A Pulsed Mass Spectrometer with Time Dispersion

Abstract. Miniaturizing instruments for spectroscopic applications requires the designer to confront a tradeoff between instrument resolution and instrument throughput [and associated signal-to-background-ratio (SBR)]. This work demonstrates a solution to this tradeoff in sector mass spectrometry by the first application of onedimensional (1D) spatially coded apertures, similar to those previously demonstrated in optics. This was accomplished by replacing the input slit of a simple 90°magnetic sector mass spectrometer with a specifically designed coded aperture, deriving the corresponding forward mathematical model and spectral reconstruction algorithm, and then utilizing the resulting system to measure and reconstruct the mass spectra of argon, acetone, and ethanol. We expect the application of coded apertures to sector instrument designs will lead to miniature mass spectrometers that maintain the high performance of larger instruments, enabling field detection of trace chemicals and point-of-use mass spectrometry.

Section: Aperture Coding Modelmentioning

confidence: 99%

Order of Magnitude Signal Gain in Magnetic Sector Mass Spectrometry Via Aperture Coding

Chen

Russell

Amsden

et al. 2015

“…By contrast, in the case of constant-momentum acceleration (CMA), employed for DOFMS, ions in the acceleration region gather speed across a constant field-strength for a specified time and, therefore, receive the same change in nominal momentum, regardless of m/z [36]. However, having the same momentum but different masses gives them m/z-dependent energies.…”

Section: Comparison Of Tofms and Dofmsmentioning

confidence: 99%

Distance-of-Flight Mass Spectrometry: What, Why, and How?

Dennis

Gundlach‐Graham

Ray

et al. 2016

Abstract. Distance-of-flight mass spectrometry (DOFMS) separates ions of different mass-to-charge (m/z) by the distance they travel in a given time after acceleration. Like time-of-flight mass spectrometry (TOFMS), separation and mass assignment are based on ion velocity. However, DOFMS is not a variant of TOFMS; different methods of ion focusing and detection are used. In DOFMS, ions are driven orthogonally, at the detection time, onto an array of detectors parallel to the flight path. Through the independent detection of each m/z, DOFMS can provide both wider dynamic range and increased throughput for m/z of interest compared with conventional TOFMS. The iso-mass focusing and detection of ions is achieved by constantmomentum acceleration (CMA) and a linear-field ion mirror. Improved energy focus (including turn-around) is achieved in DOFMS, but the initial spatial dispersion of ions remains unchanged upon detection. Therefore, the point-source nature of surface ionization techniques could put them at an advantage for DOFMS. To date, three types of position-sensitive detectors have been used for DOFMS: a microchannel plate with a phosphorescent screen, a focal plane camera, and an IonCCD array; advances in detector technology will likely improve DOFMS figures-of-merit. In addition, the combination of CMA with TOF detection has provided improved resolution and duty factor over a narrow m/z range (compared with conventional, single-pass TOFMS). The unique characteristics of DOFMS can enable the intact collection of large biomolecules, clusters, and organisms. DOFMS might also play a key role in achieving the long-sought goal of simultaneous MS/MS.

“…Constantmomentum TOF MS was first demonstrated in 1953 by Wolff and Stephens [8]. Since that time, the potential use of constant-momentum acceleration has been discussed in the literature on a few occasions from theoretical perspectives [9 -11].…”

mentioning

confidence: 99%

A constant-momentum/energy-selector time-of-flight mass spectrometer

Santacruz

Håkansson

Barofsky

et al. 2007

A matrix assisted laser desorption/ionization time-of-flight mass spectrometer has been built with an ion source that can be operated in either constant-energy or constant-momentum acceleration modes. A decreasing electric field distribution in the ion-accelerating region makes it possible to direct ions onto a space-focal plane in either modes of operation. Ions produced in the constant-momentum mode have velocities and, thus, flight times that are linearly dependent on mass and kinetic energies that are inversely dependent on mass. The linear mass dispersion doubles mass resolving power of ions accelerated with space-focusing conditions in constant-momentum mode. The mass-dependent kinetic energy is exploited to disperse ions according to mass in a simple kinetic energy filter constructed from two closely spaced, oblique ion reflectors. Focusing velocity of ions of the same mass can substantially improve ion selection for subsequent post source decay or tandem time-of-flight analyses. (J Am Soc Mass Spectrom 2007, 18, 92-101)