Page 9 - Demo

The conceptual design of the laser driven neutron source for transmutation is shown in Fig. 3A: the OPCPA laser irradiates a nanometric foil ejecting deuterons onto a solid or gaseous target in order to generate D-D or D-T fusion neutrons. The principles of the laser-foil interaction are based on the Coherent Acceleration of Ions by Laser (CAIL) method [12] and [13]
where the foil-target is over dense and its thickness is less than the collisionless skin depth (=pe/c) allowing for the laser to penetrate and resonate with electrons in the target; this is the distinguishing feature of CAIL from the Target Normal Sheath Acceleration (TNSA) [40]. In the 2D PIC code simulation we found that the transmitted laser drives electrons via collective rather than thermal acceleration leading to higher efficiency (almost 10% as shown in Table 1) of energy transfer from laser and increased ion energies with the deuteron energy spectrum shown in Fig. 3B with average deuteron energy of 100 keV at 550 fs.
The simulation of the CAIL process has been performed with the EPOCH PIC code [41]. A linearly polarized laser of intensity 7.7x1017 W/cm2 and wavelength 1 micron has been focused
(A)
(B)
Figure 3: Neutrons are generated by the laser irradiation of a nanometric deuteron foil, deuteron acceleration and interaction with tritiated solid or gas target. (A) Schematic of neutron generation using laser. (B) D+ energy spectrum @ 100 fs, 550 fs, 700 fs and 1000 fs. The average deuteron energy at 550 fs is 100 keV corresponding to ~10% energy efficiency conversion from laser to deuteron.