Engineering experience with tungsten grades And possible developments Diego Perini 15.12.08

ALICE Dimuon structures FASS Al. filter FA SAA1 SAA2 Dimuon filter Diego Perini 15.12.08 Superstructure Foundations

Steel envelopes 10.5 tonnes steel AISI304LN FASS 20 tonnes steel AISI304L Lead elements 41 tonnes Tungsten elements 7.2 tonnes Borated polyethylene 0.7 tonnes Graphite 1.7 tonnes Steel plates 10 tonnes steel AISI304 Concrete 4 tonnes Muon filter 300 tonnes of iron slabs Superstructure 8 tonnes of beams Foundations ~200 m3 of concrete Diego Perini 15.12.08

Front Absorber Tungsten – AT&M (China) Graphite – Graphite India LTD (India) Lead – Calder (United Kingdom) Borated Polyethylene – Tosti (Italy) Kundert AG (Switzerland) Steel cones – Narendra & Narendra (India) Envelope – Avesta (Sweden) Japrotek (Finland) Diego Perini 15.12.08

Production process Diego Perini 15.12.08

Diego Perini 15.12.08

Some material properties W 90.5%, Ni, Cu balance Density 17 kg/dm3 Yield strength (0.2%) 520 N/mm2 (280) Tensile strength 670 N/mm2 (580) Elongation A[%] 3 (40) For comparison in brackets there are the corresponding minimum values for austenitic stainless steel AISI 316LN During handling we dropped one plate for ALICE (200mm x 70mm x 10mm) and it broke in several parts. Diego Perini 15.12.08

Technology Tungsten grades can be machined (turning, milling, drilling). Machining parameters are very close to those of austenitic stainless steel. Tungsten grades can be welded (beam welding) but the mechanical properties of the weld and of the HAZ are extremely poor. The melting point is at 3422oC. Brazing is possible. To keep together different parts one can bolt them or use other mechanical fasteners (rivets, rods etc.). One has to be very careful to avoid stress concentration zones. Diego Perini 15.12.08

Maximum size of the parts The maximum size of the sintered parts (in 2003) was about 400mm x 400mm x 400mm. With small differences from producer to producer. The limiting factors for the size are: The size of the oven The size of the press For large quantities customized facilities are possible but one need to discuss with the producer from the early design phase. Diego Perini 15.12.08

Plates Thick plates (thickness > 20 mm) are easier to produce (less work) than thin ones. At a certain stage of the production there is a bulk of compressed power to handle. It is possible to roll the parts after sintering but this represents a further added value. This is another reason why it is important to discuss with the producer from the beginning. Diego Perini 15.12.08

Costs and market - 1 The call for tender for the tungsten grade parts for ALICE (in 2003) was gained by the Chinese firm AT&M. They quoted about 600’000 CHF for 7.2 tonnes of different parts (machining included). The European producers were aligned at about 1’000’000 CHF. Tungsten is a strategic material, there are a few manufacturers. The raw material, the sintering technique and related QA issues are expansive. China is by far the main producer of powder. Some Chinese firms started going further in the production. In 2003 we were the first non-Chinese costumer for AT&M. Diego Perini 15.12.08

Today 600 tonnes of tungsten represent about 40’000’000 Euros. Costs and market -2 Today 600 tonnes of tungsten represent about 40’000’000 Euros. This is the full production of a firm of 100 persons for one year. This is valid today but the tungsten price can vary a lot from year to year according to the health of the world economy (and to amount of wars). All strategycal metals (Nickel, chromium etc) have a similar behavior. Diego Perini 15.12.08

How could we try to reduce costs A single order of some hundreds of tonnes somewhere in the future is not going to change the market. Tungsten is a strategic material, requires expansive production techniques and high QA standards. A production site needs a lot of manpower (100 workers for 600 tonnes/year). Discussions with a producer and small tests can help in optimizing the design and the process and minimize costs (which is the realistic goal? -20% / -30% ?). A firm invests in R&D if there is a promising market in a short or medium term future. In our case we will have to pay the necessary R&D. So we have to be careful. The cheapest tungsten is the one we do not buy. Define in which regions of the detector tungsten is unavoidable Find alternative solutions for the other regions Diego Perini 15.12.08

Hybrid structures (steel + tungsten and/or lead) Compatibility of different metals in contact ! The thickness and quantity of different elements could vary according to the position in the detector. Diego Perini 15.12.08

Work to be done – List of questions Which is the size of the plates to minimize costs? How will the parts be attached together? How will the structure be supported? How much tungsten do we need? In case we can use sandwich structures how can we manufacture them? At which cost? Diego Perini 15.12.08

Conclusions Tungsten is a nasty material: it costs, it has some dangerous mechanical properties, it gives limited freedom for what concerns size of the parts. The challenge is to optimize the production and the design in order to reach affordable costs and safe construction. Alternative (less expensive) materials and configurations should be considered. It would be nice to launch a small R&D program to test them. It is important to start talking with the firms before going very far in the design. Diego Perini 15.12.08