High precision Penning trap mass spectroscopy and a new measurement of the proton's 'atomic mass'
- Department of Physics, Box 351560, University of Washington, Seattle, Washington 98195-1560 (United States)
The Penning trap mass spectrometer (PTMS) at the University of Washington has been rebuilt into a new state-of-the-art magnet/cryostat system with external Helmholtz compensation coils (controlled by a nearby flux-gate sensor). This system gives a total magnetic shielding factor of {approx}10{sup 4} (which includes the effects of a passive internal flux-stabilizing coil supplied by the manufacturer). When the new magnet/cryostat is fitted with a system to control its boil-off pressure, the typical temporal field stability is {approx}-0.017(2) ppb/h. The ultimate resolution of this improved spectrometer is expected to exceed 0.020 ppb with 100 hours of data using a single C{sup 4+} ion. The comparison of a C{sup 4+} ion with a C{sup 5+} ion suggests that the spectrometer's accuracy may indeed match its resolution. To demonstrate the spectrometer's improved performance over its previous version, the cyclotron frequency of a single proton is compared to the corresponding frequency of a single C{sup 4+} ion, yielding a determination of the proton's atomic mass given by M{sub P}=1,007,276,466.89(14) nu. The primary systematic error (overcome in this case) is due to a position sensitivity within the non-uniform magnetic field, enhanced by the electrostatic trapping potentials of these ions which differ by a factor of three. A residual limitation to the overall field stability appears to be due to a long-term temperature-dependent temporal wander in the magnetic field.
- OSTI ID:
- 21207911
- Journal Information:
- AIP Conference Proceedings, Vol. 457, Issue 1; Conference: International conference on trapped charged particles and fundamental physics, Asilomar, CA (United States), 31 Aug - 4 Sep 1998; Other Information: DOI: 10.1063/1.57450; (c) 1999 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
- Country of Publication:
- United States
- Language:
- English
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