High power molten targets for the production of radioactive ion beams

Transcription

1 João Pedro Ramos m 7 th 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 IAEA 1 st Workshop on Challenges for Coolants in Fast Neutron Spectrum Systems: Chemistry and Materials High power molten targets for the production of radioactive ion beams

2 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 Different perspective to the community Availability to discuss and collaborate 2

3 CERN 2500 staff in two sites About average of people on site everyday International organization (like IAEA, UN, WHO, etc), one of the first, founded in 1954 Presently visiting scientists from around the world (120 countries and 700 institutes) 3

4 at CERN Isotope Separator OnLine Device Produces Radioactive Ion Beams (RIB): Nuclear physics Atomic physics Solid state physics Astrophysics Life sciences PSB LINAC2 ~50 staff maintain/operate the facility A few students and fellows ~450 users for physics in more than 90 experiments ISOLDE PS 4

5 Predicted ~6000 Discovered ~3000 ISOLDE ~1000 Elements 74 t 1/2 >tens of ms *nuclide chart from Nucleonica *J. Ballof, ISOLDE database yields 5

6 ISOL Isotope Separation 230 ns OnLine 2.3 μs Pulsed beams: Thermomechanical stresses and shockwaves Also: high power deposition (can have kw/cm 3 ) Extraction optics Mass separator Target unit + OnLine chemical separation processes to purify the beam 6

7 W/cc Similarities to this community Very high temperatures of operation (up to 2300 C) High power densities (beam) Fast neutrons Al 2 O 3 brazed into Nb foils for enhanced cooling C Nb TA6V (TiAlV) 100 µm Al 2 O Neutron spectrum from ISOLDE spallation target (Log-Log) 7/14/ S. Fernandes, CERN-THESIS

8 ISOL Isotope Separation OnLine Extraction optics Mass separator Extraction electrode Target unit Proton Pulsed Protons Transfer line Ion Source +/- 8V 500 A Can be used to get information on fundamental properties of target materials through modeling of release 20 cm up to 2300 C +/- 9 V 1000 A Target heating (1 2kW), <~10% beam power 2. Diffusion 3. Effusion 4. Ionization 5. Mass Separation 6. Transport 1. Production Beam Int. = σ. j. Ν t. ε ε = ε diff ε eff ε is ε sep ε trans N t Nr of exposed atoms [dim] j Proton flux [cm -2 ] σ Cross section [mb] 8 ε Efficiency [%]

9 Facility Protons (1.4 GeV) Radioactive laboratory Low energy RIBs (up to 60 kev) Class A High energy RIBs (up to 10 MeV/u A/q=4.5) MEDICIS HRS High Resolution Separator Target area High Energy RIB Low energy RIB GPS General Purpose Separator 1 target: operation 1 2 weeks 30 targets per year Custom made for each beam Pulsed protons (1.2 s) 1.4 GeV 3.3x10 13 protons per pulse *picture courtesy of M. Delonca 9

10 Cylinder Temperature (Celsius) Target Unit Heart of Sim.T [ºC] Ta Temperature vs Cylinder Length T=680º C measured online Cylinder Lenght (m) Transfer line Length Quartz inserted here Vacuum Water cooling >2000 C Target Ion Source ISOLDE Frontend Target station *pictures courtesy of M. Delonca and J. Montano 10

11 Molten Targets (Metals) Focused p beam on Ta beam window at 2100 C Container beam window change: Rounding Thickening Pit corrosion and cracking in Ta from molten Pb targets. T = 720 C Pressure-induced waves form proton pulses simulations Proton beam changed Bunches timing Focusing E. Noah, et al., JNM 431 (2012) J. Lettry, et al., NIMB 204 (2003)

12 Molten targets (Salt) Prototype successfully tested at ISOLDE. Stable target under direct proton irradiation NaF:LiF eutetic (39:61 mol.%) 649 C melting point Low vapor pressure Highly corrosive at high T Special container Niquel rich alloy (Haynes 242) Condensation chimney to avoid salt spills or vapors into the ion source Avoids grams of material Allows for traces of material to go through T.M. Mendonca, et al. NIMB 329 (2014)

13 Molten targets (Salt) Measurement of release properties of isotope 18Ne analytical techniques Diffusion of Ne in NaF:LiF determined D=6.7E-3 mm 2 /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 CF x as expected ISOLDE targets can be a valuable asset to measure fundamental properties of many materials T.M. Mendonca, et al. Proc. IPAC2014 (2014),

14 LIEBE (Liquid Eutetic lead Bismuth loop target for Eurisol) Filling Tank HEX Diffusion Chamber Pump pipes 3D printed HEX Creation of droplets under specific proton & target conditions: faster release of isotopes LIEBE Collaboration M. Delonca, CERN-THESIS

15 LIEBE droplet formation Gain of factor 10 compared to static unit! Classification of droplet formation regimes (liquid velocity) Impact on the dimension of the droplets created Gobbling Jetting LIEBE Collaboration M. Delonca, CERN-THESIS

16 Neutron converter Spallation Source UC x p beam W rod Spallation target Collaboration launched: Continue the work on optimization of the n-converter Current design: Not very efficient Many protons still hit target 2.8 kw ( 1.2 GW ) (Shockwaves every sec) 1.4 GeV - 2 µa pulsed Both dissipated in a few cm 50 kw beam c.w. 500 MeV µa p2n-converter collaboration CERN SCK-CEN TRIUMF 16

17 W/cc Neutron converter new concept One of preliminary designs for high power for UCx ~8 kw deposited ~2 cm diameter ~2 cm length Power density of almost 1 kw/cc Temperatures in the W can reach more than 2000 C Protons Concept is in the design phase Ta oven (2000 C) Graphite container W High fission yield Challenging cooling of converter p2n-converter collaboration CERN SCK-CEN TRIUMF 17

18 Neutron converter - cooling W/Cu thermal interface Passive cooling with LBE Kelvi n Liquid PbBi capsules Water Copper Circular geometry Thermal stresses and plastic deformation Separation of W from the Cu Very preliminary results CFD simulations show that natural convection of liquid PbBi is ongoing Efficient transportation of heat p2n-converter collaboration CERN SCK-CEN TRIUMF 18

19 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 Protons Tungsten Thermocouples Preliminary results show H3, Xe127, I125 in the He. Ongoing tests of release of iodine by heating the W. 7/14/ M. Jensen, T. Stora, November 2016

20 Thank you! Merci! Obrigado! 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. 20