7th Asia-Pacific Conference on Plasma Physics, 12-17 Nov, 2023 at Port Messe Nagoya

Medical application of high energy electron beams by laser wakefieldaccelerator

Kyungnam Kim1, Jaehoon Kim1, Yonghun Hwangbo1, Kyo Tae Kim2, Sukgi Jeon1 andGeumbae Kim2
1Precision Medical Device Research Center, Korea Electrotechnology Research Institute,
2Korea Institute of Radiological & Medical Sciencese-mail(speaker): k272003@keri.re.kr:
A laser wakefield accelerator (LWFA) has theadvantage to design a compact accelerator system because
it can generate a high accelerating field in a small area
compared to conventional systems [1]. The LWFA has
attracted much interest because of its potential
applications such as ultra-short X-ray source, particle
beam irradiation and medical applications. In particular,
the very high energy electron (VHEE) beam therapy, inthe energy range of 50 MeV to 250 MeV, has been studied
because it has clinical advantages over conventional Xray methods, such as deep site treatment due to the deep
penetration depth and easy adjustment of the irradiation
direction with electromagnetic field [2~4]. Theseproperties mean that laser wakefield accelerators are goodcandidates for compact high-energy electron accelerators.
In this study, electrons were accelerated by a 20TW
Ti:sapphire laser-based LWFA system to measure themedical properties of the VHEE beam as a radiotherapy
system. The laser intensity was 6.3 × 1018 W/cm2 andnormailzed vector potentail, a0, was 1.75. A gas target wasused mixture 90% helium and 10% nitrogen. The plasma
density and profile were measured with an interferogramand a shadowgram, respectively. The beam diagnostic ofVHEE beam was measured by intergrated current
transformer (ICT), Scintillator screens (LANEX). The
electron beam diameter measured 100 irradiation was
8.7±0.4 mm, and the beam divergence were 1.4 mrad in
the horizontal and 6.3 mrad in the vertical direction,
respectively. The averatged chrage was 65±16 pC and, the(a)total charge of VHEE beam for percentage depth dose
curve (PDD) was 6.5 nC. The peak energy of eachindividual electron beam energy measured is 170 MeV
with a standard deviation of 18 MeV. The threedimensional PDD of the electron beam was measuredusing a tough phantom composed of Gafchromic films,
and the relative biological effectiveness (RBE) wasmeasured from the cell survival ratio. In addition, theirradiation direction of the electron beam was measured asa function of the electromagnetic field strength afterLWFA. The PDD of the electron beam has a low
divergence characteristic of the high energy electron beamand the size-preserving shape of the electron beam, known
as the pencil beam, was measured. The PDD results aerecompared with the Monte Carlo calculation for monoenergetic electron beam. The RBE was measured to be
1.2~1.3.
This research was supported by the KERI Primaryresearch program of MSIT/NST (No. 23A01047)
References[1] T. Tajima et al. Phys. Rev. Lett. 43, 267 (1979)[2] J. Kim et al. Plas. Phys. Cont. Fus. 60 034008 (2018)[3] C. DesRosiers et al. Phys. Med. Biol. 45 1781 (2000)[4] K.N.Kim et al. J. Kor. Phys. Soc., 77, 399(2020)(b)

Figure 1. Experimental setup and results (a) Schematic of the target chamber of laser wakefield accelerator at the KERI.
(b) Dose profile of VHEE beam at the penentrated depth