Xray Instruments

1
Development of precision hard X-ray multilayer
optics with sub-arcminute performance
X-ray Instruments
Science Goals
Columbia Astrophysics LaboratoryJim Chonko,
Chuck Hailey, Jason Koglin, Mike Sileo, Marcela
Stern, David Windt, Haitao Yu Caltech Space
Radiation LaboratoryHubert Chen, Fiona
Harrison Danish Space Research InstituteFinn
Christensen, Carsten Jensen Lawrence Livermore
National LaboratoryBill Craig, Todd Decker, Kurt
Gunderson

• Non-focusing Detectors
• Previous instruments for hard X-rays coded
  aperture (e.g. GRATIS) and collimated.
• Detector background determines the minimum
  detectable X-ray flux.
• Detector area _at_ Collecting area

• Imaging and spectroscopy of 44Ti emissions in
  young Supernova remnants
• Sensitive observations of obscured Active
  Galactic Nuclei (AGN)
• Spectroscopic observations of accreting
  high-magnetic field pulsars
• Mapping the Galactic Center

NASA/CXC/SAO/Rutgers J.Hughes
NASA/CXC/SAO H. Marshall et al.

• Focusing Telescopes
• Soft X-ray telescopes (e.g., ASCA, Chandra)
  focus via total external reflection.
• aCrit µ 1/Energy Þ very small incidence angles
  are required for hard X-rays.
• Detector area ltlt Collecting area
• Improved imaging capability

F. R. Harnden (CfA)
Correspondence koglin_at_astro.columbia.edu,
http//astro.columbia.edu/koglin This work is
supported in part by several NASA grants.
NASA/CXC/SAO
GRANAT
Þ A new generation of hard X-ray telescopes using
focusing optics are required to dramatically
improve the sensitivity and angular resolution at
energies above 10 keV
Thermally Formed Glass
Multilayer Coatings

• Enhanced reflectivity from multiple interfaces
  of two materials with large optical contrast
  (e.g. W/Si).

Optics Assembly Approach

• Broad-band energy response by using a range layer
  thicknesses.

• Glass microsheets (originally developed for the
  flat panel industry) are positioned on a Quartz
  mandrel in a commercially available oven.
• As the oven is headed, the glass slowly assumes
  the large scale figure of the mandrel
• The process is terminated just before it touches
  the mandrel by decreasing the oven temperature.
• Near net shaped optic substrates are produced
  without perturbing the excellent initial X-ray
  properties of the glass micro-sheet (3.5 Å
  roughness), even without the aid of highly
  polished and very expensive mandrels.
• The formed shells are cut to the appropriate
  size this also removes the curled edges

• Graphite spacers are epoxied onto a mandrel and
  machined to the correct radius and angle.
• Coated glass substrates are epoxied to the
  spacers.
• After epoxy cure, the next layer of spacers is
  epoxied to the previous layer of glass.
• These spacers are machined and another layer of
  glass is epoxied to the spacers.
• In a similar way, subsequent layers are added to
  the optic.

Prototype Development
Assembly Metrology

• Several prototypes were built in two-bounce
  configurations with various size and thickness of
  AF45 and D263 glass segments were cut to either
  5 or 10 cm long and 5 cm arclength (35).
• Sample LVDT measurements are shown for each type
  of glass
• The results of X-ray pencil beam scans are also
  shown for each prototype with the Half Power
  Diameter (HPD) indicated.
• The individual performance results for the 34
  segments in the 10 cm x 300 mm prototype are
  histogramed this length and type of substrate
  has been adopted for HEFT.
• The 200 mm thick glass meet the Con-X HXT
  angular resolution requirement in addition,
  these substrates are light enough to meet the
  severe weight restriction of this mission.
• The performance of our thermally formed
  substrates is largely limited by axial bows that
  are introduced in the forming process in this
  way, shorter segments yield improved performance.

The Spacers are machined very flat and uniform.
The 1.5 mm peak to valley spacer roughness is
typically on a millimeter length scale, much
shorter than the scale at which the glass can be
deformed. The conformance of the glass directly
on top of these spacers is superb (24" figure).
Much of this can be attributed to the intrinsic
figure of the substrate (60") and not to errors
in the assembly process, which is estimated to be
only 8".
10 cm long, 200 mm thick substrates
10 cm long, 300 mm thick substrates
5 cm long, 300 mm thick substrates
Metrology Techniques
A two-bounce prototype optic with three full
layers was built characterized with three
separate metrology techniques LVDT surface
metrology, X-ray pencil beam scans, full
illumination with UV all yielded consistent
results.