Preparation of 249Cf targets for the synthesis of element 120 J. Runke1, Ch.E. Düllmann1,2,3, K. Eberhardt2, P.A. Ellison4,5, K.E. Gregorich4, E. Jäger1, B. Kindler1, J. Krier1, B. Lommel1, C. Mokry2, H. Nitsche4,5, M. Schädel6, P. Thörle-Pospiech2, N. Trautmann2, A. Yakushev1 1GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany; 2Johannes Gutenberg-Universität, Mainz, Germany 3Helmholtz Institut Mainz, Germany 4Lawrence Berkeley National Laboratory, Berkeley, CA, USA 5University of California, Berkeley, CA, USA 6Japan Atomic Energy Agency, Tokai, Japan TASCA Workshop 11 – October 14, 2011 Synthesis of element 120 Targetproduction productionrequirements: requirements: Target 249Cf Chemicalpurification purificationof of249 •• Chemical Cf priorto todeposition deposition prior 50Ti 249Cf 299120 Smalland andsimple simpleset-up set-up •• Small Highdeposition depositionyields yields •• High • 4 arc shaped segments form a target wheel • Wheel diameter: 100 mm • Active area: 6 cm2 per segment • Material consumption: 12 mg per wheel @ 500 µg/cm2 • Beam spot: 8 mm diameter Purification of 249Cf • Chemical form: Chloride, Nitrate or Oxide • Dissolution in 8 M HCl • Evaporation to dryness several times Activity of 249Cf: 151,6 MBq/mg 249Cf as delivered by LBNL Purification of 249Cf 3) Cf/Pb, Ti… 0.5 M HCl Cf/Al,Fe… 8 M HCl 8M HCl 1) BioRad AGMP-1M column 2) Cf 4) 5) Cf/Pb, Ti… 1.5 M HCl Cf 8 M HCl DOWEX 50WX8 column DOWEX 50WX8 column Pb, Ti 249Cf in 8 M HCl 1) Dissolve Dissolve249 1) Cf in 8 M HCl 2) Purification Purificationstep stepwith withanion-exchanger anion-exchangerBioRad BioRadAG AGMP-1M MP-1M 2) 249Cf in 0.5 M HCl 3) Evaporate Evaporateto todryness drynessand anddissolve dissolve249 3) Cf in 0.5 M HCl 4) Removal Removalof ofPb, Pb,Ti… Ti…with with1.5 1.5M MHCl HCl 4) 249Cf with 8 M HCl. Almost 100% recovery 5) Elution Elutionof of249 5) Cf with 8 M HCl. Almost 100% recovery Cf Purification of 249Cf 3) Cf/Pb, Ti… 0.5 M HCl Cf/Al,Fe… 8 M HCl 8M HCl 1) BioRad AGMP-1M column 2) Cf 4) 5) Cf/Pb, Ti… 1.5 M HCl Cf 8 M HCl DOWEX 50WX8 column DOWEX 50WX8 column Pb, Ti 249Cf in 8 M HCl 1) Dissolve Dissolve249 1) Cf in 8 M HCl 2) Purification Purificationstep stepwith withanion-exchanger anion-exchangerBioRad BioRadAG AGMP-1M MP-1M 2) 249Cf in 0.5 M HCl 3) Evaporate Evaporateto todryness drynessand anddissolve dissolve249 3) Cf in 0.5 M HCl 4) Removal Removalof ofPb, Pb,Ti… Ti…with with1.5 1.5M MHCl HCl 4) 249Cf with 8 M HCl. Almost 100% recovery 5) Elution Elutionof of249 5) Cf with 8 M HCl. Almost 100% recovery Cf Purification of 249Cf 3) Cf/Pb, Ti… 0.5 M HCl Cf/Al,Fe… 8 M HCl 8M HCl 1) BioRad AGMP-1M column 2) Cf 4) 5) Cf/Pb, Ti… 1.5 M HCl Cf 8 M HCl DOWEX 50WX8 column DOWEX 50WX8 column Pb, Ti Cf Conversion of 249Cf chloride into nitrate with 8 M HNO3 Deposition of 249Cf by Molecular Plating Evaporate 249Cf-solution (8 M HNO3) to dryness in a teflon beaker Re-dissolve residue in 100 µl 0.1 M HNO3 and transfer it to the plating cell Wash teflon beaker with 3 x 300 µl isopropanol and transfer it to cell Fill cell with 51 ml isobutanol Deposition of 249Cf by Plating Actinide deposition byMolecular Molecular Plating Backing: 2 µm Ti-foil Ultrasonic stirrer Cooling water C A T H O D E A N O D E PEEK-cell Voltage: 200 V - 600 V Deposition time: 4-5 hours 249Cf in isobutanol Deposition of 249Cf by Molecular Plating Deposition of Cf: •Yield > 90% •Yield determination by -spectroscopy Prior to production of thick targets a thin target was prepared: Cf Thickness [µg/cm²] 249Cf 70 249Cf 484 249Cf 537 249Cf 514 249Cf 501 249Cf 497 249Cf 508 249Cf 454 •deposition test •reference sample for yield determination by -spectroscopy Deposition kinetics of 249Cf Prior to deposition and in 1-h steps 10 µl aliquots of the 249Cf-solution were evaporated to dryness for α-particle spectroscopy Yield determination by γ-spectroscopy 3m Measuring time: 5 min Dead time: ~ 5 % γ-Detector Thin 249Cf target used as reference 388 keV 249Cf 350.6 a a 5.812, 5.758 γ 388, 333 245Cm 8500 a a 5.361, 5.304 γ 175, 133 333 keV Yield determination by α-measurements • • Detector 355 mm Target wheel • • cover with five 10 mm holes for each target segment 8 mm collimator ca. 2.5 to 3 mm above the target wheel 5 x 180 s measuring time per segment efficiency determined with a 241Am reference source Summary Thanks to: Lawrence Berkeley National Laboratory for providing 249Cf Robert F. Fairchild II, Naomi E. Reeves, John A. van Wart and LBNL‘s entire Radiation Protection Group of the Environmental Health and Safety Division for their leadership and active support with the preparation and execution of the 249Cf shipment to Germany. The Target Laboratory at GSI for providing the Ti-backing foils The Mechanical Workshop of the Institut für Kernchemie in Mainz for the construction of the deposition cell ….and you for your attention
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