X-ray astronomy grazing incidence telescopes use the principle of nested shells to maximize the
collecting area. Some of the more recent missions, such as XMM-Newton , have used an
electroformed nickel replication (ENR) process  to fabricate the mirror shells. Upcoming
missions, such as Spectrum-Röntgen-Gamma  and Focusing Optics X-ray Solar Imager <sup></sup>, also
use the electroforming process to fabricate nested shell grazing incidence X-ray telescopes.
We present recent results on fabrication of replicas with multilayer coatings from Wolter-1 mandrels
using a new hardcoat release material to simplify and improve this electroforming process.
X-ray astronomy grazing incidence telescopes use the principle of nested shells to
maximize the collecting area. Some of the more recent missions, such as XMM-Newton,
have used an electroformed nickel replication process to fabricate the mirror shells. We
have been developing coatings to simplify and improve this electroforming process.
This paper discusses our most recent results from studies using TiN as a mandrel
hardcoat in the electroforming process of fabricating nickel shell optics. The results
indicate that nickel replicas separate easily from the TiN coated mandrel, and little (if
any) degradation of the mandrel occurs after more than 20 replications. AFM
characterization of the mandrel and replica surfaces is shown. Preliminary results are also
included from studies which use this same process to replicate multilayer coatings; these
results indicate no change in the multilayer stack after separation from the mandrel.
We are developing grazing-incidence x-ray optics for high-energy astrophysics using an electroform-nickel process in
which mirror shells are formed by replication off super-polished cylindrical mandrels. The optics so fabricated have a
demonstrated performance at the level of 11-12 arc seconds resolution (HPD) for 30 keV x rays. Future missions,
however, demand ever higher angular resolutions and this places stringent requirements on all aspects of the process --
the mandrels, the shell fabrication, and the mounting and alignment of the resulting mirrors in their housings. A
progress report on recent technology developments in these areas is given, including a discussion on possible post
fabrication improvements in the x-ray mirrors' quality.
The Constellation-X mission concept has been streamlined to a single Atlas V 551 configuration. This decision was reached by the project team after considering the increases in launch costs announced in 2006 coupled with the constrained budget environment apparent with the release of the NASA 2007 budget. Along with the Spectroscopy X-ray Telescopes, this new configuration continues to carry a Hard X-ray Telescope (HXT) component, with some modifications to the original requirements to adjust to the new configuration. The total effective area requirement in the 7 - 40 keV band has been reduced, but at the same time the angular resolution requirement has been increased from 1 arcmin to 30 arcsec. The Smithsonian Astrophysical Observatory, Marshall Space Flight Center and Brera Observatory (Italy) have been collaborating to develop and HXT which meets the requirements of Constellation-X. The development work we have been engaged in to produce multilayer coated Electroformed-Nickel-Replicate (ENR) shells is well suited for this new configuration. We report here on results of fabrication and testing of a prototyped optic for the HXT. Full beam illumination X-ray tests, taken at MPE-Panter Test Facility, show that these optics meet the new requirement of 30 arcsec for the streamlined Constellation-X configuration. This report also presents preliminary results from studies using titanium nitride as a release agent to simplify and improve the nickel electroforming replication process.
Cost of ownership (COO) is an area of concern that may limit the adoption and usage of Extreme Ultraviolet Lithography
(EUVL). One of the key optical components that contribute to the COO budget is the collector. The collectors
being fabricated today are based on existing x-ray optic design and fabrication processes. The main contributors
to collector COO are fabrication cost and lifetime. We present experimental data and optical modeling to
demonstrate a roadmap for optimized efficiency and a possible approach for significant reduction in collector COO.
Current state of the art collectors are based on a Wolter type-1 design and have been adapted from x-ray telescopes.
It uses a long format that is suitable for imaging distant light sources such as stars. As applied to industrial equipment
and very bright nearby sources, however, a Wolter collector tends to be expensive and requires significant
debris shielding and integrated cooling solutions due to the source proximity and length of the collector shells.
Three collector concepts are discussed in this work. The elliptical collector that has been used as a test bed to demonstrate
alternative cost effective fabrication method has been optimized for collection efficiency. However, this
fabrication method can be applied to other optical designs as well. The number of shells and their design may be
modified to increase the collection efficiency and to accommodate different EUV sources
The fabrication process used in this work starts with a glass mandrel, which is elliptical on the inside. A seed layer
is coated on the inside of the glass mandrel, which is then followed by electroplating nickel. The inside/exposed
surface of the electroformed nickel is then polished to meet the figure and finish requirements for the particular
shell and finally coated with Ru or a multilayer film depending on the angle of incidence of EUV light. Finally the
collector shell is released from the inside surface of the mandrel.
There are several potential cost and fabrication advantages to this process. There is flexibility in the choice of material
for producing the mandrel - this allows for optimizing the cost of fabrication of the mandrel. Moreover, since
the final surface and figure of the collector optic can be modified, after electroforming the optic, the mandrel, in
principle does not have a limited lifetime. Finally, the mandrel provides mechanical support to the electroformed
optic throughout the fabrication process, thereby reducing deformation of the optic during polishing and coating.
The optical design, optimization of collection efficiency, fabrication and characterization results is discussed in this
We are developing hard-x-ray optics using an electroformed-nickel-replication process off superpolished mandrels. To date, we have fabricated over 100 shells for our HERO balloon payload with typical angular resolutions in the 13-15 arcsec range. This paper discusses the factors currently limiting this resolution and various developments geared towards the production of higher-resolution optics.
The Constellation-X mission planned for launch in 2015-2020 timeframe, will feature an array of Hard X-ray telescopes (HXT) with a total collecting area greater than 1500 cm<sup>2</sup> at 40 keV. Two technologies are being investigated for the optics of these telescopes, one of which is multilayer-coated Electroformed-Nickel-Replicated (ENR) shells. The attraction of the ENR process is that the resulting full-shell optics are inherently stable and offer the prospect of better angular resolution which results in lower background and higher instrument sensitivity. We are building a prototype HXT mirror module using an ENR process to fabricate the individual shells. This prototype consists of 5 shells with diameters ranging from 15 cm to 28 cm with a length of 42.6 cm. The innermost of these will be coated with iridium, while the remainder will be coated with graded d-spaced W/Si multilayers. The assembly structure has been completed and last year we reported on full beam illumination results from the first test shell mounted in this structure. We have now fabricated and coated two (15 cm and 23 cm diameter) 100 micron thick shells which have been aligned and mounted. This paper presents the results of full beam illumination X-ray tests, taken at MPE-Panter. The HEW of the individual shells will be discussed, in addition to results from the full two shell optic test.
We are developing grazing-incidence x-ray optics for a balloon-borne hard-x-ray telescope (HERO). The instrument will have 200 cm<sup>2</sup> effective collecting area at 40 keV and an angular resolution goal of 15 arcsec. The HERO mirror shells are fabricated using electroformed-nickel replication off super-polished cylindrical mandrels. The angular resolution goal puts stringent requirements on the quality of the x-ray mirrors and, hence, on mandrel quality. We used metrology in an iterative approach to monitor and refine the x-ray mirror fabrication process. Comparison of axial slope measurements of the mandrel and the shells will be presented together with results from x-ray tests.
The Constellation-X (Con-X) mission planned for launch in 2015, will feature an array of Hard X-ray telescopes (HXT) with a total collecting area greater than 1500 cm<sup>2</sup> at 40 keV. Two technologies are being investigated for the optics of these telescopes, including multilayer coated Electroformed-Nickel-Replicated (ENR) shells. The attraction of the ENR process is that the resulting full-shell optics are inherently stable and offer the prospect of better angular resolution which results in lower background and higher instrument sensitivity. We are building a prototype HXT mirror module using an ENR process to fabricate the individual shells. This prototype consists of 5 shells with diameters ranging from 150 mm to 280 mm with a length of 426 mm. The innermost of these will be coated with iridium, while the remainder will be coated with graded d-spaced W/Si multilayers. Parts I and II of this work were presented at the SPIE meetings in 2003 and 2004. This paper presents a progress update and focuses on accomplishments during this past year. In particular, we will present results from full illumination X-ray tests of multilayer coated shells, taken at the MPE-Panter X-ray facility.
Approximately 5 billion dollars in US revenue was lost in 2003 due to open area fires. In addition many lives are lost annually. Early detection of open area fires is typically performed by manned observatories, random reporting and aerial surveillance. Optical IR flame detectors have been developed previously. They typically have experienced high false alarms and low flame detection sensitivity due to interference from solar and other causes. Recently a combination of IR detectors has been used in a two or three color mode to reduce false alarms from solar, or background sources. A combination of ultra-violet C (UVC) and near infra-red (NIR) detectors has also been developed recently for flame discrimination. Relatively solar-blind basic detectors are now available but typically detect at only a few tens of meters at ~ 1 square meter fuel flame. We quantify the range and solar issues for IR and visible detectors and qualitatively define UV sensor requirements in terms of the mode of operation, collection area issues and flame signal output by combustion photochemistry. We describe innovative flame signal collection optics for multiple wavelengths using UV and IR as low false alarm detection of open area fires at long range (8-10 km/m<sup>2</sup>) in daylight (or darkness). A circular array detector and UV-IR reflective and refractive devices including cylindrical or toroidal lens elements for the IR are described. The dispersion in a refractive cylindrical IR lens characterizes the fire and allows a stationary line or circle generator to locate the direction and different flame IR “colors” from a wide FOV. The line generator will produce spots along the line corresponding to the fire which can be discriminated with a linear detector. We demonstrate prototype autonomous sensors with RF digital reporting from various sites.
We are developing grazing incidence x-ray optics for a balloon-borne hard-x-ray telescope (HERO). The HERO mirror shells are fabricated using electroform-nickel replication off super-polished cylindrical mandrels. One of the sources for mirror resolution error is departure of the shell figure from prescription. We have modified a Vertical-scan Long Trace Profilometer (VLTP) in order to measure the figure of the inner surface of the HERO mirror shells for diameters as small as 74 mm. Metrology of the figure, the microroughness, tilt angle, the circularity for the shell mirrors and the mandrels, as well as alignment procedures are discussed. Comparison of metrology of the mandrel and the shells is presented together with results from x-ray tests.
The Constellation-X mission, planned for launch in 2013, will feature an array of hard-x-ray telescopes (HXT) with a total collecting area of greater than 1500 <i>cm</i><sup>2</sup> at 40 keV. Two technologies are currently being investigated for the optics of these telescopes including multilayer-coated Eletroformed-Nickel-Replicated (ENR) shells. The attraction of the ENR process is that the resulting full-shell optics are inherently stable and offer the prospect of better angular resolution which results in lower background and higher instrument sensitivity. The challenge for this process is to meet a relatively tight weight budget with a relatively dense material (ρ<sub><i>nickel</i></sub> = 9 g/<i>cm</i><sup>3</sup>.) To demonstrate the viability of the ENR process we are fabricating a prototype HXT mirror module to be tested against a competing segmented-glass-shell optic. The ENR prototype will consist of 5 shells of diameters from 150 mm to 280 mm with a length of 426 mm. To meet the stringent weight budget for Con-X, the shells will range in thickness from 100 microns to 150 microns. The innermost of these will be coated with Iridium, while the remainder will be coated with graded-dspaced W/Si multilayers. Mandrels for these shells are in the fabrication stage, the first test shells have been produced and are currently undergoing tests for figure and microroughness. A tentative date of June '04 has been set for the prototype X-ray testing at MSFC. Issues currently being addressed are the control of stresses in the multiplayer coating and ways of mitigating their effects on the figure of the necessarily thin shells. The fabrication, handling and mounting of these shells must be accomplished without inducing permanent figure distortions. A full status report on the prototype optic will be presented along with test results as available.
We have developed the electroformed-nickel replication process to enable us to fabricate light-weight, high-quality mirrors for the hard-x-ray region. Two projects currently utilizing this technology are the production of 240 mirror shells, of diameters ranging from 50 to 94 mm, for our HERO balloon payload, and 150- and 230-mm-diameter shells for a prototype Constellation-X hard-x-ray telescope module. The challenge for the former is to fabricate, mount, align and fly a large number of high-resolution mirrors within the constraints of a modest budget. For the latter, the challenge is to maintain high angular resolution despite weight-budget-driven mirror shell thicknesses (100 μm) which make the shells extremely sensitive to fabrication and handling stresses, and to ensure that the replication process does not degrade the ultra-smooth surface finish (~3Å) required for eventual multilayer coatings. We present a progress report on these two programs.
We are fabricating optics for the hard-x-ray region using electroform nickel replication. The attraction of this process, which has been widely used elsewhere, is that the resulting full shell optics are inherently stable and thus can have very good angular resolution. The challenge with this process is to develop lightweight optics, and to keep down the costs of mandrel fabrication. We accomplished the former through the development of high-strength, low-stress nickel alloys that permit very thin, stable, shells without fabrication- and handling-induced deformations. For the latter, we have utilized inexpensive grinding and diamond turning to figure the mandrels and then purpose-built polishing machines to finish the surface. In-house plating tanks and a simple water-bath separation system complete the process. To date we have built shells ranging in size from 5 cm diameter to 50 cm, and with thickness down to 100 micron. For our HERO balloon program, we are fabricating over 200 iridium-coated shells, 250 microns thick, for hard-x-ray imaging up to 75 keV. Early test results on these have indicated half-power-diameters of 15 arcsec. The status of these developments will be reviewed.
HERO is a balloon payload featuring shallow-graze angle replicated optics for hard-x-ray imaging. When completed, the instrument will offer unprecedented sensitivity in the hard-x-ray region, giving thousands of sources to choose from for detailed study on long flights. A recent proof-of-concept flight captured the first hard-x-ray focused images of the Crab Nebula, Cygnus X-1 and GRS 1915+105. Full details of the HERO program are presented, including the design and performance of the optics, the detectors and the gondola. Results from the recent proving flight are discussed together with expected future performance when the full science payload is completed.
We are developing high-energy grazing-incidence optics for a balloon-borne hard-x-ray telescope. When completed the instrument, termed HERO for High Energy Replicated Optics, will have 200 cm<SUP>2</SUP> effective collecting area at 40 keV and <EQ 30 arcsec angular resolution. The payload will offer unprecedented sensitivity in the hard-x-ray region, with milliCrab level sensitivity on a one-day balloon flight and 100 microCrab on an ultra-long-duration flight. While the full science payload is scheduled for flight in 2002, an engineering/proving flight is currently awaiting launch. This flight, consisting of just two mirror modules, each containing three nested shells above a pair of gas scintillation proportional counter focal plane detectors, is intended to test a newly designed gondola pointing and aspect system and to examine the stability of optical bench designs. This paper provides an overview of the HERO program.
The process of electroforming nickel x-ray mirror shells from superpolished mandrels has been widely used. The recently launched XMM mission by the European Space Agency (ESA) is an excellent example, containing 174 such mirror shells of diameters ranging from 0.3 - 0.7 meters and with a thickness range of 0.47 - 1.07 mm. To continue to utilize this technique for the next generation of x-ray observatories, where larger collecting areas will be required within the constraints of tight weight budgets, demands that new alloys be developed that can withstand the large stresses imposed on very thin shells by the replication, handling and launch processes. Towards this end, we began a development program in late 1997 to produce a high-strength alloy suitable for electroforming very thin high-resolution x-ray optics for the proposed Constellation-X project. Requirements for this task are quite severe; not only must the electroformed deposit be very strong, it must also have very low residual stresses to prevent serious figure distortions in large thin-walled shells. Further, the processing must be done reasonably near room temperature, as large temperature changes will modify the figure of the mandrel. Also the environment must not be corrosive or otherwise damaging to the mandrel during the processing. The results of the development program are presented, showing the evolution of our plating processes and materials through to the present 'glassy' nickel alloy that satisfies the above requirements.
The Constellation X-ray Mission is the next major x-ray- astronomy mission in the NASA Space Science road map. As a follow-on to the Chandra X-ray Observatory--nee, the Advanced X-ray Astrophysics Facility--Constellation X will provide high-throughput, high-resolution spectroscopy to probe the gravitational field, kinematics, temperature, density, composition and ionization state of cosmic sources. The Constellation-X observatory system comprises four separate satellites, each with one large Spectroscopy X-ray Telescope (SXT, with a pixelated microcalorimeter and a reflection-grating-CCD spectrometer) and three smaller Hard X-ray Telescopes (HXTs, with pixelated hard-x-ray detectors). Essential to the success of Constellation X is the development of large (1.6-m-diameter), lightweight optics for the SXT mirror assembly. With the Smithsonian Astrophysical Observatory, teams led by NASA's Marshall Space Flight Center, by NASA's Goddard Space Flight Center, and by Italy's Osservatorio Astronomico di Brera are currently developing competing mirror techniques for lightweight SXT optics, toward achieving the required system-level half-power diameter--better than 15 arcsec.
The Constellation-X Spectroscopy X-ray Telescope (SXT) will provide high-throughput, high-resolution spectroscopy of cosmic sources, form 0.25 keV to 10 keV. Key to this capability is the development of large, lightweight optics for the SXT mirror assembly. Teams led by NASA's Marshall Space Flight Center (MSFC), by NASA's Goddard Space Flight Center (GSFC), and by Italy's Osservatorio Astronomico di Brera are currently developing competing mirror technologies for this planned mission. Each team is making significant research progress in developing mirror technologies which satisfy the SXT requirements for lightweight optics, consistent with a system-level optical performance of better than 15 arcsec half-power diameter. The NASA MSFC, in collaboration with the Smithsonian Astrophysical Observatory, has focused its efforts on full-shell replicated optics, of electroformed nickel alloys. Recent progress in identifying a surface treatment to effect low, controlled adhesion and, more significantly, in developing new high-strength nickel alloys make this a viable, low-cost approach to satisfying the SXT requirements.
We are developing high-energy replicated optics for a balloon-borne hard-x-ray telescope. When completed, the telescope will have around 130 cm<SUP>2</SUP> of effective collecting area at 60 keV, and an angular resolution of <EQ 30 arc seconds, half power diameter. With an array of gas scintillation proportional counters in the focal plane the payload will provide unprecedented sensitivity for pointed observations in the hard-x-ray band. We present an overview of the HERO program, together with test data from the first mirror shell. The overall sensitivity of the full payload is given for planned long- and ultra-long-duration balloon flights.
The Advanced X-ray Astrophysics Facility (AXAF) ground calibration program, easily the most extensive in the history of high energy astrophysics, requires careful attention to the verification of its validity for on-orbit operations of the observatory. The purpose of the Flight Contamination Monitor (FCM) is to verify the transfer of the AXAF absolute flux scale calibration from ground to on-orbit operations and to measure or bound any changes in molecular contamination on the AXAF mirrors. This paper reports the current status of the analysis of FCM measurements taken during ground calibration. The FCM measurements during the AXAF activation phase will be the first look at the on-orbit AXAF performance.
Traditional x-ray mirrors are quite expensive because of the fabrication cost involved in achieving a very high surface finish of the order of 15 angstrom or better. Currently, zerodur, and silicon carbide are commonly used as the substrate materials of choice for x-ray mirrors, and the required surface finish is achieved thorugh traditional through traditional polishing methods, which are very expensive and time consuming. The cost of instruments for many new applications in the areas of biomedicine, nondestructive testing and space can be greatly reduced by using the replication methods for producing x-ray quality grazing-incidence type mirrors. This paper presents the optical and optomechanical design for a Wolter type I mirror and its mount, and the fabrication methods used to produce a low cost replicated nickel mirror. The finite element analysis (FEA) results for this mirror are also presented. The fabrication steps including the design and nickel and gold plating of the aluminum master mandrel used for the replication are also discussed. A surface finish of 10-15 angstrom was achieved for a mirror with a wall thickness of only 1 mm for such an electroformed mirror. These kind of replicated x-ray mirrors can result in a major saving in the weight as well as cost, while also making the resulting instruments much more compact and rugged.
Cylindrical (hyperbolic-parabolic Wolter I) mirrors have been electroformed from nickel over an electroless nickel-phosphorous (NiP) plated aluminum mandrel in support of the NASA AXAF-S x-ray spectrometer program. The electroless nickel was diamond turned and polished to achieve a surface finish of 10 angstroms rms or better. Gold was then plated on the nickel alloy after an electrochemical passivation step. Next a heavy layer of pure nickel was plated one millimeter thick with computer controlled stress at zero using a commercial PID program to form the actual mirror. This shell was removed from the NiP alloy coated mandrel by cryogenic cooling and contraction of the aluminum to release the mirror. It is required that the gold not adhere well to the NiP but all other plated coatings must exhibit good adherence. Four mirrors were fabricated from two mandrels prepared by this method. Two mirrors were made from each mandrel. Electrolytically deposited gold was used on three parts and vacuum deposited gold (1500 angstroms) on the fourth. The mandrel surface finish was about 10 angstroms rms at the time of plating in each case. The area of each part is 0.7 square meters (7.5 square feet).
Material selection and suitable low cost manufacturing processes for production of rugged man-portable lightweight optical test set components are described. Field requirements for an ultra lightweight optical test set comprised of an off-axis two mirror collimator plus source and detector optics mandated selection of extremely stable materials. The requirements include temporal, thermal and mechanical performance suitable for portable and transportable military applications. The environmental stability requirement includes operating over a temperature range of 130 degrees fahrenheit. Also military shock and vibration requirements for transportable equipment are imposed on the entire test set. The total weight budget is 5 pounds for the mirrors and the large supporting structure. The structure volume is only about 1% of the occupied space. A near-net fabrication process such as casting or HIP fabrication was required. A comparison of materials and manufacturing methods has resulted in the selection of a hypereutectic aluminum alloy containing 23% by weight silicon with stabilizing elements. This material can be cast and heat treated to produce uniform properties at low cost. The coefficient of thermal expansion (CTE) is much lower than other aluminum alloys and the modulus of elasticity is 50% higher. The alloy was machined with conventional tools and plated with nickel phosphorous of the same CTE to produce stable optics.
Focal plane array research is constrained by the fact that versatile, modular test stations are not available commercially. Typical imaging detector tests mandate fabrication of expensive unique image coupling devices simulating the actual systems under consideration. Stray light and field of view are often not well controlled during tests, leading to lowered signal-to-noise levels and ambiguity regarding performance of an actual system. The University of Alabama in Huntsville has developed an inexpensive process for producing image coupling devices suitable for testing and developing cooled focal plane array systems. Model image couplers for cryogenically cooled focal plane array detector research have been produced by this process. Electrodeposition procedures and precision single point diamond machining, combined with optical design procedures permit fabrication of unique optical systems. Aspheric designs are used permitting excellent control of distortion. Applications include laboratory and field studies of beam expanders, broadband and thermal image couplers suitable for non-contact measurement, IR spectroscopy and durable lightweight telescopes which image on focal plane arrays. Low cost deployable systems are also candidates for this technology.