Research And Development Of A Multi-Reflection Time-of-Flight Mass Analyzer

Mass is a fundamental property of an atom or a nucleus.Accurate mass values can provide key information for the study of nuclear model and structure,atomic energy,nuclear astrophysics and the test of Standard-Model.Isotopes with proton number Z>92,which are called transuranium,can only be synthesized artificially.Measuring their mass values precisely is significantly valuable to the study of shell stability of superheavy nuclides and to predict their mass values and the location on the nuclide chart of the so called "island of stability".Due to the limitations of experimental techniques,masses of only 16 among more than 300 transuranium isotopes synthesized have been measured directly by Penning trap and/or multi-reflection time-of-flight(MRTOF)mass spectrometryMRTOF mass spectrometer(MRTOF-MS)is a kind of new developed experimental apparatus based on traditional TOF-MS.It is an electrostatic ion trap which extends the flight path of ions by multi-reflection between two electrostatic mirrors.Due to the advantages of single-ion sensitivity,non-scanning,large mass range,short measurement time and less expensive construction cost,MRTOF devices have been developing very quickly in recent years.MRTOF mass analyzer is one of the main parts of an MRTOF mass spectrometer.It can operate in two different modes,mirror-switching and in-trap-lift,to capture or release ionsAt the Institute of Modern Physics,Chinese Academy of Sciences,an MRTOF-MS is under construction at the gas-filled recoil separator,Spectrometer for Heavy Atom and Nuclear Structure(SHANS).In this thesis,the MRTOF mass analyzer,which consists of ion source,beam transport line,core part of the analyzer,detector,vacuum system,control and data acquisition system,will be introduced.It will be used for direct mass measurements of short lived nuclides and mass selection for subsequent devicesThe development of our MRTOF mass analyzer includes the following steps:the simulation,optimization,design,machining,assembly and off-line test.In order to understand the kinematics of ion motions in an MRTOF-MS and to find out parameter sets as starting points for the test of device in laboratory,we developed a set of computer programs which can optimize the parameters both in the mirrors-witching mode and in-trap-lift mode.In this software,the ion trajectories are simulated by the SIMION code and the parameters are varied and optimized by a Nelder-Mead simplex algorithm.Parameters like geometries and potentials can be optimized.The results show that the mass resolving power R>1 × 105,the suggested length of the drift tube is?400 mm,and the accuracy and the stability of the power supplies should be better than 50 ppm.Based on these optimization results,we have finished the construction of the MRTOF mass analyzer for MRTOF-MS at SHANS,together with the development of subsystems like vacuum,electronics,control and data acquisition system,etc.In addition,we have also finished the primary test and realized the ion confinement in the mass analyzer.The measurement results show that the confinement time of the ions has already been longer than 2.56 ms,and the mass resolving power has reached 7000 when the ions flying 75 laps in the analyzer by applying the calculated potentials.Works shown in this thesis confirm that we have gone through all the difficulties and already have the ability to research and develop an MRTOF mass analyzer independently.