Measurement of chamber torsion versus the

1
Measurement of chamber torsion versus
the difference between the chamber sag at the Z
and Z side. G.J. Bobbink,
H.v.d.Graaf CERN, Nov. 10, 2005 Chamber
BOL 3A13 Location sector 13, on rails, in situ,
supported kinematically
2
The sag of chamber BOL 3A13 was pre-adjusted and
re-measured before (see previous reports, added
to this report). On Nov. 10, the sag at the Z
and at the Z sides was varied, in a random
way, independent of one another.
3

• InPlane data Y1, Y2, Y3 and Y4 were used. Note
  that RASNIK values are
• expressed in mask displacements equals 2x lens
  displacement.
• correct for offsets use calibration values
• differential sag Y1 Y4
• torque Y2 Y3

4
Due to the kinematical (3-point) support, the
chamber torque varies with the differential sag.
The relation appears to be linear, and quite
strong. From the previous plot one can derive
that, at the cost of a differential sag of 0.2
mm, the chamber torsion can be eliminated. At
this setting, the wire is off by ¼ x 0.2 mm from
the tube axis, at the centre of the tube. This
deviation would not affect the R-t relation. The
question is if it is useful to adjust the chamber
such that its torsion is minimal since the
torsion is monitored by the InPlane Rasnik system.
5
BOL Chamber Sag Adjustment in the ATLAS
pit Gerjan B, Harry vd G CERN,
ATLAS pit, Sept 7, 2005 Chambers BOL 1A31
(BOL59) BOL 2A13 BOL 3A13
6
Short In the period of 30 Aug Sept 7, the first
three BOL chambers were installed in sector 13 of
the ATLAS Muon Spectrometer. After their arrival
on the rails, the InPlane systems were read out,
and the chamber sag was adjusted such that the
tube sag equals the wire sag.
7
See plot above the Y values of the InPlane
systems during the sag adjustment procedure of
BOL 1A13. Since the alignment is expressed in
terms of mask displacement, the actual sag is
smaller by a factor 2. The plot shows raw data
only corrected for the offsets in the production
database see http//www.nikhef.nl/pub/e
xperiments/atlas/cosmicray/sag/sag.php The sag of
this chamber was was adjusted before see
http//www.nikhef.nl/d90/rasnik/ChaRot.ppt After
arrival on the rails, the chamber sag was off by
200 µm from its target value of 0.810 mm, which
may be expected after two rotations of 180
deg. Note that the values of InPl_2 and InPl_3
deviate in a symmetrical way from the chamber
sag. This is due to chamber torsion.
8
The RASNIK Y values for BOL 2A13 during is sag
adjustment procedure. The chamber was sag was
adjusted before for the Cosmic Ray Test Station
at NIKHEF, which corresponds roughly to the
chamber sag in ATLAS sector 5. The deviation
of 4.7 mm tallies with the known free sag of
the chamber. Note that the chamber torsion
changes during the sag adjustment. In fact, the
chamber torsion could be adjusted at the cost of
a small variation in the sag along the
Z-axis. This may be a future (new) criterion for
the final sag adjustment.
9
The sag adjustment data for BOL 3A13. The chamber
sag was probably never adjusted before, so the
the chamber sag was equal to the pure sag for a
neutral built chamber.
10

• Conclusions
• The chamber sag can be monitored and adjusted on
  the rails in ATLAS
• The kinematical support allows a reduction or
  elimination of the chamber
• torsion at the cost of s difference in sag of
  the Z and Z sides of the chamber
• A remote-controlled, preferably wireless, RASNIK
  readout system
• would be a convenient tool
• the BOL chambers behave, concerning sag, like
  ideal bars
• The BOL sag adjustment may be done exclusively
  after mounting the chamber
• onto its rails, provided that the functionality
  of the InPlane systems has been
• checked to be OK.

11
BOL Chamber Sag Adjustment Procedure Lu
do P, Gerjan B, Harry vdG CERN, ChezLudo,
August 4-5, 2005 Chamber BOL1A31 (BOL59)
12
940 Most left-hand data point sag in
CosmicRayTestStation at NIKHEF horizontal (up)
position.. This sag (-0.405 mm) equals the wire
sag. This data point has been added manually to
this plot. 942 1000 Chamber mounted in
rotation frame. Chamber sag is reduced
with respect to sag at NIKHEF due to shift of
chamber supports towards chamber centre. 1004
1011 Rotation frame is rotated 90 deg. 1011
1015 Rotation frame is lifted and shifted to
gain space for following rotation. 1015
1019 Rotation frame is rotated from 90 deg to
180 deg. 1025 1045 Sag adjustment to target
InPlane values for sector 13 position ( 0.405 mm)
13

• Chamber sag
• Concerning sag, the BOL chambers behave simply
  like perfect bars. The sag of BOL is
• negligible during construction, and so is the
  intrinsic tension. The sag of a new chamber,
• in its final common support follows the sinus in
  the previous Chamber Sag plot.
• The sinus amplitude equals 1.47 mm (for BOL).
• For horizontal chambers in sector 5, this sag
  should be reduced to 0.405 mm, being
• the wire sag. This sag reduction of 1.07 mm takes
  6 or 8 of 1/6 turns of the spindle of the
• middle cross plate.
• Since the BOL chambers behave like perfect bars,
  the sag compensation can be calculated
• in advance, and the InPlane target values can be
  calculated for each sector, and for a
• chamber in any angular position.
• Remarks on Sag Adjustment Procedure
• As soon as a chamber has been fixed in the
  rotation frame, sag adjustment could be done
• without rotating the rotation frame. The
  chamber will have its target sag when arrived in
• its final angular position (on the magnet
  rails). This limits the required adjustment time
• downstairs, and surprises are avoided.
• After arrival on the magnet rails, the InPlane
  system should be read out. A final (small)
• adjustment may take place.

14

• - It would be convenient if the RASNIK images
  could be monitored for this a large
• video monitor should be installed.
• A new version of ICARAS is in preparation in
  which the RasMux and MasterMux
• numbering is correct (NIKHEF).
• - We should agree soon about who performs chamber
  sag adjustment.
• The image analysis should be improved unsharp,
  dark, and gray images fail
• too often (NIKHEF).
• Simple means are needed to prevent too much
  false light entering the RasCam (NIKHEF)
• A palmtop (or laptop) next to the sag adjustment
  spindle, displaying images and
• sag and target values, would be convenient
  (NIKHEF).