# State of the Art of High-Flux Compton/Thomson X-rays Sources
## 3 Discussion of Different Paradigms: Low Energy Sources Operating in Classical Regime
### (i) Warm Linac + Single Shot Laser
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**ICS**} & **Electron** & \multirow{2}{*}{\(\mathbf{\lambda_{las}}\) **Energy**} & \multirow{2}{*}{\(\mathbf{\lambda_{las}}\) **Energy**} & \multirow{2}{*}{**X Energy (keV)**} & \multirow{2}{*}{**X Flux**} & **Bandwidth** & **Rep.** \\  & **(MeV)** & & & & & & **(Hz)** \\ \hline BNL [2] & 64–72 & 10 & 2 & 7–8.9 & 2\(\cdot\)10\({}^{8}\) & \textless{5\%} & \textless{10} \\ T-ReX [4] & 116 & 0.532 & 0.15 & 0.1–0.9 & 10\({}^{5}\) & 15\% & 10 \\ Sparc [5] & 30 & 0.8 & 5 & 13 & 1.4\(\cdot\)10\({}^{6}\) & 20\% & 10 \\ AIST [6] & 42 & 0.8 & 0.14 & 40 & 10\({}^{6}\) & 4–10\% & 10 \\ TTX [7] & 46.7 & 0.8 & 0.3 & 51.7 & 10\({}^{6}\) & 10\% & 100 \\ Elbe [10] & 23 & 0.8 & 2.25 & 13–25 & & 25\% & 10 \\ STAR-II-HE [35] & 140 & 1.03 & 0.5 & 350 & 10\({}^{7}\) & 6\% & 100 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Warm linacs versus high-energy laser. The number of photons is per shot. All data are measured apart the case of STAR, whose data are evaluated numerically. Figure 1: STAR machine as an example of Paradigm (i). Overall length about 12 m. 1: S-band RF Gun; 2: S-band Accelerating section; 3a,b: C-band Accelerating sections, 4a,b: low energy and high energy beam transport lines; 5a,b: low energy and high energy interaction chambers; 6: S-band RF power station; 7a,b: C-band RF power stations; 8: photo-cathode laser transport line; 9: interaction laser transport line. Courtesy of [PERSON]. diffraction based method [71], by means of filters with different K-edge energies [18; 72] or by producing a direct frequency-angle map [16] with a sophisticated spectrometer. Polarization control has been studied at Tsinghua with a cylindrical detector collecting the radiation [73]. The production of X rays with elliptical polarization and their detection [21] has been demonstrated in a single shot device based on plasma accelerated electron beams [11]. The generation of radiation with orbital momentum has also been tried [74]. The dependence of spectral properties on emittance and laser parameter have been analysed in various conditions [10] by apppositely deteriorating the electron beam for increasing the emittance, while changing the laser intensity. Occurrence, structure and polarization of the harmonics have been observed at BNL [2]. Applications involving users foreseen for this group of machines fall mostly in the imaging field. Lot of experiments have been done along this line. At AIST, microfractures in human bones have been detected [23], as well as microvessels in animal models for microangiography [75] and rat lumbar vertebrae [76]. At BNL the radiography of a wasp done with the phase contrast technique [22]. The set up can be easily upgraded in energy by adding more RF accelerating structures. The high electron beam quality (emittance less than 1 mm mrad and relative energy spread approaching \(10^{-4}\)) permit also to get down the bandwidth to few \(10^{-3}\) satisfying the requirements of the nuclear photonics applications.