New GSI Analysis System GO4  

Participants: R. Barth, W. Brüchle, H. Essel, R. Holzmann, C. Kozhuharov, N. Kurz, M. Richter, K. Schmidt, E. Stiel, H. Winter

Distribution: H. Brand, P. Braun-Munzinger, S. Glückert, H. Göringer, N. Herrmann, S. Hofmann, M. Kaspar, H. J. Kluge, P. Koczon, W. Koenig, U. Krause, U. Lynen, V. Metag, W.F.J. Müller, G. Münzenberg, V. Schaa, C. Scheidenberger, C. Schlegel, K.H. Schmidt, H. J. Specht, R. Steiner, K. Sümmerer, G. Bollen, Th. Nilsson, H. Simon, R. Fox, K. Suzuki

Different experimental set-ups have been described:

• Surrounded by detectors is a stack of 8 identical targets inline the beam axis each with a backing impervious to fission products facing the beam. The prompt fission fragments can leave the targets only in forward direction defining an angle region (open area) for each target where the fragments can hit the surrounding detectors. Fragments from delayed fission will come from locations outside the targets, i.e. some may also be seen in a "shadow" area. The detectors are multi-wire proportional chambers, 1 start and 2 stop counters on each side parallel to the beam and the target stack. The detectors give dE, time, and position information for reconstruction of each fragment's trajectory. The v - dE information selects fission products from background signals. The correlation of a fragments and its source target (one of eight) is done by polygon-conditions on the target area together with window-conditions in the beam direction (defining a volume). In addition, only coincidences between fragments found in the open area with those found in the shadow area are selected.
• a gas jet system transporting irradiated material out of the target area continuously needs to be set and controlled during the irradiation
• a rotating wheel multi-detector analyzer (ROMA) with currently 64 sectors (to be expanded to over 100) transports products of chemical separations. In steps of several, fixed seconds the wheel moves the collected activity between 8 pairs of PIPS detectors measuring the time dependent Alpha and fission radiation. The wheel stepping is controlled by a standalone PC. Both, Alpha and fission events are acquired by the MBS system and analyzed by GOOSY. In addition, the Alpha events are accumulated on a multi-channel analyzer. In case of an implantation of a Alpha-decay daughter in a detector, the wheel will be rotated just half a step, i.e. the probes are outside the detectors for a certain time. This will reduce the background to find grand-daughter Alphas for this decay. The detection of such an event is currently done by a discriminator in the Alpha detector line triggering the stepping PC. This method should be replaced by a more detailed analysis in the data acquisition processor.

Following requests on GO4 have been expressed:

• multi-indexed spectra names
• interactive histogramming under dynamic conditions of all input parameters and new parameters produced by mathematical and logical combinations of parameters.
• polygon conditions
• analysis of time correlations between events (Alpha ray mother-daughter relations) in a time scale of ms to min.
• real-time analysis in the data acquisition processor connected with set-up control
• Gamma line search programs
• Gamma line data base
• interactive graphical analysis of gamma-ray coincidence data (may be the software package RadWare http://radware.phy.ornl.gov is suitable. It is available at GSI on several platforms)
• a sort of trending storage of data, i.e. keeping events in a ring buffer for a given time window. This is needed for finding long-time correlations.
• portable data acquisition and analysis systems including front-end, workstation or PC, and storage drives for experiments outside GSI

M. Richter, August 27, 1998

Downloads-Manuals-References

GSI Helmholtzzentrum für Schwerionenforschung, GSI
Planckstr. 1, 64291 Darmstadt, Germany 
For all questions and ideas contact: J.Adamczewski@gsi.de or S.Linev@gsi.de
Last update: 27-11-13.