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Upgrading the ATLAS tracker

The current ATLAS Semiconductor Tracker (SCT) is an array of microstrips with area 6.1m2, providing the main momentum measurement and much of the pattern recognition for charged particle tracks in the experiment. The SCT EndCap engineering was led from Liverpool, with EndCap-C construction based there and Liverpool personnel led the SCT sensor R&D, the forward module programme, EndCap-C assembly, engineering, and commissioning at CERN, 400 out of a total of 2200 forward modules were wirebonded at Liverpool and over 1000 were tested here.

Liverpool continues to play a prominent role in many aspects of installation, commissioning and testing at CERN, with many personnel now based there with duties associated with the SCT. However, from July 2005, members of the UK community have started participating in discussions on a possible luminosity upgrade of the LHC sometime in the next decade, with the hit density and radiation levels implying the need for a complete replacement of all tracking layers within ATLAS. The default concept for this is to be an all-silicon tracker (see Figure 1), based mostly on the p-type sensor technology, first demonstrated for radiation hardness by Liverpool with CNM (Barcelona) and Micron Semiconductors (UK) Ltd, now being proven with Hamamatsu Photonics (HPK) Japan and also under development with e2v Technologies (UK) Ltd.

Three major international ATLAS tracker upgrade workshops have now been held in Genova (2005), Liverpool (2006) and Valencia (2007) and NIKHEF (2008). One member of the Liverpool group has been appointed to the ATLAS Upgrade Project Office, with responsibility to the Module Integration Working Group as well as being PI on the UK proposal, and one of us leads the Full Detector Systems Group within the RD50 programme developing radiation hard silicon sensors. 3 of us are UK programme work-package coordinators or deputy coordinators.

The Liverpool ATLAS group is engaged on working in the following groups (workpackages, WP):

Sensor R&D (WP3)
Hybrid (WP4)
Engineering (WP7)

Brief History of UK ATLAS Tracker Proposal

An application process was initiated by the submission of the "ATLAS Upgrade Statement of Interest" to STFC (then PPARC) in January 2006. Simultaneously many experimental particle physics groups were completing Rolling Grant submissions for the period October 2006 to September 2011, with next submission due early 2009 (3 plus 2 year roll). The programmes outlined in many of the Rolling Grants from ATLAS groups included staff becoming available from the SCT commissioning taking roles in applying their expertise to the Upgrade programme. Following invitation based on the SoI, the UK submitted the full proposal for the tracker: "Research and Development on the Replacement ATLAS Tracker Required for a High Luminosity Upgrade to the LHC" in October 2006. This was examined in detail by the Project Peer Review Panel (PPRP) and considered by STFC's Science Committee on 23rd March 07. Informally we were advised of the success of the proposal in May with formal acknowledgement coming in July 2007. The award contained detailed reductions with respect to the proposal by workpackage for the equipment, consumables and facility cost lines. The STFC (CCLRC) staff, the Particle Physics Grants Panel (PPGP) awarded university rolling grants staff relating to academic, research and technical staff and the original travel request were awarded in full. The UK group has since met with the STFC Oversight Committee on 10th October 2008 and sent its Statement of Interest for the full UK upgrade programme on 13th November 2008 including the next phases of the tracker programme after 2010 and R&D aimed at pixel detector systems.

As would be expected, aspects of the programme did need to be descoped in places and greater dependence on sharing resources with international collaborators became mandatory. However, the levels awarded corresponded to the PPRP recommended "optimal programme" and as such was taken as strong endorsement of the proposed research and development activity.

Publications and Conference Talks

1. G. Casse, P.P. Allport, A. Greenall, "Response to minimum ionising particles of p-type substrate silicon microstrip detectors irradiated with neutrons to LHC upgrade doses", Nuclear Instruments and Methods in Physics Research A, Vol.581(2007), Pages 318-321.

2. G. Casse, 9th International Workshop on Radiation Imaging Detectors, Erlangen, Germany 22-26 July 2007.

3. A. Chilingarov, I. Dawson, G. Casse et al. RD50 status report 2006: Radiation hard semiconductor devices for very high luminosity colliders.CERN-LHCC-2007-005, CERN-LHCC-RD-013, Jan 2007. 76pp.

4. G. Casse, 16th International Workshop on Vertex detectors, September 23-28, 2007, Lake Placid, NY, USA.

5. G. Casse, Nuclear Science Symposium and Medical Imaging Conference, October 27 November 3, 2007, Honolulu (Hawaii), USA.

6. A. Affolder, 11th RD50 Workshop, Geneva, Switzerland, 12-14 November 2007.

7. A. Affolder, ATLAS Tracker Upgrade Workshop, Valencia, Spain, 11-14 December 2007

8. T Jones, ATLAS Tracker Upgrade Workshop, Valencia, Spain, 11-14 December 2007

9. G. Casse, 10th International Conference on Instrumentation for Colliding Beam Physics, Budker Institute of Nuclear Physics, Siberian Branch of Russian Academy of Science, Novosibirsk, Russia, February 28 - March 5, 2008.

10. A. Affolder, ATLAS Tracker Upgrade Workshop on Modules and Service Structures, Cartigny, Switzerland 17-18 March 2008

11. A Greenall, ATLAS Tracker Upgrade Workshop on Modules and Service Structures, Cartigny, Switzerland 17-18 March 2008

12. T. Jones, ATLAS Tracker Upgrade Workshop on Modules and Service Structures, Cartigny, Switzerland 17-18 March 2008

13. P. Allport, Vertical Integration Technologies for HEP and Imaging Sensors, 6-9 April 2008, Ringberg Castle, Lake Tegernsee.

14. A Affolder, 3rd Workshop on Advavanced Silicon Radiation Detectors (3D and P-type Technologies), Barcelona, Spain, 14-16 April 2008.

15. G. Casse, 3rd Workshop on Advanced Silicon Radiation Detectors (3D and P-type Technologies), Barcelona 14-16 April 2008.

16. A. Affolder, 2008 Symposium on Radiation Measurements and Applications, Berkeley, CA, USA, 2-5 June, 2008.

17. G. Casse, A. Affolder, P.P. Allport, "Charge Collection Efficiency Measurements for Segmented Silicon Detectors Irradiated to 1×1016 n cm-2", IEEE Trans. Nucl. Sci., vol.55, no. 3 (June 2008) 1695-1699.

18. G.Casse, 17th International Workshop on Vertex Detectors, Utö Island, Sweden, July 28 August 1, 2008.

19. A Affolder, 8th International Conference on Position Sensitive Detectors (PSD8), University of Glasgow, Scotland, 1st to the 5th of September 2008.

20. P. Allport, 8th International Conference on Position Sensitive Detectors (PSD8), University of Glasgow, Scotland, 1st to the 5th of September 2008.

21. G. Casse, A. Affolder, P.P. Allport, A. Chilingarov, A. Greenall, K. Hara, B. Hommels, T. Kohriki, Y. Ikegami, T. Meguro, S. Terada and Y. Unno, "Comparison of charge collection efficiency of segmented silicon detectors made with FZ and MCz p-type silicon substrates", Nuclear Instruments and Methods in Physics Research A, Vol.591(2008), Pages 178-180.

22. A Affolder, 7th International Conference on Radiation Effects on Semiconductor Materials Detectors and Devices, Florence, Italy, 15-17 October 2008

23. P Dervan, 11th Topical Seminar on Innovative Particle and Radiation Detectors, Siena, Italy, 1 - 4 October 2008.

24. P Dervan, 2008 IEEE Nuclear Science Symposium, Dresden, Germany, 19 - 25 October 2008.