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Atomic masses – Competition worldwide K. Blaum, Phys. Rep. 425, 1-78 (2006) Penning-trap mass spectrometry groups for stable masses: D. Pritchard, MIT.

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Presentation on theme: "Atomic masses – Competition worldwide K. Blaum, Phys. Rep. 425, 1-78 (2006) Penning-trap mass spectrometry groups for stable masses: D. Pritchard, MIT."— Presentation transcript:

1 Atomic masses – Competition worldwide K. Blaum, Phys. Rep. 425, 1-78 (2006) Penning-trap mass spectrometry groups for stable masses: D. Pritchard, MIT / E. Myers, Tallahassee R. Van Dyck, Seattle R. Schuch, Stockholm G. Gabrielse, Harvard  Avoid ion-ion interactions  Use higher charge states  Minimize magnetic field fluctuations  Reduce temperature of the stored ions  Apply highly sensitive detection techniques Objectives for the next generation Penning trap mass spectrometer  m/m limit = 3· – 1· new technical developments and ideas needed

2 Atomic masses – Measurement principles Cyclotron frequency: B PENNING trap Strong homogeneous magnetic field Weak electric 3D quadrupole field ring electrode end cap Typical f c frequency q = 50e, m = 100 u, B = 7 T  f c ≈ 53 MHz q/mq/m

3 Atomic masses – The four-trap mass spectrometer at UMZ Ions from an EBIT or HITRAP (A6) ~75 mm Monitor trap Preparation trap Measurement trap Preparation trap 1 cm ± 1  m Ring electrode Machined at the Institute for Microtechnique Mainz (see B7). Electron Beam Ion Trap 20 cm ~10 mm B = 7 T

4 Atomic masses – Measurement procedure Monitor trap Preparation trap Measurement trap Preparation trap Goal:  m/m  1· Advantages: In-situ B-field calibration Direct binding energy measurement No ion-ion interaction Cryogenic temperatures Highly-charged ions Simultaneous measurement process Timing scheme: 238 U U Pb 80+ T1T1 T2T2 T3T3 ~75 mm ~10 mm … T = 4 K  B/B<10 -7 /cm 3, (dB/dt)·(1/B)< /h +/ Hz B-field monitoring Cyclotron frequency variation / mHz Time / h ,13 C 5+

5 Atomic masses – Non-destructive ion detection x y Pickup-Elektrode „FT-ICR“ Fourier-transform-ion cyclotron resonance ion current signal mass spectrum I I t f very small signal ~fA Development of cooling techniques and cryogenic traps for resonant detection. Signal-to-noise ratio: r ion : ion motion radiusD: trap dimension q: charge state Q: quality factorT: temperatureC: capacity

6 Atomic masses – Recent developments (for project B2) C. Weber et al., Eur. Phys. J A 25, 65 (2005) Precision trap Resonance of the unloaded LC-circuit at T = 4K Single-ion sensitivity! Amplification: 50000


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