Current status of developing pepper-pot emittance monitor for high-intensity ion beam

The experiment to measure the Electric Dipole Moment (EDM) of Francium (Fr) is in progress by Center for Nuclear Study (CNS), UTokyo. Fr is produced via a nuclear fusion reaction by bombarding a gold target with oxygen-18 beam, requiring a beam intensity of 18 eμA or higher. However, the transport efficiency of the current beam line decreases to 66 % when the beam intensity exceeds 10 eμA. To address this issue, we are developing a pepper-pot emittance monitor (PEM) optimized for high-intensity beams. The improvements include locating the camera far from the beam line to minimize radiation damage, achieving a distance 4.1 m while maintaining the position error of 0.13 mm. Additionally, we conducted beam tests to verify measurement errors and found the results were consistent with the measurement errors estimated from the PEM structure. Furthermore, the beam shutter time 0.27 was estimated to be acceptable up to the beam power 1000 W to prevent PEM overheating.