1 BROOKHAVEN SCIENCE ASSOCIATES S. Sharma ASAC July 17-18, 2008 Support System and Alignment Sushil Sharma ME Group Leader ASAC Review of NSLS-II July

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



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)



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



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.



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.



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.



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



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



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.



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



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



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.



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



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.



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.



Girder Vibration Tests

Constrained Girder Girder with Dummy Weights

Vibration tests were performed on:

Unconstrained girder Constrained girder Constrained girder with dummy weights



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



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



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



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.



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



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)



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



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

Documents

1 BROOKHAVEN SCIENCE ASSOCIATES S. Sharma ASAC July 17-18, 2008 Support System and Alignment Sushil Sharma ME Group Leader ASAC Review of NSLS-II July