THE DISTANCE FROM CERN TO LNGS

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1 THE DISTANCE FROM CERN TO LNGS M. JONES, D. MISSIAEN, CERN, SWITZERLAND MATTIA CRESPI, G. COLOSIMO, A. MAZZONI, UNIVERSITY LA SAPIENZA, ROMA, ITALY STEPHANE DURAND, ESGT, LE MANS, FRANCE

2 Outlook 2 Introduction First determination of the parameters Redetermination of these parameters Possible additional controls that can be added and have been realised Conclusion

3 Introduction 3 CNGS is project which aims at sending neutrinos from CERN to the Gran Sasso National Laboratory(LNGS) The goal was the study of the neutrino oscillation conversion of a given neutrino type into another during their travel from the source to the detector (for example, muon-type to tau-type neutrino oscillation). Several experiments are hosted in the underground lab (OPERA, ICARUS and Borexino) The distance between CERN and LNGS is about 730km

September 2011 : The Experiment Opera announced that «The neutrinos are circulating faster than the speed of light» The CERN SUrvey team was of

4 Status and Results 4 The project was approved at the beginning of the 2000 s The production of the neutrinos at CERN started in 2006 On May 31st, 2010, the first tau-neutrino appearing out of several billion of billions muon neutrinos sent from CERN! September 2011 : The Experiment Opera announced that «The neutrinos are circulating faster than the speed of light» The CERN SUrvey team was of course involved in these announcement as it participates since beginning of 2011 in the determination of the distance in collaboration with the University of Roma appointed by Opera for this calculation

5 Geographical situation 5

6 Ingredients to calculate the distance 6 GNSS measurements between benchmarks in CERN and Gran Sasso to get co-ordinates in a global coordinates system A network of measurements to link the benchmarks on the surface at CERN to the SPS/CNGS tunnel points including a vertical descent A network of measurements to link the benchmarks on the surface at Gran Sasso to the LNGS lab including a traverse of 11 km from the extremities of the motorway tunnel to the lab

Initial determination of the parameters 7 Initial calculation was done in the late 90 s The angular precision requested at that time in both H and V was ~15 arc seconds at 3s (~50m at

7 Initial determination of the parameters 7 Initial calculation was done in the late 90 s The angular precision requested at that time in both H and V was ~15 arc seconds at 3s (~50m at 730km) The orientation of CERN site was vital NOT the distance between both sites GPS measurements done on both sites CERN network was known at +-5mm 2 new points were determined in LNGS

8 Initial determination of the parameters 8 No link between surface benchmarks and tunnel at CERN the previous link was done in the 80 s for the LEP The uncertainty was considered to be less than mm A redetermination of the transformation between the Cern Co-ordinate system (CCS) and ITRF97 (ep ) was realised with the collaboration of OFT (Federal Office of Topography)) A new geoid was defined as the levelling measurements are linked to it Co-ordinates of the CERN target known in CCS

9 Initial determination of the parameters 9 Link between surface benchmarks and Experiments at LNGS As the access to the lab from Surface is a road tunnel of 11 km and it was difficult and expensive to close the motorway The original survey data and design plans were used to determine co-ordinates of some reference points The LNGS points were then transformed in the ROMA40 reference frame, then in ITRF97 and then in the CERN Coordinate System A (CCS) We got two angles and a distance m C B D E

10 Redetermination of the distance 10 The OPERA team observes some anomaly of 60 ns in the speed of neutrinos (equivalent to m) Interest for the distance CERN-OPERA Main uncertainty was link in LNGS July 2010 a traverse was done to link 4 benchmarks and the OPERA experiment using a total station TS30 (no gyrotheodotite measurements) Local system taking into account the geoid undulation The OPERA reference point accuracy estimated to be with 200mm September 2010, GNSS measurements done of the 4 benchmarks and on 3 permanent antennas of EPN Data processing in ETRF2000

11 Redetermination of the distance 11 On the CERN site, co-ordinates were transformed to ITRF97 and then to ETRF2000 The estimated accuracy was still mm New distance calculated m ~ +14 m difference coming from the difference of point measured in LNGS All computations were done by the University of Roma Global accuracy 200mm

12 Possible additional controls 12 Meeting at CERN in February 2011 Independant treatment of GPS and traverse measurements Simultaneous GNSS measurements on both sides Add gyrotheodolite in the traverse in LNGS Link between surface benchmarks and tunnel at CERN These possibilities were considered taking into account difficulty and cost w.r.t the decrease of the uncertainty

Additional distance controls 13 GNSS measurements done in Spring 2011 No major changes in the accuracy estimate Recalculation of the 2010 and 2011 GNSS measurements Permanent GPS Station Done by CERN

13 Additional distance controls 13 GNSS measurements done in Spring 2011 No major changes in the accuracy estimate Recalculation of the 2010 and 2011 GNSS measurements Permanent GPS Station Done by CERN in June 2012 with the collaboration of ESGT using Bernese (ITRF2008 >ETRS89) GPS Measurements transformation into CCS with a Helmert transformation All coordinates in CCS gives a new estimated distance of (difference of 75 mm)

14 Link between benchmarks and tunnel 14 On the CERN site the link was done between points at the surface and some points on the CNGS line GPS benchmarks Others stations BCT : origin of the timing measurements

Vertical descent 15 Shaft of 50-60 m deep The plumb bobs

15 Vertical descent 15 Shaft of m deep The plumb bobs technique Forced centring systems Station Station Station BCT in CNGS/TT40

Vertical descent 16 Shaft of 50-60 m deep The zenith optical

16 Vertical descent 16 Shaft of m deep The zenith optical plummet Forced centring systems Station Station Station BCT in CNGS/TT40

17 Vertical descent 17 Results Difference between points at surface and plumb bobs points underground are in the range of 0.1 mm Differences with zenith optical plummet and the value was worse 0.8 mm As a whole surface pillars and CNGS beam components relative position has been found to be within an accuracy of 16 mm But with an rotation of 14 mgon This was nonetheless a confirmation of our estimate of mm

18 Conclusions 18 The distance has been redetermined with several types of measurements The estimated accuracy of the distance between CERN and LNGS is within 200mm A number of different controls have been carried to minimise the risk of measurements and/or computations The error could be reduced by adding gyrotheodolite measurements on the LNGS side

19 Conclusions (cont d) 19 Finally it appered that a connection fault in the timing system was at the origin of the 60ns anomaly EINSTEIN is still right : particles are NOT going faster than c

Analysis and Evaluation of the CERN Reference Systems

Analysis and Evaluation of the CERN Reference Systems Nerea Ibarrola EN/ACE-SU, CERN International Workshop on Accelerator Alignment 2016 ESRF, Grenoble 04 October 2016 Index Introduction to the FCC Project