Time resolved energy measurement of the TESLA Test Facility beam through the analysis of optical transition radiation angular distribution

The study of the energy stability along the macropulse of the TESLA Test Facility Linac (TTFL) was obtained by the measurement of the angular distribution of the optical transition radiation (OTR). This technique does not require a dispersive section and can be performed at any point of the beam line. Measurements have been performed with different settings of the RF low level control and at different values of the beam current. An energy variation along the macropulse was observed in a good agreement with the measured energy spread of the whole macrobunch. The analysis of the OTR angular distribution pattern allows also, to some extent, to evaluate the beam angular spread.