APS-DNP Fall20041 Design Studies for RIA Fragment Separators A.M. Amthor National Superconducting Cyclotron Laboratory, Michigan State University Department of Physics and Astronomy, Michigan State University

AMA APS-DNP Fall20042 RIA Concept High-Resolution Separator Large-Acceptance Separator

AMA APS-DNP Fall20043 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)

AMA APS-DNP Fall20044 Motivation: Beam Energy and Momentum Acceptance Above: Fragment beam of 78 Ni produced from 86 Kr. 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 Yield (pps/pμA) Momentum Acceptance (%)

AMA APS-DNP Fall20045 Fragment Separators N Z N Z N Z Fragments after target Fragments at wedge Fragments after FP Specifications Bρ max = 6Tm Δp/p = 5% Δθ = ±40mr Δφ = ±50mr Compensated to 3 rd order Largest acceptance of current facilities Note: Isotope yield diagrams are from 86 Kr  78 Ni simulation with primary beam of 140MeV/u

AMA APS-DNP Fall20046 Thick Wedges and Two-stage Fragment Separation CAARI 2004 talk by A. Stolz Al 450 mg/cm 2 Al 300 mg/cm 2 Al 190 mg/cm 2

AMA APS-DNP Fall20047 RIA Separators Preseparator Maximized production rate 100 mr in horizontal and vertical 12% momentum acceptance low optical aberrations (< 2 mm) 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 The RIA concept makes use of two fragment separators. Preseparator Momentum Compensator Gas-Stopping CellBeam Preseparator High-Resolution Separator High-Energy AreaBeam (up to 400 kW) Target

AMA APS-DNP Fall20048 Preseparator 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%. Target Beam Wedge Isotope Slits Beam Dump Additional wedge at beam dump? Additional stage of separation for gas cell separator? Target Beam Dump (160 to 320 kW) Quad Dipole Wedge Quad Dipole Wedge Beam (400kW) Significant higher order aberrations (>3 rd order) Up to 200kW power on beam dump Primary beam often within momentum acceptance and sometimes with |δ Bρ |< 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

AMA APS-DNP Fall20049 Momentum Compensator Specifications: Full angular and momentum acceptance from preseparator Momentum resolving power R>1000 d/M = 2.5m Diagram: H. Weick et al., NIM B (2000) 168 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. FWHM = 32 atm-m 4 He FWHM = 0.93 atm-m 4 He Ion Guide, Cooler and Buncher Above: Range compression of 350 Mev/u 130 Cd produced from 500 MeV/u 136 Xe (MOCADI simulation) 130 Cd Range FWHM (atm-m) Resolving Power 350 MeV/u 130 Cd range width Gas Cell & Nozzle Monoenergetic Degrader Dispersive Elements

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

AMA APS-DNP Fall Acknowledgements Additional thanks to: 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 ) and Michigan State University. Collaborators: B.M. Sherrill 1,2 D.J. Morrissey 1,3 A. Nettleton 1,2 A. Stolz 1 O. Tarasov 1 1 National Superconducting Cyclotron Laboratory, Michigan State University 2 Department of Physics and Astronomy, Michigan State University 3 Department of Chemistry, Michigan State University Ion Optical Program GICO a combination of GIOS and COSY 5.0 written at University of Giessen, 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.