Sardana: in order to store files using our default path conventions, 
the attributes FileStartNum, SaveFilePath and FilePrefix should be
set by a pre_scan hook. See the Spock manual for
an example ( Scans-Hooks-GeneralHooks-ExampleForA...). 
Important Tango server attributes:
- ShutterTime: time per image in msecs, 1000
 
- FrameNumbers: no. of images to take, 1
 
- EnergyThreshold, unit: eV, half the beam energy
 
- SaveFilePath: the directory where the data are stored, set by the pre_scan hook. 
 
- FilePrefix: set by the pre_scan hook. 
 
- SaveAllImages: True to enable image saving
 
- OperatingMode:
- ContinuousReadWrite: 12 bit counter depth, no time gap between images
 
- TwentyFourBit: 24 bit counter depth, 1ms delay between images
 
 
- TriggerMode
- 0: no trigger
 
- 1: trigger starts image series
 
- 2: trigger starts a single image