diamond light source vacuum systems€¦ · all vacuum systems working well. performance within...
TRANSCRIPT
OLAV-3 Oak Ridge July 2011
Matthew CoxDiamond Light Source, [email protected]
Diamond Light Source Vacuum Systems:
The First Four Years of User Operations
1
Topics
OLAV-3 Oak Ridge July 2011
Overview of Diamond Vacuum Systems
Operational performance
Upgrades
Challenges and issues
Future plans
2
What is Diamond Light Source?
OLAV-3 Oak Ridge July 2011
• The UK national synchrotron facility, 100 km from London
• Generates brilliant beams of light, from infra‐red to hard X‐rays,
for a range of science applications
• 3rd generation light source making heavy use of insertion devices
in straight sections (undulators and wigglers)
• Construction began in early 2003
• User operations began in January 2007 with 7 beamlines
operational (Phase 1)
• Now 20 beamlines operational + 2 being installed (Phase 2)
• Will increase to 32 beamlines over the next 6 years (Phase 3)
3
Beamline
3 GeV electron storage ring562m circumference
<10-9 mbar
Booster synchrotron
100 MeV Linac
Front end
Diamond layout
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Aerial view
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Why ultra‐high vacuum?
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• Storage ring• p < 10‐9 mbar• Interactions between circulating electrons and residual gas molecules
– Stored beam lifetime– Gas Bremsstrahlung radiation
• Scales as Z2 – minimise high Z gases
• Beamlines• Hydrocarbon contamination of x‐ray optics (mirrors, gratings, crystals)• Some sample environments require UHV• Gas phase absorption and scattering
• Residual gas• Hydrogen often predominant but not a problem – low Z, non‐contaminating• Water and hydrocarbons need attention
• Electrons• Disappear after use!
6
Storage ring vacuum engineering
OLAV-3 Oak Ridge July 2011
• High radiation environment in shielding tunnel• Materials – stainless steel, copper, ceramic• Electronics• Personnel access• Remote control and monitoring
• High heat loads and power densities – up to 30kW some insertion devices
• Locally high magnetic fields• Long narrow beam channels with little space for vacuum pumps:
conductance limited, many pumps• High reliability
• 24/7 operation, 5 shutdowns a year
• Quality control at every stage is vital
• Protection from vacuum accidents and electron and photon beam damage is important
7
Diamond Storage Ring Vacuum Equipment
OLAV-3 Oak Ridge July 2011
• Pumps– 500 Noble diode ion pumps– 50 Titanium sublimation pumps– 50 Non‐ evaporable getter (NEG) cartridge pumps– 9 NEG coated vessels– Mobile turbomolecular / scroll pump carts for interventions
• Instrumentation– 200 Inverted Magnetron Gauges (IMGs) and 200 Piranis– 80 Residual Gas Analysers (RGAs)
• Valves– 50 RF‐shielded pneumatic gate valves– 50 All‐metal pneumatic gate valves to front ends / absorbers– 150 Right‐angle manual valves
8
Bakeout policy
OLAV-3 Oak Ridge July 2011
Generally do not bake out in‐situCostLimited intervention timeLabour intensive and prone to human errorThermal expansionGood results achieved without in‐situ bakeout
Instead: Ex‐situ prebake and installation under dry nitrogen purgeEx‐situ bakeout typically 250°C vessel at supplier, 200°C assemblies at DiamondDry nitrogen flow helps to prevent water vapour from entering the system
In situ bake out where:Non‐evaporable Getter (NEG) coating activationWhere significant exposure to atmospheric moisture is unavoidableWhere ultimate pressure or gas composition is particularly critical
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Storage ring vacuum performance
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All vacuum systems working well. Performance within specification
3700 A.h beam conditioning dose (July 2011)
Machine has been tested at 300 mA. Routinely operating at 225 mA in top‐up mode (every 10 minutes). Short term will incrementally increase to 300 mA targeting 500 mA longer term.
Average gauge reading (nitrogen equivalent pressure)
Static pressure (no beam) 2.8 x 10‐10 mbar
Dynamic pressure at 225 mA = 4.5 x 10‐10 mbar
Residual gas composition typically > 95% H2, balance mainly CO – (RGAs not calibrated)
Beam lifetime typically 20 h at 225 mA (not dominated by gas lifetime)
OLAV-3 Oak Ridge July 2011
1.0E-12
1.0E-11
1.0E-10
1.0E-09
1.0E-08
0.0001 0.001 0.01 0.1 1 10 100 1000Beam dose (A.h)
Dyn
amic
pre
ssur
e (m
bar/m
A)
1
10
100
1000
10000
Cur
rent
x li
fetim
e (m
A.h
)
PressureLifetime
300mA 10‐9 mbar = 3.3x10‐12 mbar/mAPSD yield (η) vs dose (Γ)
follows:η ∝ Γ-0.73
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Storage ring beam conditioning
Operational reliability 2007 ‐ 2011
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2007 2008 2009 2010 2011 (to June 2nd)
User beam (h) 3160 4092 4536 4753 2184
Uptime (%) 92.3 94.9 96.4 97.4 98.2
MTBF (h) 10.64 14.5 21.1 27.3 48.5
MTTR (h) 0.71 0.6 0.77 0.72 0.84
Total beam trips 297 282 217 174 43
Vacuum beam trips 26 22 15 1 3
SR RF beam trips 130 171 114 112 18
Unofficial statistics!Longest stored beam with no trip 172 hours
Operational reliability 2010
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1 1 1
24
1 0 1 1
7
30 0
37
46
2 3
19
1
1
05
22
2
11
11
7
6
05
101520253035404550556065707580859095
100105110115120
# Tr
ipss
Groups
Beam Trips by Group During Each Run (2010)
Run 06-10
Run 05-10
Run 04-10
Run 03-10
Run 02-10
Run 01-10
Operations calendar 2011
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Main vacuum mechanical upgrades since initial build
OLAV-3 Oak Ridge July 2011
• 6 of 72 girders replaced with new builds (Synchrotron Radiation (SR) aperture, magnetic lattice)
1 x B22 IR beamline3 x I13 Double mini beta2 x I09 Double mini beta
• 21 front ends installed (17 ID, 4 BM)
• 18 of 22 insertion device straights installed 12 in-vac undulator (including 1 cryo)9 NEG coated vessel for ex-vac ID2 superconducting multipole wiggler
• 20 (+ 2 in progress) beamlines installed
• Superconducting RF cavity exchanges and pumping improvements (to reduce hydrogen cryo-pumping in cavities thought to be linked to RF breakdown events)
15
Main vacuum controls and equipment upgrades since initial build
OLAV-3 Oak Ridge July 2011
• Many refinements to interlock system to reduce unwanted beam trips
• Permanent magnet filters fitted to prevent stray electrons affecting IMG gauges
• Some Piranis stop working in the presence of stored beam. Thought to be RF heating but not well understood. Pirani interlocks overridden
• Development of new fast valve control system
• Introduction of new ion pump controller
• Introduction of new cold cathode / Pirani gauge controller
• Improved RGA integration with EPICS
16
New girders and straight installation for I13
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New vacuum string build,bakeout and integration
on to girderOld 8.3m straight Straight vessels and
girders removed
New girder lift New girder installationNew 9.4m straight
with quadrupole magnets
Beam conditioning of new I13 girders and straight
1 10
0
50
100
150
200 C
urre
nt (m
A)
SR-DI-DCCT-01:SIGNAL SR-DI-DCCT-01:LIFE120 SR12A-VA-IMG-04:P
Beam dose (A.h)
0
2
4
6
8
10
12
14
16
18
20
22
Life
time
(h)
1E-9
1E-8
1E-7
p (m
bar)
Slope -0.74
1 101E -10
1E -9
1E -8
1E -7g g p p
p (m
bar)
B eam dose (A .h )
2 H 2 18 H 2O 28 C O
New 22m section of storage ringinstalled Sept 2010 (for beamlineI13)
Beam conditioning at 200 mA
Main gases: H2, CO, H2O
Pressure rise due to PSD ~10-7
mbar
PSD yield (η) vs dose (Γ) follows:
η ∝ Γ-0.74
18OLAV-3 Oak Ridge July 2011 Lifetime recovery after girder swap June 2011
Conditioning plots after girder swap Sept 2010
Beamline I13 vacuum layout• Complex beamline with two main
branches (CO and IM)• External vacuum duct
• Two 150m long x‐ray beam pipes 100 to 200 mm diameter
• Windowless• Pumped from ends only (except
during installation)• Differential pumping to achieve
UHV ∼5x10‐9 mbar at both ends• Exposed to ambient
temperature variation = outgassing rate variation
• In‐situ baked• New design fast‐closing mask to
protect normal fast‐closing valve from synchrotron radiation heating to give more vacuum protection options
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Beamline I13 schematic (CO branch only)
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Beamline I13 external duct
1.00E-09
1.00E-08
1.00E-07
1.00E-06
1.00E-05
0 10000 20000 30000 40000 50000 60000 70000 80000 90000 100000 110000 120000 130000 140000 150000 160000 170000 180000 190000 200000
Pre
ssur
e (m
Bar
)
z (mm)
Ext Transfer lineOH1 OH2 OH3Int Tfr Differential pumping
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Bakeout of external vacuum duct
Measured pressure in external duct CO branch
Calculated pressure in beamline (CO and IM branches)
10‐7 mbar
Some accelerator component failures
Titanium coating damage inside ceramic
kicker vessel
Electrical insulation failure caused melted
hole in septum vacuum vessel (x2)
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Some beamline vacuum issuesBroken window on
beamline (x2)
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Failed shutter bellows after a few hundred cycles – mechanical
design error (x4)
Pressure spikes from ferrofluidic vacuum seals
Carbon deposition on x-ray optics
Synchrotron radiation heating damage
Melted LN2 pipe in monochromator due to undulator beam heating
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Melted hole in fast closing vacuum valve titanium plate due to undulator beam
Kapton insulated wire problemPressure spikes trip interlock system
Beam on only
IR mirror and x‐ray absorber in beamline
B22
RGA
Mass 69
CF3+
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Kapton insulated wire problem
Kapton insulated wire contains unexpected FEP binder which
breaks down due to scattered x‐rays
CF3+ also seen with electron irradiation (5keV) in test system
Solution: remove Kapton insulated wire near strong x‐ray beam
absorber or scatterer
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Multiple occurrences in different front ends and beamlines
Future upgrades and challenges
OLAV-3 Oak Ridge July 2011
• Complete phase 2 then phase 3 and beyond:• Complex beamlines• Complex vacuum experimental stations and detectors• 7.9 m long NEG vessel for I05?• “Superbend” dipole magnet?• Additional IDs in existing straights?
• Optimisation of vacuum interlock protection system: beamline protection vs machine reliability
• Maintain and improve supplier vacuum QA for beamlines and small quantities of vessels
• One-offs of complex vessels for spares and upgrades: manufacturers maybe unable or unwilling
• Obsolescence of equipment and spares• Direct integration of RGA systems into EPICS (currently via Windows PC
intermediate)• Increase beam current to 500 mA
27
Summary
OLAV-3 Oak Ridge July 2011
• Diamond has a large and complex UHV system
• It is operating reliably to specification (<10‐9
mbar in the storage ring). The main residual gas is hydrogen
• Many small and medium size upgrades have been installed over the past 4 ‐ 5 years
• A number of vacuum challenges had to be solved along the way
• The journey is not over yet and there will be more challenges to come
28
Acknowledgements
OLAV-3 Oak Ridge July 2011
• Diamond Technical Groups
Vacuum
Engineering
Controls
• Suppliers
• Other labs for helpful advice
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OLAV-3 Oak Ridge July 2011
Thank you
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