Over the last 6-8 years there has been an extensive collaboration between SINTEF, Dep. of Physics, UiO and the Institute for Informatics, UiO within ASIC developments for silicon strip readout systems at LHC. As the ASIC is being concluded, most of the electronics work has been concentrating on hybrid development and module testing. Concerning hybrids for the ATLAS SCT the Dep. of Physics in Oslo has played a leading role in design and layout. Two examples are given :
A new low mass beryllia, thickfilm technology with thin conductors (2-3um) has been tried out at CERN. These hybrids are designed, processed and tested before being assembled into complete modules. The final version of these kinds of designs are now being developed but the process is unfortunately only partly available in industry. One dr.scient student and an electrical engineer at UiO have made the electrical design and layout of these hybrids for ATLAS.
An even more advanced hybrid technology is being explored at CERN. In this process thinfilm aluminium tracks on kapton are fused to a low mass, highly thermally conducting substrate (TPG). The result is thinfilm hybrid with extremely good thermal conductivity (crucial for electronics cooling) and low radiation length (crucial for the detector performance). Also for this technology the designs and layouts are made at UiO. The process is being pursued by CERN and Advances Ceramics for other applications.
The hybrid development in ATLAS is now completed, and Ole Dorholt, the engineer who has layed out most of the circuitry, has now moved on to module production and testing responsibilities.
4.0 ATLAS Common Fund.
The Norwegian Common Fund contribution to ATLAS will take two forms. The ATLAS Common Fund contribution corresponds to 43% of the total Norwegian funding, as specified in the MoU. Funding shall be allocated to items as magnets, mechanical constructions, infrastructure cooling and ventilation, etc. The contributions can be provided in cash or as items delivered to ATLAS with predetermined specifications and price.
4.1 Common Fund item of interest for Norway
Norway will deliver four cryogenic tanks for the ATLAS liquid argon calorimeter proximity cryogenics. The cryogenics systems has to maintain uniform temperature conditions of the calorimeters which are immersed in liquid argon baths, by making use of saturated liquid nitrogen as cooling source. In addition to the temperature control the system should handle the purge, the cool down, the filling, the emptying and the warm up of the cryostats housing the detectors. The vendor, SB-verksted is in close contact with SINTEF-NTNU/Trondheim to ensure proper expertise for design of the tanks.
Agreement is reached for delivery of :
Two liquid argon storage tanks which are to be installed close to the cryostats in a retention pit. The capacity of each vessel is 50,000 litres. Each vessel is equipped with a liquid nitrogen cooler with a capacity of 5000 W to keep the gas at constant pressure and re-condense the gas vaporized during the cooling of cryostats, cryo-lines and the tank itself. The construction of the tanks will be of the same type as standard custom cryogenic vessels, power and vacuum insulated. They will be equipped with a pressurizer and one of the two with a vaporizer to produce pure argon gas for flushing the whole installation. The feet of the tanks are made of stainless steel to ensure mechanical stability in the case the retention pit is swamped by a liquid argon spill.
In addition three liquid nitrogen tanks are needed, two on the surface (50 m3 each), and one (15 m3) in the cavern. SB-verksted will deliver the two surface tanks. The specifications for these are similar but slightly more relaxed than for the LAr tanks.
4.2 Project background
SB-verksted will manufacture and transport the equipment to CERN. NTNU-SINTEF will do the thermal engineering and guide SR-verksted in the documentation and testing phase. SB-verksted has experience in building systems for storage and distribution of liquid nitrogen through the delivery of a cryogenic system installed at a floating construction in the North Sea. Furthermore, SB-verksted has experience as a supplier to CERN as they have delivered helium surface pressure tanks to the LEP-project. NTNU/SINTEF is currently supporting SB-verksted in their development into new business areas.
SINTEF/NTNU has had several people engaged in the cryogenic groups of CERN and therefore has experience in cryogenic design and thermodynamic calculations of cryogenic installations. Prof. Geir Owren, NTNU/SINTEF, developed a simulator for cryogenic plants, CryoSim. This code has since been used both by CERN and NTNU, and could be used to support the design and manufacture of cryogenic deliveries from Norway to CERN/ATLAS.
4.3 Project status
After approval in the ATLAS Collaboration Board in February and final endorsement in the ATLAS RRB in April an order was placed with SB-Verksted in June 00, worth 6500 kkr corresponding to 1250 kCHf at today's exchange rates. This is 100 kChf above the value of this in-kind item in the ATLAS CORE lists.
The first tank is scheduled for delivery in August 2001 and the remaining three in June 2002. Acceptance tests at CERN will take place within 6 weeks (3 months) for the first (last) delivery. The order is placed through CERN purchase office.
Furthermore, an agreement is signed between NTNU (Owren) and SB-verksted for the thermal engineering and specifications of the tanks. We expect to spend around 1000 kkr on follow up of this project, specific manpower and travels for the NTNU-team. This has to be taken for the normal operation budget of the ATLAS project, while we would have liked to extract it from the CORE-budget by placing a cheaper contract. However, after several months of negotiations we could not find any way to reduce the price which is largely determined by unfavorable raw material prices.
4.4 Common Fund summary
This project has developed well over the last year in every respect except the raw material price in the months ahead of placing the contract. For the remaining Common Fund contribution we are not actively pursuing further in-kind contributions and will consider to make a cash contribution.
5. Tracking studies, physics studies and the GRID.
5.1 Tracking and pattern recognition.
The pattern recognition problems in the ATLAS ID are very challenging. Around 500-800 particles are produced every 25ns and the reconstruction is based on information from over 100 mill. readout channels in the ATLAS ID. One dr.scient student (Are Strandlie) has, in collaboration with the Vienna group (Regler, Fruhwirth) and INRIA-Nice, developed new optimised algorithms for track reconstruction and track fitting in ATLAS. This work has resulted in a number of publications and reports. Dr.Jørn Wroldsen, HiG, is strongly involved in this work as supervisor, and six (four last year and two this year) students at HiG have carried out project work within the same field.
5.2 Physics studies.
This is a joint effort with the Norwegian Physics Analysis project, much of the activity is well described in the status report of that project. The work at LEP related to Higgs-searches within the SM and the MSSM is important for the preparation of physics analysis at ATLAS. Likewise, B-physics will be an important topic at LHC and the work in BABAR and HERAB are very important for the Norwegian ATLAS physics analysis preparation. The area to be strengthened is within SUSY (beyond the extended Higgs-sector being explored at LEP-II). In the Norwegian ATLAS project we have therefore over the last years installed fast simulation packages for detector simulation and started work for simulations of various SUGRA points and experimental exploration of the SUSY mass-spectrum. The first goal has been to install the most central software packages and generators for SUSY-studies and offer master and Ph.D projects within this field. So far one post.doc (Ole M. Røhne who left Sept 99 and is now at CERN), one Ph.D student and one master student at UiO have worked with these problems. Two Scandinavian LHC physics workshops over the last year, and the recent involvement of Prof. P.Osland in these workshops, have strengthened this work in Norway. A third workshop will be held in Oslo in March 2001. It is expected that one of the ATLAS project’s doctoral stipends will be filled by a student who is inclined to do ATLAS relevant physics studies which are closely connected to the theoretical activities of prof. Osland.
These activities should lead to a strong analysis activity at LHC within a wide range of physics topics. Within the limited resources devoted to this work very good progress has been made since the end of 1998.
5.3 The GRID
It is at present not clear how the data collected by ATLAS (and other LHC experiments) are going to be processed. A strategy is identified through the CERN-GRID initiative, where the plan is to develop software to run farms of commodity computers in parallel to achieve the necessary data throughput. Data processing centers could be established in different countries which would be tied together through fast communication lines. Interest to develop this concept is large in informatics communities all over the world. Norway is at present not directly involved in the CERN-GRID activities. However, if funding gets available through a separate application to the research council, there will be some Norwegian manpower available.
Discussions between Nordic LHC experimenters have started to try to coordinate the Nordic efforts and maybe establish a Nordic center for LHC data processing and mock data production (through Monte Carlo simulations of the experiments). An application is sent to NORDUNET-II which seeks support for such an activity. In addition to the fact that we need to find additional resources for ATLAS computing, it is also necessary to get involved in the efforts to develop ATLAS software in order to build up competence and infrastructure necessary to be able to make optimal use of ATLAS data for physics studies when they arrive in 2005.
6.0 Summary of the main points.
The project is progressing well. After a delay in the SCT electronics development pre-production chips are now available. The schedule is still acceptable and potentially there is still some float in the Norwegian schedule for module-production. The main uncertainty in the module construction is related to amount of testing and rework needed on the completed modules.
The financial situation is tight, and the cooling system overrun which has recently become unavoidable, will strain the situation further. The contracts placed the last 12 months for sensors and cryogenic tanks are both slightly on the high side. Finally, the cost of necessary equipment and infrastructure upgrades has turned out to be higher than expected. However, there are other factors which might be more important in determining the final cost, namely exchange rates and the unknown yield factors during the different phases of the detector module production. To keep engineering and post. doc. positions free to save money will not be possible in the SCT module production phase ahead of us.
Over the last year ATLAS has made detailed estimates of the costs involved in integrating, maintaining and operating (M&O) the detector before the data-taking starts in 2005. Taken face value these costs will add around 2000 kkr to the operation costs in our planning. Even if we manage to reduce our operation expenses at home in 2004-2005 we cannot manage such a contribution. We will expect that the M&O budget will be discussed in the RRB in October (briefly) and more completely in the Spring 2001.
Technically and scientifically the project is developing along three main lines :
Pre-production and testing of silicon sensors for ATLAS.
Finalizing construction and test methods for the SCT modules.
Execution of a Common Fund project for the ATLAS Liquid Argon cryogenics.
The additional activities related to silicon system cooling, the detector control system, hybrid developments, tracking and physics analysis preparation are important, and unfortunately more costly than foreseen, and involve a number of students.
For the three main activities mentioned above the challenges for next year will be to:
Move into silicon sensor production and correct production rates after the pre-production conclusions are drawn.
Establish material control and storage routines for the sensor and module production.
Gain experience with construction and electrical testing of modules through the module 0 production.
Monitor and follow the Common Fund project with SB-verksted.
In addition we have to :
Control the cooling system cost overrun.
Participate in preparation of the computing for LHC on a level appropriate for us
We expect that by late 2002 and certainly in 2003 we will be able to give a fairly complete overview of the Norwegian ATLAS project spending, as well as the foreseen spending for the remaining part of the project. At that time we should also be able to outline an ATLAS physics analysis project for 2006-2015.
Scientific UiB, UiO, NTNU, HiG (note that many of these are only part time on ATLAS, as explained in the status reports for the Physics Analysis Project and ALICE):
S.Stapnes is currently (from Febr. 1999) ATLAS Inner Detector (ID) Project leader. This covers the ATLAS PIXEL system, the SCT system and Transition Radiation Tracker. The ID project involves around 55 institutes and 450 physicists. The system corresponds to around 1/5 of the full ATLAS detector in resources, manpower and complexity.
B.Stugu is representing Bergen in the ATLAS Collaboration Board, and in the Institute Boards of the ID and SCT groups. S.Stapnes is doing the same for UiO.
Bjarne Stugu is a member of the ATLAS publication policy working group.
Farid Ould-Saada will represent us in the National Computing Board in ATLAS (replacing Bjarne Stugu).
Bjarne Stugu is National Contact Physicist for Norway.
Until February 1999 Steinar Stapnes was member of the SCT and ID steering groups plus the Collaboration Chair Advisory Group in ATLAS.
He was also until that time the SCT and PIXEL testbeam coordinator.
S.Stapnes is President of the Norwegian Physical Society..
Publications and Reports :
C. M. Buttar, L.G. Johansen, S. Stapnes, B. Stugu, A. Werner et al.:
“Recent results from the ATLAS SCT irradiation programme.”