Transverse Twiss parameter measurement with space charge in CADS Injector I

The test stand of CADS Injector I is built at the Institute of High Energy Physics (IHEP). The 3.2 MeV, 10 mA beam from the RFQ will be transported and matched by medium energy transport line (MEBT1) to the superconductive accelerating section. To minimize the beam loss from mismatch, the Twiss parameters at the exit of RFQ should be got. The method of scanning quadrupole strength with wire scanner is used in CADS Injector I. As to the data process, the traditional method based on matrix will bring errors for high intensity accelerators, especially at low energy when the space charge force is very strong. This paper introduces the traditional method and the new method considering space charge effect, which is based on MOGA. The result proves that the space charge should be considered when calculating the Twiss parameters for high intensity low energy accelerators. (authors)