Project: "Development of a GOOSY-PAW Successor System"

Minutes of the 6th Meeting on August 20, 1998

Participants: R. Barth, H. Essel, S. Hofmann, N. Kurz, M. Richter, H. Winter

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


1. Various Topics

The ISOLDE collaboration (Georg Bollen, Haik Simon, Thomas Nilsson) will be involved in the go4 definition phase.

2. Experiments at SHIP by S. Hofmann

The experiments at the Velocity Filter SHIP (Separator for Heavy Ion Production) measure decay chains of alpha-, proton-emitting and spontaneously fissioning nuclei far from stability with half-life times as short as microseconds and formation cross-sections down to picobarn region. To acquire all data from decays in the microsecond region the parameters are stored currently in parallel in FIFOs of 128 words depth.

The beam is produced currently with 50 Hz and a 27.5 % duty factor, i.e. beam-on for 5.5 ms every 20 ms. The average current is 400 particles nA and 1,450 particles nA in the beam-on time. The event rate for background is about 50 events/s and in-beam 150 events/s. The maximum half-life time currently measured is 100 s.

With the intensity upgrade of the accelerator currently under construction there will be 1 ms beam in 100ms intervals with an average current of 4,000 particles nA and 400,000 particles nA in-beam. The background will raise to 500 events/s and 50,000 events/s in-beam. The maximum half-life time to be measured will be 1,000 s.

The resolution of the position sensitive 16 strip detector for fission and alpha decay is 16 * 5 mm horizontal and about 0.15 mm vertical (via strip resistor), i.e. 233 pixel/strip = 3,728 pixel/detector. For each strip there are 6 "slow" analog and 6 "fast" analog energy channels, a time of flight and 2 logic channels. In addition, a 32-fold segmented backward detector produces 128 energy and 64 logic parameters. Since the number of ADCs, FIFOs and readout modules is limited, the valid input channels are selected by trigger signals and then converted in parallel within 15 microseconds and stored in FIFOs.

In the future, x- and y-position sensitive strip detectors with all together 62,666 pixels will be used. The number of parameters will grow to over 3,000 energy signals, 532 logic signals and the time of flight information.

For pileup detection it might be necessary to sample the signals with flash ADCs. This would make front-end processors for data reduction essential.

The combination of the current setup with Ge clusters for gamma detection around the target or behind the SHIP will be used for recoil-decay-tagging. SHIPTRAP, an ISOL facility for transuranic isotopes is planned for precise measurements on the reaction products. This will need an integrated fast control system for the separation fields and the ion trap.

For the setup time of the experiments automatic procedures for the detector calibration (including 2-dimensional parabolic fits), SHIP beam transport calculations, and SHIP field settings for transmission optimization (including Monte Carlo methods) are missing.

The data analysis needs fit procedures for alpha spectra using specific, complicated functions, like $MYFIT of SATAN.

A simple protocol of many setup parameters should run all the time during an experiment. Currently this is done by a multi-channel plotter.

A control system for the target must be installed including an infra-red camera, a beam profile, energy and intensity control, and a target thickness control.

A fast real-time analysis with correlation check of about 10 s range is needed to switch of the beam for background reduction is case of a valid event. This analysis could also reduce the raw data flow. A setup control and a self-test of the whole setup is needed. A common precise clock (1 microsec) should synchronize different setups running together, e.g. SHIP + Gamma clusters. The accumulation of single spectra with high data rates is needed.

The new system should include all features of SATAN and GOOSY. The analysis of old SATAN and GOOSY data formats must be possible. The system must be longtime stable and reliable.

3. Next meeting

The project members agreed in first regular meetings twice a week on

Monday 14:00 and Thursday 14:00,

always in the meeting room of the DV&EE department

The next meetings and their agenda:

Monday, August 24, 1998, 14:00
Various Topics

Thursday, August 27, 1998, 14:00
E. Stiel: Nuclear Chemistry Experiments

M. Richter, August 20, 1998