Studies On The Beam Dynamics Of High Intensity Linear Injector

The compact linear injector is a research project of the Peking University. Thegoal is to accelerate100-mA proton beam to the energy of4MeV with the length lessthan3m. The linear injector consists of RFQ、 DTL and the matching sectionbetween them. Two gaps of the DTL and a doublet are used as matching. Thefrequency of the linac is200MHz. It achieves the transmission efficiency of90.9%within the length of276cm. The final energy is4.15MeV. The RFQ is150cm andaccelerates protons from45keV to0.618MeV with the transmission efficiency of97.8%. The DTL is126cm and accelerates protons to the final energy of4.15MeVwith the transmission efficiency of93%.The beam dynamic and optimized strategy of the linear injector is presented.Beam dynamic design of RFQ with Parmteq is completed by two steps. The first,preliminary design with transmission efficiency of92.8%is completed byfour-section procedure developed by LANL. Analysis of preliminary results suggeststhe reasons of the normalized RMS emittance growth and the beam loss mainly arethe beam mismatch, the longitudinal motion instability and the local parametricdiscontinuous. Then I vary the transverse focusing strength along the RFQ accordingto the different space-charge conditions, to smoothly the change modulation factorsand the synchronous phases. It makes longitudinal motion stable, and avoids thebeam mismatch and the local parametric discontinuous. The emittance growth getssmaller and the transmission efficiency goes up to97.8%. The beam dynamics designof DTL is completed according to the KONUS by using the LORASR code.Optimization of DTL transversal twiss-parameter matching from the exit of the RFQto the entrance of KONUS parts of the DTL is accomplished by using the 93%.A heavy ion IH-DTL was designed for the High Intensity heavy ion Facility(HIAF) too. It is one of the options of the section of0.3~1.4MeV. The beamdynamics are also presented. The238U34beam, whose current is5.0emA, isaccelerated from injection energy of0.35MeV/u to output energy of1.30MeV/u. Itachieves the transmission efficiency of95%with the cavity length of267.8cm. thedesigned average acceleration gradient is about2.48MV/m.