-rays




Hard X-ray nanoflash

X-ray from PF-400J

∼ 90±5 keV energy




Neutrons




0

20

200ns/divSHOT 13

J290802

Voltaje

-1

0

1 dI/dt

-50

0

50

100

150

I(kA

)d

I/d

t (T

A/s

)V

(kV

)

I

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

Vo

lta

ge (

kV

)

-0.4

0.0

0.4

0.8

dI/d

t (1

01

2A

/s)

-3

-2

-1

0

FM

2 (

vo

lt)

0 200 400 600

-0.8

-0.4

0.0

FM

2 (

vo

lt)

t (ns)

68 ns

∆L = 1.5 mSHOT84

270603

PF-400J

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




CR39 Plastic Nuclear Track Detector

CR39 (0º)

CR39 (90º)CR39 (-90º)

CR39 (-45º)CR39 (45º)

r = 50cm

in collaboration with F. Castillo and J. Herrera, UNAM, Mexico




-90 -60 -30 0 30 60 90

500

1000

1500

2000

Ne

utr

on/c

m2

Angle (degrees)

-90 -60 -30 0 30 60 90

500

1000

1500

2000

Neu

tron

/cm

2

Angle (degrees)

Analysis Method (Castillo et al. Plasma Phys. Control. Fusion 45, p.289, 2003).

)2/exp(2

)( 22 σϑπσ

ϑ −+=C

Bf

The data could be adjusted by a

Gaussian function of the angle θsuperposed on a pedestal:

∫ +==π

ϑϑϑπ0

sin)(2 YaYidfY , where: BYi π4= KC

Yaσ

π2=,

There are clearly isotropic and anisotropic contributions, which most probably originate

from different neutron generation mechanisms.




Isotropic components accounts for 56.7% of the accumulative emission,

while the anisotropy component accounts for the remaining 43.3%.Isotropic component appears between +50º and –50ºapproximately as show the normalized neutron yield graphic




Time of Flight

1.0m 1.5m2.0m

2.5m

3.0m

Scintillator System Array

In collaboration with F. Castillo and J. Herrera, UNAM, Mexico




0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0

0

1

2

3

4

5

6

7

8

9

energy (MeV)

PF-400J




Plasma Focus that works withonly tens of joules




Neutron nanoflash

PF-50J a plasma focus of tens of Joules

L. Soto, A. Esaulov, J. Moreno, P. Silva, G. Sylvester, M. Zambra, A. Nazarenko, and A. Clausse. Phys. Plasmas 8, 2572 (2001)

P. Silva, L. Soto, J. Moreno, G. Sylvester, M. Zambra, L. Altamirano, H. Bruzzone, A. Clausse, and C. Moreno, Rev. Sci. Instrum. 73, 2583 (2002)




System for measurement of low yield neutron pulses from D-D fusion reactions based in a

3He proportional counter

José Moreno, Lipo Birstein Roberto E. Mayer, Patricio Silva, and Leopoldo Soto

Submitted to Meas. Sci. Technol.




In addition as the neutron signal is preceded by the electromagnetic pulse of the plasma focus discharge, the neutron signal is coincident with the discharge and it is possible secure that the signal is from the plasma focus event. In discharges in hydrogen in which neutrons are not emitted only the electrical noise is register in the signal, background radiation is not detected in that small temporal windows of hundreds of microseconds.

The moderator (paraffin) offers three functions to the system detector: a) thermalize the fast neutrons of ~ 2.45 MeV, b) the neutrons generated in the plasma focus pulse (~ 10-100 ns) are dispersed in time (~

300µs), reducing saturation effects in the detector, and c) as PF devices generate intense electromagnetic

pulses associated with the main discharge (~1µs) that could contribute to a very significant distortion to the measurement signal, the moderator assures the

separation (∼30µs between the electromagnetic noise and the maximum of the neutron signal) of these two signals namely, the true neutron signal from the electromagnetic pulse.




Count rate vs. area under the curve of the signal and the count rate vs. the maximum intensity of the signal, show that a linearrelation exists in both cases.




• We will use the linearity with the area under the curve because the objective is use the detector in the region of very low neutron emission, it becomes evident in that independent pulses may not contribute to the ‘height’ of the recorded signal, but contribute to the total area under the signal.




• In fact individual neutrons produce a voltage signal like

Vi exp(-t/RC), with RC the decay time of the preamplifier (50µµµµs in this case)

• and its integrated area is Ai = RC Vi.

• From the nominal gain, αααα, of the preamplifier (Canberra model 2006),

αααα = 47mV/Mpi, it is obtained that the charge per volt is 1/αααα = 3.4x10-12 C/V.

• Thus the charge produce for one neutron is Qi = Vi/αααα = Ai /RCαααα.

• The total charge produced, QT, is obtained summating all the individual events, and

QT= AT /RCαααα, where AT is the total area under the curve of the signal.

• Therefore the total number of neutrons is proportional to the total charge (or to the total area under the curve of the signal).




Calibration of the system




25kV, 50J

4 5 6 7 8 9

4,0x103

8,0x103

1,2x104

1,6x104

2,0x104

Y

Pressure (mbar)

PF-50J

L. Soto, A. Esaulov, J. Moreno, P. Silva, G. Sylvester, M. Zambra, A. Nazarenko, and A. Clausse. Phys. Plasmas 8, 2572 (2001)

P. Silva, L. Soto, J. Moreno, G. Sylvester, M. Zambra, L. Altamirano, H. Bruzzone, A. Clausse, and C. Moreno, Rev. Sci. Instrum. 73, 2583 (2002)

P. Silva, L. Soto, W. Kies, and J. Moreno, Plasma Sources Sci. and Technol. 13, 329 (2004).

“Measurement of low yield neutron pulses from D-D fusion reactions using a 3He proportional counter” Submitted to Meas. Sci and Technoll.

“Demonstration of neutron production in a table-top plasma pinch deviec operating at only tens of joules” Submitted to EPL



GOBIERNO DE CHILECOMISION CHILENA DE ENERGIA NUCLEAR PF-50J

-0,4

0,0

0,4

-2

0

0 100 200 300 400

-2

0

dI/dt

∆∆∆∆ t = 22 ns => En= 2.48MeV

FM1

a. u

.

FM1 at 30.5 cm from the axisFM2 at 78.5 cm from the axis

FM2

time (ns)

Average over 20 shots →→→→ mean energy of 2.7 Mev

dispersion of 1.8 MeV




66.768

7.3x1010

5.2x1010

96

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

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




• Energy density parameter and drive parameter are practically constant in the energy range from 1MJ to 50J

• Surface effects?

S/V~1/a

It increases at small dimensions

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

• When the scale rules start to be not valid?



GOBIERNO DE CHILECOMISION CHILENA DE ENERGIA NUCLEAR Design considerations

Energy density parameter

28E/a3~5x1010J/m-3

Drive parameter

I/ap1/2 ~ 77kA/cm mbar1/2

• L. Soto, Plasma Phys. Control. Fusion 47, A361 (2005)

• T. Zhang, R. S. Rawat, S. M. Hassan, J. J. Lin, S. Mahmood, T. L. Tan, S. V.

Springham, V. A. Gribkov, P. Lee, and S. Lee, IEEE, Trans. Plasma Sci. 34, 2356

(2006)




MINIATURIZATION

NANOFOCUS

E < 1J

Conceptual 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




0

500

1000

1500

2000

2500

3000

3500Voltaje

I (k

A)

dI/d

t (k

A/n

s)

V (

V)

-0.5

0.0

0.5 dI/dt

0 50 100 150 200-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

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



GOBIERNO DE CHILECOMISION CHILENA DE ENERGIA NUCLEAR Nanofocus

0

2

4

6

8

10

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

I (k

A)

dI/d

t (k

A/n

s)

V (

kV

)

-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



GOBIERNO DE CHILECOMISION CHILENA DE ENERGIA NUCLEARNF: 6.5kV, 4.5kA, 15ns, 0.1J, a=0.8mm

Al filters: 15, 30, 45, 60, 75µm…

Ti filters: 12.5, 25, 37.5, 50µm…

1000 shots

2000 shots

2000 shots



GOBIERNO DE CHILECOMISION CHILENA DE ENERGIA NUCLEAREstimation of X-ray energy

• Assuming a monoenergetic emission, I = I0 e-µ∆∆∆∆x

0,001 0,002 0,003 0,004 0,005 0,006

0,00674

0,01832

0,04979

0,13534

0,36788

1

Ln(I/I0) = -µµµµx

µµµµ = (-786.7 +/- 50)cm-1

ln(I

/I) 0

(a

.u.)

thickness (cm)

0,01 0,1 1 10 100

0,01

0,1

1

10

100

1000

10000

100000Coeficiente de atenuación

lineal para el Al

µA

l(cm

-1)

E(keV)

E~ 4 – 4.3 keV

Al



GOBIERNO DE CHILECOMISION CHILENA DE ENERGIA NUCLEAREstimation of X-ray energy

• Assuming a monoenergetic emission, I = I0 e-µ∆∆∆∆x

E~ 4 – 4.3 keV

Ti

0,001 0,002 0,003 0,004 0,005

0,13534

0,36788

1

Ln(I/I0) = -µµµµx

µµµµ = (592.7 +/- 50 ) cm-1

ln(I

/I) 0

(a.u

.)

thickness (cm)

1 1010

1

102

103

104

105

Linear Attenuation coefficient for Ti

(Z=22)

µ (

cm

-1)

E (keV)

E~ 9.3 – 9.6 keV




Is it useful? Has some advantage?

Consider application like X-rayradiography with high spatial resolution(lithography). To increase the spatialresolution it is necessary:

• To decrease λ

• To decrease the source size




zp ≈≈≈≈ 0.8 a

Source Size

• X ray from thermalbremstrahlung and lineradiation are from the plasma column, thus the

source size is ≤≤≤≤ 2rp ~ 0.24a

size of hot spots ~ 0.2rp

• X ray from beam-targetbremstrahlung (-e beams onanode)

source size is ≤≤≤≤ 2rp ~ 0.24a

a3 αααα Ea

rp ≈≈≈≈ 0.12 a




1.6 mm

Spot of the order of 200µm on the anode




I~ 4.5kA,

a = 0.021cm,p = 3mbar

I/a(p)1/2 ~ 130kA/cm mbar1/2

0

2

4

6

8

10

Voltaje

I (k

A)

dI/d

t (k

A/n

s)

V (

kV

)

-1.0

-0.5

0.0

0.5

1.0

dI/dt

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

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

Corriente

t (ns)




In deuterium similar results (preliminary) have been obtained

Energy 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




-19.1 ns -11.1 ns

0.1 ns

-3.1 ns

4.9 ns 8.9 ns

30 ns

3 mm

a = 0.21mm

E=1/2 CV2

C~ 5 ±±±± 1nF, V=9±±±±0.5kV

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




Neutrons have been detected fromNanofocus

Fusion in a flashbulb

200 400-0,02

-0,01

0,00

0,01

0,02

Volta

ge

(V

)

time (µs)

200 400-0,02

-0,01

0,00

0,01

0,02

Voltage

(V

)

time (µs)

∼∼∼∼ 500 n /shot ∼∼∼∼ 1000 n / shot



GOBIERNO DE CHILECOMISION CHILENA DE ENERGIA NUCLEAR Repetation rate

0 1 2 3 4 5-3000

-2000

-1000

0

1000

2000

3000

4000

5000

6000

A.U

.

time (s)

0 1 2 3 4 5-3000

-2000

-1000

0

1000

2000

3000

4000

5000

6000

A.U

.

time (s)

9 Hz 18 Hz

a = 210µµµµm p = 16mbar

V= 6.5kV E=0.1J

<P> ~ 1W <P> ~ 2W

Ppeak ~ 10MW

Lantern of neutrons




104 n/sfor short periods (less

than 1 min.)

3.3x104 n/s106 n/sMaximum neutron flux

-2.7±1.82.5±1Energy of the neutrons

± dispersion (MeV)

55050Weight (capacitor bank and discharge chamber) (kg)

25cmx25cmx5cm50cmx30cmx20cm50cmx30cmx30cmSize (capacitor bank and discharge

chamber)

103

with low reproducibility3.3x104

at 70J and 9mbar in D2

1.1x104


1.1x106


Neutron yield per shot

50

1-20

1

single shot

1

single shot

Maximum repetition rate (Hz)

Typical operation

12.42.1Insulator lenght (cm)

0.040.480.7Effective anode lenght (cm)

-1.11.3Cathode radius (cm)

0.08-0.0220.30.6Anode radius (cm)

155-10

7050-60

168127

Peak current (kA)MaximumTypical operation

0.560.1

10050-70

540400

Stored energy (J)MaximumTypical operation

16150300Time to peak current (ns)

53838Inductance (nH)

155-10

3525-30

3530

Charging voltage (kV)MaximumTypical operation

5160880Capacity (nF)

NFPF-50JPF-400JDevice




Next steps

• A whole characterization of the neutron

emmission from Nanofocus and optimization.

• To increase the repetation rate up to the

maximum possible without cooler system.

• To explore the region of E

50J > E > 0.1J




104 - 105 n/sNeutron flux

3Weight (kg)(capacitor bank and discharge chamber)

25cmx5cmx5cmSize (capacitor bank and discharge chamber)

103 to 104Neutron yield per shot

10Typical repetition rate (Hz)

0.1Anode radius (cm)

4715

Peak current (kA)Maximum

Typical operation

22.5

2.5

Stored energy (J)

MaximumTypical operation

155

Charging voltage (kV)MaximumTypical operation

20020

100

Capacity (nF)Inductance (nH)Time to peak current (ns)

PF-2JProjected Device




The work plan for the next 18 months, divided in period of 3 months (Q) is the following:

• Q1: Study of the performance of the Nanofocus device operating at 10 and 20 Hz. To determine the reproducibility of neutrons emission per shot using 3He proportional counters in current mode.

• Q1: Neutron yield characterization of the Nanofocus device operating at 10 and 20 Hz. To determine the neutron flux operating in repetitive regime, 10 and 20Hz, using activation counters and CR39 plastics, and bubble detectors.

• Q1: Design of a portable device that operate at 2 joules (200nF, 20nH, 5kV, 16kA), with a repetition rate of 10Hz.

• Q2 - Q3: Construction of a portable device that operate at 2 joules (200nF, 20nH, 5kV, 16kA), with a repetition rate of 10Hz.

• Q4 - Q6 : Characterization of the portable device that operate at 1 to 5 of joules (200nF, 20nH, 5kV, 16kA), with a repetition rate of 10Hz. To determine the reproducibility of neutrons emission per shot using 3He proportional counters in current mode. To determine the neutron flux operating in repetitive regime, 10 and 20Hz, using activation counters and CR39 plastics, and bubble detectors.




• References.• 1.- L. Soto, A. Esaulov, J. Moreno, P. Silva, G. Sylvester, M. Zambra, A. Nazarenko, and A.

Clausse, Physics of Plasma 8, 2572 (2001).• 2.- L. Soto, Plasma Phys. Control. Fusion 47, A361 (2005)• 3.- P. Silva, J. Moreno, L. Soto, L. Birstein, R. Mayer, and W. Kies, App. Phys. Lett. 83, 3269

(2003).• 4.- P. Silva, L. Soto, J. Moreno, G. Sylvester, M. Zambra, L. Altamirano, H. Bruzzone, A. Clausse,

and C. Moreno, Rev. Sci. Instrum. 73, 2583 (2002).• 5.- J. Moreno, P. Silva, and L. Soto, Plasma Sources Sci. and Technol. 12, 39 (2003).• 6.- P.Silva, L. Soto, W. Kies and J. Moreno, Plasma Sources: Sci. and Technol. 13, 329 (2004)• 7.- "Demonstration of neutron production in a table-top plasma pinch device operating at only tens

of joules", L. Soto, P. Silva, J. Moreno, M. Zambra, W. Kies, R. E. Mayer, A. Clausse, L. Altamirano, C. Pavez, and L. Huerta, submitted to Journal of Physics D: Applied Physics, September 2007.

• 8.- "An Ultra Miniature Pinch Focus Discharge Operating with submillimetric Anodes and Energy of 0.1 Joule: Nanofocus", L. Soto, C. Pavez, J. Moreno, 6th International Conference on Dense Z-pinches, Oxford, 2005, AIP Conf. Proc. 808, 211 (2006)

• 9.- "System for measurement of low yield neutron pulses from D-D fusion reactions upon 3He proportional counter", J. Moreno, L. Birstein, R. E. Mayer, P. Silva and L. Soto, submitted to Meas. Sci. and Technol., October 2007.

• 10.- S. Lee and A. Serban, IEEE Trans. Plasma Science 24, 1101 (1996).

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