Acceleration of light ions from an expanding ultrathin foil of complex ion composition
- PDF / 421,600 Bytes
- 10 Pages / 612 x 792 pts (letter) Page_size
- 4 Downloads / 166 Views
R PLASMA
Acceleration of Light Ions from an Expanding Ultrathin Foil of Complex Ion Composition E. A. Govrasa, V. Yu. Bychenkova, and V. F. Kovalevb a
b
Lebedev Physical Institute, Russian Academy of Sciences, Leninskii pr. 53, Moscow, 119991 Russia Institute for Mathematical Modeling, Russian Academy of Sciences, Miusskaya pl. 4a, Moscow, 125047 Russia Received August 26, 2009; in final form, December 24, 2009
Abstract—The problem of the Coulomb explosion of a thin homogeneous foil with light and heavy ions is solved analytically in the context of laser ion acceleration. Spatiotemporal and spectral distributions of the accelerated light ions are obtained. The ions parameters are calculated as functions of the atomic composition of the target. It is shown that, in the interaction between highpower ultrashort highcontrast laser pulses and thin foils with light impurity ions, it is possible to produce accelerated ion bunches that contain a significant fraction of the total number of particles and have a small energy spread (ⱗ10%). DOI: 10.1134/S1063780X10080076
1. INTRODUCTION Progress in creating highpower ultrashort (femto second) lasers [1, 2] opens up unique opportunities to study the interaction of radiation with matter under extreme conditions—a process that involves a rich variety of new physical phenomena and suggests their interesting applications. A possible application of such lasers is to use them to generate accelerated ion beams in the interaction of their pulses with ultrathin foils and microtargets [3, 4]. In this way, the greatest atten tion is paid to targets in the form of a layer of heavy ions with a large charge, coated with an ultrathin layer of light ions [5, 8]. The concept of such targets was proposed by Esirkepov et al. [5]. When a submicron target is irradiated by a relativ istic laser pulse (such that Iλ2 > 1018 (W/cm2) μm2, where λ is the laser wavelength), light atoms are ion ized almost instantaneously and a substantial fraction of electrons is ejected from the target. The electrons, the Debye radius of which exceeds the characteristic sizes of the target, can be excluded from consider ation, and one can assume that the target ions explode via the Coulomb mechanism alone [7, 9]. In this model, the motion of heavy ions behind the acceler ated light ions can play an important role in the accel eration of the latter. The corresponding mechanism has come to be called a Coulomb piston [8]. At ultrarelativistic laser pulse intensities such that Iλ2 ⲏ 1023 (W/cm2) μm2, the effect of ion acceleration by the ponderomotive force can also play an important role [10]. In what follows, however, we restrict ourselves to considering lower laser intensities in order to study the expansion of the target due to a Coulomb explosion. For practical purposes, e.g., for laserbased proton (hadron) therapy [11], it is required that the ion beams
not only have the necessary energies but also be (quasi) monoenergetic. One possible method for creating the corresponding ion sources is based on the us
Data Loading...
