Detailed Design Report
Chapter 6 Stability and Tolerances
MAX IV Facility
STABILITY AND TOLERANCES • 1(39)
CHAPTER 6.
6.
Stability and Tolerances
6.0 6.1.
Stability and Tolerances (Vibrations, Settlements and Alignment) .... 2
Overall Stability Criteria ................................................3
6.1.1. 6.1.2. 6.1.3.
Dealing with Stability and Tolerances throughout this Report............................ 3 e-Beam Design Values .......................................................................................... 4 e-Beam Position and Stability ............................................................................... 5
6.2.
Vibration Conventions...................................................7
6.2.1.
Tolerance Conventions and Basic Relations ........................................................ 7
6.3.
Vibration Tolerances ....................................................10
6.3.1. 6.3.2. 6.3.3.
Beamline Tolerances ............................................................................................10 Accelerator Tolerances ......................................................................................... 11 Summarizing Tolerances......................................................................................15
6.4.
Vibration Measurements .............................................16
6.4.1. 6.4.2. 6.4.3. 6.4.4.
Early Measurements.............................................................................................16 NGI Measurements..............................................................................................17 Traffic ...................................................................................................................19 Detailed Investigation PEAB/MAX-lab............................................................. 20
6.5.
Vibration Management ...............................................21
6.5.1. 6.5.2. 6.5.3. 6.5.4. 6.5.5. 6.5.6. 6.5.7. 6.5.8.
Passive Damping and Isolation ...........................................................................21 Active Damping of Mechanical Vibrations......................................................... 22 Orbit Feedback.................................................................................................... 23 Sources for Vibrations ......................................................................................... 25 Civil Engineering................................................................................................. 26 Ring Girders ........................................................................................................ 30 Other Mechanical Structures ............................................................................................. 35 Conclusions, Recommendations, Pointing at Solutions..................................... 35
6.6.
Alignment, Positional Tolerances ...............................36
6.6.1. 6.6.2. 6.6.3.
MAX IV Rings ..................................................................................................... 36 Linac and e-beam Transport............................................................................... 36 Beamlines ............................................................................................................ 36
6.7.
Conclusions ...................................................................37
6.8.
References ....................................................................38
DETAILED DESIGN REPORT ON THE MAX IV FACILITY
Detailed Design Report
Chapter 6 Stability and Tolerances 6.0. Stability and Tolerances (Vibrations, Settlements and Alignment)
MAX IV Facility
STABILITY AND TOLERANCES • 2(39)
CHAPTER 6.
6.0. Stability and Tolerances (Vibrations, Settlements and Alignment)
In order to ensure that the facility will perform as expected in a cost effective way a lot of care has to be put into both • •
Finding the proper tolerances Achieving these goals the proper way
This chapter deals with structural tolerances – both regarding alignment and stability. “Stability” covers vibrations, long term settlements and also thermal stability. Some issues are dealt with in other sections of this report. Ground vibrations will displace the focusing magnets in a storage ring. These vibrations might be amplified by the magnet girders. The magnet lattice parameters define the amplification factor giving the displacement of the electron beam for a given magnet displacement. Also beamline components are affected by vibrations. In general it is possible to write down specifications for how much magnets or optical components are allowed to move, however there is no lower limit where one can say it is good enough, since less vibrations are always better. This is partly because new emerging technical possibilities will put even harder demands on stability. Because of the unknown future demands it is recommended that the present vibration level at the “green field” should not be significantly increased. Long term stability affected by settlements or thermal drift is a crucial task, especially in the first time phases for the facility. It might take a long time before the site gets into equilibrium. There is even a risk of periodic drift with seasons. The list of mechanisms contributing to the amount of vibrations of ring and beamline components is long. All fields have to be analyzed and addressed. For beamline components even acoustic noise needs to be addressed. The alignment of ring and beamline components is an important task to deal with since it also affects the performance.
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Detailed Design Report
Chapter 6 Stability and Tolerances 6.1. Overall Stability Criteria
MAX IV Facility
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CHAPTER 6.
6.1. Overall Stability Criteria
As starting point for writing down tolerances a quality analysis of our “product” (well defined photon beams) is needed. What does quality mean for the user? Some of the parameters are •
Continuous availability (no unplanned beam losses)
•
Reached Design values • Resolving power • Flux • Polarization • Speed of systems (undulator, monochromator etc.)
•
Stability • Flux • Position of light source • Direction of light beam • Source position (x,y,z)
Several parameters are interconnected and can be boiled down to a few machine parameters.
6.1.1.
Dealing with Stability and Tolerances throughout this Report The following table points at sections in the DDR where stability and tolerances are discussed. Ch1 Ch2
2.4. Lattice Errors and Correction 2.9. Diagnostics
Ch3
3.4. Lattice Errors and Correction 3.9. Diagnostics
Ch4 Ch5 Ch6
Vibration, General Comments Alignment, General Comments
Table 6.1: Switchboard to other chapters.
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6.5. Vibration Management, 6.6. Alignment, Positional Tolerances
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CHAPTER 6.
6.1.2.
e-Beam Design Values The electron beam performance parameters are directly connected to the achievable performance for the beamlines. Several of the first beamlines are designed for top performance and are thus taking advantage of the planned e-beam properties. Therefore it will have consequences if the design values are not met. Table values are chosen for the most demanding operation mode. An asterisk indicates at the center of the ID.
MAX IV, 3 GeV
Damping wigglers included
MAX IV, 3 GeV
Strong ID
MAX IV, 1.5 GeV
βx*
9m
βy*
4.8 m
εx
~300 pm rad (includes damping wigglers, Landau cavities, and IBS)
εy
~ 8 pm rad (1Å diffraction limit, i.e. coupling 2.7 %)
σx*
52 µm (σx'* = 5.8 µrad)
σy*
6 µm (σy'* = 1.3 µrad)
βx*
9m
βy*
>=1 m
εx
~3 pm rad (includes damping wigglers, Landau cavities, and IBS)
εy
300 pm rad (includes damping wigglers, Landau cavities, and IBS), coupling 1 %
σx*
52 µm (σx'* = 5.8 µrad)
σy*
2 µm (σy'* = 1.7 µrad)
βx*
5.66 m
βy*
2.85 m
εx
6 nm rad (bare lattice)
εy (1% coupling)
60 pm rad
σx*
184 µm (σx'* = 33 µrad)
σy*
13 µm (σy'* = 4.6 µrad)
Table 6.2: Design values.
The design values give a base for setting several tolerances.
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CHAPTER 6.
6.1.3.
e-Beam Position and Stability The electron beam is the source for the beamlines. Fluctuations in the e-beam position will degrade the performance. If fluctuations in the e-beam are much smaller than the beam itself, it will not be noticed by the beamline. A tolerance for the fluctuations of 10 % RMS of the beam size seems reasonable.
Stability criterion rms
Δy
3 GeV
