Production target and muon collection studies for an experimental muon source at CSNS

Intense muon beams have very important applications by using μSR techniques and other methods. An experimental muon source (EMuS) as a parasitic facility at China Spallation Neutron Source (CSNS) is proposed. EMuS makes use of a small portion of the high power proton beam from the CSNS accelerator complex. It will provide an excellent platform for muon beam based multidisciplinary research, and will also serve as the development base for a future full-scale muon source at CSNS. The available proton beam power of 4 kW at 1.6 GeV can produce intense muon flux with a thick production target. The muon yields with different target materials and shapes, and the muon collection efficiency have been simulated by using the FLUKA code. It is found that the graphite target of about 10–12 cm in thickness and rectangular in cross-section is a good choice, and that the collection at 90° from the beam direction is the best for surface muons. It is found that 4-D emittance volume instead of two independent 2-D emittances should be used to define the relation between the optimal muon intensity and the muon channel acceptance, due to the asymmetry between the distributions in the two transverse phase planes. The collected muon intensities for both surface muons and cloud muons with different emittances have also been studied, which are important for designing the muon beam transport line. The intensities of positive and negative muons are in the orders of 105 μ+/s and 104 μ−/s, respectively.