TASCA Workshop 2009 Towards SHIPTRAP @ TASCA Michael Block
SHIPTRAP Physics Program High-Precision Mass Measurements Trap-Assisted Nuclear Spectroscopy In-Trap Nuclear Spectroscopy Laser Spectroscopy Chemistry? Super Heavy Elements proton emitters rp-process, ν p-process N =Z nuclei
SHIPTRAP Setup 50 MeV Gas Cell Buncher Transfer Penning Traps SHIP ion beam Entrance window Extraction RFQ Cooler and Buncher RFQ Laser or surface ionization source Quadrupole deflector 1 ev Superconducting magnet Diaphragm MCPdetector DC cage RF funnel Purification trap Measurement trap
SHIPTRAP Performance 60 50 147 Ho + A = 147 Mass resolving power of No. of counts / bin 40 30 20 147 Er + 147 Dy + 147 Tb + m/ δm 100,000 in purification trap: 10 separation of isobars 0 732350 732400 732450 732500 Excitation frequency / H z Mean time of flight / µs 91 90 89 88 87 86 85 310 kev isomeric state 11/2 - ground state 1/2 + 143 Dy 2+ Mass resolving power of m/ δm 1,000,000 in measurement trap: separation of isomers -2 0 2 4 6 (Excitation freq. - 1505390.8) / Hz
Requirements for Mass Measurements high overall efficiency high cleanliness for low background stable and reliable operation over long time Present reach of SHIPTRAP Half-life Rate of trapped ions > 100 ms > 0.01 / s mass measurements with 0.3 pps ( σ 200 nb) demonstrated
Direct Mass Measurements of 252-254 No August 08: 206-208 Pb( 48 Ca,2n) 252-254 No doubly-charged nobelium ions ME(AME2003) - ME(SHIPTRAP) extracted production rates 220 200 180 Preliminary 160 140 120 100 80 60 40 20 0-20 -40 252 253 254 A 1 / s First direct mass measurements in the region Z > 100 AME2003 SHIPTRAP Mean time of flight / µs 92 90 88 86 84 82 80 78 76 74 253 72 No 2+ -3-2 -1 0 1 2 3 Excitation frequency / Hz - 850012 April 09: 209 Bi( 48 Ca,2n) 255 Lr rate of incoming ions of 255 Lr only 0.3 pps singly and doubly-charged ions extracted
TRAPspec: Trap-assisted Spectroscopy Idea: combine high mass resolving power of Penning traps with decay spectroscopy Benefits: only one nuclide - clean spectra detailed nuclear structure information in one experiment great potential for studies of isomers isomeric beams possible
TRAPspec Setup
TRAPspec commissioning experiment 110.1 X-rays 214.7
The Route to higher Z improve production rates and targets cw accelerator for SHE research increase sensitivity and efficiency non-destructive detection system with single-ion sensitivity cryogenic gas stopper for high cleanliness and higher efficiency extend reach to more neutron-rich nuclides hot-fusion reactions with actinide targets connection to gas-filled separator TASCA
Penning trap mass spectrometry Mass via cyclotron frequency measurement ν C = 1 2 π qb m reference ion to calibrate magnetic field ν ref 1 qref = 2 π m B ref Primary experimental Result: frequency ratio ν Re f ν C = m m ref Atomic mass m = q q ref ν ( ) ref mref qref me + q me ν c
Limitations for Mass Measurements with present technique about 100 ions have to be detected several hours measurement time for low production rates measurement time limited by temporal magnetic field fluctuations Magnetic Field Strength B / T 7,003186 7,003184 7,003182 7,003180 7,003178 7,003176 25.09.2009 12:00 26.09.2009 12:00 27.09.2009 12:00 29,5 29,0 28,5 28,0 27,5 27,0 26,5 26,0 25,5 1004,0 1003,5 1003,0 1002,5 1002,0 1001,5 1001,0 1000,5 1000,0 Temperature / C Pressure / mbar Diplomarbeit C. Droese
Improvements for Rare Isotopes Stabilize pressure in LHe cryostat Stabilize temperature in bore 1010 1008 Pressure [mbar] 1006 1004 Standard Deviation = 0.137mbar 1002 1000 Pressure stabilzation turned on 10:00 22:00 10:00 22:00 10:00 11/05/09 12/05/09 13/05/09 Diplomarbeit C. Droese
Coupling of TASCA and SHIPTRAP C-Aerosol Gas-jet Skimmer + Ion source RFQ Buncher M. Schaedel Ch. E Duellmann F. Herfurth K. Eberhardt K. Blaum C. Smorra M. Eibach SHIPTRAP D Q 1 Q 2 TASCA RTC
Gas-jet with Carbon-Aerosols at the TRIGA Mainz C-Aerosol generator γ - detector Filter catcher Martin Eibach He 45 40 A B Core Reactorpool RTC: U-235 (310 Target µg) He @ 2.7 bar D 45 50 C
Coupling of TASCA and SHIPTRAP: Ion Source (I) High-pressure ECR source currently developed at TRIGA Mainz Destruction of C-aerosoles and ionization of released reaction products in ECR-ion source RTC Christian Smorra Separation of aerosol from transport gas with skimmer
TRIGA-SPEC Experiment Experiment-control Skimmer-Ionensource-unit at 60 kv TRIGA-reactor Roots-pump Microwave 2.45 GHz HV-cage ECR-source Skimmer MW-inlet ECR-magnet Plasma
Coupling of TASCA and SHIPTRAP: Ion Source (II) Alternative approach Laser ablation Aerosoles from RTC Rotor, cooled Extraktion electrodes to ECR-source Desorption laser (pulsed) Rootspump Turbopump BEARS-Projekt (LBNL): Powell et al., NIM A455 (2000) 452
Summary and Outlook first direct mass measurements of nobelium isotopes performed high-precision mass measurements of stopped rare isotopes with production rates of only 0.1 per second demonstrated trap-assisted decay spectroscopy successfully established at SHIPTRAP synergy with TRIGA-SPEC project for gas jet connection to TASCA will widen the range of accessible nuclides Thank you for your attention!
Collaborators C. Breitenfeldt, D. Ackermann, K. Blaum, C. Droese, M. Dworschak, S. Eliseev, E. Haettner, F. Herfurth, F. P. Heßberger, S. Hofmann, J. Ketter, J. Ketelaer, H.-J. Kluge, G. Marx, M. Mazzocco, D. Nesterenko, Yu. Novikov, W. R. Plaß, A. Popeko, D. Rodríguez, C. Scheidenberger, L. Schweikhard, S. Stolze, P. Thirolf, G. Vorobjev, C. Weber For TRAPspec: D. Rudolph, L. Anderson, U. Forsberg, R. Hoischen, H. Schaffner, I. Kojouharov,
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Connecting SHIPTRAP to TASCA high transmission for asymmetric reactions actinide targets available highest separation not crucial long-lived chemistry isotopes suitable for SHIPTRAP gas jet transport routinely used
Entering the Gateway to the Transactindes Extend direct mass measurements to higher Z 255 Lr 103 252 No 253 No 254 No Rf, Sg,... 255 Lr + April 09: 209 Bi( 48 Ca,2n) 255 Lr rate of incoming particles for 255 Lr only 0.3 ions/s singly and doubly-charged ions extracted 255 Lr nuclide with lowest rate ever measured in a Penning trap
Long time Measurements 1,80E-007 pressure stabilization off on 1,60E-007 1,40E-007 stdev (B-B int /B) 1,20E-007 1,00E-007 8,00E-008 6,00E-008 4,00E-008 2,00E-008 time-dependent magnetic field fluctuations without pressure stabilization: σ o = 6.5*10-8 /h with pressure stabilization: σ p = 3.5*10-9 /h 0,00E+000 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 t [min] Diplomarbeit C. Droese
Cyclotron Frequency Measurement Step1: Excite radial motion Step 2: Convert E rad into E axial, measure TOF B Inhomogeneous part of magnetic field z Detector U RF Record TOF as function of excit. frequency Resonance 1 0 0 E - ~1meV E + ~ 1eV 60 50 mean TOF /µs 9 8 9 6 9 4 9 2 9 0 It s time for experiment counts 40 30 20 10 8 8 8 6 f c -4-2 0 2 4 E x c ita tio n F re q u e n c y / H z - 8 0 9 5 4 8.8 0 0 20 40 60 80 100 120 140 160 TOF / us G. Bollen et al. J. Appl. Phys. 68 (1990) 4355 M. König et al., Int. J. of Mass Spectr. and Ion Proc. 142 (1995) 95