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Design Studies for RIA Fragment Separators

Design Studies for RIA Fragment Separators. A.M. Amthor National Superconducting Cyclotron Laboratory, Michigan State University Department of Physics and Astronomy, Michigan State University. RIA Concept. High-Resolution Separator. Large-Acceptance Separator.

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Design Studies for RIA Fragment Separators

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  1. Design Studies for RIA Fragment Separators A.M. Amthor National Superconducting Cyclotron Laboratory, Michigan State University Department of Physics and Astronomy, Michigan State University APS-DNP Fall2004

  2. RIA Concept High-Resolution Separator Large-Acceptance Separator APS-DNP Fall2004

  3. Motivation: ISOL and Gas Stopping Optimum production method for low-energy beams Standard ISOL technique Two-step fission In-flight fission + gas cell Fragmentation + gas cell ISOL Committee Task Force Report (1999) APS-DNP Fall2004

  4. Motivation: Beam Energy and Momentum Acceptance Fragmentation 110Zr ISOL In-flight fission 138Sn Δp/p = 10% 100 114Zr Relative Mass Separated Yields 78Ni 159Nd 10 80Zr 211Fr 11Li 132Sn,96Kr 1 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 E/A ( MeV/u ) Yield (pps/pμA) Momentum Acceptance (%) Above: Fragment beam of 78Ni produced from 86Kr. At the RIA energy of 400MeV/u the acceptance should be greater than 10%. Left: Production of various fragments for fixed current and acceptance. Acceptance determines energy of turnover point (here 10% dp/p) J. Nolen ANL APS-DNP Fall2004

  5. Fragment Separators Fragments after FP Fragments at wedge Fragments after target Z N Z Z N N Note: Isotope yield diagrams are from 86Kr78Ni simulation with primary beam of 140MeV/u Specifications Bρmax = 6Tm Δp/p = 5% Δθ = ±40mr Δφ = ±50mr Compensated to 3rd order Largest acceptance of current facilities APS-DNP Fall2004

  6. Thick Wedges andTwo-stage Fragment Separation CAARI 2004 talk by A. Stolz Al 190 mg/cm2 Al 450 mg/cm2 Al 300 mg/cm2 APS-DNP Fall2004

  7. RIA Separators Target High-Resolution Separator Beam Preseparator High-Energy Area (up to 400 kW) Momentum Compensator Beam Gas-Stopping Cell Preseparator The RIA concept makes use of two fragment separators. • High-Resolution Separator • Maximized quality and purity • Two-stage fragment separation • 80 mr in horizontal and vertical angular acceptance • 6% momentum acceptance • d/M = 2.5m • Preseparator • Maximized production rate • 100 mr in horizontal and vertical • 12% momentum acceptance • low optical aberrations (< 2 mm) APS-DNP Fall2004

  8. Preseparator Dipole Quad Quad Wedge Beam (400kW) Target Beam Dump (160 to 320 kW) Dipole Wedge Quad Quad The compensated third order system passes approximately 73% of fragments uniformly distributed in a 6-D phase space ellipse with a and b from ±50mr and with δ distributed over a full width of 12%. Wedge Isotope Slits Beam • Significant higher order aberrations (>3rd order) • Up to 200kW power on beam dump • Primary beam often within momentum acceptance and sometimes with |δBρ|< 1% • Higher energy and greater neutron excess of fragment beams increases magnetic rigidity (10Tm) • Range compressed fragments to be stopped in 0.5 atm-m gas cell, requires aberrations < 2mm Beam Dump Target Additional wedge at beam dump? Additional stage of separation for gas cell separator? APS-DNP Fall2004

  9. Momentum Compensator 350 MeV/u 130Cd range width Diagram: H. Weick et al., NIM B 164-165 (2000) 168 Range FWHM (atm-m) Resolving Power 130Cd • Specifications: • Full angular and momentum acceptance from preseparator • Momentum resolving power R>1000 • d/M = 2.5m FWHM = 32 atm-m 4He Ion Guide, Cooler and Buncher Gas Cell & Nozzle Monoenergetic Degrader Dispersive Elements FWHM = 0.93 atm-m 4He Insert graph of dependence of gas stopping efficiency on system resolving power from 500 to 2000 (or d/m .5 to 2) Calculate by changing Xo instead of system. Above: Range compression of 350 Mev/u 130Cd produced from 500 MeV/u 136Xe (MOCADI simulation) APS-DNP Fall2004

  10. Simulation Methods& Needed Improvements Fragment production in thick wedges (x|θδ) aberration – angled wedges Dispersive focal plane A. Stolz, CAARI 2004 Profile wedge degrader APS-DNP Fall2004

  11. Acknowledgements Collaborators: B.M. Sherrill 1,2 D.J. Morrissey 1,3 A. Nettleton 1,2 A. Stolz 1 O. Tarasov 1 1National Superconducting Cyclotron Laboratory, Michigan State University 2Department of Physics and Astronomy, Michigan State University 3Department of Chemistry, Michigan State University Additional thanks to: Ion Optical Program GICO a combination of GIOS and COSY 5.0 written at University of Giessen, 1986 -  1998 by Martin Berz, Bernd Hartmann, Klaus Lindemann,  Achim Magel, Helmut Weick • The MOCADI program was developed in PL/I • by T. Schwab, H. Geissel, and A. Magel at Giessen University in Germany. • N. Iwasa translated MOCADI 1.34 into C on a DEC VMS operating system and developed it further. RIA R&D is funded in part by the U.S. Department of Energy (Grant No. DE-FG03-03ER41265) and Michigan State University. The NSCL is funded in part by the National Science Foundation (Grant No. PHY-01-10253) and Michigan State University. APS-DNP Fall2004

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