AVS 52nd International Symposium
    Applied Surface Science Monday Sessions
       Session AS-MoA

Paper AS-MoA8
Throughput Advantages of PRBS Modulation in TOF Electron Spectroscopy and Mass Spectrometry

Monday, October 31, 2005, 4:20 pm, Room 206

Session: Electron Spectroscopies
Presenter: R.H. Jackson, Stillwater Scientific Instruments
Authors: R.H. Jackson, Stillwater Scientific Instruments
Z. Yang, Univ. of Maine
L.J. LeGore, Stillwater Scientific Instruments
B.G. Frederick, Stillwater Scientific Instruments
P.H. Kleban, Stillwater Scientific Instruments
C.B.H. Crothers, Stillwater Scientific Instruments
D.P. Martin, Stillwater Scientific Instruments
Correspondent: Click to Email
Pseudo-random binary sequence (PRBS) modulation is a method of multiplexing in the time domain to increase the time domain efficiency of an analyzer. We have combined PRBS modulation in a time-of-flight velocity analyzer with maximum likelihood signal recovery methods in both high resolution electron energy loss spectroscopy (HREELS) and mass spectrometry (MS). In previous TOF-HREELS measurements, we have decreased data acquisition times from hours per spectrum to a few minutes, while maintaining resolution in the 2-4 meV range. Although time-of-flight instruments typically trade improvements in time domain throughput for decreases in the etendue, the use of a Bradbury-Nielsen gate chopper allows our optical design to maintain large acceptance angles from the source while achieving high throughput and resolution. We characterize the throughput advantages of a broadband input lens for use in the TOF-HREELS analyzer. Similar advantages are achieved in our GC/MS implementation of a TOF mass spectrometer, compared to the state-of-the-art orthogonal acceleration TOF-MS configuration. We also report order of magnitude improvements in the time resolution and throughput of the timing and control electronics and computational capabilities for implementation of the data recovery algorithms.