12/12/2014L. Proserpio – AXRO meeting, Prague  Definition of terms  Description of the problem wrt the x-ray thin mirrors technologies  Possible solution to the problem  Activities at MPE  Discussion  Description of the problem wrt the slumping technology  Possible solution to the problem  Activities at MPE  Discussion SCOPE: to share our mutual experience on the two proposed topics, stimulate the discussion and maybe set the floor for future collaborations in order to try to focus the currently available resources on what still need to be study. ROUNDTABLE DISCUSSIONS GLASS THICKNESS VARIATION REFLECTIVE LAYER DEPOSITION

12/12/2014L. Proserpio – AXRO meeting, Prague GLASS THICKNESS VARIATION DEFINITION OF THE PROBLEM: when flat substrate are procured on the market, they present variations in the thickness that might translate in profile errors with consequent effects on the reflection of x-ray.  INDIRECT SLUMPING APPROACH: the thickness variations influence the optical surface of the slumped mirror  DIRECT SLUMPING APPROACH: thickness variation do not influence the optical side of the glass  SPO or other Si wafer technologies: polishing step during wafers production should guarantee low TTV

12/12/2014L. Proserpio – AXRO meeting, Prague GLASS THICKNESS VARIATION D263 AF32

12/12/2014L. Proserpio – AXRO meeting, Prague GLASS THICKNESS VARIATION Key characteristics:  Fire-polished surface with surface roughness < 1 nm  Wide thickness range, from 1.1 mm down to 25 μm  Fast changeover between different glass types  High flexibility regarding throughput and thickness Schott Down-Draw Process

12/12/2014L. Proserpio – AXRO meeting, Prague GLASS THICKNESS VARIATION PtV thickness variation on entire map [micron] = mean thickness value[micron]= PtV single long line (min-max-mean) [micron]: HEW single long line (min-max-mean) [arcsec]:

12/12/2014L. Proserpio – AXRO meeting, Prague GLASS THICKNESS VARIATION Possible solutions to the problems of thickness variation in glass foils  Address the problem at the source  discussion with glass producer  Address the problem after glass procurement (polishing)  one side  double side Contact with Schott establish, meeting planned for end of Jan 2015: for discussion on the possibility of production glass foils with lower thickness variation or possible selection of better glasses Zeiss “manual” approach Schott “industrial” approach

12/12/2014L. Proserpio – AXRO meeting, Prague MPE ACTIVITIES Past ExperiencePresent activitiesFuture plansPast ExperiencePresent activitiesFuture plans Single-side polishing at Zeiss ADVANTAGES: Preservation of surface roughness of one side of glass DISADVANTAGES: Not-industrialized process (time and cost) RESULT:  TTV < 1 μm reached  the process is technologically feasible (NO Show Stopper) but currently present some limitations in terms of dimension of glass that can be treated

ADVANTAGES: Industrialized process (relatively faster, machine availability, cost ↓) DISADVANTAGES:  Loss of good surface finishing characteristics of the original glass  Available for thicker glasses at the required dimension (200x100 mm, 0.7 mm thickn.)  Available for smaller glasses at the required thickness (diam. 200 mm, 0.4 mm thickn.) RESULT:  TTV < μm reached  the process is technologically feasible but needs further development 12/12/2014L. Proserpio – AXRO meeting, Prague MPE ACTIVITIES Past ExperiencePresent activitiesFuture plans Double-side polishing at Schott

12/12/2014L. Proserpio – AXRO meeting, Prague MPE ACTIVITIES Past ExperiencePresent activitiesFuture plans Roughness = [0.802 – 1.099] nm rms, window mm TTV = [ ] nm

12/12/2014L. Proserpio – AXRO meeting, Prague MPE ACTIVITIES Past ExperiencePresent activitiesFuture plans  Plan to go on with the discussion at Schott  Start using the available glass foils at constant thickness to deeply address it implication on the slumping process results  Continuing exploring the possibility of polishing of thin, relatively big glass foils (also taking in mind future industrialization needs)

12/12/2014L. Proserpio – AXRO meeting, Prague REFLECTIVE LAYER DEPOSITION DEFINITION OF THE PROBLEM: to improve the reflection of x-ray in the wanted energy range, a proper reflective layer is required. However, the application of coating can causes stresses into the glass producing shape deformations.  FREE INTEGRATION PHILOSOPHY: stresses cannot be neglected because they distort the shape of the mirror (avoid them or account for them)  “STRESS INTEGRATION” PHILOSOPHY: possibility of correct shape distortion during the integration Start considering the problem for single layer of Ir Ir layer, 30nm thick, roughness 5 Å, Incidence angle 0.5, 1.0, 1.5, 2.0 deg

Possible solutions to the problem of stress  Address the problem at the source  deposition of not-stressed layer  deposition of coating also on glass back side  sub-layer of material with different stress  Address the problem after deposition  annealing thermal cycle for stress relaxation  correction of deformation introduced by stress (  accept the stress has mean to shape the glass as wanted) 12/12/2014L. Proserpio – AXRO meeting, Prague REFLECTIVE LAYER DEPOSITION Starting test for the evaluation of stresses and deformation introduced by coating deposition

12/12/2014L. Proserpio – AXRO meeting, Prague REFLECTIVE LAYER DEPOSITION Aschaffenburg University sputtering facility  Can fit 200x100mm glass  Thickness uniformity < 3% (flat, Al coating on glass)  Target 150 mm diam. (> euro for Ir)

12/12/2014L. Proserpio – AXRO meeting, Prague MPE ACTIVITIES Past ExperiencePresent activitiesFuture plans  Start with Al 100nm coating on flat sample to set parameters and get experience on test procedure with the idea of plan for Ir testing  Al because of Ascahffenburg experience, availability, cheaper  100 nm to maximize the effect of stress that we what to measure by comparing shape merology before and after coating deposition (gravity effect subtracted)

12/12/2014L. Proserpio – AXRO meeting, Prague REFLECTIVE LAYER DEPOSITION Parameters that can be varied during coating deposition  substrate temperature  coating time  Power at cathodes  pressure  Ar-flow Deposition rate = [0.093 – 0.350] nm/sec

12/12/2014L. Proserpio – AXRO meeting, Prague MPE ACTIVITIES Past ExperiencePresent activitiesFuture plans  Plan to go on with these activity to gain experience and test also “more realistic” coating (Ir)  Literature search and discussion with other group to concentrate on what really needs to still be done  Discussion on possible collaborations