The Research Of The Dual-beam Drift Tube Linac

The multi-beam type accelerator is a new accelerator cavity structure,which will be expected to resolve the problem of particle space charge effect and be applied to achieve heavy ion acceleration with utral-high intensity.The multi-beam type RFQ in the low energy region,such as two-beam RFQ and four-beam RFQ,had been successfully designed and commissioned,which verified the principle-feasibility of the multi-beam type accelerator.In order to prove the feasibility of multi-beam type accelerator in middle and high energy region,an 81.25 MHz dual-beam drift tube linac?DB-DTL?was firstly proposed and designed at the Institute of the Modern Physics,University of Chinese Academy Science.The DB-DTL is an innovative accelerator structure with two identical beam-apertures,which can be applied to simultaneously accelerate two beams with same intensity and be expected to double the currently existed beam intensity limit.This paper aims to prove the principle-feasibility of the DB-DTL,which verifies the accelerating ability of the two beam-apertures is same and it can be applied to simultaneously accelerate two beams.With this purpose,the beam dynamics design,RF structure design,machine design and cavity machining,performance measurement with low power and high RF power conditioning have been done and introduced in this paper.In Pi MLOC beam dynamic design,this DB-DTL works at 81.25 MHz and can accelerate 1mA proton from 0.56 MeV up to 2.5 MeV.In addition,the TraceWin code was used to verify the beam dynamics design.The thin-gap model and the RF field map of the DB-DTL were separately adopted to perform particle simulation,and their simulation results were consistent with the dynamics design.Particle simulation result of the RFQ plus the middle energy beam transport?MEBT?matching section and the DB-DT shows that the transmission is more than 90%.The DB-DTL cavity will adopt IH structure and innovatively design two identical beam-apertures.The electromagnetic calculation results show that the electric field distribution of the two beam-apertures is same,which indicates that the corresponding accelerating ability is same.The DB-DTL cavity will operate at pulse mode,and the multi-physics analysis results show that the maximum operational duty is 10%with cooling-water in cooling-water routes.The DB-DTL cavity will be consisted of three parts,namely core part called drift tube plate and two half-cavity shell,which were assembled likely a sandwich type cavity.Before the proton acceleration experiment,the performance quality with low power was measured and the measurement results shown that the cavity resonant frequency,Q₀ value,frequency tubing ability of tuner and the electric field distribution of two beam-apertures were consistent with the simulated results.After that,the DB-DTL cavity will perform proton acceleration experiment.The proton will be separately accelerated by the two beam-apertures of the DB-DTL,and the output proton energy of each beam-aperture will be 2.5 MeV.The accelerating ability of the two beam-apertures will be proved by comparing their output proton energy.The innovations of this thesis are listed below.?1?The DB-DTL cavity is innovatively provided with two identical beam-apertures,which are symmetrically distributed on the drift tube.And the electromagnetic field distribution of the two beam-apertures is same,which indicates that their accelerating ability is same and the DB-DTL can be applied to simultaneously accelerate two beams.The research of the DB-DTL is the verification of the principle-feasibility of the multi-beam accelerator in middle and high energy region,which is expected to double the current beam-intensity limitation and to provide a new optional technology for realizing heavy ion acceleration of hundreds mA.?2?The core part of the DB-DTL called drift tube plate is consisted of ridge,stem and drift tube structure.The drift tube plate is milled by using the machining method of integral cutting and forming,which ensure the machining accuracy and high-frequency connection between all structure parts to the greatest extent.Meanwhile,it verifies that the integral cutting and forming is suitable for all large-scale drift tube type accelerators.