Stability Requirements: Buildings, thermal, electrical, Feed back, top-up, etc.

Tuesday 23 Nov 2010 at 10:00 (01h00')

Primary authors : Dr. BORDAS, Joan (ALBA CELLS) Co-authors : Presenter : Dr. BORDAS, Joan (ALBA CELLS)

Ring Energy

Ec (keV) = 0.665 Ee(GeV)2 B(T)

High field insertion devices, e.g. wavelength shifters or multi-pole wigglers, can be used to increase the range of photon energies.

However, there might be penalties to pay such as deterioration of emittance and high thermal loads to deal with!

The range of photon energies accessible with undulators and the flux from the various undulator orders increases with Ee2!

Accelerator energy is important and not only for undulators working at high photon energies!

Straightforward conclusions are:

The most important fundamental influence on the source brilliance is the emittance of the accelerator.

For a given emittance source size and collimation can be traded off against each other and thus optimize the use for a given type of experiment

e.g. in the case of ALBA it was a decision to optimize the lattice for intensity (i.e. have the smallest possible source size) at some points of light extraction).

ALBA’s Construction Budget 2004-2009 (k!; VAT excluded)

• ! Capital project! ! ! ! !! 163.160,300

Land!! ! ! ! ! 13.209,340 (*)Complex of accelerators! ! ! 36.386,644Beam-lines! ! ! ! ! 30.378,895Buildings and conventional services ! ! 64.058,940CC+Dacq. Infrastructure! ! ! 8.568,501Laboratories! ! s! ! 2.666,247Other Capital Items! ! ! ! 1.889,662Local electrical infrastructure! ! ! 6.002,071 (*)

• ! Personnel ! ! ! ! ! ! 27.742,455

• ! Personnel for installation ! ! ! ! 979,097• ! Running costs! ! ! ! ! !

16.317,132• ! Taxes! ! ! ! ! ! 3.113,279 (*)

Grand Total! ! ! ! ! ! 211.312,263

(*) Highly sensitive to local conditions

Beam Stability

Demands from Challenges on Science Program accelerator design

Range of Photon Energies Ring Energy

Brilliance Small Emittance

Flux Insertion Devices

Stability High Current; Feedbacks

Polarization Buildings&infrastructure; Vibrations;Top-up

Time Structure Short bunches; Short pulses

A SL FACILITY IS A PROJECT MADE UP OF THE FOLLOWING MAJOR SUB-PROJECTS;

TRANSVERSAL INFRASTRUCTURES:

• BUILDINGS AND CONVENTIONAL SERVICES (!).• CONTROLS AND DATA ACQUISITION SYSTEMS.• SPECIALIZED INSTRUMENTATION.

COMPLEX OF ACCELERATORS:

• LINAC.• LINAC-BOOSTER TRANSFER LINE.• BOOSTER.• BOOSTER-STORAGE RING TRANSFER LINE. • STORAGE RING..• INSERTION DEVICES. • FRONT-ENDS.

EXPERIMENTS:

• BEAM-LINES.• EXPERIMENTAL STATIONS..

Mechanical, Thermal and Electrical Stability!:

Complex of buildings and services therein.

Mechanical stability (the example of ALBA)

The loads on the Critical Floor Area, with inner and outer diameters of 74 and 120 m, respectively, are estimated as:

Total static load:

Mechanical stability (the example of ALBA)

Tolerances to ground motions and to vibrations:

Slow relative displacements: < 250 µm/10m/year < 50 µm/10m/month < 10 µm/10m/day < 1 µm/10m/hour

Maximal differential displacement around the perimeter: 2.5 mm/year

Amplitudes for vertical vibrations between 0.05 and 1 Hz:

The geological characteristics of the site and its environment are very important for the requirements on mechanical stability of the accelerator!

The choice of a good site will make the project easier and cheaper.

If the site cannot be ideal, at least it must be well understood!

The example of ALBA’s site

The site of ALBA:

A railway line at ca. 0.8 Km and a motorway at ca. 1.2 Km!

Next to ALBA’s site there was a ceramics factory. This factory has ceased production activities.

TERTIARYClay&Lime

(27-40)

TERTIARYClay&Fossil

(27-52)

TERTIARYClay&Marl

(52-70)

QUATERNARYClay&Sand (0-27)

Also extensive measurements of the vibration levels were made. Power spectral densities (PSD) and vibrations rms were determined.

Some facts about the site:Long term stability appeared acceptable. However, top layer (< 30 m) consisted of quaternary deposits that have to be distrusted.

Solution: the best floating slab that we could afford!

Environmental vibrations were bad primarily because of a ceramic’s factory next door. Measured amplitudes were up to 150 nm.

Solutions:a) Place elsewhere main source of noise (machinery in nearby factory); b) Treat soil under the CFA slab to absorb offending frequencies (welldefined), and;c) Implement active feed-back corrections in the storage ring (frequencies are within range).

ALBA’ solution:

The site is on top of > 700m of uniformly amorphoustertiary/quaternary deposits of red clays. These rather good for the absorption of vibrations but no so good for long term differential movements.

A viable, and economical, solution was chosen involving the floating of a 1 m thick concrete slab on a 2 m thick bed of graded gravels laid on top of an excavated doughnut with the dimensions of the Critical Floor Area, and equipped with a network of draining holes. This slab has been maintained physically decoupled from the rest of the building and its metallic network is used for electrical earthing of the facility.

ALBA’ solution:

The site is on top of > 700m of uniformly amorphoustertiary/quaternary deposits of red clays. These rather good for the absorption of vibrations but no so good for long term differential movements.

A viable, and economical, solution was chosen involving the floating of a 1 m thick concrete slab on a 2 m thick bed of graded gravels laid on top of an excavated doughnut with the dimensions of the Critical Floor Area, and equipped with a network of draining holes. This slab has been maintained physically decoupled from the rest of the building and its metallic network is used for electrical earthing of the facility.

ALBA’ solution:

The site is on top of > 700m of uniformly amorphoustertiary/quaternary deposits of red clays. These rather good for the absorption of vibrations but no so good for long term differential movements.

A viable, and economical, solution was chosen involving the floating of a 1 m thick concrete slab on a 2 m thick bed of graded gravels laid on top of an excavated doughnut with the dimensions of the Critical Floor Area, and equipped with a network of draining holes. This slab has been maintained physically decoupled from the rest of the building and its metallic network is used for electrical earthing of the facility. DICIEMBRE 2006

ALBA’ solution:

The site is on top of > 700m of uniformly amorphoustertiary/quaternary deposits of red clays. These rather good for the absorption of vibrations but no so good for long term differential movements.

A viable, and economical, solution was chosen involving the floating of a 1 m thick concrete slab on a 2 m thick bed of graded gravels laid on top of an excavated doughnut with the dimensions of the Critical Floor Area, and equipped with a network of draining holes. This slab has been maintained physically decoupled from the rest of the building and its metallic network is used for electrical earthing of the facility. DICIEMBRE 2006

FEBRERO 2007

Other lines at 15.9, 19.9, 25.0, 37.6, 74.4 Hz

whose sources are mostly electrical motors.

The supports for the accelerator sub-systems, e.g. magnets, e-BPMs, etc.. must be designed with the site’s instabilities in mind!

e.g. because of the site characteristics the Storage Ring girders for ALBA had to undergo a significant R&D effort.

Alignment and fixation.

PEDESTALSSTRUT FOR LONGITUDINAL

ALIGNMENT

JACK FOR VERTICAL ALIGNMENT VERTICAL FIXATION

LONGITUDINAL FIXATION

TRANSVERSAL FIXATION

2 STRUTS FOR TRANSVERSAL

ALIGNMENTSurfaces with common

flatness tolerance 30 !m for magnets supports, BPM

supports, for alignment holes and level measurement

A girder prototype was designed, built, tested,

improved and refined well before series production

could start!

Assembly with dummy magnets and deflection measurementTest at Factory 20 – 22.03.2007

10 Dial indicators

10 !m

10 !m

40 !m

40 !m

40 !m

Deflection of the beam smaller than 30 !m

TEST was repeated at ALBA

20 !m

10 !m

Dipole on the girder

SR Girder prototype

?

TEST PROGRAM at CELLS - Dimensional accuracy measurement- Static deformation under load- Alignment system and fixation tests- Determination/control of resonance frequencies

SR Girder prototype

Girder prototype – vibration test

Thermal stabilities (the example of ALBA)

Tolerances:

• Temperature in the Ring Tunnel: 23.0 ±0.2 oC• Temperature in the Experimental Hall: 23.0 ±1.0 oC• Temperature of water in cooling loops: 23.0 ±0.2 oC • For a water flow of: 25.0 m3/hour• and a water conductivity: < 0.2 µS/cm

AGOSTO 2008

Workshop

Electricalregulation

Cooling,HVAC

Offices

Car Park

Warehouse

Cooling watertowers

910

11 12

13

14

9.- Low conductivity water plant10.- Heaters room11.- Cooling pumps, tanks and manifolds12.- Chillers13.- Cogeneration access point14.- Cogeneration exchangers

Technical Building: Ground Floor

1.- Fire prevention water tank2.- Fire prevention pumps3.- Water treatment plant4.- Cooling towers water tank5.- Water tank

1 2 35 4

Technical Building: Basement

Cooling, HVAC

Electrical

regulation

Offices

Perimetral Laboratories

Service tunnel

Diameter of storage ring = 85.6 m

Diameter of Exp.-Hall = 125 m

Workshop

Thermal stability in the Experimental Hall is achieved by air injection by diffusers. The air is stratified up to a height of ca. 4 m and above this level the shape of the roof generates a convection motion. The stratified air keeps a stable temperature.

Thermal stability in the tunnel is ensured by cool air injection into, and circulation through, a spiral like flow.

Electrical stabilities (the example of ALBA)

Tolerances:• Power dips lasting t 12% in 2 phases: < 3/year• Power dips lasting t > 0.6 s): < 1/year

Redundancy of electrical supply!

Redundancy of electrical supply!Mains stability is important and given the higher stiffness to earth of the 220 kV line it is convenient to have a dedicated transformer to convert to 25 kV.

Also, a SL facility can be very badly affected by long term power cuts and because of this redundancy may be necessary.

In the case of ALBA redundancy is achieved by deriving power either from a co-generation power plant that also supplies cold and hot energy or, via a dedicated transformer , from a 220 kV line in the national grid.

Once again the site environment is fairly critical on how to organize the necessary supplies of energy: electrical, cold and hot.

Electrical energy: redundancy and stability.

The scheme of ALBA

1

2

34 5

6 78

9

1.- Mechanical workshop2.- Electrical workshop3.- Changing room and offices4.- Diesel generators5.- Dynamic UPS6.- Transformers room 25kV 400 V7.- Electrical cabinets8.- Static UPS9.- Compressed air plant

Technical Building: Ground Floor

Beam Stability:

Motions in accelerator elements are amplified in the beam orbit ca. 35-70 times (i.e. amplification factor = 35-70)

So, for the ca. 35 nm amplitudes in the vibrations measured at ALBA one expects the electron beam to move 1.225-2.45 µm.

If sub-micrometer stability is wanted, then not only slow orbit corrections but also fast orbit feed back (FOFB) has to be implemented!

Beam Stability:! ! Slow orbit correction ! ! ! ! ! ! and fast orbit feedback

Slow orbit correction compensates orbital errors created by “large” static perturbations, e.g. misalignment of magnets due to slow floor deformation. Errors of up to a few mm can be compensated using corrector strengths of up to 1 mrad. It also adjusts the frequency of the RF to have a centred horizontal orbit. It is essentially a static system.

The FOFB is used to achieve sub-micrometer stability of the electron beam orbit for motions with frequencies of up to, at least, 100 Hz, due to: Vibrations: Fast time scales (up to kHz) but of small amplitude (hopefully!) and, therefore, require only small amplitude of the correction.Thermal drifts: Slower time scales but can have bigger amplitudes. Correction by the FOFB as well as by the slow orbit correction is needed. This can be greatly reduced by using Top-Up!Insertion devices: If mechanical and thermal stabilities are well controlled, ID usually are the main source of noise (typically around 10 Hz and with moderate amplitudes).

ALBA’s FOFB:• ! Elements: ! e-BPM detectors and electronics;! ! ! corrector magnets and power supplies;! ! ! Iron lamination, corrector coil and vacuum chamber, ! ! ! and; ! ! ! Computer system and network.

• ! Shares correctors and BPMs with the slow orbit correction. Only a few ! µ-radians of corrector strengths are required

• ! Uses a fast data sharing network to distribute the information between ! BPMs, the CPUs for calculating the settings and the correctors power ! supplies.

• ! It is inspired on the system used at the SLS.

Lots of beam diagnostics are needed, e.g. for ALBA:

eBPM

Corrector

DC

Fluorescent Screen

Fast Current Transformer

DC Current Transformer

Beam Loss Monitor

Scraper

Stripline

DCPin Hole X-Ray

ALBA’S DIAGNOSTICS

Beam Stability:! ! TOP-UP:

Top-up is a mode of operation where electrons are continuously injected into the Storage Ring to compensate electron losses and thus run at constant current.

Advantages: greatly enhances stability of SL beams because the Storage Ring runs at practically constant circulating current and that results in a constant thermal load on accelerator components and, particularly important, on the optical elements of the beam-lines.

Disadvantages: More complicated/expensive solutions for injection system (e.g. Booster needs to ramp to high energy and be of relatively low emittance) and for radiation safety; somewhat higher running costs, and; somewhat more demanding geometries for the accelerator complex in order to reduce stress in the injection system.

LINAC

LBTL

Storage Ring

BSTL

Booster

Shield Wall

e.g. ALBA’s complex of accelerators for Top-Up operation

LINAC TO BOOSTER TRANSFER LINE

LINAC to Booster Transfer Line

Conditions at LINAC’s exit: #norm = 30 $ mm.mrad; #100 = 150 $ mm.mrad; % = 2 to 10 m/rad; & = -2 to 0, and; "E/E = 0.005

'x-tot 'y-tot

'to

t (m

)

At LINAC’s exit: 'x-tot = 1.2 mm 'y-tot = 0.6 mm

s(m)

ALBA’s BoosterSynchrotron has4-fold symmetry

Booster Lay-out

Arc with 8 unit cells.Each unit cell contains a 10o bending dipole.

Unit cell x 32.

Pre-straight cell (5o dipole) x 4.

Post-straight cell (5o dipole) x 4. Straight section

for injection

Straight section for cavity

Matching section

Booster lattice: • Design uses defocusing bending magnets and focusing quadrupoles; • Sextupole components within the bending magnets and quadrupoles;• achieves low emittance, higher flexibility and lower costs, and; • #x =10 nm.rad

%x(s) %y(s) 10 x D(s)

Mac

hine

func

tions

(m)

s (m)SF SD

QF QD QD

Booster Synchrotron

Beam size at injection: #x = 140 nm.rad; 100% coupling.'x,tot = 1.3 mm, 'y,tot = 1.25 mm

Beam size at extraction: #x = 9 nm.rad; 10% coupling.'x,tot = 0,5 mm, 'y,tot = 0.1 mm

'x-tot(s) 'y-tot(s)

'x-tot(s) 10 x 'y-tot(s)

s (m)

s (m)

'to

t (m

)'

tot (

m)

BOOSTER TO SR TRANSFER LINE

Storage RingInjection Straight

Booster Synchrotron

Transfer Line

Kicker

Septum

Quadrupoles Bending magnets

Booster to Storage Ring Transfer Line

Beam size at injection: #x = 9 nm.mrad; 'x,tot = 0,5 mm, 'y,tot = 0.2 mm

The injection scheme for a 3rd generation light source: All elements (4 kickers and one septum) have to be in one straight. For 3 GeV the length has to be at least 8 m.

Diamond’s concept

'x-tot 'y-tot

'to

t (m

)

s(m)

Booster to Storage Ring Transfer Line

Beam size at injection: 'x,tot = 0,5 mm and 'y,tot = 0.2 mm