Data Acquisition

The Generic Data Acquisition (GDA) framework is a Java-based distributed system used on Diamond’s beamlines to control experiments and collect data. The project to develop the software was initiated at SRS, Daresbury until release 4.2 in October 2003. From then it was co- developed by teams from both facilities until release 7.0.0 in late 2007. Since then Diamond’s GDA has been purely developed by the Data Acquisition and Scientific Computing Group.

Each beamline uses a copy of the GDA software configured for its own particular hardware and experimental requirements. Experiments can be controlled using beamline- or technique-specific GUI panels, a command-line terminal or by writing and running scripts (macros).

Logging in
Starting the GDA
Data storage

The GDA software is run from workstations on the beamline. Beamlines use one of two methods to log into these workstations:

Shared user account login. On some beamlines you will login to the same shared user account. The name of this account is the name of the beamline followed by ‘user’ all in lower case. For example, if your beamline were I01 the account would be ‘i01user’. The password to login using this type of account will be given to you by the beamline staff. Note however that the workstations on beamlines that use this method will be automatically logged in to this account when started or rebooted.

FedID account login. On other beamlines you will login using your own Facilities user FedID name and password issued to you by the User Office.

As of March 1st, 2007 all beamlines use the first, shared account method, but this will change. It is sometimes possible to control the beamline from the outside by logging into one of these workstations remotely.

Regardless of how you login on the beamline the GDA system will store your data (and some other files) in a shared location on your beamline’s storage server. Read access control to this data will be determined by beamline staff. Let them know if you are concerned about the security of your data. This storage server is described in the following section.

Before starting the GDA software you may have to set up the shell environment. If you login with your own FedID account type:

source /dls/ixx/etc/ixx-profile.sh

Starting the GDA is a two step process. The bulk of the GDA software is started from a terminal by typing:

from a Linux terminal

gdaservers

from a Windows terminal

gdaservers.bat

This starts up the GDA server software on one of the beamline’s central control server machines. This software may be running before you start using the system, but asking it to start again causes no harm. A GUI client is used to interact with this server. About 30s after starting the server you should see the message “Server Initialisation Complete”.

Then type the following to start the GUI client:

from a Linux terminal

gdaclient

from a Windows terminal

gdaclient.bat

The GUI client will ask you for a name and password when it starts up. This name is used by the GDA to determine where to put your data. If you have logged in to your own user account using a FedID, select the option to automatically use the FedID of that account. Otherwise if you are logged into a shared user account, give it your FedID and password allocated by the User Office.

If you try to start the GDA client and get a string of connection errors followed by a final “Can’t find a Command Server” error, either the server is not running and needs to be started or you didn’t wait long enough before starting the client. You may close the GDA client software running on your workstation without effecting the operation of the command server. If you need to leave your computer, rather than locking the screen to prevent access to the GDA command server, you may close the client software and log off. You may then login and start up the client server again and begin where you left off.

All experimental results will be saved initially on a beamline’s central storage area. You will not normally have much choice in where your experimental data is stored. The GDA software saves the results from each experiment or scan in a standard place. This rigidity allows the data to be migrated away from the beamline and to be backed up, archived, and made accessible via projects such eScience and iGrid.

For specific information on the storage directory and the transition to NeXus data files, see the advanced data storage pages

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