A new type of micromesh, based on etching techniques, has been developed fo
r the Micromegas detector. III this paper, we will briefly describe this ne
w design and give some results about the performances obtained in different
gas mixtures. The geometry of the mesh allows good uniformity of the elect
rostatic field. An energy resolution of 11.7% full-width at half-maximum is
obtained with X-rays at 5.9 keV and 5.4% at 22 keV in an argon/isobutane (
90%/10%) gas mixture. This is a significant improvement for a gaseous detec
tor operating at high gain (about 5000). (C) 2001 Elsevier Science B.V. All
rights reserved.