X-ray Interferometer Mirror Module ISAL Study

Pre-work Overview

Science Team

• Webster Cash - University of Colorado– 303-492-4056

• Ann Shipley - University of Colorado– 303-492-1875

• Keith Gendreau - NASA/GSFC Code 662– 6-6188

Science Driver for MAXIMScience Driver for MAXIM• Current best estimates for the size of the event

horizon of a blackhole: a few microarcseconds

• Variability and spectral data describe an x-ray bright region near the event horizon.

• Baselines at 1-10Å are a factor of of 1000 shorter than at 1000-10000Å

• The MAXIM mission will have resolution of 0.1 as.

– Resolve the event horizon– Study physics and dynamics of inner accretion

region near event horizon

• For Scientific and Technical context, we are exploring MAXIM Pathfinder mission concepts.

– Discover where AGN Jets take off– Study Stellar Coronae

http://maxim.gsfc.nasa.gov

Science Driver for MAXIMScience Driver for MAXIM

A Simple X-ray InterferometerA Simple X-ray Interferometer

FlatsBeams Cross

Detector

d

Ls

λ=

s

Ld

Fringe Spacing:

• Grazing Incidence softens tolerances by ~2 orders of magnitude. Optics that are diffraction limited for normal incidence UV is diffraction limited for grazing incidence X-rays.

• Use “simple” optics to keep diffraction limit.

• Demonstrated in lab at ~10 Angstroms (1.25 keV). W. Cash et al, Nature 407 14 September 2000

• Demonstrated at GSFC with 23.6 Angstroms 27September 2002

How to implement the simple X-ray Interferometer

How to implement the simple X-ray Interferometer

MAXIM Pathfinder•“Easy” Formation Flying (mm control)

•Optics in 1 s/c act like a thin lens

Full MAXIM- the black hole imager

•Nanometer formation flying

•Primaries must point to milliarcseconds

Pre FY02 Baseline Mirror Grouping Improved Mirror GroupingGroup and package Primary and Secondary Mirrors as “Periscope” Pairs

•“Easy” Formation Flying (microns)

•All s/c act like thin lenses- Higher Robustness

•Possibility to introduce phase control within one space craft- an x-ray delay line- More Flexibility

•Offers more optimal UV-Plane coverage- Less dependence on Detector Energy Resolution

•Each Module, self contained- Lower Risk.

A scalable MAXIM concept.

The Periscope Module- the subject of this ISAL study

• The Periscope module is a convenient place to break out two radically different tolerance levels– Nm and ~mas relative positioning and pointing within

the modules

– Micron and arcsecond module to module alignment

• Some further study makes our Periscope mirror “pairs” into mirror “quads”– 4 bounce optical situation required to maintain coarse

module to module alignment

MAXIM Pathfinder IMDC Study May 2002

MAXIM Pathfinder IMDC Study May 2002

Launch

Transfer Stage

Science Phase #1

Low Resolution (100 as)

200 km

Science Phase #2

High Resolution

(100 nas)

1 km

20,000 km

Goals for this Study• How do you make these light weight mirrors so they are flat to better than λ/200?• How do you hold these mirrors with actuators to move them by ~nm over microns

of range? Which Actuators and controlling electronics? Do you put actuators on all the mirrors?

• How does the structure provide an environment suitable to maintain the mirror figure and stability?

• Do we need internal metrology? How to implement?• How do we register one module’s mirror surfaces to another modules mirror

surfaces at the micron level?• How to mass produce these? By how much does this save costs?• What would the alignment procedures be?• Trade Studies- three different mirror module sizes,..• We need the usual IMDC cost/mass/power inputs. Drawings.

Periscope Configuration

Detector

Periscope ModulesX

Z

Mirror Parameters

30 cm TBD

•Active area is 30 cm long by either 2,10 or 30 cm wide- so THREE different types of mirror modules for a trade study

•Surface figure requirement: λ/200 rms (at 633nm)

•Mirror mass must be minimized

2,10, and 30 cmTRADE STUDY

Mirror surface

Thermal Precolimator?

Door/Shutter

Thermal Precolimator?

Sketch of a module

Alignment window?

X-rays

More on module tolerance later by Ann Shipley

• See PPT presentation by Ann and other supporting material.

tansin

*cos2

+2=180 degrees

+=180=2

OPD= (1-cos2)= 2sin2

The CCD will produce several images at different wavelengths at the same time.

The total bandpass of the CCD will be from 50 angstroms to 1.5 angstroms.

Over this bandpass there will be several “colors” due to the energy resolution of the CCD.

At an energy E (in eV) the energy resolution will be dE=1.9*SQRT(E) in eV.

So, one color will be centered at an energy E with a energy width of dE.

Convert this “color” into units of lambda and d_lambda…. Lambda and delta lambda will determine the “ultimate visibility” you could get for that color image. Lambda will also give you the fringe period .

You will have different fringe periods and ultimate visibilities for each color.

A common term will also affect all the visibilities of all the colors- and that term is the OPD between the channels- we are trying to optimize this.

For each color, we will “fit” a curve of event probability (a function of lambda, d lambda, and the OPD) through a bunch of points. One color will not look very exciting.

The fit will actually be a joint fit of ALL the colors for the common parameter of OPD…..