A new diagnostic for the measurement of the ionic emission generated by an electron-photon conversion target

A beam diagnostic made of a double sheet sensor is designed measure ions emitted by an electron-photon conversion target under the impact of an intense relativistic electron beam. This device is tested on the PIVAIR prototype accelerator. Signals attributed to ions emitted from the target are observed for different target elements: Ta, C, Ti, Au and light species are identified by their time of flight. The mean velocities of C⁺ and H⁺ ions are found to be respectively equal to 1.2 ×10⁸ cm/s and 5 ×10⁸ cm/s for C and Ta targets. The ionic appearance and rise time signals are closed to the expected values. Besides, the current signals are characterized by a plateau to which level corresponds to the Child-Langmuir current (25 A for H⁺ ions). Furthermore, the fall-off of this signal is found to be in synchronism with the electron beam signal. This behaviour represents the deconfinement of the ion beam under the effect of its own space charge. These experimental results confirm the preliminary calculations obtained with the M2V Maxwell-Vlasov PIC code which has been coupled with an ionic emission model