Greifswald MR-ToF mass spectrometer

Implemented in 2016, the Greifswald MR-ToF setup is based on a multi-reflection time-of-flight (MR-ToF) mass spectrometer, an ion-storage device which is also referred to as an electrostatic ion beam trap (EIBT). Two opposing electrostatic mirrors are utilized to reflect trapped ions back and forth and thus utilize a drift tube hundreds to thousands of times. At identical total energies, ions with different mass-to-charge ratios will exhibit different revolution periods und thus different overall flight times for a fixed number of laps. The device’s precision and mass resolving power can thus be increased by elongating the flight path of investigated ions.

A high-vacuum laser-ablation source is used to produce cluster ions (amalgamations of a certain number of same- or different-species atoms) by irradiation of target plates with a pulsed laser. Measurements of production, fragmentation, or electron-detachment rates of atomic clusters with different sizes yield information about their structure and, thus, the evolution of their properties between atomic and bulk behavior. Modern cluster physics reaches for more and more complex molecules and their fine-tuned application as biomedical markers or reaction catalysts.

At the Greifswald setup, a second laser is set up to excite stored ions and thus investigate cluster photodissociation and photodetachment. Measurement techniques focusing on ion separation and the parallel handling of large mass ranges are developed to tackle the unique challenges of large clusters. Simultaneously, techniques for MR-ToF precision mass spectrometry as used in, e.g., nuclear physics are adjusted and advanced.

Experimental setup

Setup of the Greifswald MR-ToF experiment. Ions produced by laser ablation are guided onto the MR-ToF analyzer’s axis by a quadrupole deflector (red arrow). Laser beams for production and in-trap photoexcitation are indicated by green arrows.

Potential configuration

Axial potential of the MR-ToF analyzer for confinement of a positive ion with a kinetic energy of about 1.2 keV. The central drift tube can be utilized as a potential lift to energetically lower and raise ions in and out of the well. Alternatively, the reflecting walls can be switched off for a short time to inject or eject ions.

Time-of-flight spectra

Time-of-flight spectra of Pb10- clusters for increasing revolution numbers (20, 60, and 100 from top to bottom). Different combinations of stable lead isotopes lead to ion species with different mass numbers (“isotopologues”), as labeled in the bottom spectrum. Increasing separation between species highlights a rise in mass resolving power.
Time-of-flight spectra of Bi- clusters after 400 revolution periods. (a) No ion selection and no photoexcitation is employed. (b) A target ion species (Bi7-) is selected by use of synchronized in-trap deflector pulses. (c) Photoexcitation of the selected species leads to fragmentation into smaller cluster sizes.

Publications

2024

2023

2022

2021

2020

2019

2018

2017

Theses

2022

  • Investigations of a combination of magnetron ion source, quadrupole mass filter, linear Paul trap, and multi-reflection time-of-flight mass spectrometer
    Paul Florian Giesel, Master Thesis

2021

  • Das Auflösungsvermögen eines Flugzeitmassenspektrometers als Funktion des Anregungszeitpunktes bei der Photofragmentation von Bismutclustern
    Lukas Roscher, Bachelor Thesis
  • Zeitabhängigkeiten bei der Produktion von Metallclustern durch Laserablation
    Lukas Richter, Bachelor Thesis

2020

2019

2017

  • Weiterentwicklung eines Multireflexionsmassenspektrometers für Clusteruntersuchungen
    Florian Simke, Master Thesis

2016

  • Erzeugung und Untersuchung von Clusterionen
    Paul Fischer, Master Thesis