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Export Restriction Free Travelling wave tubes Materials

Periodic Reporting for period 1 - ERFTM (Export Restriction Free Travelling wave tubes Materials)

Reporting period: 2016-04-01 to 2017-03-31

ERFTM address two key materials of TWT, the helix ribbon and the helix support rod which are currently provided by a non-export restriction free supply source, due to the complexity of the manufacturing processes. Indeed, this proposal is dedicated to the development of new travelling wave tube (TWT) key components and innovative solutions that will not be governed by existing or even potential future export restrictions.
The process of helix ribbon manufacturing is an extremely difficult process, especially when the wire is made of tungsten material, as is often the case. This is a refractory material with a high melting temperature and high hardness which is not compatible with easy transformation. An alternative approach is the use of MoLaO ribbon, which is a bit easier to transform into ribbon. The procurement of round wire (W and MoLaO) used for the manufacturing of ribbons for TWT is associated with a lower risk of export restriction.
Furthermore, in the case of tungsten helix ribbons, the supporting rods are made of an unusual material, Anisotropic Pyrolitic Boron Nitride (APBN), which is easy neither to produce nor to machine to the high level of specifications required for TWT, such as high density. Indeed, the difficulty to manufacture such parts increases as size of TWTs decreases in respond to market pressures for higher power, higher frequency TWTs.
The skills of each partner are following:
• TED is providing the specifications for ground applications and leads the ground qualification process.
• TES is providing the specifications for space applications and leads the space qualification process.
• KL TMG is developing the processes and machines required to prepare the helix ribbon materials and to ensure their quality online, in real-time using a non-destructive technique.
• CVT is developing the processes and machines required to prepare the APBN material.
• MIC is implementing the processes and machines required to machine the APBN into rods and to ensure its quality.
• ARMINES is ensuring the high-precision characterisation of the ribbons during their development by LPI and perform further characterisations contributing to the space and ground qualification of both critical technologies (ribbons and rods).

The project will result in European solutions to both technologies currently provided by a single US source, thereby eliminating the risks of export restriction.
In conclusion the measurable objectives of ERFTM are:
• To develop two critical space TWT components technologies needed by the European space manufacturing sector in such a way as to ensure their security of supply (export restriction free access): The helix ribbon wire (in refractory materials such as tungsten (W) or molybdenum doped with lanthanum oxide (MoLaO); The tungsten helix supporting rods.
• To provide new, European sources to the two critical TWT technologies for power amplification in line with “U7” of the Urgent Actions identified by the EC-ESA-EDA Joint Task Force (JTF) on Critical Technologies.
• To develop the necessary new processes and equipment by the European technology providers companies in the consortium ( KL TMG (Spain), CVT an SME in Germany for the APBN plates and MIC an SME in France for the machined APBN rods).
• To develop new non-destructive processes to ensure compliance with specifications of these critical components.
• To qualify the space and ground tubes containing, new critical components, the helix ribbon and the APBN helix supporting rods.
• To carry out a commercial evaluation of both technologies in order to maximise the stability of supply by minimising commercial and business-related risks. A WP dedicated to the development of a commercial evaluation of the technology will address how to access the commercial market with a full range (preload) of recurring products.
• To secure and further develop European space and ground TWT leadership in rapidly growing Asian markets,
The aim of ERFTM will be to define the best conditions for APBN machining in the respect of improved Thales specifications.
Goals and technical jumps:
- To increase knowledge and expertise in APBN machining
- To increase knowledge and expertise in “soft” materials, not requiring diamond tools
- TO introduce a new type/generation/family of materials (APBN)
- To develop a surface finish measurement (roughness)
- To develop an innovative inspection process for the straightness of the slope
- To improve efficiency of machining APBN (speed, tools, etc….)
- To develop better know-how than American competitors
ERFTM’s ambition is to address several bottlenecks related to materials, technologies, processes, equipment, characterization, qualification and commercial evaluation as shown in the table below.
Manufacturing helix :
The review of the state of the art demonstrates that rolling round wire to flat ribbon is a challenge for any supplier who intends to manufacture W ribbon. Moreover, there is a unique worldwide supplier at the present time. ERFTM will address those difficulties and confirm the capability of KL TMG with the help of third party LPI to supply helix ribbon components for TWTs.
Indeed previous study has demonstrated that a hot roller is mandatory to achieve requirement of such ribbon for space TWT application (and terrestrial in a second manner). Third party LPI which has a strong knowledge on stainless steel rolling, participated to the development of a specific rolling equipment with Armines and TED. This rolling machine will be installed to KL TMG to form W (and MoLaO to a lesser extent) ribbon. This development will allow improving the quality of W and MoLaO ribbon in order to increase the thermal resistance of the helix which is a key parameter to achieve the highest performance of TWT.

Manufacturing dielectric helix support rods :
The manufacturing of Pyrolytic Boron Nitride is also a challenging process, especially to obtain high density, thick plates and a controlled dielectric constant required for TWT applications. The machining of this APBN is rather difficult to get the helix support rod with the small and accurate dimensions needed for TWT. ERFTM will demonstrate that two European companies are able to procure such component for space TWTs as well as for terrestrial applications. Moreover some advances in mastering the roughness of the helix rod are expected which will allow the team to obtain further progress in new coating development done by TED.

Qualification for Space :
ERFTM will aim to demonstrate the reliability of these new European components in Space TWT, and in terrestrial tubes for telecommunication applications. With a strong experience in the space qualification process, both TES and TED will validate with tube prototypes that the new supply source is well compliant to ensure a high reliability of its space product and its terrestrial TWT for telecommunication application.
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