Ribbed Silicon Plate Stack for X-ray Telescope Mirrors

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Solution Overview

Problem

Existing optical instruments for X-ray telescopes face challenges in achieving a balance between high reflectivity, low weight, and good surface properties at grazing incidence, as they require large, heavy reflecting surfaces to effectively focus X-rays, which are highly energetic and easily absorbed or passed through conventional materials.

Innovation Solution

The use of a stack of ribbed silicon plates with accurately defined inter-plate spacings and reflective surfaces, allowing for precise shaping and coating to create a lightweight, rigid structure that maintains desired optical shapes, such as parabolic and hyperbolic configurations, while enabling efficient X-ray reflection at grazing incidence.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If large reflecting surfaces are used to effectively focus X-rays at grazing incidence, then reflectivity and surface quality are improved, but weight increases significantly

Engineering Contradiction:

ImprovereflectivityVSAvoidweight

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The mirror is divided into multiple thin plates (58 concentric shells in XMM-Newton) rather than using a single large solid reflector. Each plate is spaced from others to create a lightweight structure that maintains the necessary reflecting surface area for X-ray focusing at grazing incidence.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent uses thin foil structures (gold-covered nickel foils in XMM-Newton) to create the reflecting surfaces. These thin films provide the necessary reflective properties while minimizing weight compared to solid structures of equivalent size.

Inventive Principle:

Principle #30Flexible shells and thin films

2Strength

If conventional materials (glass, lead) are used for optical instruments, then structural integrity is maintained, but X-rays are either passed through or absorbed rather than reflected

Engineering Contradiction:

Improvestructural integrityVSAvoidX-ray reflection capability

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent employs composite material structures, specifically gold-covered nickel foils, that combine the structural properties of nickel with the high reflectivity of gold for X-rays. This composite approach maintains structural integrity while enabling effective X-ray reflection at grazing incidence.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention changes the interaction parameter between X-rays and material by using grazing incidence angles (small angles relative to the surface). This parameter change allows reflection instead of transmission or absorption, overcoming the limitations of conventional materials.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If multiple concentric shells are used to increase collecting surface area, then sensitivity is improved, but device complexity and alignment requirements increase

Engineering Contradiction:

ImprovesensitivityVSAvoidcomplexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The telescope uses 58 concentric shells segmented along the optical axis, each contributing to the collecting area. This segmentation allows the system to achieve high sensitivity through large effective area while managing complexity through modular construction and common focal point design.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

All concentric shells are designed to focus X-rays to a common focal point, providing a universal function across multiple elements. This multi-functional design simplifies the overall system compared to having separate focal points for each shell, reducing alignment complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This configuration significantly reduces the overall weight of the optical system while maintaining high reflectivity and surface quality, allowing for more sensitive and efficient X-ray telescopes with reduced dimensions, suitable for space missions and other applications.

Implementation Method 1

X-rays therefore can be reflected only on striking a reflecting surface at grazing incidence

Methodology Applied

Scientific EffectGrazing incidence reflection: Reflection

Data Source

PatentUS7321127B2Optical reflector element, its method of fabrication, and an optical instrument implementing such elements

Publication Date: 2008.01.22 EUROPEAN SPACE AGENCY

AI summary

The invention provides an optical reflector element (1) for a beam of X-rays (RX) or of gamma-rays or of high-energy particles at grazing incidence, the element being constituted by a stack of superposed silicon plates (10-12). Each plate (10-12) has a reflecting top face (101-121) possibly coated with a metallic film, a multilayer or a dispersive grating and a bottom face carrying ribs (100-120) forming spacers between two successive plates (10-11, 11-12), and defining determined spacing between two successive reflecting faces (101-121). The invention also provides optical instruments comprising several such elements, in particular a type I Wolter telescope comprising two mirrors in tandem having respective paraboloid and hyperboloid surfaces of revolution or a conical approximation thereof or a Kirkpatrick-Beaz system.