Fast magnetic peak switching for thermal ionization mass spectrometers |
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| Affiliation: | 1. Department of Dermatology, Mayo Clinic School of Graduate Medical Education, Rochester, MN;2. Department of Quantitative Health Sciences, Mayo Clinic, Rochester, MN;3. Division of Dermatopathology, Department of Dermatology, Mayo Clinic, Rochester, MN;4. Division of Dermatologic Surgery, Department of Dermatology, Mayo Clinic, Rochester, MN;1. College of Nursing of Ribeirao Preto, University of Sao Paulo, Brazil;2. School of Pharmaceuticals Sciences of Ribeirao Preto, University of Sao Paulo, Brazil;1. Department of Animal Science, Aarhus University, Blichers Allé 20, 8830 Tjele, Denmark;2. Department of Agroecology, Aarhus University, Blichers Allé 20, 8830 Tjele, Denmark;3. Department of Food Science, Aarhus University, Blichers Allé 20, 8830 Tjele, Denmark;1. College of Pharmacy, Keimyung University, Daegu, 42601, Republic of Korea;2. College of Pharmacy, Yeungnam University, Gyeongsan, Gyeongbuk 38541, Republic of Korea;1. School of Mechanical Engineering, Faculty of Engineering, Tel-Aviv University, Tel-Aviv, Israel;2. Bolton Photosciences Inc., 628 Cheriton Cres., NW, Edmonton, AB T6R 2M5, Canada;1. Elettra – Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, Trieste, Italy;2. Dipartimento di Fisica, Università degli Studi di Trieste, 34127 Trieste, Italy;3. Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA;4. International Faculty, University of Cologne, Albertus-Magnus-Platz, 50923 Cologne, Germany |
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| Abstract: | Common practice in thermal ionization mass spectrometry is to make repeated and rapid comparisons between isotopes of interest by switching the magnetic deflection field sequentially between the values required to deflect each isotope through the collector slit. After each step in the field value (peak switch) it is necessary to pause before logging data, in order to allow the system response to settle to the point where it does not affect the precision of the isotopic ratio determination. The dynamics of the field stabilization system are the principle contributors to this delay period.The system characteristics applicable to a field-controlled magnet system are analyzed in this paper. Possible areas where the step response may be improved by the application of modern control theory are outlined. It is shown that any field-stabilized magnet system can be optimized for step response by the synthesis of a discrete control system. Discrete digital control, i.e. a software implementation, allows system optimization without the necessity for hardware modification, which would be difficult, expensive and possibly in some cases impractical. |
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