Cavity optimization for compact accelerator-based free-electron maser
In previous works [1] we have successfully commissioned pre-bunched beam pumped free electron maser based on Stimulated Coherent Diffraction Radiation (SCDR) generated in an open resonator. An ultra-fast Schottky Barrier Diode (SBD) detector has enabled us to investigate the properties of the radiation in the range from 3 to 5 mm of wavelengths among broad frequencies stored in the cavity as well as the intrinsic properties of the cavity itself. We observed a turn-by-turn SCDR generated by a multibunch electron beam and directly measured the opened cavity quality factor of 11.4. In this report we represent the work directly related to optimization of both the maser system to achieve higher quality factor of the cavity essential to gain soft X-ray production via Thomson scattering in the next stage of the experiment and measurement system for better characterization of the maser light. One way of optimization is to minimize losses of energy due to transmission through resonator mirrors. For this purpose we have designed and constructed a test setup to investigate reflection and transmission properties of different mirror materials. Theoretical calculations have been performed using optical constants and theoretical models of electrical permittivity to compare with experimental results. In this report we summarize the experimental activity, represent new experimental results and represent steps undertaken to achieve the new resonator mirror design. For better understanding of the resonator performance a test of the SBD detector linearity is also demonstrated.
Upgrade of the accelerator for the laser undulator compact X-ray source (LUCX)
Abstract We have developed a compact X-ray source based on inverse Compton scattering of an electron beam and a laser pulse, which is stacked in an optical super-cavity, at the Laser Undulator Compact X-ray Source (LUCX) accelerator at KEK. The plan is to upgrade the accelerator and the super-cavity in order to increase the number of X-rays and to overcome the problems that have become clear in the experiments so far. A new RF gun with a high mode separation and a high Q value and a new klystron for the gun will be installed to provide good compensation with a high-intensity multi-bunch electron beam. A new optical super-cavity that consists of four mirrors is also being developed to increase the stacking power in the cavity and to reduce the laser size at the focal point. The final goal is to produce a long multi-bunch electron beam with 8000 bunches/train, 0.5 nC/bunch, and 5 MeV and to generate a soft X-ray with 6.5×107 photons/train after the upgrade. The upgrade plan is reported in this paper.
The Near Ultra-Violet Band-System (D-X) of Silicon Monosulphide
The rotational analysis of the near ultra-violet band-system, D1Π-X1Σ+, has been extended Twelve bands have been analysed, namely the 7,1, 6,0, 6,1, 5,0, 5,1, 4,0, 4,1, 3,0, 2,0, 1,0, 1,1 and 0,0 bands. The constants derived for D1Πare Bν' = 0.26647 - 0.00216 (ν' + ½); Dν' = [2.91 - 0.03(ν'+½)] ×10-7, Gν' = 513.12(ν' + ½) - 2.93 (ν' + ½)2, νe = 35026.86 cm-1, re' = 2.0589 A. A number of perturbations have been found in the upper state. They appear to arise from interactions with two electronic states, a 3Σ- state and a singlet state, 1Π or 1Δ. It has not been possible to determine the absolute numbering of the vibrational levels of the perturbing states, but in all other respects fairly complete information has been obtained about the 3Σ- state. The perturbations are similar to those already known in the spectrum of CO, and the analogy between the electronic states of the molecules is thus strengthened.