Achromatic beamline design for a laser-driven proton therapy accelerator

K D Wang,K Zhu,X Q Yan,Matthew J Easton,Y J Li,C Lin

doi:10.1103/physrevaccelbeams.23.111302

Abstract

A new laser-driven proton therapy facility is being designed by Peking University. The protons will be produced by laser--plasma interaction, using a 2-PW laser to reach proton energies up to 100 MeV. We hope that the construction of this facility will promote the real-world applications of laser accelerators. Based on the experimental results and design experience of existing devices in Peking University, we propose a beam transmission system which is suitable for the beam produced by laser acceleration, and demonstrate its feasibility through theoretical simulation. It is designed with two transport lines to provide both horizontal and vertical irradiation modes. We have used a locally-achromatic design method with new canted-cosine-theta (CCT) magnets. These two measures allow us to mitigate the negative effects of large energy spread produced by laser-acceleration, and to reduce the overall weight of the vertical beamline. The beamline contains a complete energy selection system, which can reduce the energy spread of the laser-accelerated beam enough to meet the application requirements. The users can select the proton beam energy within the range 40--100 MeV, which is then transmitted through the rest of the beamline. A beam spot with diameter of less than 15 mm and energy spread of less than 5% can be provided at the horizontal and vertical irradiation targets.

Highlights

With the increasing demand for accelerators with higher energies and smaller footprints, the research of novel particle acceleration mechanisms is attracting more attention in the accelerator community
Considering the above characteristics of laser-driven beams and the requirements for the first phase of the project, we determined the design objectives as follows: (a) proton beams with energy in the range 40–100 MeV can be transmitted, fulfilling the treatment requirements planned for phase 1; (b) beamlines can provide both horizontal and vertical irradiation, to reach tumors in different parts of the body; (c) beam spot with energy spread of less than 5% and diameter of less than 15 mm can be formed at the irradiation terminal
We can keep the energy spread below 5% by adjusting the first moveable slit in the collection section and the two moveable slits in the deflection and energy selection (DES) sections

Summary

INTRODUCTION

With the increasing demand for accelerators with higher energies and smaller footprints, the research of novel particle acceleration mechanisms is attracting more attention in the accelerator community. The laser system will be a 2-PW, 1-Hz Ti:sapphire system using chirped pulse amplification (CPA) technology delivering pulses with 60 J energy, 30 fs duration, and a contrast of 1010 at 100 ps Utilizing this petawatt laser system, we will be able to repeatedly generate proton beams with high peak flux and short temporal duration on the energy level of many hundred MeV. The first phase, as described in detail below, is to produce a 100 MeV proton beam with pulses of more than 108 particles and continuously adjustable energy with 5% spread. Such a beam passing through the transmission system can meet many of the therapeutic requirements. We use an achromatic lattice to control the envelope growth caused by the large dispersion and energy spread, and use superconducting solenoids and curved canted-cosine-theta (CCT) magnets to make the vertical beam line lighter and more compact [21], as part of an exploration for the subsequent construction of a superconducting gantry

MAIN PARAMETERS AND OPTICS DESIGN

Beam collection section

Application section

Findings

SUMMARY