Download Cryomodule B: Transfer methodology of the cavities beam axis

Survey and Alignment Concept for Construction
of SPIRAL2 Accelerator
R. Beunard, A. Lefevre, F. Legruel, GANIL, B.P. 55027 14076 CAEN, CEDEX 5, France
Alignment/Instrumentation Group/Physics Technical Department
Thanks to all members of the GANIL design offices, as well as the colleagues from the other laboratories
involved in this project, particularly from IPN Orsay and the DAPNIA Saclay
1. Surveying instruments
Abstract
This poster covers the survey and alignment techniques selected
for installation of the SPIRAL2 accelerator devices.
Reflector
To determine the best technique for aligning any equipment, it is
essential to know the precision required for the six degrees of
freedom, and to understand the reasons for the requested
precision. An object is “located” by its fiducial marks. High quality
of mechanical connection to these marks is important in the final
precision of the location of the object.
Tacheometer
T3000A
Tacheometer
TDA 5005
2. The RFQ
Laser Tracker
3D measuring
portable arm
coded
invar rod
Level NA3003
Digital CCD System
connected to the Alignment
Telescope
3. The injector beamlines
RFQ Fiducialization
The localization of the RFQ
requires
fiducial
points
transferred on the top of the
vacuum vessel by adjustable
plates equipped with a conical
centering-surface for a TaylorHobson-Sphere. These spheres
are the only reference points
which will be accessible. Their
spatial coordinates will be given
in the reference system of the
object.
Network measurement for
metrological control of the vanes
and the fiducial points
Final survey
Wall
monument
The network measurement will be made with a laser tracker.
The reference network will consist of approximately 6 pillars
(green), 6 floor monuments (blue) and 4 laser tracker stations.
Two sets of angles and 8 interferometer distances will be
observed from each tracker station to all points.
Estimated global error: 60 m (RMS at 2).
Magnets Fiducialization
The fiducials are the points
located on the magnet with
respect to the theoretical
beam trajectory. Each beam
line
magnet
will
be
fiducialized with a reference
socket cup (CERN - type)
installed on the plate during
the process of alignment.
Tilt-meter
plate
Survey
reflector
Dipole
Fiducial
nest
Floor
monument
Diagnostic boxes
Fiducialization
alignment
target
0.5m
The tolerated maximum static errors for the global alignment of the
quadrupole and dipole magnets are:
• displacement (mm): ± 0.1
1 m
As opposed to surveying with a theodolite,
the use of a laser tracker will thus avoid
dismounting certain equipment such as
vacuum pumps or beam diagnostic devices
during the shutdown period to permit
alignment.
reflector
• rotations (X,Y) (deg): ± Qr  Qr=d/L with d the displacement and L the length of
the element
• rotations (Z) (deg): ± Qz  Qz=d/R with d the displacement and R the radius of
the element
The tolerated maximum static error for the global alignment of the diagnostic
devices is: ± 0.2 mm
4. The Superconducting Linac
Cryomodule A
 = 0.06
Cryomodule B
 = 0.12
The solution adopted to support the linac
components, is a welded-frame structure
equipped with guide rails. One advantage
of this solution is the possibility of bringing
a component into a laboratory together with
its support in order to do, for example, a
realignment of the cavities inside the
cryostat then to put it back on the beam line
under the same conditions, using the guide
rails.
Cryomodule B: Transfer
methodology of the
cavities beam axis
During assembly process, once the
cryomodule is closed, the interior of the
superconducting cavities cannot be
accessed outside a clean room. As a
result, the cavities are equipped with
optical targets “Taylor and Hobson”
mounted on an arm in order to facilitate
its adjustment inside the cryostat. The
optical targets fixed on the helium tank
are adjusted to be parallel to the cavity
axis.
The transfer was carried out by means of
inter-dependent tools in the two beam
tubes. The axis defined by the two beam
tubes and the nut drift tube is also
measured in order to define an average
axis between the three cylinders.
The adjustment was performed with an
error on the reported axis position of the
order of 0.1 mm.
Alignment concept
component fiducialization
tilt
As the components cannot be aligned
through the beam tube, the solution adopted
is to transfer new axes outside the object,
i.e. to the sides of their supports by
adjustable target boxes (fiducials). The
three-dimensional coordinate measurements
of these fiducials would be given in the
reference system of the accelerating tubes of
the cavities and the mechanical axis of the
poles for the magnets. The measurements
will be done by means of a portable-arm
coordinate-measuring machine.
fiducial
The measuring accuracy given by this
system is ± 0.06 mm (at 2 ).
fiducial
Cryomodule A:
Transfer
methodology
of the cavities
beam axis
The tolerated maximum static errors for the
global alignment are:
• ± 0.1 mm for the displacement of the
quadrupoles
• ± 0.03 deg for the rotations (X,Y) of the
quadrupoles
• ± 0.1 deg for the rotations (Z) of the quadrupoles
• ± 1.0 mm for the displacement of the cavities
• ± 0.3 deg for the rotations (X,Y) of the cavities.
Guide rail
Bench for component fiducialization
Qualifying cryomodule B: Measurement of the cavities
displacements during vacuum tests and cooling down
The measurement campaign was conducted in two stages because stability to 4K is obtained only after 2 to 3 days. The first campaign concerns the impact
due to the vacuum and the second due to the cooling down. The technical principles include an optical method by using a Taylor and Hobson telescope. The
displacements were measured on the optical targets inserted into the arms outside cavities.
Once the cryomodule is closed,
it is no longer possible to
change the cavity position with
respect to the vacuum tank.
External references of the
cavity position will allow the
alignment of one cryomodule
cavity with respect to the other
ones. Previous measurements
of the cavity beam axis
displacement during cool-down
will be necessary to check the
calculation. This will be made
using a bare cavity.
View of cryomodule
installed on the bench for
measuring
tilt meter
fiducial
Transfer
beam axisBeam axis
Transfer
beam axis
Location of the measured
points
QWR (beta =0.12)
2 cavities
QWR (beta =0.07)
1 cavity
Journées Accélérateurs de la SFP
Roscoff, 12-14 octobre 2009