Data Acquisition Scheme for Nuclear Physics Experiments
The data acquistion set up for nuclear physics experiments at ELBE is based on a mixed synchronized readout of various digitizers in different form factors (crates). The central processor unit (CES CPU) resides in a VME crate and runs the readout software MBS  developped at GSI. The operating system is LynxOS RTOS. Readout procedures for each component had been developped and tested, and a simple CAMAC ESONE library has been implemented. CAMAC readout is performed using CAMAC crate controllers (WIENER CC32) connected to the VME CAMAC branch driver (WIENER VC32) via standard SCSI cables.
Synchronous readout for list-mode data:
- VME-based trigger module (GSI TRIGGER) allows for multiple hardware trigger conditions and local event counter.
- VME-based peak-sensing analog-digital converters enabling readout of up to 80 channels of silicon detector electronics of RoSiB (CAEN V556 ADC).
- CAMAC-based charge-sensitive analog-digital converters with time-to-charge converters enabling readout of up to 32 channels of HPGe timing information (LRS TFC + LRS QDC).
- CAMAC-based interfaces for peak-sensing analog-digital converters enabling readout of up to 11 channels of HPGe energy information (GIE NFI).
Asynchronous readout for single spectra and scaler data:
- CAMAC-based peak-sensing analog-digital converters enabling readout of 4 channels Si(Li) energy information from deuteron breakup.
- CAMAC-based scaler modules (LRS SCAL).
Data exchange with accelerator control:
- Several data exchange paths have been set up to exchange data between the user experiment and the accelerator control system. Since, the nuclear physics setup is based on a real-time unix system running on PowerPC platforms, the whole accelerator works with Siemens Simatic and Windows-based Intel systems. Therefore, the data exchange is done by TCP/IP communication stacks via the local ethernet connections. Right now, three data paths are used for various purposes:
- OPC data exchange from the accelerator control to the user experiment. Multiple parameters of the accelerator are included into the online data acquisition flow (electron gun current, micro-pulse and macro-pulse repetition rates, acceleration gradients in the accelerator, electron beam dump currents, radiator target position, beam shutter and hardener position, status of the interlock system, etc.)
- OPC data exchange form the user experiment to the accelerator. Online detector count rates allow for monitoring beam adjustment and focussing.
- TCP/IP data exchange with the online beam control sytem provides data from beam-position monitors and pick-up currents.
 N. Kurz, et al., IEEE Transactions On Nuclear Science 47 (2000) 337-339