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A multi-reflection time-of-flight mass analyzer for SHANS at IMP/CAS

A multi-reflection time-of-flight mass analyzer for SHANS at IMP/CAS. Yulin Tian. Motivation Setups (HIRFL, SHANS) Simulation and construction of mass analyzer Present status of MRTOF mass analyzer for SHANS. 1 Aug. 2019. Basic theory of MRTOF-MS. Confinement. Injection. Ejection.

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A multi-reflection time-of-flight mass analyzer for SHANS at IMP/CAS

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  1. A multi-reflection time-of-flight mass analyzer for SHANS at IMP/CAS Yulin Tian • Motivation • Setups (HIRFL, SHANS) • Simulation and construction of mass analyzer • Present status of MRTOF mass analyzer for SHANS 1 Aug. 2019

  2. Basic theory of MRTOF-MS Confinement Injection Ejection • mirror-switching • in-trap-lift • Reference ions with well-known masses are needed • Mass resolving power：

  3. MRTOF-MSs for nuclear research High sensitivity Fast operation cycle Non-scanning Low construction cost……

  4. Motivation Mass first directly measured by Penning trap or MRTOF-MS Average life s Average life s Data from IAEA & AME2016 To measure the mass value of fusion-evaporation products, especially for the transuranium nuclei, directly.

  5. SHANS at HIRFL Spectrometer for Heavy Atoms and Nuclear Structure SSC SFC SHANS ECR CSRe CSRm Heavy Ion ResearchFacility at Lanzhou

  6. SHANS setup Z. Y. Zhang, et al. (2013). NIMB. 317: 315-318.

  7. Nuclei from SHANS [1] Z.Y. Zhang et al., Phys. Rev. C 89 (2014) 014308. [2] L. Ma et al., Phys. Rev. C 91 (2015) 051302. [3] H.B. Yang et al., EPJ A 51 (2015) 1-4. [4] M.D. Sun et al., Phys. Lett. B 771 (2017) 303-308. [5] H.B. Yang et al., Phys. Lett. B 777 (2018) 212-216. [6] T.H. Huang et al., Phys. Rev. C 98 (2018) 044302. [7] Z.Y. Zhang et al., Phys. Rev. Lett. 122 (2019) 192503. α decay chains of products are identified by energy, spatial and time correlations. Published To be published

  8. Layout of MRTOF-MS at SHANS • Gas catcher collects the heavy nuclei separated by SHANS and thermalizes them. • RF ion trap provides high quality pulsed beam for mass analyzer. • SPIG extracts the thermalized ions from gas catcher . • Mass analyzer separates the ions with different m/q. • BN Gate deflects the unwanted ions. • MCP is a time-of-flight detector. • LPT is a Penning trap system.

  9. Optimization of MRTOF-MS • Why? • --The initial conditions are complex. • --The parameter space is large, but the usable parameters are limited. • Goal? • --To find out the optimal parameters. • How? • --SIMION code for ion trajectory calculation. • --Local code developed using C++ with Nelder–Mead simplex algorithm for parameter search.

  10. Optimization procedure A model which is consistent with the actual size of the MRTOF mass analyzer is created in SIMION. Global search: the initial parameters are elements from a potential matrix estimated roughly according to the knowledge of the beam optics. Local refine: inputting a few sets of parameter with relatively high resolving power from global search, a large number of local minima can be obtained and the best are chosen to be the optimal parameter sets. Advantages: the best parameter sets can be found; easy to change or expand the configuration. Disadvantage: very time consuming.

  11. Optimization conditions • Geometry • Initial conditions

  12. Potential optimization The optimal voltages can be found in different conditions (6.5 ms as example )

  13. Length of the drift tube Drift tube • Optimal length：398-402 mm

  14. Rmax at different revolutions Mirror-switching In-trap-lift • The mass resolving power is increased with the increase of revolution number. • Beam size affects Rmax little at optimal parameter sets, but shows more significant influence at other set points.

  15. TOF,TOF, R with fixed potentials Mirror-switching In-trap-lift • TOF is increased linearly with increasing the number of revolutions. • The temporal spread decreases until a minimum, . • Resolving power .

  16. Potential inaccuracy influence Mirror-switching In-trap-lift Potential inaccuracy on electrodes where the ions turn around shows more significant influence to mass resolving power.

  17. Off-line experimental setups

  18. Preliminary test results (40Ar+ ) • Hot cathode discharge ion source • Vacuum: mbar • 120 revolutions, linear relationship between TOF and the number of revolutions. • Mass resolving power at 75 laps.

  19. Preliminary test results (133Cs+ ) • Surface ion source • Vacuum: mbar • 250 revolutions, linear relationship between TOF and the number of revolutions. • Mass resolving power at 150 laps.

  20. Conclusion • An MRTOF-MS at SHANS/IMP/CAS is under construction. • A new method for MRTOF-MS design is presented. Geometry, potential parameters can be optimized. • By simulation, Rmax for 1.5 keV 40Ar1+ in a 4-electrodes mirror MRTOF-MS is >100 000 both in switching-mirror and in-trap-lift modes. • Preliminary experimental test shows that the mass resolving powerof 133Cs1+ achieved 18,000. • Collaborators • Wenxue HUANG, Yongsheng WANG, Junying WANG, Zaiguo GAN, Xiaohong ZHOU • Acknowledgement • Michiharu WADA, Yuta ITO, Peter SCHURY, Tommi ERONEN, Ryan RINGLE …… Thanks for your attention!

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