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Enhancing the mass resolving power of FRIB's proposed high-voltage MR-ToF mass separator and spectrometer: addressing non-ideal conditions

Christian Michael Ireland, Franziska Maria Maier, Einstein Dhayal, Erich Leistenschneider, Ryan Ringle, Austin Sjaarda

TL;DR

This study evaluates how non-ideal conditions affect the mass resolving power of FRIB's proposed high-voltage MR-ToF MS. Using SimIon-based simulations and mitigation strategies (HV stabilization, environment control, active time-centroid corrections), the authors quantify the impact of voltage instabilities, thermal expansion, misalignments, and helium leakage on $R$ and demonstrate pathways to recover high resolving powers, potentially reaching $R \sim 7.5\times 10^6$ or higher. The work shows that with state-of-the-art stabilization and calibration, the FRIB device can approach the performance of existing low-voltage MR-ToF devices while delivering much higher ion throughput. The results provide practical guidance for achieving robust high-resolution mass separation at FRIB and inform design choices for future high-throughput MR-ToF mass spectrometry systems.

Abstract

Multi-reflection time-of-flight mass separators and spectrometers (MR-ToF MSs) are indispensable tools at radioactive ion beam (RIB) facilities. These electrostatic ion beam traps act as highly selective mass separators and high-precision mass spectrometers for rare and exotic nuclei. When well-tuned and designed to minimize higher-order flight-time aberrations, state-of-the-art MR-ToF MSs approach, and slightly exceed, mass resolving powers of \( m / Δm = 10^6 \). Achieving \( m / Δm > 3 \cdot 10^6 \) would provide the ability to resolve \( >90\% \) of all known isomeric states with half-lives above 10~\text{ms}. However, the ability to mass separate in all practical setups is limited by non-ideal conditions which place such resolving powers out of reach. To this end, we present a simulated analysis of these conditions in the newly proposed high-voltage MR-ToF MS for the Facility for Rare Isotope Beams (FRIB). It is expected to store ions at 30~\text{keV} beam energy and increase ion throughput by two orders of magnitude compared to current devices. Existing efforts to mitigate the effects of non-ideal conditions employed for current MR-ToF devices storing ions at \( <3~\text{keV} \) beam energy will already enable mass resolving powers approaching \( 10^6 \) for FRIB's high-voltage MR-ToF device. Simulations of newly proposed mitigation strategies show that even mass resolving powers approaching \( 10^7 \) might become feasible.

Enhancing the mass resolving power of FRIB's proposed high-voltage MR-ToF mass separator and spectrometer: addressing non-ideal conditions

TL;DR

This study evaluates how non-ideal conditions affect the mass resolving power of FRIB's proposed high-voltage MR-ToF MS. Using SimIon-based simulations and mitigation strategies (HV stabilization, environment control, active time-centroid corrections), the authors quantify the impact of voltage instabilities, thermal expansion, misalignments, and helium leakage on and demonstrate pathways to recover high resolving powers, potentially reaching or higher. The work shows that with state-of-the-art stabilization and calibration, the FRIB device can approach the performance of existing low-voltage MR-ToF devices while delivering much higher ion throughput. The results provide practical guidance for achieving robust high-resolution mass separation at FRIB and inform design choices for future high-throughput MR-ToF mass spectrometry systems.

Abstract

Multi-reflection time-of-flight mass separators and spectrometers (MR-ToF MSs) are indispensable tools at radioactive ion beam (RIB) facilities. These electrostatic ion beam traps act as highly selective mass separators and high-precision mass spectrometers for rare and exotic nuclei. When well-tuned and designed to minimize higher-order flight-time aberrations, state-of-the-art MR-ToF MSs approach, and slightly exceed, mass resolving powers of . Achieving would provide the ability to resolve of all known isomeric states with half-lives above 10~\text{ms}. However, the ability to mass separate in all practical setups is limited by non-ideal conditions which place such resolving powers out of reach. To this end, we present a simulated analysis of these conditions in the newly proposed high-voltage MR-ToF MS for the Facility for Rare Isotope Beams (FRIB). It is expected to store ions at 30~\text{keV} beam energy and increase ion throughput by two orders of magnitude compared to current devices. Existing efforts to mitigate the effects of non-ideal conditions employed for current MR-ToF devices storing ions at beam energy will already enable mass resolving powers approaching for FRIB's high-voltage MR-ToF device. Simulations of newly proposed mitigation strategies show that even mass resolving powers approaching might become feasible.

Paper Structure

This paper contains 18 sections, 1 equation, 9 figures, 1 table.

Table of Contents

  1. Introduction
  2. Design and simulation procedure of FRIB's high-voltage MR-ToF setup
  3. Proposed experimental setup
  4. Simulation procedure for mass resolving power
  5. Voltage instabilities
  6. Description and simulated impacts
  7. Long-term voltage drifts
  8. Short-term voltage instabilities
  9. Mitigation of impacts
  10. Thermal expansion of the spectrometer
  11. Description and simulated impacts
  12. Mitigation of impacts
  13. Further expected non-ideal conditions
  14. Voltage inaccuracies
  15. Realistic high-voltage switches
  16. ...and 3 more sections

Figures (9)

  • Figure 1: A cross-sectional view of the simulated FRIB MR-ToF design as presented in Ref. FRIBMRToF. The various optical elements, including mirror electrodes 1-9, grounded electrodes (G), the deflector (D) and pickup (P) electrodes and the drift tube are labeled in black. The beam profile of the stored ions, as delivered from an upstream room-temperature buffer-gas-filled Paul-trap cooler-buncher, along with the direction of beam propagation from injection to extraction, is displayed in red.
  • Figure 2: The simulated time of flight distribution of stored ions when applying the optimal voltage (red peak) or a $\pm10$ ppm shift (blue peaks) to the outermost mirror electrode (#9) after $\approx12$ ms of storage time in the FRIB design. The black arrows display the window that the time centroid varies under this long-term instability, resulting in a broader spectrum on the downstream detector compared to the initial bunch width given by black brackets.
  • Figure 3: The simulated change in time of flight (ToF) as a function of change in voltage (in units of parts-per-million ppm) for the FRIB MR-ToF device mirror electrodes (labeled vertically as they appear on the left-hand side of the plot). Each of the nine mirror electrodes (ME) individually has their set voltage varied up to $\pm10$ ppm around their optimal value. The error bars are smaller than the individual data markers.
  • Figure 4: (a.) The change in the bunch width and (b.) the mass resolving power $R$ of stored 5 ns ion bunches as a function of storage time for various 60 Hz sinusoidal noise amplitudes with a random initial phase per ion.
  • Figure 5: (a.) The change in the bunch width and (b.) the mass resolving power $R$ of stored ions as a function of storage time for various initial bunch widths assuming a 60 Hz sinusoidal noise amplitude of 0.5 V and a random initial phase per ion. The blue curve is the same as depicted in Fig. \ref{['fig:Sinus1']}.
  • ...and 4 more figures