Compact and intense parametric x-ray radiation source based on a linear accelerator with cryogenic accelerating and decelerating copper structures

This paper describes a proposal for a compact x-ray source based on parametric x-ray radiation (PXR). The PXR, which is produced when a single crystal is bombarded with relativistic electrons, has good monochromaticity and spatial coherence, and is expected to be well suited for imaging of low-Z materials and medical application. The proposed system employs a pair of copper accelerating structures which are operated at a cryogenic temperature of 20 K and arranged to form a resonant ring configuration. The electron beam is once accelerated up to 75 MeV in one of the structures, being decelerated down to lower than 7 MeV in the other structure after generating PXR at a single crystal, and then dumped. The expected x-ray yield is $10^9\mathrm{photons}/\mathrm{s}$ at a center energy of 15 keV or higher.

Figure 1

Layout of PXR source based on linear accelerator.

Figure 2

Number of emitted neutrons dependence of electrons energy dumped at lead and graphite.

Figure 3

(a) rf system of the PXR source and (b) the resonant ring.

Figure 4

Time dependence of the energy gain in the resonant ring for different coupling constants.

Figure 5

Drawing of PXR generation.

Figure 6

Schematic of the PXR chamber.

Figure 7

The dependence of $\chi$ on x-ray energy for diamond and Si with the Miller index (111).

Figure 8

Scattering angle estimated from fitting a Gaussian function depending on crystal thickness of Si and diamond. The beam tail is ignored.

Figure 9

The dependence of PXR yield on the x-ray energy for Si and diamond with the Miller index (111).

Figure 10

Electron’s energy loss after the electron beam of 75 MeV passes through Si and diamond crystals of different thickness. Symbol t in the legend means crystal thickness.

Figure 11

Temperature change of the 0.1 mm thick Si crystal during a micro-pulse duration of $2\mu \mathrm{s}$ for different beam sizes at the crystal.

Figure 12

Gamma rays generated when a beam with $10^7$ electrons at 75 MeV collides with copper, stainless steal and graphite.

Figure 13

Neutrons generated when a beam with $10^7$ electrons at 75 MeV electrons collides with copper, stainless steal and graphite.

Figure 14

Beam optics from the exit of the buncher to the exit of the decelerating structure, when interactions of the beam with the target (location indicated by red arrows) are ignored. (a) $\sqrt{\beta }$ function, (b) dispersion function and (c) beam size. Blue and red lines show the horizontal and vertical planes. Blue boxes are accelerating and decelerating structures, green boxes are quadrupole magnets, and yellow boxes are bending magnets.

Figure 15

Beam optics from the collision point to the decelerating structure along the path length, when the target (location indicated by a red arrow) is inserted (lines) and not inserted (dotted lines). (a) $\sqrt{\beta }$ function and (b) beam size. Blue and red lines show the horizontal and vertical planes. Blue boxes are decelerating structure, green boxes are quadrupole magnets, and yellow boxes are bending magnets.

Figure 16

Bunch length at the exit of the buncher (green), the collision point (blue), and the decelerating structure (red).