Broadband normal-incidence mirrors for a range of 111–138 Å based on an a-periodic Mo/Be multilayer structure

Abstract

Broadband Mo/Be multilayer structures were designed for maximum uniform normal-incidence reflectivity in a broad range of 111–138 Å, which lies near and beyond the L2,3 absorption edge of Si. A comparison was made of the capabilities of two classes of aperiodic structures and of so-called “stack” structures, which are composed of several periodic structures with different periods stacked one over the other. Six-stack Mo/Be 80-layer structures were synthesized on concave (R = 1 m) superpolished fused silica substrates. Their absolute reflectivity was measured at 13% – 14% in the 111–138 Å optimization range using a laboratory reflectometer with a laser-plasma radiation source. The normal-incidence reflection spectra of the mirrors were recorded in the configuration of a transmission-grating spectrograph using the slowly varying quasicontinuum of a laser-driven tungsten plasma. Comparing the reflectivity data with the reflection spectra recorded with a CCD permitted estimating a decrease in the detector responsivity beyond the Si L-edge. The broadband normal-incidence multilayer mirrors facilitate the development of a high-resolution imaging spectrograph covering a usable range about the Si L-edge to characterize, for instance, the L-edge fine structures and chemical states. These mirrors will also find use in imaging solar instruments with a high spectral resolution operating aboard a spacecraft and in laboratory instruments for plasma diagnostics.

Design of a broadband reflection mirror for the water window region using a stacked multilayer with optimized structure

“…These results also exhibit the direct correlation between the good uniform reflection and enough designable parameters of SMs. Among the cases with RMSD = α 0 , the mean reflectivity for SMs with (m, N) = (20, 20), (25,16), (40,10) all converge to nearly the same value (4.90%) after 10 000 generations optimization, while the one for SM with (m, N) = (80, 5) is not completely convergent, leading to a lower mean reflectivity (4.18%) than other SMs. By comparing the optimization results of SMs with different structural parameters, it is found that the number of PMs plays an important role in the design of a broadband reflection mirror.…”

“…In this part, the broadband reflection mirrors centered at 380 with 20 eV bandwidth (370-390 eV) are designed by five Cr/Sc SMs with different structural parameters (m, N). The cases of (m, N) = (10, 40), (20,20), (25,16), (40, 10), (80, 5) are considered, and the total bilayer number for each SM is set to be less than 400 bilayers, to avoid the reduction of optimization efficiency caused by the presence of redundant bilayers in a SM. In addition, the layer thickness range for optimization in GA is set to be d 0 ± ∆d, in which d 0 = 0.8174 nm is the quarter wavelength of center energy (380 eV), and ∆d is the preset thickness variation interval, which is set to be 0.1 nm here.…”

“…A stacked multilayer (SM), also called block multilayer, is composed of several PMs stacking in sequence, and is another approach for broadband reflection [22,23]. Barysheva et al used Mo/Si and Mo/Be SM mirrors to achieve 16% and 13% constant reflectivity in the EUV region of 17-21 nm and 11.1-13.8 nm respectively [24,25]. Yao et al used block multilayer mirrors to achieve mean reflectivity over 15% in the super broad hard x-ray region of 45-60 keV [26].…”

Instruments for best target position determination in the high-intensity laser-solid interaction experiment

“…This kind of spectrograph was used in many experiments, including diagnostics of laboratory plasmas 34 and registration of XUV radiation generated in relativistic experiments on frequency up-conversion during reflection of laser pulses from a relativistically moving 'flying mirror' electron surfaces 35 or in the pioneering studies of singularity-based soft X-ray radiation sources like BISER 36 . The most common combination in this XUV spectrometer is a broadband normal-incidence multilayer mirror with a transmission diffraction grating 37 , but there is also a possibility to enhance the spectral resolution if a reflective VLS-grating is employed instead 38,39 . Figure 5.…”

Research and creation of broadband X-ray mirrors with a spectral transmission band coinciding with emission lines and the possibility of filtering

“…According to the method described above, stock mirrors were calculated based on the Mo/Be structure, which has already demonstrated its promise for creating broadband stack mirrors [16]. The shape of the emission line was set as the objective function.…”