Gaskin, Jessica A.

Gubarev, Mikhail

Kilaru, Kiranmayee

ODell, Steve

Ramsey, Brian D.

Zhang, William

NASA Technical Reports Server

Differential deposition for figure-
  d  X  corrections in grazing-inci ence -ray
optics
Kiranmayee Kilaru1, Brian D. Ramsey2, Mikhail V. Gubarev2, Jessica A. 
Gaskin2, Steve O’Dell2,  William Zhang3
1 NASA Postdoctoral Program Associate
2 NASA Marshall Space Flight Center
3 NASA Goddard Space Flight Center
https://ntrs.nasa.gov/search.jsp?R=20110015848 2019-08-30T17:33:17+00:00Z
X-ray mirror fabrication at MSFC
Astronomical applications
Non-astronomical applications
X-ray mandrel Mandrel polishing Electroform replication R li t d X  h llep ca e -ray s e
Axial figure errors – Limit the resolution of the optics
Sensitivity of figure variation
100.00
10.00
r
 
[
a
r
c
s
e
c
]
1000
RMS height 
variation
[nm]
0.10
1.00
R
M
S
 
i
m
a
g
e
 
b
l
u
r
300
100
30
10
0.01
0 100 200 300 400 500 600 700 800 900 1000
R
Spatial wavelength [mm]
Minimizing height variation → Improves the imaging quality
Addressing profile deviations through 
differential deposition
corrected  shell 
region
uncorrected  shell 
region
measured shell profile
optic 
motion 
desired shell profile
mask with slit
target rod
sputtered 
material
Process sequence - differential deposition
Surface profile 
metrology
Develop correction 
profile “Hitmap”
Simulations – translation 
velocity of shell 
Differential deposition
Surface profile 
metrology
Proof of concept on miniature optics
Platinum-Xenon Platinum-Argon
power pressure roughness deposition rate power pressure roughness deposition rate
75 15 1.950 0.130 75 15 2.060 0.140
90 15 2.043 0.230 90 15 1.933 0.190
75 30 1.895 0.170 75 30 1.868 0.160
90 30 1.810 0.250 90 30 2.083 0.220
Nickel-Xenon Nickel-Argon
Requirements for 
sputtered filler material 
power pressure roughness deposition rate power pressure roughness deposition rate
75 15 1.915 0.290 75 15 1.995 0.180
90 15 2.070 0.360 90 15 1.778 0.240
75 30 3.093 0.240 75 30 2.260 0.220
•High deposition rate
•Low roughness
•Good adhesion
90 30 3.630 0.310 90 30 2.210 0.290
Tungsten-Xenon Tungsten-Argon
power pressure roughness deposition rate power pressure roughness deposition rate
Experiments 
75 15 1.965 0.300 75 15 1.900 0.120
75 30 1.805 0.290 75 30 2.125 0.290
90 30 1.993 0.370 90 30 - -
75 50 2 075 0 290 75 50 1 998 0 310
•Filler material
•Inert gas
•Power . . . .
90 50 2.423 0.370 90 50 1.868 0.370
Units: power-Watts, pressure-mTorr, roughness- Å rms, deposition rate – Å/sec
•Pressure
Proof of concept on miniature optics
0.3
0.4
u
d
e
 
(
µ
m
)
family of sputtered 
beam profiles
desired coating 
profile
0.1
0.2
A
m
p
l
i
t
u
0
0 5 10 15
Axial position along mirror (mm)
0 4
0 0
0.2
.
h
t
 
(
µ
m
)
‐0.4
‐0.2
.
0 5 10 15 20 25
P
r
o
f
i
l
e
 
h
e
i
g
desired profile
profile before coating
‐0.6
Axial position along mirror (mm)
   
profile after coating
Scale the process to larger size shells
•Larger size astronomical X-ray shells
•Use of VLTP – better accuracies
Depositions
•For larger-size astronomical X-
ray shells
•Preliminary experiments
•Optimize mask design
•Diameter of target rod  
Custom vacuum chamber
•Coatings on glass samples to 
check
•Deposition rate
•Sputtered beam profile
Coatings on glass 
samples Mask configurations
Theoretical performance improvement
Average l  
1000
2000
3000
g
s
t
r
o
m
s
)
Before Correction
After Correction
Correction
stage
deposition 
amplitude
(nm)
Slit-size
(mm)
Angu ar
resolution
(arc secs)
3000
‐2000
‐1000
0
0 200 400 600
H
i
t
m
a
p
 
h
e
i
g
h
t
 
(
A
n
g
1 300 5 3.61
2 40 2 0 68
‐4000
‐H
Axial position along mirror (mm)
.
3 4 1 0.22
4
6
8
10
g
s
t
r
o
m
s
)
Before Correction
After Correction
4 1 0.25 0.14
‐6
‐4
‐2
0
2
0 100 200 300 400 500 600
H
i
t
m
a
p
 
h
e
i
g
h
t
 
(
A
n
g
‐10
‐8H
Axial position along mirror (mm)
Possible practical limitations
•Simulations performed on X-ray 
Correction Average Slit-size Metrology Angular 
shell that has 8 arc sec HPD
•Potentiality for arc-second-level 
stage deposition
amplitude
(nm)
(mm) uncertainty
(nm)
resolution
(arc secs)
± 0 3.6
resolution –with existing 
metrology equipment
1 300 5 ± 10 3.6
± 50 7.3
± 0 0.6
± 1 1
•First stage of correction 
requires +/- 10 nm accuracy
2 40 2
± 5 2
± 10 3.5
± 0 0.2
0 5 0 2
•Progressively finer accuracies 
required for further stages of 
3 4 1
± . .
± 1 0.5
± 2 0.8
correction
Refinements
• Use of customized slit to correct full length of shell at 
single instance
A im th l i ti ns in  t ti n l sp d• z u a var a o – vary g ro a o a ee
• Use on mounted optics to correct mounting errors
Other X-ray optics
• Technique equally applicable to the planar geometry of segmented optics
• Can correct deviations low-order axial-figure errors and azimuthal axial slope 
variations in Slumped glass mirrors – one of the competing versions of ˆIXO flight 
the late
mirrors
• WFXT – maintaining high angular resolution - 5 arc sec over wide field of view -
avoiding shell end effects and mounting errors
Differential deposition conclusions
• Significant improvement in angular resolution of the X-ray shells 
is theoretically possible
• Concept proven on smaller-size medical imaging optics
• Cost-and time-efficient method of improving the imaging quality 
f th  tio e op cs
• Profile and mounting error correction
• Can be applied to different kinds of X-ray optics - full-shell as 
well as segmented optics


Differential Deposition for Figure-Corrections in Grazing-Incidence X-Ray Optics

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