Measurement of emittance at CSNS ion source without analyzing magnet

Purpose High current beam is required for CSNS update in future. Over 50 mA H⁻ will be designed to deliver to the linac in CSNS II. For the present state of CSNS ion source, the beam emittance cannot satisfy the requirement of RFQ entrance at the 50 mA H⁻ beam. In order to improve the beam quality, CSNS ion source is required further improvement.
Methods Simulation shows emittance growth due to the space charge force in the intense H⁻ beam when the beam transports through the analyzing magnet. After considering the neutralization of space charge, the emittance growth could be suppressed. The analyzing magnet thus is considered to removed, which might destroy the neutralization of space charge. The beam emittance is measured at the revised CSNS ion source.
Results Measured results show that beam emittance without the analyzing magnet becomes smaller than that of CSNS ion source. At the requirement of 0.2 πmm mrad, beam current is larger than 30 mA. It reveals that analyzing magnet could destroy space charge neutralization and result in the significant increase of emittance.
Conclusions Although the results presented are preliminary, it is important to improve the beam quality. This paper details the ion source improvement and measurement process.