Real Life in an Accelerator: the Diamond Synchrotron Light Source

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Real Life in an Acceleratorthe Diamond
Synchrotron Light Source

• R. Bartolini
• Diamond Light Source Ltd
• and
• John Adams Institute, University of Oxford

Undergraduate Accelerator Physics
Option Lindemann Theatre, 20 May 2009
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Outline

• Introduction to synchrotron light sources
• synchrotron radiation
• storage ring synchrotron radiation sources
• users requirements and Accelerator Physics
  challenges
• The Diamond Light Source
• basic parameters
• commissioning procedure
• measurements in routine operation orbit,
  dispersion, tunes,
• overview of performance emittance, stability

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What is synchrotron radiation

• Charged particles when accelerated emit
  electromagnetic radiation

The electromagnetic radiation emitted when the
charged particles are accelerated radially (v ?
a) is called synchrotron radiation It is produced
in the synchrotron radiation sources using
bending magnets undulators and wigglers
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Layout of a synchrotron radiation source (I)
Electrons are generated and accelerated in a
linac, further accelerated to the required energy
in a booster and injected and stored in the
storage ring
The circulating electrons emit an intense beam of
synchrotron radiation which is sent down the
beamline
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Layout of a synchrotron radiation source (II)
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Synchrotron radiation sources properties
Broad Spectrum which covers from microwaves to
hard X-rays the user can select the wavelength
required for experiment
synchrotron light
High Flux high intensity photon beam, allows
rapid experiments or use of weakly scattering
crystals High Brilliance (Spectral
Brightness) highly collimated photon beam
generated by a small divergence and small size
source (partial coherence) High Stability
submicron source stability Polarisation both
linear and circular (with IDs) Pulsed Time
Structure pulsed length down to tens of
picoseconds allows the resolution of process on
the same time scale
Flux Photons / ( s ? BW)
Brilliance Photons / ( s ? mm2 ? mrad2 ? BW )
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Applications
Medicine, Biology, Chemistry, Material Science,
Environmental Science and more
Biology
Archeology
Reconstruction of the 3D structure of a
nucleosome with a resolution of 0.2 nm
A synchrotron X-ray beam at the SPEAR3 facility
illuminated an obscured work erased, written over
and even painted over of the ancient mathematical
genius Archimedes, born 287 B.C. in Sicily.
The collection of precise information on the
molecular structure of chromosomes and their
components can improve the knowledge of how the
genetic code of DNA is maintained and reproduced
X-ray fluorescence imaging revealed the hidden
text by revealing the iron contained in the ink
used by a 10th century scribe. This x-ray image
shows the lower left corner of the page.
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Life science examples DNA and myoglobin
Franklin and Gosling used a X-ray
tube Brilliance was 108 (ph/sec/mm2/mrad2/0.1BW)
Exposure times of 1 day were typical (105
sec) e.g. Diamond provides a brilliance of
1020 100 ns exposure would be sufficient
Nowadays pump probe experiment in life science
are performed using 100 ps pulses from storage
ring light sources e.g. ESRF myoglobin in action
Photograph 51 Franklin-Gosling DNA (form B) 1952
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A brief history of storage ring synchrotron
radiation sources

• First observation
• 1947, General Electric, 70 MeV synchrotron
• First user experiments
• 1956, Cornell, 320 MeV synchrotron

• 1st generation light sources machine built for
  High Energy Physics or other purposes used
  parasitically for synchrotron radiation
• 2nd generation light sources purpose built
  synchrotron light sources, SRS at Daresbury was
  the first dedicated machine (1981 2008)
• 3rd generation light sources optimised for high
  brilliance with low emittance and Insertion
  Devices ESRF, Diamond,
• 4th generation light sources photoinjectors
  LINAC based Free Electron Laser sources FLASH
  (DESY), LCLS (SLAC),

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3rd generation storage ring light sources
1992 ESRF, France (EU) 6 GeV ALS, US 1.5-1.9
GeV 1993 TLS, Taiwan 1.5 GeV 1994 ELETTRA,
Italy 2.4 GeV PLS, Korea 2 GeV MAX II,
Sweden 1.5 GeV 1996 APS, US 7 GeV LNLS,
Brazil 1.35 GeV 1997 Spring-8, Japan 8
GeV 1998 BESSY II, Germany 1.9 GeV 2000 ANKA,
Germany 2.5 GeV SLS, Switzerland 2.4
GeV 2004 SPEAR3, US 3 GeV CLS, Canada 2.9
GeV 2006 SOLEIL, France 2.8 GeV DIAMOND, UK 3
GeV ASP, Australia 3 GeV MAX III, Sweden 700
MeV Indus-II, India 2.5 GeV 2008 SSRF, China
3.4 GeV
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Accelerator Physics challenges
Photon energy Brilliance Flux Stability Polari
sation Time structure
Ring energy Small Emittance Insertion Devices
High Current Feedbacks Vibrations Orbit
Feedbacks Top-Up Short bunches Short pulses
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Peak Brilliance
diamond
X-rays from Diamond will be 1012 times brighter
than from an X-ray tube, 105 times brighter
than the SRS !
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Brilliance and low emittance
The brilliance of the photon beam is determined
(mostly) by the electron beam emittance that
defines the source size and divergence
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Main components of a storage ring
Dipole magnets to bend the electrons
Quadrupole magnets to focus the electrons
Sextupole magnets to focus off-energy electrons
(mainly)
RF cavities to replace energy losses due to the
emission of synchrotron radiation
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Low emittance lattices
Low emittance and adequate space in straight
sections to accommodate long Insertion Devices
are obtained in Double Bend Achromat (DBA)
Triple Bend Achromat (TBA)
TBA used at ALS, SLS, PLS, TLS
DBA used at ESRF, ELETTRA, APS, SPring8,
Bessy-II, Diamond, SOLEIL, SPEAR3 ...
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Brilliance with Insertion Devices
Critical frequency of sync. rad. from a dipoles
Thanks to the progress with IDs technology
storage ring light sources can cover a photon
range from few tens of eV to tens 10 keV or more
with high brilliance
Medium energy storage rings with In-vacuum
undulators operated at low gaps (e.g. 5-7 mm) can
reach 10 keV with a brilliance of 1020
ph/s/0.1BW/mm2/mrad2
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Insertion Devices (I)
Four independent arrays of permanent magnets
Sliding the arrays of magnetic pole it is
possible to control the polarisation of the
radiation emitted
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Insertion Devices (II)
In vacuum undulator at Diamond
Superconducting Multipole Wiggler at Diamond
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Diamond aerial views
June 2003
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Diamond Layout
100 MeV Linac 3 GeV Booster C 158.4 m 3 GeV
Storage Ring C 561.6 m
technical plant
Experimental Hall and Beamlines
peripheral labs. and offices
office building
235 m
future long beamlines
235 m
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Diamond storage ring (I)
Low emittance lattice
Energy 3 GeV Circumference 561.6 m No.
cells 24 Symmetry 6 Straight sections 6 x 8m, 18
x 5m Insertion devices 4 x 8m, 18 x 5m Beam
current 300 mA (500 mA) Emittance (h, v) 2.7,
0.03 nm rad Lifetime gt 10 h Min. ID gap 7 mm
(5 mm) Beam size (h, v) 123, 6.4 mm Beam
divergence (h, v) 24, 4.2 mrad (at centre of 5 m
ID)
48 Dipoles 240 Quadrupoles 168 Sextupoles ( H
/ V orbit correctors Skew Quadrupoles ) 3 SC
RF cavities 168 BPMs
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Diamond Storage Ring (II)
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Diamond Girders
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Storage Ring Commissioning
First beam after SR injection septum (04 May 2006)
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First turn (05 May 2006)
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First turn celebration 5th May 2006 4am
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5 turns (06 May 2006) 600 turns (07 May 2006)
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Storage ring commissioning 700 MeV
2000 turns (19 May 2006)
stacking to 2 mA (30 May 2006)
Sextupoles on RF off
Sextupoles on RF on
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Storage Ring Closed Orbit lt 1?m (22th October
2006)
The beam orbit is corrected to the BPMs zeros by
means of a set of dipole corrector magnets the
BPMs can achieve submicron precision and the
orbit rms is corrected to below 1 ?m rms
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Orbit Correction with the Orbit Response Matrix
(I)
To correct the orbit with the system of
horizontal and vertical corrector dipoles we need
to know what is the effect of each correctors on
the orbit itself, first. Then we can use this
information to correct orbit distortion. The
orbit response matrix collects all this
information in one matrix The orbit response
matrix R is the change in the orbit at the BPMs
as a function of changes in the steering magnets
strength.
1682 rows 1682 columns
orbit reading at all BPMs
V
V
H
H
dipole corrector angle kick
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Orbit Correction with the Orbit Response Matrix
(II)
Once the matrix R is known we can correct an
orbit distortion by inverting the matrix
The matrix R generally is not a square matrix so
it might be non-invertible but in general we can
use the Singular Value Decomposition (SVD) of the
response matrix R to invert it and correct the
closed orbit distortion
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Beam Based Alignment quadrupole scan
dipole corrector
BPM
quad
BPM
BPM
When the beam is at the centre of the quadrupole,
the variation of the quadrupole gradient will not
change the orbit of the beam (at the centre of
the quadrupole the magnetic field is zero)

• First scan (21/09) noisy orbit and large spread
  in results
• However using the BPMs offset made good
  improvement on
• residual closed orbit after orbit correction
• new BBA scan much cleaner

quad. centre
orbit change
BPM reading
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Optics functions 08 November 2006 ?functions
circles model cross measurements Very good
control of the linear optics
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Emittance and energy spreadmeasured using two
X-ray pinholes cameras
Measured emittance very close to the theoretical
values confirms the optics
Emittance 2.78 (2.75) nm Energy spread 1.1e-3
(1.0e-3) Emittance coupling 0.5
Emittance coupling is now routinely corrected to
0.1 with LOCO Closest tune approach ?0, rms Dy 1
mm
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Diamond betatron tunes

• The betatron tunes are carefully selected to
  avoid dangerous resonances which might spoil the
  dynamic aperture available to the beam

10 quadrupoles per cell
Diamond has 10 families of quadrupoles four
families are used in the arcs and six families
are in the straight section. The families in the
straight section are also used for tune
adjustment. Some families are more effective in
changing the horizontal tune others are more
effective in changing the vertical tune
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Physics Applications tune measurement

• The tune is measured by exciting betatron
  oscillations with a kicker or with a swept
  harmonic excitation with a stripline and
  recording the turn-by-turn data.
• The time series is Fourier analysed with an FFT
• The peak of the frequency response gives the
  fractional part of the betatron tune
• amp ix max(abs(fft(x))) tunex
  ix/length(x)

excitation from injection oscillations
excitation from harmonic sweep
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Physics Applications dispersion measurement
Dispersive orbits can be measured by changing the
energy of the electron beam and measuring the new
orbit and using the formula
A change in the energy of the beam is achieved by
changing the RF frequency according to the formula
where we have used the definition of momentum
compaction factor
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Diamond dispersion function

• The dispersion function gives the closed orbit
  for off-energy particles
• In the vertical plane it gives a measure of the
  vertical bending errors and of the skew
  quadrupole component present in the ring

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Orbit stability disturbances and requirements

• ground settling
• tidal motion
• day/night (thermal variations)
• re-injection
• thermal drifts of the electronics
• insertion device gap movements
• ground vibrations
• air conditioning units
• compressor (cooling systems)
• cooling water flow
• power supplies

0.01 Hz
0.1 Hz
1 Hz
10 Hz
100 Hz
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Stability requirements at Diamond
Beam stability should be better than 10 of the
beam size and divergence
but IR beamlines will have tighter
requirements for 3rd generation light sources
this implies sub-?m stability
For Diamond nominal optics (at the centre of the
short straight sections)

• Strategies and studies to achieve sub-?m
  stability
• identification of sources of orbit movement
• passive damping measures
• orbit feedback systems

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Ground vibrations to beam vibrations
Amplification factor girders to beam H 31
(theory 35) V 12 (theory 8)
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Global fast orbit feedback at Diamond
Significant reduction of the rms beam motion up
to 100 Hz Higher frequencies performance
limited mainly by the correctors power supply
bandwidth
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Sichuan earthquake as seen in UK it starts at
6.39 am (about 11 minutes to travel from
China)the ground activity lasts for tens of
minutes
The Sichouan earthquake (May 2008)
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Sichouan earthquake seen at SSRF (Shangai)
Orbit vibrations in horizontal direction (300-700
?m) Orbit vibrations in the vertical were 10
times smaller
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Sichouan earthquake at Diamond
FOFB was on The orbit is nailed to the BPMs
centre Only H steerers moved
V steerer
H steerers
V steerer
ID tilt sensors (blue and red)
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Conclusion
Diamond is a state of the art third generation
light sources provide a very reliable source of
high brightness, very stable X-rays leading edge
emittance in 3rd generation light sources high
(electron) beam stability, well within 10 of
beam size up to 100Hz high capacity (more
undulator per straights with canted
undulators) Uses state of the art technology
IDs (lots of in-vacs, SCW, CPMU), BPMs high
resolution, digital PS, Superconducting RF,
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Conclusions (III)
3rd generation light source are still popular
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On-line modelling of the CERN-LHC
PhD in Accelerator PhysicsJohn Adams Institute
University of Oxford and CERN
A Phd studentship is available in the John Adams
Institute at the University of Oxford. The
project will be in collaboration with CERN and
the Diamond Light Source. The student will have
the opportunity to contribute to the
commissioning of the CERN-LHC and work alongside
professional accelerator scientists.
Description of the programme For the LHC
commissioning a online model is foreseen, a
prototype of which has been used for LHC
injection lines and LHC proper till September
2008. The main goal of the PhD will be to
complement the theoretical model such that a
"real" model of the LHC can be constructed for
the on-line model. The candidate will be heavily
involved in providing online model applications
needed for the LHC commissioning and beam
optimization. He/She is also expected to be
involved in the nonlinear dynamics optimization
ongoing at the Diamond Light Source in view of
application in the LHC.
Applicants should submit a CV with the contact
details of two referees by post or by e-mail to
Dr. Riccardo Bartolini, University of Oxford,
Keble road, OX1 3RH, UK r.bartolini1_at_physics.ox.a
c.uk
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Diamond operation schedule for 2009