Beam profile monitors for slow extracted beam using multi-layered graphene in the J-PARC

Extracted-beam profiles in slow extraction at the J-PARC can be measured by using secondary electrons emitted from thinner target array made by multi-layered graphene, in real time during spill time of around 2 seconds. The target consists of 20 ch ribbons with width of 1 mm, pitch of 2 mm, and thickness of 1.1 micron. Secondary-electron current at each channel is measured by a current amplifier having sensitivity more than 1 pA. These configuration produces useful information for beam dynamics in slow extraction. We have successfully measured 51 kW extracted-beam recently. (author)