Optimization of the ion-polishing process for e-beam produced Co/C and Ni/C
mirrors with periods of 2.4, 3.9 and 6.5 nm.

E. Louis, H.-J.Voorma, N.B. Koster, F. Bijkerk

FOM-Institute for Plasma Physics Rijnhuizen, Edisonbaan 14, P.O. Box 1207,
3430 BE  Nieuwegein, The Netherlands, tel. 31-30 6096999, fax 31-30 6031204,
e-mail: louis@rijnh.nl


E. Spiller

Physics Institute of the Technical University of Denmark, building 307,
2800 Lyngby, Denmark.
Present adress: 60 Lakeside Road, Mt. Kisco, NY 10549. e-mail:
Spiller@watson.ibm.com

S. Abdali, F.E. Christensen, A. Hussain.

Danish Space Research Institute, Gl. Lundtoftevej 7, 2800 Lyngby, Denmark,
e-mail: salim@dsri.dk

We produced multilayer coatings on a panel of flat super-polished Si(111)
crystals to be used in a spectrometer at the spectrum r=F6ntgen-gamma
satellite. We optimized the e-beam deposition parameters and ion-polishing
process for Co/C and Ni/C coatings. For the optimization we monitored the
soft x-ray reflectivity during production and we determined the interface
roughness with grazing incidence reflectivity of 0.154 nm radiation.
The coatings developed for the satellite mission have a period of 3.9 nm.
The effect of ion-polishing with Kr+- and Ar+-ions of energies ranging
between 300 eV and 1000 eV incident at an angle of 20 degrees to the mirror
surface will be discussed. We investigated the interface roughness as a
function of the thickness removed by ion-polishing. To study the
implantation of the ions in the layers we performed XRF-analysis.
The parameters that are found to be most effective for the reduction of the
interface roughness were used as a starting point for the production of
coatings with a much shorter period (2.4 nm). These coatings are made on
very curved substrates (radius of curvature 50 mm) and are to be used as
focusing elements in an X-ray photo-ionization experiment. The dependence
of the optimum polishing parameters on the layer thicknesses will be
discussed and reflectivity data of the coatings will be presented.
=46urthermore we tested the applicability of the process developed to
coatings with a period of 6.5 nm. Grazing incidence reflectivity
measurements on these coatings will be presented.