Owned and operated as a joint venture by a consortium of Canadian universities via a contribution through the National Research Council Canada

Propriété d’un consortium d’universités canadiennes, géré en co-entreprise à partir d’une contribution administrée par le Conseil national de recherches Canada

Canada’s National Laboratory for Particle and Nuclear Physics Laboratoire national canadien pour la recherche en physique nucléaire

et en physique des particules

Operational experience and upgrade of the TRIUMF

cyclotron vacuum system

3rd UK Vacuum Symposium October 17-18, 2012

Dimo Yosifov | TRIUMF, Canada

Outline

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• Facility overview• Cyclotron vacuum system upgrade

• Vacuum seals experience• Summary

TRIUMF

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TRIUMF…• Is Canada’s national laboratory for nuclear and particle physics research and related sciences. It is located

on the campus of the University of British Columbia in Vancouver. • Is owned and operated as a joint venture by a consortium of universities. Operations are supported by the

Government of Canada via a contribution through the National Research Council. The Government of British Columbia provides additional support for building infrastructure.

• Serves the Canadian particle and nuclear physics, molecular and materials science, and nuclear-medicine communities.

• Has a staff of 340 scientists, engineers, and technicians, and a further 140 postdoctoral fellows, graduate students, and co-op students.

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Layout

New H- source

500 MeV Cyclotron:

• 5 material science ( µµµµSR) facilities

• ISOL facility for RIB experiments

• 2 isotope production facilities

• Proton therapy facility

• Proton irradiation facility

• Neutron irradiation facility

Cyclotrons owned by Nordion

ISAC-I & ISAC-II Rare Isotope Beam Facilities

� TRIUMF flagship program

� Isotope Separation On Line (ISOL) facility with high power driver beam

� Single user facility(single driver, two target stations)

� Fourteen experiments on the floor in three areas: low, medium, high energy

ISAC-ILow and medium energy

ISAC-IIHigh energy

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ISAC-I Experimental Facilities

TITAN

TUDA

DRAGON

EDM

TRINAT ββββ-NMR

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ISAC II SRF Heavy Ion Linear Accelerator

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ISAC-II Experimental Facilities

DENEX

IRIS

TIGRESSEMMA

TUDA

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Cyclotron Capability

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Last decade routine operation: 220-250 µA extracted

Recently achieved:

MuSR program & 500 MeV isotopes:

• BL1A (120µA)

ISAC program:• BL2A (100µA)

Sr production:• BL2C (80µA)

• Total (300µA)

Long term plan: 400 µABL4=>100 µA

BL1A

BL2A

BL2C

BL4

Cyclotron operation statistics

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0

1000

2000

3000

4000

5000

6000

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Del

iver

ed h

ours

Year

Cyclotron availability

Operation statistics

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0

100

200

300

400

500

600

700

800

900

1000

2005 2006 2007 2008 2009 2010 2011Year

Annualy Delivered Beam Charge

BL2A BL2C4 BL1A

mAhrs

M20 upgrade & T2/M9 leak

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Built in 1972 for $12M ($66M in 2012)First beam accelerated in Dec. 1974

Cyclotron constructionThe 500 MeV Cyclotron at TRIUMF: The World’s Largest Cyclotron

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Cyclotron Tank

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Volume ~ 105 m3 Vacuum ~ 2x10-8 Torr

VACUUM TANK

Defines the volume where the beam can be accelerate d in vacuum.

Diameter: about 17.9m diameter, or min/max dia. 1702cm - 1788cm)

Area (top or bottom) : ~235 square metersHeight: 46cm when closed Floor and Lid: 2.2cm thick, 316SSTSides: 3.5cm thick, 316 SSTSeal: Double Buna N seal at edge of lid with the space

between the seals pumped out. Pumping system: Six cryogenic pumps, two turbo-

molecular pumps, two 10.6m long cryo-panels (each h as both 77K & 20K lines).

Pressure achieved: Less than 8 x 10-9 Torr (2012) with out beam, pressure when the beam is on is < 5 x 10- 8 Torr

• Atmospheric load: 2660 tons pushing down on the lid and the same pushing up on the bottom. The tank is held apart by the center post, tank wall and 664 1.5-inch (3.8cm) diameter tie-rods (332 on the tank floor and 332 on the lid), resulting in about 7 tons (6350kg) of tensile force on each tie-rod. The centre post and tank wall take up the remainder of the load.

• A 12-arm "spider" support structure, weighing about 120 tons, was fabricated from 3.6 m high, 0.9 m wide steel I-beams. Its primary purpose is to anchor the upper tie-rods thus resisting the atmospheric load on the lid. It also supports the upper magnet sectors, tank lid and internal components when the lid is lifted. When lowered, the spider rests on the top of the 12 jack columns.

VACUUM TANK SUPPORT STRUCTURE

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Cyclotron vacuum system controls page

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Cyclotron Tank Pumping

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4 Mech. Pumps (D250) with 3 (2xWS2000+1xWS500) Blowers – for initial evacuation of the tank to less than 1E-3 Torr pressure.2 Turbo pumps (Leybold 3500 L/s + Leybold 1500 L/s) – used during cryo-panes defrost 6 Cryo-pumps ( 5x CTI 400 + 1x CTI 8) – for H pumping.2 Cryo-panels (x10.6 m long) – main pumping capacity ~ 50000 L/s.

LHe

LN2

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80K

Cyclotron4.5K

LINDE 1630

LN2 tank

He Buffer TankCompressor

Vaporiser

Heat Exchanger used to vent the

tank

NitrogenRe-cooler

Cryo-panel

Cryo-panel

Cyclotron cryo -pumping infrastructure

Cyclotron vacuum system upgradeNew He Refrigerator LINDE-1630

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• In 2007 the 30-year -old Stirling cycle Philips cry o-generator was replaced with LINDE-1630 He refrigerator.

• Cooling agent (He) temperature was reduced from 18K to 4.5K.

• H2 pumping speed increased from 5700 l/s to 26000 l /s.

• Vacuum improved from 5x10 -8 to 2x10 -8 Torr.

• Maintenance interval increased from 800 to 3500 hou rs!

• Cryo-pumps replacement with high H pumping capacity units is ongoing.

• New cryo-absorber techniques are being tested.

Primary beams operational conditions and radiation

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• High intensity beams are accelerated (~300 µA) and transported (<150 µA)

• H acceleration inherits ~5% beam losses:• Residual gas stripping (~1%)• Transmission losses in the vertical plane (~1%)

• Lorenz stripping losses (~3%)

• Non-achromatic beam transport causes losses (<0.1%)

• Beam interaction with thick targets for meson & RIB production create extremely harsh radiation environment.

• Components service must be minimized to reduce personnel exposure - TRIUMF’s shutdown dose budget is 100-150 mSv

• Remote handling have to be applied to highly radioactive parts.

Vacuum seals experience

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• Original installation employed multiple sealing technologies:

I. Elastomer (Buna N) seals.

II. Aluminum wire seals.

III. Indium seals.

• Some of elastomer seals survived over decades of service

• Majority of Buna N seals are replaced with metal seals.

• Others are periodically exchanged.

Cyclotron seals

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• Cyclotron tank main seal:

• Two Buna N rings ~60m long each

• Inter-seal space evacuated.

• Needs replacement every 5 years due to radiation damage.

• Replacement involves 16 people for 2 work days and 12 mSv total dose ~10% of shutdown dose budget.

• All cyclotron ancillary ports are sealed with Aluminum wire

• Some of ancillary devices employ Buna N seals, which are periodically replaced.

Air at 1atm

~20 mTorr

2x10-8 Torr

Beam lines (BL) seals experience

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• Original Buna N seals in some locations were exposed to excessive radiation due to beam losses of up to 1 nA/m

• Elastomer seals break within a year after direct exposure to beam current of 20 pA.

• Seals radiation damage caused frequent vacuum leaks.

• BL seals replacement is extremely dose intensive: o Service time must be minimized!

• Over last decade ~80% of BL elastomer seals were replaced with metal seals of two types:o Helicoidal seal – Delta Helicoflex.

o Knife edge seals - ConFlat, “Diamond” edge.

• All metal seals demonstrate high reliability.

Helicoidal spring loaded seals

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The sealing principle of this family ofseals is based upon the plastic deformationof a jacket of greater ductility than theflange materials. This occurs between thesealing face of a flange and the elasticcore composed of a close-wound helicalspring. The spring is selected to have aspecific compression resistance. Duringcompression, the resulting specificpressure forces the jacket to yield and fillthe flange imperfections while ensuringpositive contact with the flange sealingfaces. Each coil of the helical spring actsindependently and allows the seal toconform to surface irregularities on theflange surface.Application of these seals:• from UHV to high pressure• From -270 C to ~400 C

Knife edge Aluminum seals

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• Installed between flat surfaces

• Tightened with chain clamp

Seals in high radiation areas

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• Remote handling operations are used to service vacuum joints in high radiation areas:

– Cyclotron tank to beam line gate valves– Production targets interconnecting joints, located at BL1A

• Indium seal with constant spring load applied.• Joint design incorporates convoluted bellows in the adjacent beam pipe:

– It helps the seal joint assembly.– provides joint flexibility to support seal’s controlled compression.

• In stationary conditions Indium seals show excellent performance and it is easy to service.

Indium seals

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Indium joints issue

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• The radiation shielding is composed of concrete and iron oreblocks, weighting from several to 20 tons each.

• Due to water leaks the heavy concrete swelled and deformed.• Crumbling shielding blocks affect the beam line components

positioning.• Meson production target stations experienced mechanical

displacement beyond the flexibility margin of the Indium jointconfiguration (~1 cm) and repeatedly developed vacuum leaks

• Each leak repair required ~6 weeks intervention.• The repairs often didn’t last long because of the indium joints

exposure to high neutron fluxes causing thermo-cycles.• Possible solutions:

– Address shielding blocks interference – new blocks.– Improve joint’s flexibility – use welded bellows.– Modify joint – use different type metal seal, but – RH to be solved.

Compromised T2/M9 joint (top view)

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Remote Handling setup for 2011 M9 joint repair

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Summary

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• Cyclotron Vacuum system has shown to be reliable andafter 200t upgrade is working at longer beam productionintervals and requires less maintenance time.

• For reducing the beam downtime and eliminating radiationdose to TRIUMF employee the Buna N seals are beingreplaced with metal seals.

• TRIUMF has accumulated reach experience of vacuumcomponents handling in extreme radiation conditions.

• 500 MeV Cyclotron remains TRIUMF’s “workhorse” and itsvacuum system is being continuously upgraded to maintainhigh reliability.

Canada’s National Laboratory for Particle and Nuclear Physics Laboratoire national canadien pour la recherche en physique nucléaire

et en physique des particules

Thank you!Merci!

4004 Wesbrook Mall | Vancouver BC | Canada V6T 2A3 | Tel 604.222.1047 | Fax 604.222.1074 | www.triumf.caNovember 17, 2012 Dimo Yosifov 3rd Vacuum Symposium UK

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