Slide 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 = 310 -10 110 -11 new technical developments and ideas needed Slide 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 Slide 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 Slide 4 Atomic masses Measurement procedure Monitor trap Preparation trap Measurement trap Preparation trap Goal: m/m 110 -11 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 92+238 U 91+208 Pb 80+ T1T1 T2T2 T3T3 ~75 mm ~10 mm T = 4 K B/B Slide 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 Slide 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