Fig. 1. Optical-transition radiation patterns, single foil

Fig. 2. Schematic of the OTR angular-distribution pattern

Fig. 3. Schematic of the focus-at-the-object（beam spot）and focus-at-infinity （angular distribution）techniques

Fig. 4. Time-resolved beam parameter measurement system for a series of Dragon LIAs

Fig. 5. Fieldwork layout of time-resolved beam parameter measurement system for DragonⅡ LIA

Fig. 6. Beam divergence image in sequence captured by the system

Fig. 7. Typical measurement series results of electron beam envelope from congregation to divergence in the injector

Fig. 8. Profile images and corresponding OTR angle distribution patterns of triple-pulse beam from shot 4555#

Fig. 9. Beam divergence image and fit result