High power molten targets for the production of radioactive

High power molten targets for the production of radioactive

ion beams

IAEA 1st Workshop on “Challenges for Coolants in Fast

Neutron Spectrum Systems: Chemistry and Materials”

João Pedro Ramos

7th of July, 2017

R. Augusto, P. Bricault, M. Delonca, M. Dierckx, L. Egoriti, A. Gottberg,

D. Houngbo, T. Mendonca, L. Popescu, J.P. Ramos, S. Rothe, T.

Stora, S. Warren

http://www.joaopedroramos.co

m

1st IAEA Workshop Challenges for coolants in fast neutron spectrum: chemistry and materials

J.P. Ramos, et al. | 07/07/2017

Structure • CERN, ISOLDE

• Radioactive ion beams

• Target unit of ISOLDE

• Case studies: • Molten salt target

• LIEBE – PbBi eutectic loop

• Proton to neutron converter

• ESS W tests

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Different perspective to the community

Availability to discuss and collaborate


J.P. Ramos, et al. | 07/07/2017

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• International organization (like IAEA, UN, WHO,

etc), one of the first, founded in 1954

• Presently 12’000 visiting scientists from around

the world (120 countries and 700 institutes)

CERN

• 2500 staff in two sites

• About average of

10000 people on site

everyday


J.P. Ramos, et al. | 07/07/2017

4

LINAC2

PSB

PS

ISOLDE

~50 staff – maintain/operate the facility

• A few students and fellows

~450 users for physics in more than 90 experiments

at CERN

Isotope Separator

OnLine Device

Produces Radioactive Ion

Beams (RIB):

• Nuclear physics

• Atomic physics

• Solid state physics

• Astrophysics

• Life sciences


J.P. Ramos, et al. | 07/07/2017

Predicted

~6000

Discovered

~3000

ISOLDE

~1000

Elements

74

t1/2 >tens of ms

*nuclide chart from Nucleonica

*J. Ballof, ISOLDE database yields

5


J.P. Ramos, et al. | 07/07/2017 6

ISOL Isotope Separation

Extraction optics Mass

separator

Target unit

OnLine

2.3 μs

230 ns

Pulsed beams: Thermomechanical stresses and shockwaves

Also: high power deposition (can have kW/cm3)

+ OnLine chemical

separation processes to

purify the beam


J.P. Ramos, et al. | 07/07/2017

Nb

Al2O3

TA6V (TiAlV) – 100 µm

Similarities to this community

7/14/2017 7

Al2O3 brazed into

Nb foils for

enhanced cooling

• Very high temperatures of

operation (up to 2300 °C)

• High power densities (beam)

• Fast neutrons W

/cc

1000

100

10

1

0.1

Neutron spectrum from ISOLDE

spallation target (Log-Log)

S. Fernandes, CERN-THESIS-2010-170

970 – 1330 °C


J.P. Ramos, et al. | 07/07/2017

Pulsed

Protons

+/- 8V 500 A

+/- 9 V 1000 A

Ion Source

Proton

Transfer

line

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4. Ionization

3. Effusion

2. Diffusion

1. Production 𝐵𝑒𝑎𝑚 𝐼𝑛𝑡. = 𝜎. 𝑗. 𝛮𝑡. 𝜀

𝜀 = 𝜺𝒅𝒊𝒇𝒇𝜺𝒆𝒇𝒇𝜀𝑖𝑠𝜀𝑠𝑒𝑝𝜀𝑡𝑟𝑎𝑛𝑠

ISOL Isotope Separation

5. Mass Separation

6. Transport

Extraction optics Mass

separator

Target unit

OnLine

Extraction

electrode

up to 2300 °C 20 cm

Target heating (1 – 2kW), <~10% beam power

Can be used to get information on

fundamental properties of target materials through

modeling of release

𝑁𝑡 – Nr of exposed atoms [dim]

𝑗 – Proton flux [cm-2]

𝜎 – Cross section [mb]

𝜀 – Efficiency [%]


J.P. Ramos, et al. | 07/07/2017

9 *picture courtesy of M. Delonca

Protons (1.4 GeV)

Facility

Pulsed protons (1.2 s)

1.4 GeV

3.3x1013 protons per pulse

GPS General Purpose Separator

HRS High Resolution Separator

High energy RIBs (up to 10 MeV/u – A/q=4.5)

Low energy RIBs (up to 60 keV) MEDICIS Radioactive laboratory

Class A

Low energy RIB

High Energy RIB

Target area

1 target: operation 1 – 2 weeks • 30 targets per year

• Custom made for each beam


J.P. Ramos, et al. | 07/07/2017

10 *pictures courtesy of M. Delonca and J. Montano

Target Unit – Heart of

ISOLDE Frontend

Target station

Transfer line

Ion Source

Ta Temperature vs Cylinder Length

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20 0.22

Cylinder Lenght (m)

Cy

lin

de

r T

em

pe

ratu

re (

Ce

lsiu

s)

T=680º C

measured online

Sim.T [ºC]

Length

Quartz inserted here

>2000 °C

Water

cooling

Target

Vacuum


J.P. Ramos, et al. | 07/07/2017

Molten Targets (Metals)

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Pit corrosion and cracking in Ta from molten Pb

targets. T = 720 °C

• Proton beam changed

• Bunches timing

• Focusing

Focused p beam on Ta

beam window at 2100 °C

Pressure-induced waves form

proton pulses simulations

E. Noah, et al., JNM 431 (2012) 60-65

J. Lettry, et al., NIMB 204 (2003) 251-256

Container beam window change:

• Rounding

• Thickening


J.P. Ramos, et al. | 07/07/2017

Molten targets (Salt)

T.M. Mendonca, et al. NIMB 329 (2014) 1-5 13

Special container

• Niquel rich alloy (Haynes 242)

NaF:LiF eutetic (39:61 mol.%)

• 649 °C melting point

• Low vapor pressure

• Highly corrosive at high T

Prototype

successfully tested

at ISOLDE. Stable

target under direct

proton irradiation

Condensation “chimney” to avoid salt

spills or vapors into the ion source

• Avoids grams of material

• Allows for traces of material to go

through


J.P. Ramos, et al. | 07/07/2017

Molten targets (Salt)

T.M. Mendonca, et al. Proc. IPAC2014 (2014), 2142-2145

14

Measurement of release properties of

isotope 18Ne – analytical techniques

Diffusion of Ne in NaF:LiF determined

D=6.7E-3 mm2/s at 740 °C

• Not known in the literature

• Close to other noble gases in

fluoride salts)

Very high production of 11C

• Released as CO instead of CFx

as expected

ISOLDE targets can be a

valuable asset to measure

fundamental properties of

many materials


J.P. Ramos, et al. | 07/07/2017

LIEBE (Liquid Eutetic lead Bismuth loop target for Eurisol)

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Creation of droplets under

specific proton & target

conditions: faster release

of isotopes

Diffusion

Chamber

HEX

Pump

pipes

Filling Tank

3D printed HEX

LIEBE Collaboration

M. Delonca, CERN-THESIS-2015-368


J.P. Ramos, et al. | 07/07/2017

LIEBE – droplet formation

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Gain of factor 10

compared to static

unit!

Classification of

droplet

formation

regimes (liquid

velocity)

Jetting Gobbling

Impact on the

dimension of the

droplets created

LIEBE Collaboration

M. Delonca, CERN-THESIS-2015-368


J.P. Ramos, et al. | 07/07/2017

Neutron converter – Spallation Source

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p beam

Current design:

• Not very efficient

• Many protons still hit target

50 kW beam – c.w. 500 MeV - 100 µA

2.8 kW (“1.2 GW”) (Shockwaves every sec)

1.4 GeV - 2 µA pulsed Collaboration launched:

Continue the work on

optimization of the n-converter

p2n-converter collaboration

CERN | SCK-CEN | TRIUMF

W rod

Spallation target

UCx

Both dissipated in a few cm


J.P. Ramos, et al. | 07/07/2017

Neutron converter – new concept

17

UCx

W

Ta oven

(2000 °C) Graphite

container

Protons

• High fission yield

• Challenging cooling of

converter



~8 kW deposited

• ~2 cm diameter

• ~2 cm length

Power density of

almost 1 kW/cc

One of preliminary designs

for high power for

W/c

c

1000

100

10

1

0.1

Temperatures in the W can

reach more than 2000 °C

Concept is in the design phase


J.P. Ramos, et al. | 07/07/2017

Neutron converter - cooling

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Kelvi

n

• Circular geometry

• Thermal stresses and plastic

deformation

• Separation of W from the Cu

Water

Liquid

PbBi

capsules

• Very preliminary results

• CFD simulations show that

natural convection of liquid

PbBi is ongoing

• Efficient transportation of heat

W/Cu thermal interface



Passive cooling

with LBE

Copper


J.P. Ramos, et al. | 07/07/2017

ESS Tungsten Irradiation at ISOLDE

• Irradiation of ESS target tungsten

slab with 1.4 GeV protons

• 0.2 bar of He atmosphere

• Study Iodine release from W in He

atmosphere (and by heating W)

• Thermocouples installed to monitor

temperature of the assembly

• Assembly shipped to PSI for tests

7/14/2017 19 M. Jensen, T. Stora, November 2016

Protons

Tungsten

Thermocouples

Preliminary results show H3, Xe127, I125 in the He.

Ongoing tests of release of iodine by heating the W.


J.P. Ramos, et al. | 07/07/2017

Thank you! Merci! Obrigado!

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By far not only my work…Many thanks to all collaborating authors and institutes.

Many thanks to the organization of the workshop for the opportunity to present.

Documents

High power molten targets for the production of radioactive