Requirements on Structural Stability Reflected in Design ... · 1 BROOKHAVEN SCIENCE ASSOCIATES S. Sharma Jan. 18-19, 2018 Requirements on Structural Stability Reflected in Design

1 BROOKHAVEN SCIENCE ASSOCIATES

S. Sharma

Jan. 18-19, 2018

Requirements on Structural Stability Reflected in Design Guidelines for Machine Enclosures and Girders

Sushil Sharma For the ME(ASD) Group


S. Sharma

Jan. 18-19, 2018

Acknowledgment

C. Channing, W. Cheng, L. Doom, T. Dilgen, R.

Hubbard, A. Jain, P. Joshi, B. Kosciuk, F. Lincoln, V.

Ravindranath, C. Spataro, W. Themann, J. Tuozzolo


S. Sharma

Jan. 18-19, 2018

Outline

• Mechanical Stability Specifications (vibration and

thermal)

• Ambient Motion and Temperature Stability

• Magnet Support Systems Design

• Performance – Vibration and Thermal

• BPM Support System Design and Performance

• Conclusions


S. Sharma

Jan. 18-19, 2018

Stability Specifications - Physics

Tolerance Limits ΔX RMS Quads (µm) ΔY RMS Quads (µm)

Random Quad Motion <0.157 <0.022

Random Girder Motion <0.31 <0.072

Plane Wave < 5 Hz ~ 2 ~ 0.1

Plane Wave > 10 Hz ~ 0.08 ~ 0.04

NSLS-II PDR, Chapter 4, page 4-30

Mechanical Stability Tolerances without Feedback Correction

• Random motion had no time structure

• Thermal stability was not included initially.


S. Sharma

Jan. 18-19, 2018

Stability Requirements - Mechanical

Stability Requirements (Vibration and Thermal):

Limits on Uncorr. Motion ΔX RMS (nm) ΔY RMS (nm)

Magnet to Magnet < 150 < 25

Girder to Girder < 600 < 70

BPMs (on vacuum chambers) <200 <200

BPMs (High Stability) <100 <100

• For vibrations RMS uncorrelated motion is in 2-100 Hz band.

• For thermal stability uncorrelated motion is maximum relative displacement.


S. Sharma

Jan. 18-19, 2018

RMS Displacements at CFN (N.

Simos, 2007)

(2 -100 ) Hz: 21 nm

(30-100) Hz: 1 nm

Ambient Ground Motion

The ambient motion below 2 Hz is correlated between adjacent multipole girders.


S. Sharma

Jan. 18-19, 2018

NSLS-II SR Floor Motion(2-100 Hz)

0

500

1000

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0102030405060708090

100110120130140150160170180190200

9:3

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RM

S F

loo

r M

oti

on

(n

m)

Time

RMS Floor Motion (2-100 hz) and LIE Traffic Count vs TimeCenter of Each Pentant

Pentant 5 Cell 19 Wednesday 1/9/13-Thurs. 1/10/13

Pentant 4 Cell 13 Friday 1/11/13-Saturday 1/12/13

Pentant 3 Cell 7 Wednesday 1/16/13-Thursday 1/17/13



LIE Traffic Count

LIE Traffic C

ou

nt

• The floor motion (rms, 2-100 Hz) varies from 25 nm to 120 nm during a day.

• The floor motion appears to be related to the traffic on the LI Expressway.


S. Sharma

Jan. 18-19, 2018

24.00

24.10

24.20

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24.90

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Tem

pe

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re ⁰

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Time

20130508 Temperature Run Pentant 1 Temperature vs Time 1 Hour Period

RTD1

RTD2

RTD3

RTD4

RTD5

RTD6

RTD7

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RTD22

RTD23

RTD24

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RTD26

RTD27

RTD28

RTD29

RTD30

0.1⁰C

Temperature Stability in Pentant 1

NSLS-II tunnel air meets the temperature specifications (± 0.10 C) by a factor of ~ 2.


S. Sharma

Jan. 18-19, 2018

Temperature Stability of the Floor

APS, Sector 17

August 2009

The floor temperature is expected to be stable to within ± 0.05 ⁰C.

Air, ± 0.2 ⁰C

Floor, ± 0.05 ⁰C

.


S. Sharma

Jan. 18-19, 2018

Support System Design Approach

Support System Design Approach: resonant frequency > 30 Hz the rms motion

that will be amplified by the girder-magnet assembly is only ~ 1 nm.

Stiff System


S. Sharma

Jan. 18-19, 2018

Key Design Features:

• Beam Height = 1.2 m

• Several girder support points (~ 1.5 m apart)

• Simple alignment mechanism (50 mm threaded rods)

5 m 3 m

Support System Design

1.2 m


S. Sharma

Jan. 18-19, 2018

Support System Design (contd.)

• Girders are stiff box-type structures with 25 mm

thick stiffening plates 0.8 m apart.

• Viscoelastic Pads are used for thermal stability.

Stiffening Plates

Solid Pad

Viscoelastic Pads

Viscoelastic Pad


S. Sharma

Jan. 18-19, 2018

34 Hz

50 Hz

Rocking Mode (34 Hz) Torsional Mode (50 Hz) Impact Hammer Modes: 30 Hz, 50 Hz

FE Modal Analysis: Rocking Mode at 34 Hz, torsional mode at 50 Hz

Impact Hammer Test: First two modes at 30 Hz and 50 Hz.

Natural Frequencies of the Support System


S. Sharma

Jan. 18-19, 2018

Integrated RMS displacement (Vertical)

Correlation between the two magnets

• Good correlation between the magnets for

frequencies below 25 Hz.

• Transmissibility (2-100 Hz): 1.07 (H), 1.08 (V)

• Uncorrelated Integrated RMS motion (vertical)

between the magnets (2-100 Hz) = 8 nm

(Specification: 25 nm).

4 m

Relative Motion between Magnets on a Girder-G4

Girder- Cell 7 G-4


S. Sharma

Jan. 18-19, 2018

Correlation Plot • Vibration measurement taken on two farthest

magnets on two separate girders: Cell 7, G2 and

G4

• Good correlation between the girders for

frequencies below 5 Hz

• Uncorrelated Integrated RMS motion (2-100 Hz)

= 28.8 nm, Girder-Girder Spec: 70 nm

13 m

Relative Motion between Magnets on Two Separate Girders

Integrated RMS displacement


S. Sharma

Jan. 18-19, 2018

Tunnel Air Temperature Fluctuations

• The tunnel air temperature specification is ± 0.1⁰ C with 1 hour cycle.

• Because of thermal inertia, the girder experiences only ± 0.01 °C

temperature cycles.

Temperature-Controlled Experiments


S. Sharma

Jan. 18-19, 2018

Air Temperature Fluctuations – Fixed Supports versus Viscoelastic Pads

Fixed Supports Viscoelastic Pads

• Thermal bending of the girder is reduced substantially with the viscoelastic pads.

• Magnets’ misalignment is reduced from 15 nm to 4 nm.


S. Sharma

Jan. 18-19, 2018

Experimental Verification of FEA Model- Fixed Supports

FEA Results Showing Vertical

Displacement

Measured Girder Vertical Displacement on the Bottom Plate

Absolute vertical displacement on the

bottom plate = 77 nm

• The measured absolute vertical displacement of ~ 70 nm for a girder temperature

change of 0.010 C is consistent with the FEA results.


S. Sharma

Jan. 18-19, 2018

Floor Expansion and Contraction

• Floor expansion is tracked by a MicrostrainTM

displacement sensor attached to an Invar rod.

• Floor expands/contracts about ~1 μm/m over 24 hour (diurnal).

Invar

Horizontal Displacement Measured on the

Invar Rod

Invar’s Temperature


S. Sharma

Jan. 18-19, 2018

Floor Expansion – Fixed Supports versus Viscoelastic Pads

• In some light-source facilities, diurnal floor expansion/contraction of ~ 1μm/m has been

observed.

• Bending deformations in the girder are up to 478 nm with the fixed supports, but only 7 nm

with the viscoelastic pads.

Fixed Supports Viscoelastic Pads


S. Sharma

Jan. 18-19, 2018

Maximum vertical deflection at the BPM locations (near composite-plate

supports) : ~ 70 nm (Girder) + 30 nm (Composite Plate) = ~ 100 nm

Carbon Fiber Composite Plates

CTE: 0.7 µm/m. ⁰C 30 nm for a ΔT of 0.1 ⁰C

Supports for RF-BPM (on Vacuum Chambers)

B. Kosciuk. MEDSI2010


S. Sharma

Jan. 18-19, 2018

High stability RF-BPM stand consists of four 50 mm diameter Invar rods joined by steel spacers

plates.

• Measured lowest natural frequency: ~ 45 Hz.

• Measured thermal expansion: ±35 nm

Courtesy – B. Kosciuk

High Stability RF BPMs

Invar rods

Low coefficient of thermal expansion CTE = 1.3 µm/m.⁰C

Low thermal diffusivity: 2.5 e-06 m2/s

Young’s Modulus: 148 GPa


S. Sharma

Jan. 18-19, 2018

XBPM Stand

• The XBPM stand is made from 1/8- inch Invar sheet rolled and welded into a cylinder. The

cylinder is then welded to top and bottom 1-inch thick steel plates.

• Transmissibility (2 – 100 Hz): < 1.2

XBPM

Invar Stand

Cross Section – Invar Stand


S. Sharma

Jan. 18-19, 2018

BPM (C02BPM6) data with active orbit feedback off. Integrated beam motion (37- 43 Hz)

is ~ 100 nm vertical and ~ 10 nm horizontal.

B. Podobedov (2017)

PSD of Beam Motion


S. Sharma

Jan. 18-19, 2018

Summary & Conclusions

• Magnet stability specifications (vibration) are met due to a support system

design consisting of:

Lower beam height (1.2 m).

Stiff girders with simple alignment mechanisms.

Multiple support points, ~ 1.5 m apart.

• Magnet stability specifications (thermal) are met due to:

Excellent air temperature stability (± 0.1⁰ C, 1 hour cycle).

Multiple support points.

Viscoelastics pads.

• BPM stability specifications are achieved by:

Stiff supports made from low CTE material (Invar, carbon composite)

Excellent air temperature stability.


S. Sharma

Jan. 18-19, 2018

Backup Slides


S. Sharma

Jan. 18-19, 2018

Vibration Hardware & Software

Equipment Used:

2 Sercel seismometers (#101 & #103)

NI 6259 USB 16 bit A/D

2 Amplifiers (gain=100-500)

Cables with compensation box

Laptop

LabView Vibration acquisition software


S. Sharma

Jan. 18-19, 2018

Data Acquisition/Analysis


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Jan. 18-19, 2018


S. Sharma

Jan. 18-19, 2018


S. Sharma

Jan. 18-19, 2018


S. Sharma

Jan. 18-19, 2018

Typical Vibration Plots, Sensors Separation, 0.1 m

-1.5

-1.0

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0.0

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1.5

0.1 1 10 100 1000

Corre

lati

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nce

Frequency (Hz)

Separation= 0 m

CorrRe(0-1) CorrIm(0-1)

20130307_155443.bin/07-Mar-2013 15:54:43 20130307_155443_01.csv/08-Mar-2013 12:53:46

1E-07

1E-06

1E-05

1E-04

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0.01 0.1 1 10 100 1000

Inte

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MS

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pla

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ent (m

m)

Frequency (Hz)

Ch0 Ch1 Ch(0-1)

20130509_174603.bin/09-May-2013 17:46:03 20130509_174603_01.csv/13-May-2013 10:37:02


S. Sharma

Jan. 18-19, 2018

Typical Vibration Plots, Sensors Separation, 10.2 m

1E-07

1E-06

1E-05

1E-04

1E-03

1E-02

1E-01

1E+00

1E+01

1E+02

0.01 0.1 1 10 100 1000

Inte

g. R

MS

Dis

pla

cem

en

t (m

m)

Frequency (Hz)

Separation= 10.2 m

Ch0 Ch1 Ch(0-1)

20130307_162527.bin/07-Mar-2013 16:25:27 20130307_162527_01.csv/08-Mar-2013 12:53:53

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

0.1 1 10 100 1000

Corre

lati

on

or

Coh

ere

nce

Frequency (Hz)

Separation= 10.2 m

CorrRe(0-1) CorrIm(0-1)

20130307_162527.bin/07-Mar-2013 16:25:27

Documents

Requirements on Structural Stability Reflected in Design ... · 1 BROOKHAVEN SCIENCE ASSOCIATES S. Sharma Jan. 18-19, 2018 Requirements on Structural Stability Reflected in Design