LAPD_DAQ

Data acquisition script using Ethernet motor and LeCroy scope as digitizer on LAPD. Modified from Scope_DAQ used on process plasma chamber

HDF5 Data Structure

The data acquisition script (Data_Run_0D.py) creates HDF5 files with the following structure:

experiment_name.hdf5/
├── attrs/
│   ├── description          # Overall experiment description
│   ├── creation_time        # Time when file was created
│   └── source_code          # Python scripts used to create the file
│       ├── Data_Run_0D.py
│       └── multi_scope_acquisition.py
│
├── magnetron/              # First scope group
│   ├── attrs/
│   │   ├── description     # Scope description
│   │   ├── ip_address      # Scope IP address
│   │   ├── scope_type      # Scope identification string
│   │   └── external_delay(ms)  # External delay in milliseconds
│   │
│   ├── time_array          # Time array for all channels (in seconds)
│   │   ├── attrs/
│   │   │   ├── units      # "seconds"
│   │   │   └── description # "Time array for all channels"
│   │
│   ├── shot_0/            # First shot data
│   │   ├── attrs/
│   │   │   └── acquisition_time
│   │   │
│   │   ├── C1_data        # Channel 1 voltage data
│   │   │   └── attrs/
│   │   │       └── description  # Channel description
│   │   ├── C1_header      # Channel 1 binary header
│   │   │   └── attrs/
│   │   │       └── description
│   │   ├── C2_data        # Channel 2 voltage data
│   │   ├── C2_header      # Channel 2 binary header
│   │   └── ...            # Additional channels
│   │
│   ├── shot_1/            # Second shot data
│   └── ...                # Additional shots
│
├── x-ray_dipole/          # Second scope group
│   └── ...                # Same structure as above
│
└── Bdot/                  # Third scope group
    └── ...                # Same structure as above

Key Features

1. Root Level

   • Contains experiment metadata and scope groups
   • Stores source code used to create the file
   • Includes experiment description and creation time

2. Scope Groups

   • Each scope has its own group with metadata
   • Time array stored once per scope (in seconds)
   • External delay and scope configuration information

3. Shot Data

   • Numbered shots under each scope group
   • Each shot contains:
     • Voltage data for each channel
     • Binary header data for each channel
     • Channel descriptions
     • Acquisition timestamp

4. Time Arrays

   • Stored in seconds in HDF5 file
   • Used in milliseconds for plotting
   • Saved once after first acquisition
   • Reused for all subsequent shots

Reading the Data

Example Python code to read the data:

import h5py

# Open the HDF5 file
with h5py.File('experiment_name.hdf5', 'r') as f:
    # Read experiment description
    description = f.attrs['description']
    
    # Access source code
    source_code = eval(f.attrs['source_code'])
    
    # Read scope data
    for scope_name in f.keys():
        scope_group = f[scope_name]
        
        # Get time array (in seconds)
        time_array = scope_group['time_array'][:]
        
        # Read shots
        for shot_name in [k for k in scope_group.keys() if k.startswith('shot_')]:
            shot_group = scope_group[shot_name]
            
            # Read channel data
            for channel in [k for k in shot_group.keys() if k.endswith('_data')]:
                data = shot_group[channel][:]
                description = shot_group[channel].attrs['description']

Notes

• Time values are stored in seconds but displayed in milliseconds in plots
• Binary headers contain scope-specific metadata for each channel
• Source code is preserved with data for reproducibility
• Each scope can have different time arrays based on its settings