# Current Status and Future Developments of Micromegas Detectors for Physics and Applications
## 2 Micromegas Fabrication Techniques
### Optical Readout  
A recent development in Micromegas technology is the optical readout concept. The development follows the work of [PERSON] et al., who demonstrated the potential of an optically coupled standard triple GEM with Ar-CF\({}_{4}\) to a sensitive optic camera, obtaining good resolution and fast X-ray projection imaging [33].  
Figure 5: Integrated Micromegas grid (InGrid) on a Timepix chip.  
Photons intervene in all branches of science and technology. During the charge multiplication through avalanches in gaseous detectors a significant amount of scintillation photons is also present. Using an appropriate gas mixture, part of this light can be emitted at wavelengths were optical cameras or other sensors are sensitive. Given the rapid evolution of the technology in terms of the resolution, speed and noise level, the use of a digital camera to readout a Micromegas detector has an enormous potential for imaging applications, compared to costly conventional electronics.  
Normally, Micromegas detectors deploy an opaque plate with a metalized surface that acts as an anode. To create the amplification field and to be able to collect the scintillation light at the same time, the metal surface is replaced by a glass with a thin (\(\sim\)2000 A) Indium Tin Oxide (ITO) layer. The ITO + glass has a transparency \(>\)80%, while the surface is electrically conducting (100 Ohm/\(\square\)), thus, allowing for photon and charge collection. Apart from this modification, a standard bulk Micromegas manufacture technique can be used to create the pillars on the ITO surface and to attach a woven or a flat-type mesh.  
The first tests of this technology were performed using the same setup and cameras as in [33] with an Ar (80%)-CF4 (20%) gas mixture at atmospheric pressure. Despite the fact that the gain in Micromegas detectors in CF4 mixtures is relatively poor compared to a double or triple GEM structure, satisfactory images were collected. The photon to charge (\(\gamma\)/e) ratio was of a similar order as GEMs, while the image resolution was improved by a factor of almost two with respect to the triple GEM [34]. Ongoing studies are aiming at improving the gain by investigating new gas mixtures/pressures and exploring other electro-mechanical settings. In parallel, detailed simulations of the optical components are taking place in order to optimize the setup in terms of the image resolution.  
A first application of the optical readout concept will be the use of a glass Micromegas as a neutron imager for highly radioactive samples (Figure 6). The cathode will be replaced by a B4C coated plate to render the ensemble compatible with an intense neutron flux. The base interest here is to selectively detect \(\alpha\) particles from the \({}^{10}\)B(n,\(\alpha\))\({}^{7}\)Li reaction and to reduce the gamma sensitivity of the active gas volume, based on the difference of the specific ionization power of electrons compared to \(\alpha\) particles.  
Another project of a different and enterprising nature will be the imaging of betas from solid biological samples, appropriately deposited on the plate that consists of the cathode of the detector following the recent developments in [35]. Furthermore, this project is envisaged to include integrated 2D as well as tomography [36] with integrated image rectification treatment codes.