Towards TASCA

Transcription

1 TASCA Workshop 2009 Towards TASCA Michael Block

2 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

3 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

4 SHIPTRAP Performance Ho + A = 147 Mass resolving power of No. of counts / bin Er Dy Tb + m/ δm 100,000 in purification trap: 10 separation of isobars Excitation frequency / H z Mean time of flight / µs kev isomeric state 11/2 - ground state 1/ Dy 2+ Mass resolving power of m/ δm 1,000,000 in measurement trap: separation of isomers (Excitation freq ) / Hz

5 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

6 Direct Mass Measurements of No August 08: Pb( 48 Ca,2n) No doubly-charged nobelium ions ME(AME2003) - ME(SHIPTRAP) extracted production rates Preliminary A 1 / s First direct mass measurements in the region Z > 100 AME2003 SHIPTRAP Mean time of flight / µs No Excitation frequency / Hz 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

7 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

8 TRAPspec Setup

9 TRAPspec commissioning experiment X-rays 214.7

10 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

11 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

12 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, , , , , , : : :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

13 Improvements for Rare Isotopes Stabilize pressure in LHe cryostat Stabilize temperature in bore Pressure [mbar] Standard Deviation = 0.137mbar 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

14 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

15 Gas-jet with Carbon-Aerosols at the TRIGA Mainz C-Aerosol generator γ - detector Filter catcher Martin Eibach He A B Core Reactorpool RTC: U-235 (310 Target µg) 2.7 bar D C

16 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

17 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

18 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

19 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!

20 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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22 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

23 Entering the Gateway to the Transactindes Extend direct mass measurements to higher Z 255 Lr No 253 No 254 No Rf, Sg, 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

24 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 t [min] Diplomarbeit C. Droese

25 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 E - ~1meV E + ~ 1eV mean TOF /µs It s time for experiment counts f c E x c ita tio n F re q u e n c y / H z 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