Survey and Alignment

							GPS Survey and Alignment

           NP04(nu)
         Aug. 24, ２００４
      Takanobu ISHII (KEK)




                             1
GPS Survey and Conventional Survey
 •GPS (static) survey
    •accuracy d = a*L + b
       a = 1*10-6
       b = 5mm : horizontal, 10mm : vertical
       L : baseline, 1000km possible
    •direct survey possible for a long baseline
    •four or more GPS satellites needed in the sight
    •several hours of data taking
 •Conventional survey
    •accuracy d = a*L + b
       a = several*10-6
       b = 2mm
       L : baseline, < several km
    •survey network needed for a long baseline
      we do not know well the error coming from this network
                                                               2
          GPS Survey for T2K
•Long-baseline GPS survey had been performed in 2001.
•Then, GPS 0th reference points: TT, TH and TR were
 established at the Tokai site.

•Local GPS survey was done in May 2004.
•GPS 1st reference points: K1, K2, K3, K4, K5 and K6
 were established near the neutrino beam line.
•Reference points D1, T and D2 were established on
 the designed decay-volume line based on
 the construction reference points: B0 and B1, and
 were surveyed based on the GPS 1st reference points.




                                                        3
    Survey Points at the Tokai Site

           TT                          TH



N


                    B-0




                               GPS 0th points
                  TR           Target point
                   Beam        Construction
                   direction    reference points 4
GPS 1st Reference Points and Decay-Volume Reference Points
                  Established in May 2004




                                                         5
Decay-Volume Reference Points



                           D2



                           T



                           D1

                                 6
          Results of the GPS Survey
Based on B0, B1                    Based on the GPS survey
T : X=49754.835, Y=69409.449 T : X=49754.884, Y=69409.430
D2: X=49753.112, Y=69280.721 D2: X=49753.154, Y=69280.710
                (X: north-south, Y: east-west)
         Difference T : dX=-49mm, dY=19mm
                      D2: dX=-42mm, dY=11mm
         We do not care a parallel shift.
         Direction difference: 7mm/129m = 6x10-5
                       Good accuracy
    B0, B1                              K1, K2, K3, K4, K5, K6
                       for physics

 A1, A2, A3, A4                                TT, TH, TR

Triangulation points                   GPS-based control points
                                                                  7
GPS-based Control Points Near Tokai


            Tokai site   Since about 10 years ago
                         About 1000 points in Japan




                                                      8
Network of Triangulation Points

                Established about 100 years ago.
                Accuracy is about 10cm.




                                                   9
Triangulation Points near Tokai

                     Construction reference points:
                     B0 and B1 had been surveyed
                     based on three triangulation points
                     near Tokai.
                     B0 and B1 are the reference points
                     for all the surveys of the J-PARC
                     construction.


       B0    B1


        Tokai site
                                                           10
     Penetration Holes to the Underground
             (Secondary datum points)


        M2
N2                                T

 N1     M1                              T1
                                   T2




 N
                                             P1




                                                  11
    Image of a Penetration Hole
                             Have to be covered
            Datum point      usually
            (monument)

      100-200mmf pipe


Penetration holes will be
located in the sub-tunnels
due to radiation.




                                              12
Survey at the Underground




                            13
    Required Alignment Precision
From the beam optics (Ichikawa-san),
in order not to reduce admittance,
   Dx, Dy should be smaller than 300 mm.
   Dz should be smaller than 5 mm.
   Df should be smaller than 0.1 degree.




                                           14
        Survey Accuracy
ms = m0√Q
 m0 : intrinsic accuracy
 √Q : constant of the survey network

 m0 = 100mm : conventional survey
       20mm : laser tracker

 √Q depends on the survey network.


                                       15
       Use of a Laser Tracker
Characteristics of a laser tracker
•better intrinsic accuracy (20mm)
•effective for arc section
 (For a straight survey, conventional method is easier)
•expensive (we may borrow from other group)
•needs experts to operate
•needs to place tables for a reflector along the tunnel
  and on each component
•straight section by a conventional method ?


               Table for a reflector
               standard design for
               the B-factory
                                                      16
Laser Tracker Survey at the PF Ring




                                      17
Reflector at a PF Magnet




                           18
Base of the Reflector and Precise Hole
for the Base on a 50GeV-Ring Magnet




Base for
quick and precise attachment
                                         19
       Comment from the nuTAC
Comment:
Some method of checking the amount of settling and correcting
the component alignment, if necessary, should be considered.

Survey will be repeated several times to check sinking
after installation of all the components at least till the beam
starts.
Final focusing section is important for the beam direction.
So, it will be surveyed every year based on T1 and T2
during the maintenance period.



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