support system and alignment
DESCRIPTION
Support System and Alignment. Sushil Sharma ME Group Leader ASAC Review of NSLS-II July 17-18, 2008. Support System and Alignment Team. - PowerPoint PPT PresentationTRANSCRIPT
1 BROOKHAVEN SCIENCE ASSOCIATES
S. SharmaASAC July 17-18, 2008
Support System and Alignment
Sushil SharmaME Group Leader
ASAC Review of NSLS-IIJuly 17-18, 2008
2 BROOKHAVEN SCIENCE ASSOCIATES
S. SharmaASAC July 17-18, 2008
Support System and Alignment Team
R. Alforque, M. Anerella, C. Channing, L. Doom, G. Ganetis, P. He, A. Jain, P. Joshi,P. Kovach, F. Lincoln, S. Plate, V. Ravindranath, J. Skaritka
and
Alexander Temnykh(Cornell University, Ithaca, NY)
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Outline
Introduction Alignment specifications
Support design concept Magnet alignment and positioning Girder alignment and positioning
Stability specifications Vibration – FE analyses and measurements Thermal – FE analyses and test setup
Conclusions
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Introduction
Storage Ring Cell
LOBBooster
Storage Ring
• Energy: 3 GeV• Circumference: 792 m• Lattice: 30 DBA Cells (15 Super periods)• Low Emittance: 2 nm-rad without damping wigglers 0.6 nm-rad with damping wigglers (56 m)
The low-emittance lattice has stringent alignment and stability requirements that have been met by innovative and cost-effective solutions.
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Design Requirements – SR Support System Alignment
Alignment Requirements ΔX RMS (μm) ΔY RMS (μm) Roll (mrad)
Magnet-to-Magnet Alignment < 30* < 30* < 0.2
Girder-to-Girder Alignment < 100 < 100 < 0.2
BPMs (standard and user) < 100 < 100 < 2.0
For acceptable dynamic aperture the SR support system must meet the following alignment requirements:
* 30 µm is the goal; acceptable limit is 50 µm. An analysis of tolerance stack-up shows that 30-50 µm alignment is not possible with conventional support designs and alignment techniques.
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Girder Support Design
Dispersion Girder:Weight - 3200 kgLength - 4.83 mWidth - 0.86 mHeight - 0.55 m
Floor Plate
Vacuum Chamber
Corrector Magnet
Quadrupole Magnet
Sextupole Magnet
Girder
The design was developed incorporating alignment and stability requirements.
Beam height of 1.2 m. The design is cost-effective –
conventional fabrication. 8 point support system to raise
resonant frequencies. The girder and the magnets are
aligned by removable alignment mechanisms.
After alignment the components are locked in place by stiff bolts.
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Vibrating Wire Alignment Technique - R&D A tensioned wire is stretched
through the bore of the magnets. The wire is mounted on high-precision X-Y translation stages.
An AC current is passed through the wire. The AC frequency is chosen to generate a resonant anti-node at the magnet to be aligned.
Any transverse magnetic field excites the resonant mode of the wire.
The vibration amplitude is measured with LED detectors . The wire is displaced in both x-y directions to obtain a minimum vibration amplitude.
Magnet movers are then used to position the magnet on the nominal wire axis.
The wire sag can be determined to within 1 from its first resonant frequency. The vertical position of the magnet is adjusted for this sag.
X-Y Stages
Wire Vibration detectors(LED phototransistors, ~ 13 mV/micron)
Magnet movers
(1 micron resolution)Granite table for supporting magnets during R&D phase
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Vibrating Wire Alignment Technique (contd.)
Magnet Torque Test
Software is being developed to automate the entire alignment process. In the final step, the magnets are fastened to the girder by manually applying torques to the 4 sets of nuts.
Tests have shown that the magnets can be fastened to the desired positions to within 5 µm in 3-5 minutes.
Magnet Movers
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Quadrupole Measurements: Horizontal ScansHorizontal Scans in SLS Quad
-800
-600
-400
-200
0
200
400
600
800
-1.2 -1 -0.8 -0.6 -0.4 -0.2Wire X-Position (mm)
X-d
etec
tor
Sig
nal
s (
By)
0A_X1 40A_X1 60A_X1 80A_X10A_X2 40A_X2 60A_X2 80A_X2
Current X1_Center X2_Center40 A -0.691 -0.69060 A -0.694 -0.69380 A -0.690 -0.691
X Center is given by intersection with 0A line14-Jan-2008
The magnet center can be located to within 4 μm.
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SLS Sextupole SR110 at 80 A (Mode = 6); 22-Jan-08
-120
-80
-40
0
40
80
120
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0
Wire Horizontal Position (mm)
Sign
al (
arbi
trar
y un
its)
X1 Sensor (B_y)Y1 Sensor (B_x)
X2 Sensor (B_y)Y2 Sensor (B_x)
Sextupole Measurements: Horizontal Scan
Horizontal center, defined as the point of zero slope in B_y Vs. X, can be located to within 5 μm.
Parabolic fits
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Girder Positioning and Alignment
Differential screws provide .002mm per degree of hand wheel rotation
Integral air jack
Girder with positioning fixtures installed
X-Y positioning fixture
Removable girder positioning fixtures are placed under each end of the girder. Horizontal position adjustment is made by differential screws , vertical by open-end wrenches. 90% to 95% of girder weight is supported by flexible air jack to minimize loads on adjustment
assembly All girder positioning is accomplished to within 50 μm with a laser tracker.
Laser tracker
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Recovery of Girder Profile
Lower fiducial
Upper fiducial
Right indicator
Left indicator
The girder deflection under the combined weights is ~ 140 µm. The “elastic” deflection has a scatter of ~ 15 µm. Laser trackers can be used to recover the girder profile to within ~ 15
µm. Digital inclinometers are being considered to recover the profile to
within ~ 5 µm.
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Tightening Torque
• Resonant frequency tests showed that it is necessary to torque the bolts to ~1000 lb-ft.
40
50
60
70
80
90
100
0 200 400 600 800 1000 1200 1400 1600 1800 2000
Torque (ft-lbs)
1st
Mo
dal
Fre
qu
ency
(H
z)
Torque wrench with 13:1
torque multiplier
Hydraulic torque wrench with split head design
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Stability Requirements
Stability Requirements (Vibration and Thermal)
Requirement ΔX RMS (nm) ΔY RMS (nm)
Magnets (uncorrelated) < 150 < 25
Girders (uncorrelated) < 600 < 70
Standard BPM < 500 < 200
User BPM < 250 < 100
Up to 4 Hz the motions of the magnets-girder assemblies are assumed to be correlated (the wavelength of shear waves at 4 Hz is ~ 70 m, as compared to the 26.4 m length of a DBA cell).
The global orbit feedback system is expected to correct the motion in this low frequency range.
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RMS Displacements at CFN (N. Simos)
( 0.5 - 4) Hz : 145 nm
(4 - 30) Hz : 14 nm
(30 - 100) Hz : 1 nm
Ambient Ground Motion
Support System Design Approach: First resonant frequency > 30 Hz the rms motion that will be amplified by the magnets-girder assembly is only 1 nm.
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Girder Vibration Tests
Constrained Girder Girder with Dummy Weights
Vibration tests were performed on:
Unconstrained girder Constrained girder Constrained girder with dummy weights
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Modal Analysis – Unconstrained Girder
1.00E-06
1.00E-05
1.00E-04
1.00E-03
1.00E-02
1.00E-01
1.00E+00
1.00E+01
0 20 40 60 80 100 120 140 160 180 200
Freq (Hz)
PS
D (
mic
ron
/sq
rt(H
z))
GROUND
Girder_left
Girder_right
First natural freq = 38 Hz
Twisting mode freq = 116 Hz
Second natural freq = 50 Hz
Impact testing: Horizontal impulse excitation provided by a soft-tipped hammer.
Peaks in the PSD curve –natural frequencies Good agreement between FEA and experiment
Rocking Mode, 42 Hz
Twisting Mode, 112 Hz
Bending Mode, 58 Hz
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FEA Model Calibration
• With the modification, the modal analysis
results agree better with the measured natural
frequency of the girder at 1000 ft-lbs
• FEA Rocking mode = 86 Hz (Measured 85
Hz)
• FEA Twisting mode = 110 Hz (Measured
120 Hz)
Young’s modulus of the 2” bolt
reduced by a factor of 10
Rocking Mode
Twisting Mode
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Vibration Tests on the Girder with Weights
1.00E-05
1.00E-04
1.00E-03
1.00E-02
1.00E-01
1.00E+00
1.00E+01
0 20 40 60 80 100 120 140 160 180 200
Freq, Hz
PS
D,m
icro
n/s
qrt
(Hz)
Weight_Left
Weight_Center
Weight_Right
Girder_Left
Girder_Center
Girder_Right
• Modal analysis of the adjusted girder model with 5000
lbs weight
• FEA Rocking mode:45 Hz (Measured 40 Hz)
• FEA Twisting mode:56 Hz (Measured 60 Hz)
MODE 1 ~40 Hz
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Modal Analysis - Girder- Magnet Assembly
• The calibrated model was used to estimate the natural frequencies
of the final girder-magnet system
• Rocking mode = 34 HZ
• Twisting mode = 51 HZ
Vibration tests will be performed with prototype magnets. Modeling of the interface between the girder, bolts and base plates will be refined.
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Maximum vertical misalignment between the magnets: ~0.014 μm (tolerance = 0.025 μm )
Maximum vertical deflection of the vacuum chamber at the BPM locations (near Invar supports) : ~ 0.14 μm (tolerance = 0.20 μm)
Thermal Stability of the Girder Support System
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Thermal Stability Tests
A thermally stable (± 0.1 ºC) enclosure has been built.
Displacement sensors (DVRTs) of 15 nm resolution have been procured and tested.
1.00E-06
1.00E-05
1.00E-04
1.00E-03
1.00E-02
1.00E-01
1.00E+00
1.00E+01
0 20 40 60
Freq, Hz
PS
D,m
icro
n/s
qrt
(Hz)
DVRT
Accl_isolationtable
Accl_granite
DVRT (Displacement Variable Reluctance Transducer)
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User-BPM Support Stands
Four 10-inch diameter carbon-fiber composite support stand are in procurement.
Thermal expansion coefficient :< 0.1 μm/m/ºC. The BPM assembly is supported at its mid-plane. First natural frequency = ~ 100 Hz
Mechanical stability requirement: ±0.1 μm (rms, 4-50 Hz)
User-BPM Supports
BPM Assembly
Composite Support Stand
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Conclusions
FE analyses, alignment tests and vibration measurements show that the prototype designs can meet the alignment and stability requirements.
Vibrating wire alignment tests have proven that the multipole magnets can be aligned to within 5 μm.
Girder alignment and positioning tests are ongoing. Initial results show that the girder can be positioned to within 50 μm with a profile repeatability of 15 μm.
With a calibrated FE model the lowest resonant frequency of the girder-magnet assembly is estimated to be ~ 34 Hz. This ensures that there is essentially no magnification of the ground motion by the girder-magnet assembly.
A temperature-controlled enclosure has been built for thermal stability tests on the girder and user-BPM support systems.
Acknowledgment: Stability – L-H Hua, S. Kramer, S. Krinsky, I. Pinayev, O. Singh, F. WillekeDesign – T. Dilgen, B. Mullany, D. Sullivan, W. Wilds