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Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P21
Multifragment Imaging of Photon and Ion induced Processes
Lutz Foucar 1 , Achim Czasch 1,2 , Ottmar Jagutzki 1,2 , Klaus Ullmann 1,2 , Daniel
Wald 2 , Lothar Schmidt 1 , Sven Schößler 1 , Till Jahnke 1 , Reinhard
Dörner 1 , Horst Schmidt-Böcking 1
1 Institut für Kernphysik, Universität Frankfurt, Max-von-Laue-Str.1,60438 Frankfurt,
FRG – 2 Roentdek GmbH, Im Vogelshaag 8, 65779 Kelkheim
Correlated many-particle dynamics in Coulombic systems, which is one of the unsolved
fundamental problems in physics, can now be experimentally investigated with
unprecedented completeness and precision. The recent development of the COLTRIMS
reaction microscope (COLd Target Recoil Ion Momentum Spectroscopy) [1,2] provides
a coincident multi-fragment imaging technique for eV and sub-eV particle detection.
In its completeness it is as powerful as the bubble chamber in high energy physics.
The technique is widely applied for single but also for multiple photon absorption
processes. More and more complex fragmentation systems are being investigated. The
multi-channel plate detectors with delay-line anode read out are ideally suited for
multi-hit detection. However, pile-up effects in the fast read-out electronics are presently
the bottle neck of the system. Fast transient recorders (ADCs), which digitize
the in-coming signals on a sub-nanosecond scale, can be used to overcome this problem.
Using standard fitting algorithms multi-hit signals can be separated as two pulses even
if the two signals are separated by only two nanoseconds. Additionally the test experiments
showed that the internal detector and electronic timing can thus be improved to
yield a timing resolution of well below 100 picoseconds. In combination with improved
readout electronics the COLTRIMS imaging technique is prepared for the next step -
multiple fragmentation processes of large molecules.
Acknowledgements: We acknowledge the great help of C.L. Cocke, M. Prior and many
other colleagues as well as the support of BMBF, DFG and by Roentdek GmbH.
[1] J. Ullrich et al., J. Phys. B: At.Mol.Opt.Phys. 30:2917, (1997)
[2] R. Dörner et al. , Physics Reports 330:95, (2000)