Laser-wakefield application to oncology

Abstract

Recent developments in fiber lasers and nanomaterials have allowed the possibility of using laser wakefield acceleration (LWFA) as the source of low-energy electron radiation for endoscopic and intraoperative brachytherapy, a technique in which sources of radiation for cancer treatment are brought directly to the affected tissues, avoiding collateral damage to intervening tissues. To this end, the electron dynamics of LWFA is examined in the high-density regime. In the near-critical density regime, electrons are accelerated by the ponderomotive force followed by an electron sheath formation, resulting in a flow of bulk electrons. These low-energy electrons penetrate tissue to depths typically less than 1 mm. First a typical resonant laser pulse is used, followed by lower-intensity, longer-pulse schemes, which are more amenable to a fiber-laser application.

High-Density Dynamics of Laser Wakefield Acceleration from Gas Plasmas to Nanotubes

“…Consequently the radiation need only have limited penetrative power. With electrons used as the source of radiation, the desired energies are then 1 MeV, which yields a penetration depth between microns and millimeters [18]. By tuning the laser intensity and plasma density, specific depths can be produced as desired.…”

“…Limitations on pulse length are also stringent; the shortest pulse length likely achievable in a fiber laser system is around 100 fs, which is several times longer than was used in Figure 2. Fortunately, Raman scattering effects and self-modulation may allow the "black", low-energy electron regime to be accessible for a long pulse, even at very low intensity (a 0 1) and low density (n c /n e = 10) [18,44]. The bulk of this work addressed a scheme were a laser is injected parallel to the axis of a modeled bundle of carbon nanotubes.…”

“…The phase space density is plotted in units of pseudo-particles per p x /mc × x/λ p . A run of this type was first made in prior work [18], and a similar run is produced here to examine the acceleration mechanism more closely. The group velocity of the laser is reduced to zero, v g = 0, and the dephasing the pump-depletion lengths are reduced to less than one plasma wavelength, L p,d λ p .…”

“…One is attracted in this case to the "black" regime, which has D/D 0 ∼ 1. For long, low-intensity laser pulses, as would be amenable to a fiber laser, this regime can also be accessed even at moderate plasma densities (n c /n e ≈ 10) due to Raman forward scattering [18].…”

“…To this end, robust laser-plasma interaction is desired, and so we employ higher laser intensities than would likely be possible to achieve in a medical application based on fiber lasers, though CAN techniques may ultimately mitigate such concerns. Previous work [18] treated the practical considerations of fiber lasers and medical applications more explicitly.…”