Evaluation of multi‐turn time‐of‐flight mass spectrum of laser ionization mass nanoscope

Abstract

We have evaluated the performance of a multi-turn time-of-flight mass spectrometer (MULTUM II) equipped with the ion injection optics of a laser ionization mass nanoscope (LIMAS). We surveyed the optimal parameters for the ion injection optics, which consist of ion extraction from a sample surface and ion introduction into MULTUM II. We developed mass calibration methods for correcting the modulation of load voltage for MULTUM II and injection timing for the ion injection optics. As a result, the mass-resolving power of LIMAS increased linearly with increasing the flight path length, and reached 6.2 × 10 5 (full width at half maximum) at 1000 multi-turn cycles of MULTUM II (flight path length: 1.3 km). The transmittance of LIMAS decreased to 60-70% after 20 multi-turn cycles of MULTUM II, compared with the linear mode transmittance. The transmittance per multi-turn cycle became constant (99.96%) after 20 multi-turn cycles. A useful yield of 3 × 10 À3 for Si ions was obtained for LIMAS at 30 multiturn cycles of MULTUM II.

Quantitative analysis of helium by post‐ionization method using femtosecond laser technique

“…An SNMS instrument called LIMAS was used for our measurements. Operation timings of the measurement sequence for LIMAS were described in this study .…”

Electronic data acquisition and operational control system for time‐of‐flight sputtered neutral mass spectrometer

“…The dynamic range of the system was determined using a Mg metal substrate with the natural isotope abundance, ie, 24 Mg (79%), 25 Mg (10%), and 26 Mg (11%). The mass spectra of 24 Mg 2+ , 25 Mg 2+ , and 26 Mg 2+ were not interfered with interference ions such as 12 C + (less than 0.1% of the objective peaks), which were obtained at 20 multiturn cycles in MULTUM II . A mass resolving power of 11 000 (FWHM) was achieved at the multiturn.…”

“…The mass spectra of 24 Mg 2+ , 25 Mg 2+ , and 26 Mg 2+ were not interfered with interference ions such as 12 C + (less than 0.1% of the objective peaks), which were obtained at 20 multiturn cycles in MULTUM II. 7 A mass resolving power of 11 000 (FWHM) was achieved at the multiturn. In this study, secondary ion signals have not been resolved from post ionized signals, but the secondary ion intensities of Mg 2+ were more than two orders of magnitude lower than secondary ion intensities at their m/z.…”

“…The postionization method indicated that the almost all elements in an area focused on the femtosecond laser were totally ionized. A useful yield of laser ionization mass nanoscope (LIMAS) was 0.5% for Si ions with higher power femtosecond laser of 6 mJ of the pulse energy and 35‐femtosecond pulse width . Therefore, the ion signals of TOF‐SNMS are much more intense than those of time‐of‐flight conventional secondary ion mass spectrometry (TOF‐SIMS) for the same sputtered atom numbers.…”

“…A useful yield of laser ionization mass nanoscope (LIMAS) was 0.5% for Si ions with higher power femtosecond laser of 6 mJ of the pulse energy and 35-femtosecond pulse width. 7 Therefore, the ion signals of TOF-SNMS are much more intense than those of time-of-flight conventional secondary ion mass spectrometry (TOF-SIMS) for the same sputtered atom numbers. As a result, improvement of an electronic data acquisition system is demanded to adapt full performances of TOF-SNMS.…”