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AGATA is a 4-pi array of high purity Ge detectors for in-beam gamma-ray spectroscopy based on the novel concepts of pulse shape analysis (PSA) and gamma-ray tracking. Tracking and PSA require the concurrent digitization--at a sampling rate of 100 Msamples/s--of preamplifier signals of the 36-fold segmented Ge crystals composing the array. Locally digitized data are optically transferred to remote pre-processing nodes for pulse energy computation. The design of the front-end readout and level-1 (L1) trigger in AGATA follows a synchronous pipeline model: the detector data are stored in pipeline buffers at the global AGATA frequency, waiting the global L1 decision. A global timing system provides a reference clock and time tag to the digitizers and the pre-processing units by means of a tree of optically connected timing units. Pre-processing nodes are integrated in AdvancedTCA-based carrier cards with full mesh connectivity in the backplane and read-out through pci-express based optical links. The front-end data readout and its integration in the global trigger and synchronization system will be described. Index Terms--AdvancedTCA, digital trigger, distributed synchronization, full mesh readout, Pci-Express.

A gamma-ray tracking algorithm has been implemented and tested, using simulated data, for gamma rays with energies between 0.1 and 2 MeV, and its performance evaluated for a 90-mm-long, 60-mm-diameter, cylindrical, 36 (6 x 6) segment detector. The performance of the algorithm in two areas was determined: Compton suppression and Doppler shift correction. It was found that for gamma rays of energies around 1 MeV, a ratio of photopeak counts to total counts of 2:3 could be obtained using the tracking algorithm, with only a 2% reduction in detection efficiency, compared to the untracked data. Approximately 80% of first interaction points could be correctly identified, enabling a good Doppler shift correction. A detector of the type simulated has recently been delivered, together with a compactPCI digital data acquisition system comprising 36 12-bit, 40-MHz flash ADCs, and 6 200-MHz DSPs. Some initial data has been recorded using this system, and the performance of the tracking algorithm on this real data is comparable to its performance on simulated data.

During 1992-1993 the Nuclear Structure Facility at Daresbury Laboratory hosted phase one of the EUROGAM[1] experimental programme. These were the first nuclear physics experiments to make large scale use of the VXIbus standard for electronics and data acquisition. EUROGAM phase 1 was made up of an array of 45 escape suppressed Germanium (Ge) detectors. It was used for gamma-ray spectroscopy both stand-alone and in conjunction with external detectors including the Daresbury Recoil Separator (RS)[2], isomer detectors and various particle detectors. An overview of the system, details of special VXI cards, the readout and trigger systems for EUROGAM have been previously reported at the 1991 IEEENSS. Here we report on how they worked in real experiments.

The new VXIbus standard was tested for use in the packaging of an Anglo/French gamma ray detector, a high density signal processing and data readout system. The EUROGRAM detector is composed of an array of up to 70 high purity Germanium detectors, each accompanied by a multi-element Bismuth Germanate escape suppression shield and is planned to serve between the 20 millivolt Van der Graaf accelerator at Daresbury and the Vivitron in Strasbourg. Results of the test show that the VXIbus standard is compatible with high-precision, multi-channel spectroscopy amplifiers.

A VME-based readout system was used for the EUROGRAM gamma-ray detection system. Its primary features include its combination of VMEbus and an environment suitable for housing analog electronics. The readout system reads an event's data form acquisition modules within the VMEbus crate using a single, slightly modified, VMEbus block transfer. This set-up allows dense packing of both analogue signal processing and data acquisition electronics within a unified framework.

Recoil decay tagging (RDT) is a very powerful method for the spectroscopy of exotic nuclei. RDT is a delayed coincidence technique between detectors usually at the target position and at the focal plane of a spectrometer. Such measurements are often limited by dead time. This paper describes a novel triggerless data acquisition method, which is being developed for the gamma recoil electron alpha tagging (GREAT) spectrometer, that overcomes this limitation by virtually eliminating dead time. Our solution is a total data readout (TDR) method where all channels run independently and are associated in software to reconstruct events. The TDR method allows all the data from both target position and focal plane to be collected with practically no dead-time losses. Each data word is associated with a timestamp generated from a global 100-MHz clock. Events are then reconstructed in real time in the event builder using temporal and spatial associations defined by the physics of the experiment. Index Terms--Alpha-particle spectroscopy, beta-ray spectroscopy, coincidence circuits, data acquisition, gamma-ray spectroscopy, nuclear physics, triggering.

An Advanced GAmma Tracking Array (AGATA) symmetric prototype high purity Germanium (HPGe) detector has been tested. The detector was illuminated with a 1 mm collimated, beam of 137Cs (662 keV) gamma rays. The beam was raster scanned across the front and sides of the detector and the charge sensitive preamplifier output pulse shapes from all 37 channels (36 segments plus the centre contact) were digitised and stored for off-line analysis. Rise time and image charge asymmetry magnitudes were measured as a function of interaction position to study the charge transport properties through the crystal volume. These parameters were then utilised as a calibrated look up table with which in-beam data was analysed and Doppler corrected. An average position resolution of approximately 9 mm (FWHM) was achieved with a crude analysis. [ABSTRACT FROM AUTHOR]

A four-channel VERSAmodule Eurocard (VME) with 14 bit, 80 MHz digitizers and powerful on-board processing has been designed, built, and used in tests of digital pulse processing techniques for gamma-ray tracking. This paper explains the background, describes the VME card (known as the GRT4) and presents a 64-channel GRT4 digitizing system which was used to instrument two segmented Germanium detectors during in-beam tests. Results obtained using the GRT4 card are presented as well as some applications. [ABSTRACT FROM AUTHOR]