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ATLAS SCT detector alignment and field map

VIEWS: 4 PAGES: 23

									                   A year of ATLAS preparation.            Steve Snow
                                                           New Year 2006
                                 What I did last year


• Inner detector magnetic field map fit.
• SCT detector alignment.
• NMR probe preparation.
• Write/edit endcap module paper
• SCT status paper at PSD7.
• Organise seminars
• SuperNEMO tracker.
•   CALICE thermal simulation.



                                 My ATLAS aims

The resolution of tracks reconstructed in ATLAS ID should be:
• Good enough for some physics from the first collisions
• Rapidly improved by using track-based alignment tools
• Eventually good enough that track systematic errors do not
dominate the measurement mW to ~15 MeV
This and following slides
copied from Paul
Miyagawa's talk at the
2nd ATLAS magnetic field
workshop
                                Field map objectives
       •   A useful test of the Standard Model would be measurement of W mass with
           uncertainty of 25 MeV per lepton type per experiment.
       •   W mass derived from the position of the falling edge of the transverse mass
           distribution.
       •   Momentum scale will be dominant uncertainty in W mass measurement:
            – Need to keep uncertainty in momentum down to ~15 MeV.
       •   Measure isolated muon tracks with pT ~ 40 GeV over large range of η:
            – Uncertainty in energy loss negligible.
            – Concentrate on alignment and B-field.
       •   Momentum accuracy depends on ∫ r(rmax - r)Bzdr :
            – Field at intermediate radii, as measured by the sagitta, is most important.
       •   Typical sagitta will be ~1 mm and target accuracy would be 0.02%, implying a
           systematic error on sagitta of 0.02 μm:
            – Technically impossible!
            – Will need to use Z mass, which is nearby and very well known.
       •   In reality, the limit on silicon alignment, even with infinite statistics and ideal
           algorithms, will be ~1 μm.
       •   We target an accuracy of 0.05% on sagitta to ensure that B-field measurement
           is not the limiting factor on momentum accuracy.
                                 Field shape.
                    25000                                               r=0.2
                                                                        r=0.4
                    20000                                               r=0.6
                                                          Z component   r=0.8
                    15000                                               r=1.0
                                                                        r=1.2
                    10000
                                                                        r=0.2
    Field (gauss)




                     5000                                               r=0.4
                                 R component
                                                                        r=0.6
                        0                                               r=0.8
                                                                        r=1.0
                               0




                             36




                             72
                              2

                              4

                              6

                              8



                              2

                              4

                              6

                              8



                              2

                              4
                            27

                            54

                            81

                            08



                            63

                            90

                            17

                            44



                            99

                            26
                     -50001.




                          2.
                         0.

                         0.

                         0.

                         1.



                         1.

                         1.

                         2.

                         2.



                         2.

                         3.
                                                                        r= 1.2
                                          Bending power
                    -10000                                              r=0.2
                                                                        r=0.4
                    -15000                                              r=0.6
                                                                        r=0.8
                    -20000
                                                                        r=1.0
                                      Z (m)
                                                                        r=1.2

The field is very non-uniform at the ends of the coil; the Z component drops off
and the R component rises sharply at z=2.65 m. Also plotted is the bending
power per unit of radial travel for straight tracks coming from the origin.
                                                                 Mapper Survey Requirements
      •                          At first workshop, survey requirements
                                 of mapper machine relative to Inner                                                                   8
                                 Detector were reported as ~1 mm and                                                                   6
                                                                                                                                                                        Effect of 1 mm displacement in X direction
                                                                                                                                                                                                                                    phi 1
                                 ~0.2 mrad.




                                                                                                                       Relative sagitta error x 10^4
                                                                                                                                                                                                                                    phi 2
                                                                                                                                       4
      •                          Reinvestigated these requirements.                                                                    2
                                                                                                                                                                                                                                    phi 3
                                                                                                                                                                                                                                    phi 4
      •                          1 mm survey error in x (or y) significant                                                             0
                                                                                                                                                                                                                                    phi 5
                                 for high η tracks.                                                                                                                                                                                 phi 6




                                                                                                                                  .5

                                                                                                                                                          .1

                                                                                                                                                                  .7

                                                                                                                                                                           .3

                                                                                                                                                                                   .9

                                                                                                                                                                                   .5

                                                                                                                                                                                           .1

                                                                                                                                                                                                  3

                                                                                                                                                                                                        7

                                                                                                                                                                                                              1

                                                                                                                                                                                                                    5

                                                                                                                                                                                                                          9

                                                                                                                                                                                                                                3
                                                                                                                                                                                                0.

                                                                                                                                                                                                      0.

                                                                                                                                                                                                            1.

                                                                                                                                                                                                                  1.

                                                                                                                                                                                                                        1.

                                                                                                                                                                                                                              2.
                                                                                                                                     -2                                                                                             phi 7




                                                                                                                               -2

                                                                                                                                                       -2

                                                                                                                                                               -1

                                                                                                                                                                        -1

                                                                                                                                                                                -0

                                                                                                                                                                                -0

                                                                                                                                                                                        -0
      •                          1 mm survey error in z significant for                                                              -4
                                                                                                                                                                                                                                    phi 8

                                 endcap tracks.                                                                                                                                                                                     phi 9
                                                                                                                                                                                                                                    phi 10
                                                                                                                                     -6
      •                          0.1 mrad rotation around x (or y) axis
                                 significant for high η tracks.
                                                                                                                                     -8
                                                                                                                                                                                     Pseudorapidity
      •                          Conclusions remain unchanged.

                5                                                                                                                       8
                                                        Effect of 1 mm displacement in Z direction                                                                     Effect of 0.1 mrad rotation around the X axis
                4                                                                                                                       6
                                                                                                              phi 1                                                                                                                 phi 1



                                                                                                                       Relative sagitta error x 10^4
Relative sagitta error x 10^4




                3                                                                                             phi 2                                                                                                                 phi 2
                                                                                                                                        4
                2                                                                                             phi 3                                                                                                                 phi 3
                                                                                                              phi 4                     2                                                                                           phi 4
                1
                                                                                                              phi 5                                                                                                                 phi 5
                0                                                                                                                       0
                                                                                                              phi 6                                                                                                                 phi 6
                                                                                                                                  .5

                                                                                                                                                          .1

                                                                                                                                                                  .7

                                                                                                                                                                           .3

                                                                                                                                                                                   .9

                                                                                                                                                                                   .5

                                                                                                                                                                                           .1

                                                                                                                                                                                                  3

                                                                                                                                                                                                        7

                                                                                                                                                                                                              1

                                                                                                                                                                                                                    5

                                                                                                                                                                                                                          9

                                                                                                                                                                                                                                3
           .5

                                   .1

                                           .7

                                                   .3

                                                           .9

                                                           .5

                                                                     .1




              -1
                                                                            3

                                                                                  7

                                                                                        1

                                                                                              5

                                                                                                    9

                                                                                                          3




                                                                                                                                                                                                0.

                                                                                                                                                                                                      0.

                                                                                                                                                                                                            1.

                                                                                                                                                                                                                  1.

                                                                                                                                                                                                                        1.

                                                                                                                                                                                                                              2.
                                                                                                                                     -2                                                                                             phi 7
                                                                          0.

                                                                                0.

                                                                                      1.

                                                                                            1.

                                                                                                  1.

                                                                                                        2.




                                                                                                              phi 7
                                                                                                                               -2

                                                                                                                                                       -2

                                                                                                                                                               -1

                                                                                                                                                                        -1

                                                                                                                                                                                -0

                                                                                                                                                                                -0

                                                                                                                                                                                        -0
        -2

                                -2

                                        -1

                                                -1

                                                        -0

                                                        -0

                                                                  -0




              -2                                                                                              phi 8                                                                                                                 phi 8
                                                                                                                                     -4
              -3                                                                                              phi 9                                                                                                                 phi 9
                                                                                                              phi 10                 -6                                                                                             phi 10
              -4
              -5                                                                                                                     -8
                                                                Pseudorapidity                                                                                                       Pseudorapidity
Field Mapping Simulation
  •   Field model sampled on a grid of 90 z-
      positions × 8 -angles (defined by encoder
      values of machine).
  •   4 calibration points (2 near centre, 2 near one
      end) visited after every 25 measurements.
  •   Used current design of machine to determine
      positions of 48 Hall + 1 NMR probes.
  •   At each map point, wrote the following data
      to file:
        – Time stamp
        – Solenoid current
        – z and  encoder values
        – Field modulus measured by 5 NMR
             probes (1 moving + 4 fixed)
        – 3 field components measured by 48 Hall
             probes
                              Simulated Errors
Six cumulative levels of error added to simulated data:
1.    No errors.
2.    Random errors in each measurement of:
     •       Solenoid current, 1 A
     •       NMR B-field modulus, 0.1 G
     •       Each component of Hall probe B-field, 3 G
3.       Drifts by random walk process in each measurement of:
     •       Solenoid current, 1 A
     •       Each component of Hall probe B-field, 0.1 G
4.       Random calibration scale and alignment errors, which are constant for each
         run:
     •       Each component of Hall probe B-field, 0.05% scale
     •       Rotation about 3 axes of each Hall probe triplet, 1 mrad
5.       Symmetry axis of field model displaced and rotated relative to the mapper
         machine axis. These misalignments are assumed to be measured perfectly
         by the surveyors.
6.       Each Hall probe triplet has a systematic rotation of 1 mrad about the axis
         which mixes the Br and Bz components.
                Correction for Current Drift
•   Average B-field of 4 NMR probes
    used to calculate “actual” solenoid
    current.
•   Scale all measurements to a
    reference current (7600 A).
•   Effect of drift in current removed
•   Calibration capable of coping with
    any sort of drift.
            Correction for Hall Probe Drift

• Mapping machine regularly
  returns to fixed calibration
  positions
    – Near coil centre to calibrate Bz
    – Near coil end for Br
    – No special calibration point for B
• Each channel is calibrated to a
  reference time (beginning of run)
• Offsets from calibration points
  used to determine offsets for
  measurements between
  calibrations
    Fit Quality with Expected Performance
                                                           0.6
                                                                                                                                             phi 1




                           Relative sagitta error x 10^4
                                                           0.5                                                                               phi 2
• Expected mapper                                          0.4
                                                                                                                                             phi 3
                                                                                                                                             phi 4

  performance                                              0.3
                                                                                                                                             phi 5
                                                                                                                                             phi 6

  corresponds to error                                     0.2                                                                               phi 7
                                                                                                                                             phi 8
                                                                                            Geometrical fit. Error level 5
  level 5.                                                 0.1                                                                               phi 9
                                                                                                                                             phi 10
                                                            0

• Both fits accurate

                                                              .5

                                                              .1

                                                                             .7

                                                                             .3

                                                                             .9

                                                                             .5

                                                                             .1

                                                                                                           3

                                                                                                                 7

                                                                                                                       1

                                                                                                                             5

                                                                                                                                   9

                                                                                                                                         3
                                                                                                         0.

                                                                                                               0.

                                                                                                                     1.

                                                                                                                           1.

                                                                                                                                 1.

                                                                                                                                       2.
                                                           -2

                                                           -2

                                                                          -1

                                                                          -1

                                                                          -0

                                                                          -0

                                                                          -0
                                                                                                 Pseudorapidity
  within target level of
  5×10-4.                                                  6


                                                           4                                                                                 phi 1
                           Relative sagitta error x 10^4




                                                                                                                                             phi 2
                                                                                                                                             phi 3
                                                           2
                                                                                                                                             phi 4
                                                                                                                                             phi 5
                                                           0
                                                                                                                                             phi 6
                                      .5

                                                                    .1

                                                                            .7

                                                                                    .3

                                                                                            .9

                                                                                            .5

                                                                                                    .1

                                                                                                           3

                                                                                                                 7

                                                                                                                       1

                                                                                                                             5

                                                                                                                                   9

                                                                                                                                         3
                                                                                                         0.

                                                                                                               0.

                                                                                                                     1.

                                                                                                                           1.

                                                                                                                                 1.

                                                                                                                                       2.
                                                                                                                                             phi 7
                                   -2

                                                                 -2

                                                                         -1

                                                                                 -1

                                                                                         -0

                                                                                         -0

                                                                                                 -0
                                                           -2
                                                                                                                                             phi 8
                                                                                           Fourier-Bessel fit. Error level 5                 phi 9
                                                           -4
                                                                                                                                             phi 10

                                                           -6
                                                                                               Pseudorapidity
                             Probe normalisation and alignment corrections
                                 Hall probe triplets are accurately perpendicular to each other, but their mounting
                                 on mapper can have ~1 mrad errors.
                                 Hall probe calibration will probably be good to 0.1% but we can improve it by
                                 taking normalisation from the NMR probe at Z=R=0.
                                 We get best results by calculating PNA corrections with a variant of the Fourier-
                                 Bessel fit and using the corrected values in the geometrical fit :
                   30                                                                                                                     6
                                   Before probe normalisation and alignment corrections                                                                Before probe normalisation and alignment corrections
                                   After probe normalisation and alignment corrections                                                                 After probe normalisation and alignment corrections

                   20                                                                                                                     4




                                                                                                          Relative sagitta error * 10^4
                   10                                                                              Mean                                                                                                                Mean
                                                                                                                                          2
                                                                                                   RMS                                                                                                                 RMS
Bz error (Gauss)




                                                                                                   Max                                                                                                                 Max
                                                                                                   Min                                                                                                                 Min
                    0                                                                                                                     0
                                                                                                   Mean                                                                                                                Mean
                         1   2      3        4       5        6        7        8         9   10                                               1   2   3        4        5        6        7        8         9   10
                                                                                                   RMS                                                                                                                 RMS
                                                                                                   Max                                                                                                                 Max
                   -10                                                                                                                    -2
                                                                                                   Min                                                                                                                 Min



                   -20                                                                                                                    -4



                   -30                                                                                                                    -6
                                        Ten runs with different random errors                                                                              Ten runs with different random errors
                Field fitting conclusions
• With no simulated errors, both fits have excellent technical
  accuracy.
• With realistic simulated errors, both fits give results within
  target of 5×10-4.
• Fourier-Bessel fit more sensitive to random measurement
  errors:
   – Due to more free parameters.
   – F-B fit designed for any solenoid-like field, whereas geometrical
     fit is specifically for the ATLAS solenoid.
• Probe normalisation & alignment correction from F-B fit
  helps significantly.
• Require survey of mapper machine relative to Inner
  Detector to be accurate to ~1 mm.
             Modified copy of slide from last year

                                    Initial SCT Alignment
            I have been promoting the idea making an initial SCT alignment based on
X-ray
            conventional surveys. This is a backup / alternative to the Oxford plan for
survey
now         an X-ray survey combined with FSI monitoring. The accuracy of the SCT
cancelled   endcap as built, and as surveyed is now becoming clear
            Intrinsic resolution of SCT detector; 22 mm (just under pitch/12).
            Detector positions in module; build 4 mm , survey 1 mm (Joe's talk).
            Location holes in module; build 10 mm , survey 3 mm.
            Module mounting pins on disc; build 100 mm , survey 10 mm.
            Discs in support cylinder; build 200 mm , survey 100 mm.
            Hole to pin clearance; <10 mm .
            Stability of mounting pins on disc; 20 - 50 mm . (temperature, moisture,bending )
                                     7 microns random + 50 microns systematic (proportional to distance)
                        SCT endcap alignment from surveys
   Module internal alignment                       Pin alignment                              Disc alignment
  Relative positions of the four           Relative positions of the module           Relative positions of the 9 discs
  detectors and two mounting               mounting pins on discs.                    in each endcap
  holes.
                                           Corrections of ~100 um known to            Corrections of ~200 um known to
  Corrections of ~5 mm known to            ~10 um.                                    ~100 um.
  ~1 mm.

  Module production database              Tables of pin position offsets            Survey reports of disc alignment
                                          from nominal in each disc.                in each endcap.
  Completed July 05
                                          Collecting data from surveys done         First few reports available from
                                          at Liverpool (Peter Sutcliffe) and        endcap C.
                                          NIKHEF (Patrick Werneke).
 Understand and correct for small                                                   Surveys should be repeated when
 (1-2 um) systematic differences          Steve Snow. Endcap C complete,            the endcaps reach CERN.
 between surveys done at different        endcap A discs 9,8,7,6,5,4 done.
                                                                                    Steve Snow. In progress.
 sites.
 Joe Foster. In progress.
                                                            Detector/module
                                                            offsets from nominal                   Detector/module
                                            combine
   Corrected final module data.                             in each disc.                          offsets from nominal
   Joe Foster. Expected Jan 06                                                                     in each endcap.
                                                            Steve Snow, Joe
                                                            Foster.                                Steve Snow, Joe Foster.
                                                            Expected March 06.                                  Expected
Tables associating module serial number                                                            May 06.
with position mounted on disc.
Joe Foster. Endcap C complete. Endcap A                         Learn how to load data into, and use data
expected December 05.                                           from, the conditions database. Upload this ?
                                                                or this ? data
                                                                Paul Miyagawa. Expected July 06.
                                              Disc surveys
 Survey of module mounting pins on all endcap C (UK) discs is complete.
                           150
                                                   Overlap statistics

                                                                                    O-rms
                           100                                                      O-max
                                                                                    O-min
                                                                                    M-rms
                            50                                                      M-max
       Overlap (microns)




                                                                                    M-min
                                                                                    I-rms
                             0                                                      I-max
                                  1   2   3    4         5         6    7   8   9   I-min
                                                                                    O-tol
                            -50                                                     M-tol
                                                                                    I-tol
                                                                                    O-tol
                           -100                                                     M-tol
                                                                                    I-tol


                           -150
                                                   Disc number




Actual phi overlap between neighbouring modules will always be within 120
microns of the design value, and typically within 50 microns.
Strip pitch is 80 microns, design overlap is 5,8,18 strips. (I,M,O rings)
There will always be a small but useful overlap between modules to use for
alignment with tracks.
                                       Steve Snow
             NMR system                26/10/05

                                       Technical support
                                       in Manchester:
• Purpose and description of the NMR   Julian Freestone,
                                       Mike Perry
• Overview of system                   CERN contact:
                                       Pippa Wells
• Parts of the system
• Software for:   Noise tests
                  Signal tests
• Installation and Commissioning
• Configuration during field mapping
                                 Overview
    Aim is to measure the magnetic field strength in the Inner Detector.
NMR requires a very uniform field (<250 ppm/cm) so we must place the
probes at z=0. Extrapolation to other parts of the Inner Detector relies
increasingly on the field map as one moves towards the end-caps.
NMR is intrinsically accurate; it it works at all we get a result accurate
within a few x 10 ppm.
Based on a system supplied by Metrolab, with modifications to improve
radiation hardness of the probe and cables.
Operating at/beyond the limits of some specifications:
        • expected field gradient is 310 ppm/cm
        • probe-amp cable length is 15m, Metrolab standard is 7m
        • amp-readout cable length is 125m, standard is up to 100m
Metrolab say their specifications are conservative and this should be no problem.
   NMR
  system

Standard Metrolab
system with the
addition of Pico
2-channel digitiser
and PC to monitor
noise, pickup,
signal size, etc.
Grounded only at
ID ground point.
Readout using
LabVIEW on PC.
Interface to DCS
not yet defined.
       Parts of the system                  Probe in
                                           clamp on
All of the hardware is ready.           cryostat wall
Some software still being developed.

                                Probe

                                                            Amplifier




                                                        Readout
                          Cables
Noise Tests          The only thing likely to prevent the NMR
                     system from working is noise pickup.
      In lab, pickup depends strongly on layout of cables ; as soon as cables are laid
      in Atlas we want to measure noise and check it is not excessive.
      Maybe an opportunity to immediately re-route or bundle cables more tightly together. Final
      test is the ability to lock onto the NMR resonance - not possible until much later, when
      solenoid is turned on.


                                                   NoiseTest.VI - automates all
                                                   the NMR tests we can do in
                                                   absence of field.


                                                                  100

                                                                   80

                                                                   60

                                                                   40
                                                                                                                         r.m.s.
                                                                   20                                                    Max




                                                     Noise (mV)
                                                                                                                         Min
                                                                    0                                                    50 Hz
                                                                         28   38   48      58             68   78   88   100 Hz
                                                                   -20                                                   150 Hz
                                                                                                                         200 Hz
                                                                   -40

                                                                   -60

                                                                   -80

                                                                  -100
                                                                                        Frequency (MHz)



                                                     Noise test results in good conditions:
                                                                 r.m.s. ~ 20 mV, peaks < 100 mV
                                                                 mains pickup < random noise
                               Signal Tests
When the Teslameter is locked on the NMR resonance, as well as reading out the
field value we monitor peak height, peak asymmetry and noise (between peaks).


                                                                     SignalTest.VI
                 Mapping time scale
Latest ATLAS schedule shows mapping in April/May.
We will prepare for that date but I would be surprised if it
does not slip by 2 or 3 months.
                  Looking forward



100%
 90%
 80%                                                 Field map
 70%                                                 NMR
 60%                                                 Survey alignment
 50%                                                 Track alignment
 40%                                                 SuperNEMO
 30%
 20%
 10%
  0%
   2006                              2007



          My changing priorities in the next year.
                              Seminars
     11/01/06
     18/01/06    Experiment    Brian Fulton (York)       COBRA
     25/01/06    Theory
     01/02/06    Schuster
     08/02/06    Experiment    Yoshi Uchida (Imperial)   KamLAND
     15/02/06    Experiment    Tara Shears               LHCb
     22/02/06    Theory
     01/03/06    Schuster
     08/03/06    Experiment    Amanda Cooper-Sarkar
     15/03/06    Theory
     22/03/06    Experiment    Chris Booth               MICE
     29/03/06    Experiment    Alfons Weber              MINOS
     30/03/06    Experiment    Emily Nurse               CDF
     05/04/06    Schuster


Not yet fixed:
Martin Erdmann - Auger,        Dino Jaroszynski - plasma acceleration.

								
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