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Fullerene-Coated Graphite Target Rod for Ion Accumulation and Detection

This system utilizes a fullerene-coated graphite target rod to generate a molecular beam for ion accumulation in an ICR cell. The ions are detected using a high magnetic field and converted to frequency signals. The process involves laser vaporization, supersonic expansion, and ion transfer.

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Fullerene-Coated Graphite Target Rod for Ion Accumulation and Detection

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  1. fullerene-coated graphite target rod Cluster Source Block Valve emits a helium pulse Fullerenes react with carbon vapor (C, C2) in the “clustering zone”. Then, the gas exits the channel and undergoes a supersonic expansion to create a cooled, molecular beam Nd:YAG laser (532 nm, 3-5 ns, 5mj/pulse) vaporises the target rod by a single pulse/shot The rod is continuously translated and rotated by a stepper motor

  2. stepper motor target rod accumulation octopole transfer octopole pulsed valve ICR cell skimmer pulsed valve source 10-7 torr diffusion pump 10-7 turbo pump 10-8 turbo pump 10-10 turbo pump

  3. After 3-10 single laser shot accumulations, the ions are transferred to the ICR cell, which is located within in the bore of a 9.4 tesla superconducting magnet. Under the influence of the high magnetic field, the ions exhibit cyclotron motion. The ions induce a current on electrodes, which is detected as an “image current” in the time domain, and then the signal is converted to the frequency domain by an FT. Thus, the mass of the ion is detected as a frequency. the ions which enter the ion optics, where they are acuumulated in the central octopole segment Fullerenes react with carbon species in the vapourisation zone, then exit reaction channel …undergo supersonic expansion and are skimmed into beam 10-7 turbo pump 10-8 turbo pump 10-10 turbo pump 10-7 torr diffusion pump

  4. Answer to questions from email. Q: How do you stop the pulse of ions in the accumulation trap A: The ions are confined radially by an oscilating radiofrequency within in octopole, and axially by voltages at the ends of the “accumulation octopole:.

  5. Answer to questions from email. Q: How many pulses do you need to accumulate? A: A single laser shot is used vaporize the target during a single Helium pulse. Ten singe laser shot + He pulse are used to accumulate ions. Q:How do you decide when to transfer them. A: After the final laser shot, a voltage at the “back” of the accumulation octopole switched, and the ions are transferred to the ICR cell. The switching of the voltage is controlled by the computer program interface. Q: How many runs do you need in general for an average result? A: 3 time-domain aquisitions are averaged for when “growing” a preformed fullerene…….the signal is extremely strong. And 10 time-domain acquisitions are averaged when form endohedrals from a graphite-metal target. Thus, up to 10 time-domain acquisitions are averaged.

  6. Fullerenes react with carbon vapor in the “clustering zone”, then the gas exits the channel and undergoes a supersonic expansion. As the clusters move from a region of high pressure through a small orifice into a high vacuum, they undergo a supersonic expansion. The random thermal energy of the clusters is converted into a directed motion (creating a cooled, molecular beam in which very few collisions occur) toward the skimmer and the ions subsequently enter the ion optics where they are accumulated and then transferred to the ICR cell for detection.

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