Research On Helium Diffusion Experiment And The Preparation For The High-frequency Electrodeless Mercury Lamp In Linear Ion Trap

The technique using electric or magnetic field to trap ions in a small region iscalled "trap". Ions are trapped in the super-high vacuum ,approximately without anyperturbations.With these advantages,it is feasible to acquire stable spectral line in the iontrap, consequently acquire high accuracy and high stability standard frequency sourcewhich can work without cease.The linear ion trap has many advantages for trapping ions,such as more iondensity, good signal to noise ratio,and smaller second-order Doppler frequency shift.Sofar, the JPL(Jet Propulsion Laboratory) has successfully made two models LIT-â… (LinearIon Trapâ… ) and LIT-â…¡(Linear Ion Trap-â…¡) using ¹⁹⁹Hg⁺ as the working material and²⁰²Hg⁺ lamp as the pump light source,with the feature of short-term frequency stabilityof 1.0^*10^-13/Ï„^1/2 (Ï„is the sampling time),long-term stability of 1*10^-15/Ï„(τ＞10⁴seconds), we have designed our own isolated region ¹⁹⁹Hg⁺ frequency standard system,in which the resonance region is separated from the state-selection region. Using thissystem, we have acquired the trapped ions signal with the radio-frequcncy resonancedetection techniques and some other experiment such as fluorescencemeasurement. Using the isotope lamp as the light source is one feature of ¹⁹⁹Hg⁺frequency standard,hence, we have developed the apparatus for the light making andmade several lamp examples.Furthermore,we have done some experiment to comparetheir different features and to acquire some data for the next lamp manufacture.we use the buffer gas to cool the ions. With this method, the ions temperature canbe degraded to the room temperature, hence decrease the second-order Dopplerfrequency shift. In our own experiment, we select the helium gas as the buffer gas andhave finished the helium diffusion experiment. At last we find the helium diffusion rules,such as diffusion pressure vs the change of the temperature. This experiment is so important for the further research of the relation between the ion numbers or iontemperature and the buffer gas pressure.