FRS stand-alone system

Sorry, still under construction!

System architecture

The FRS data acquisition is based on VME electronics, which process the detector signals, according to the trigger logic, digitize and send them to the front-end computer. The standard FRS front-end computer is a RIO3 processor which runs in a Multi-Branch System (MBS) under the Lynux operating system. This RIO3 (named R3-8) and resides in the FRS-standard VME crate is usually consider as the master. The standard FRS detectors are read out via the itwhile any user specific detectors should be handled by the user using the other crate, the User one. The standard branch also includesand controls a Camac crate containing the CFDs for MWPC detectors. The data are usually sent over the GSI Ethernet network to be sample by the on-line analysis clients by means of another processor, the event builder (named X86-11). A view of a single-system architecture is here.

The FRS acquisition in stand-alone mode

The FRS data acquisition can be run in stand-alone mode or as part of more complicated systems. The stand-alone mode, schematically described in Figure 1, is based on two processors: a data sender and a data receiver.

FRS Standalone Scheme
Figure 1. A schematic representation of the FRS acquisition in stand-alone mode.

The data sender is a RIO-3 processor, running under Lynx-OS, which resides in the FRS VME crate. It handles the readout of the digitizers (ADCs, QDCs etc.) and then passes the data via TCP/IP on to the second processor. This is a PC, also running Lynx-OS, which acts as data receiver. Its job is to act as event builder, and to make these available for further processing, such as storage or by analysis clients. The PC is situated next to the storage cabinets in the electronics area of the FRS Messhütte.

At present the RIO-3 also controls access to two CAMAC crates - one can be used for digitizers if needed, and the other houses the constant fraction discriminators and multiplexers used for slow-control of the MW detector signals. The slow-control Labview program connects to the CAMAC crates via the Esone server task running as part of the normal data acquisition environment of the RIO-3 processor. (If MBS is not running, the slow-control applications are also disabled!)

FRS Trigger

At present, the standard FRS trigger consists of only one trigger (#1), which can be obtained from the logic operation of the standard detector signals. They can be included simply turning on the corresponding switches of the FRS Trigger-Box 1 and 2. The FRS Crate and any other VME crate included in the DAQ must be equipped with a GSI Trigger Module which controls the hardware readout timeing cycle. The GSI Trigger Module is programmable, for example, conversion time (CVT) can be programmed into it. The FRS system works in a polling mode for triggering. The FRS Trigger Module represents usually the Master Trigger Module. Only it should receve the signal trigger provided by the trigger logic set up. All the other trigger Modules, in case additional VME crates are present, have to be connected to the Master one via a bus cable. In this way the correct syncronization of the hardware readout is guaranteed. The trigger Module also provides some usefule output signals, including the accepted trigger (#1) and the total dead time (TDT) (#4). When trigger input #1 occurs, the trigger Module check if the system is busy. If it is not, the trigger word is sent to the processor and an accepted trigger is given as output. If the system is already busy, processing a preavious event, the trigger is not accepted. The TDT signal, present when the system is busy, can be used to gate other electronics.

Since August 2006, a VME Universal Logic Unit (vers.1), (VULOM1) has been added in the VME FRS crate. In this way the trigger scheme is much simplified because dead time protection is automatically executed by this logic unit, and several different triggers (up to 8) can be used and just send directly to the trigger module by the ENV1 module (see VULOM1 Cabling Scheme)


Until now, the VME-based DAQ at FRS were being running and read out only in single event mode. When working within the MBS framework, all the individual user has to provide are routines for the initialization and readout of the specific digitizers being used. To this end, a standard init & readout function (f_user.c) has been developed for use with the FRS detector setup. This can be modified in order to include other, user-specific, components (see more about the init & readout function ).

Usually one standard FRS-event readout takes about 110 us, limiting the rate to around 10kHz. A more efficient readout can be performed by using BLock Transfer mode (BLT), giving a possible rate of 100 kHz. A multi-event readout function has been developed and tested.

Single-event mode

Information about the computational environment and the main software packages used for data taking at the FRS in single-evnt mode are here described. Some basic instructions how to set up a running FRs data acquisition with the FRS and User branch are also given.

Starting up MBS

First, be sure that all the VME crates in the FRS Messühutte are turned on. Log in as profi user (password is required) in one of the Lynx PC of the FRS Messühutte and create a working directory under /lynx/Lynx/frs/usr/profi/mbsrun/runxxx, where xxx is the run number assigned to the FRS experiment. Copy there all files including subdirectory from /lynx/Lynx/frs/usr/profi/frs_single_event/user/.

Check that the subdirectory /vme_user_branch contains all the correct files. If not you have to set them according to your VME configuration. It means that you could need to edit the f_user.c function, add new ADCs, TDCs, etc., or change threshold values. To do that it is not difficult but you need to be very careful! All the files in the subdirectory /vme_frs_branch are correct and normally you do not need to make any change there. Then log in as profi (different password is required) into the RIO3 processor and make the executable; it is called m_read_meb. Perform a reset of all the processor

R3-8> reset The following massage should appear:

The system tries to close the connections, if none was. You can check the status CLOSE_WAIT or TIME_WAIT with the command R3-8> net600

You can repeat this command after some time. When you do not see them anymore, invoke the MBS environment. R3-8> prm

The nodes of the environments to be controlled by the prompter are in this case 3, R3-8, R3-19 and X86-11,as appairs from the file node_list.txt.

All the MBS tasks can be started executing the command file startup.scom. mbs> @startup

The following messages should appear saying that crate inizialitations take place:

and you can start your acquisition with the command mbs> start acq if trigger #14 is found, everything was correct.

You will get X86-11> as a prompt. From there you can see the contents of an event on the screen with the command X86-11> type ev -v

Check what is going on and if the physics trigger is there by log into R3-8 from another terminal and giving the command

R3-8> rate

In this case the acquisition rate will be continously monitorised every second. The monitoring ca nbe exited with Ctrl-C.

If you want to transfer or analyse your data with a client you have to start the remote event server from a new terminal

profi> mrevserv X86-11

and you will get the connection to a port (defaultnumber 6003). This will be indicated also where the mbs prompt is. To stop the acquisition, enter

mbs> stop acq

In case you need to close your MBS session before to quit, first stop the remote event server in the teminal window where you started it with Ctrl-C and later give the command mbs> @shutdown in order to stop all the preaviously started MBS tasks.

Multi-event mode — Under construction!

Click here to see the new trigger scheme.

Click here to see the spill-on-off scheme.

An example of comparison between the single- and multi-event mode is here summarised and plotted in Fig. 1 and Fig. 2, respectively. The DAQ rate has been tested in both cases with one VME crate setup with two Caen TDCs V775. The multi-event DAQ was able to run up to 40 kHz without any relevant increasing of the dead time. It means a factor 2.6 more in the rate, compared to the single-event mode.

Data visualization

Experience has shown that it is very important to sample and visualize the data stream on-line - i.e. as it is being collected. To this end, several different software packages can be used, including LeA, Go4 and PAW. Of these, Go4 represents the latest development, and is recommended by the GSI DVEE department. A Go4 version for general FRS use has been developed.

Common to all approaches is the need for unpacking the FRS-specific data structure and implementation of the algorithms needed to extract physics parameters, e.g. for particle identification purposes, from the raw data.
  • FRS data structure in single-event mode
  • FRS algorithms
  • Sample GO4 unpacking — Under construction!
Topic attachments
I Attachment Action Size Date Who Comment
cabling_VULOM1.pdfpdf cabling_VULOM1.pdf manage 550.7 K 2008-06-24 - 14:25 TillDettmering VULOM1 Cabling Scheme
frs-standalone.gifgif frs-standalone.gif manage 8.4 K 2008-06-24 - 14:49 TillDettmering FRS Standalone Scheme
gm_vme_trig.pdfpdf gm_vme_trig.pdf manage 424.4 K 2008-06-24 - 14:15 TillDettmering GSI Trigger Module Description
trigger-scheme.pdfpdf trigger-scheme.pdf manage 10.6 K 2008-06-24 - 14:23 TillDettmering Trigger Scheme
vulom1.pdfpdf vulom1.pdf manage 386.9 K 2008-06-24 - 14:24 TillDettmering VULOM1 Manual
Topic revision: r1 - 2008-06-24, TillDettmering
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