the birmingham experience; problem solving at the birmingham … wheldon_copenhagen_2017... ·...

June 2017 Copenhagen, Scanditronix meeting 1

The Birmingham experience; problem solving at the Birmingham MC40

Carl WheldonCarl Wheldon


Overview

● Operation and uses

● Technical changes and challenges

● A look to the future

● Summary

● (Brief history)


History of accelerators at Birmingham

RDI 3MV Dynamitron(1970 - )

3 MeV p on Li for Boron Neutron Capture Therapy(BNCT).



MC40 cyclotron(2002-2004) transferred from Minneapolis, USA (installed 1988, run 1991-2001).



MC40 cyclotron(2004 - )In 2005 we added a 12-way switching magnet (blue) [ex Vivitron, Strasbourg, France]


Beam lines

More recently, we were asked to provide high dose-rate damage studies (LHC ATLAS group and metallurgy) so extended a second beam-line into a specially shielded area.


Beam lines

High current irradiation cell:(Left) ATLAS line on the (Right) Metallurgy chamber

Low current irradiation line:(Right/upstream) Radiobiology, space applications.(Left/downstream) Nuclear physics scattering chambers.


Isotope production

In 2009 Birmingham acquired most parts from the decommissioned Hammersmith MC40 cyclotron.

Spare parts critical to the low down-time necessary for medical isotope production.


MC40 cyclotron – uses

Hot filament ion source

Beams available:p: 11-39 MeV and 3-9 MeV (N=2)d: 5.5-19.5 MeVα: 11-40 MeV3He 33-54 MeV and 13-27 MeV.

Also 46 MeV 14N4+ and 70 MeV 14N5+ for nuclear physics.

•Producing positron emitting nuclides for Engineering PET [NOT FDG1].•Producing 81Rb for 81mKr generators.•Thin Layer Activation.•Other isotope production:

• 69Ge for labelling oil,• 62Zn supplied to St Thomas’ Hospital, London,• Various irradiations for NPL.

•Radiation effects studies:• Radiobiology + dosimetry (proton imaging),• Space electronics etc.,• ATLAS components,• Metallurgy of nuclear materials.

•Nuclear physics• Research,• Undergraduate research projects,• Postgraduate training.

1FDG = fluorodeoxyglucose.


MC40 cyclotron – uses

81Rb (4.6 h)● Parent of 81mKr (gas), which decays

(13s) to ground state emitting 190 keV gamma; (parent/daughter generator).

● 81mKr used for imaging lung function using gamma camera

Production 5 evenings per week, 50 weeks per year


Rubidium-81 production

Using the technique developed at Medical Reserach Council (MRC) Cyclotron Unit (Hammersmith Hospital, London):

● Irradiate target containing 82Kr gas (6 bar pressure) with 29 MeV protons (30 A).

● 81Rb is produced and deposits on walls of target.

● At end of irradiation, recover 82Kr gas cryostatically.

● Then elute 81Rb from target: 3 x 40ml transferred to dispensing room.

● Finally evacuate target ready for reuse.● Currently making approx 60 generators per week – fairly stable.

Entire procedure is controlled by Beckhoff Programmable Logic Controller (PLC).

Same PLC has gradually been extended to control cyclotron interlocks etc.


Positron emission particle tracking (PEPT)

Modular camera installed on Modified Leistritz 27mm TSE

Label a single particle (e.g. grain of sand) with positron-emitter

(usually 18F from 3He on natural oxygen) and track it as it moves

inside equipment


Tracer particles of PEPT

Most are labelled with 18F (half-life 110 min.) produced by cyclotron irradiation of oxygen [16O(3He, p)18F]:

● “Large” (>1mm) particles of silica, alumina etc. are directly activated – activity firmly fixed in bulk

● Smaller particles, and other materials (plastics etc.) are indirectly labelled – produce 18F in solution and then attach it to particle using appropriate surface chemistry (bridging ions, etc.) - these tracer particles are generally OK except in aqueous environments, when the activity rapidly leaches off again.

For aqueous environments, we have developed other radioisotope labels. For example, 66Ga (9 hours) produced by proton irradiation of Zn, followed by cation exchange separation.


Thin layer activation

Steel:• 56Fe(p,n)56Co (77 days, 0.85 MeV and 1.24 MeV gammas).• 56Fe(d,n)57Co (270 days, 0.122 MeV gammas).

Can activate different surfaces with each for simultaneous studies.Aluminium:

• 27Al(3He, 2α) 22Na (2.7 yrs, 0.511 MeV & 1.27 MeV gammas)Diamond-like carbon (DLC) coatings•12C(3He, 2α )7Be (53 days, 0.47 MeV gamma).

For measuring wear on components (especially automotive parts, for R&D): ● Irradiate surface with beam to create long-lived

radionuclide in well-defined surface layer (typically ~ 50 μm deep).

● Subsequently monitor surface removal by detecting gamma-rays either from remaining layer or from wear debris.


ATLAS radiation hardness testing

Samples in cold box (fed with liquid nitrogen) scanned through 27 MeV proton beam.


A difficult year

TragedyOn the 24th January 2017 Mike Smith, our cyclotron manager, died unexpectedly.

Mike dismantling the MC40 in Minneapolis.


Current view

Rb production targets

System 8500, MPS854T900A/150V output


Recent technical issues

● October 2016: Main magnet power supply failure due to cooling water leak.

● Approximately four weeks to repair supply.

● March 2017 new Danfysik power supply installed.

● March 2017 deflector change to solve extraction problems

● Due for change – typically once per year

● ‘New’ deflector conditioning lost every 24-48 hours.

● Might be due to a tiny water leak. Not a problem for running at the moment if machine is well used. Better than previous.

● Three or four usable deflectors available.


Magnet supply change

Old and new magnet supplies

System 8500, MPS854T900A/150V output. Accuracy +/-10ppm over 8 hours.


Recent technical issues

● January 2017, RF braid problems in cavities.

● Burnt hole through cavity to water jacket – water leak in cavity

● Changed from 27 MeV protons to 26 MeV (~2 cm apart).

● Cleaning in resonator but problem persisted, new holes, moved to 29 MeV protons.

● Found PLC air pressure threshold set too low…leading to catastrophic damage. Now running at 28 MeV.

● Have tried four different braid suppliers. Too tight pressure, and tube won’t inflate, too slack and tube protrudes.

● Ultimate solution might be to swap to taller, Hammersmith resonators.


Resonator cavity damage

Fixed leaks with combination of soldering and plumbers compound. Access difficult even to see problem. Need to solder using mirror.


Difficult to clean after problem

After several attempts at cleaning in situ – dismounted plate.

Difficult to reach outer surface for cleaning following burning from bad contact. Removal was less time consuming that thought.

braid Grounding plate


Rubidium/krypton production

Rubidium statistics: since 2006 made rubidium for 35252 generators.

– 1 for a successful production run,– 0.5 for a run where production was less than requested– 0 for a complete failure.

On this basis:– 2015 we had a 99.1% reliability– 2016 88.5% (disappointing) 224 runs out of 253 requested were successful (2167 generators produced in total).

Overall since 2006, success rate 96.2%(2673.5 out of 2778 successful).


Dose recording

Improvements made:

● Development of a touch-screen interface for entering dose information per task. Justification, optimisation, limitation.


Summary and perspectives

● One new appointment (March 2017).● One operator retired (June 2017).● Power supply replaced (spare) and new one installed.● RF braid and air pressure threshold issues in

resonators resolved.● Deflector short circuits – deflector change.

Future

Discussion under way for post-5-year future. Uncertain. Thanks to Prof. David Parker and Robert Goodwin for providing information shown in this presentation.


Thanks for your Thanks for your attention.attention.


Birmingham in the sunshine

The tallest free-standingclock tower in the world.



60” Nuffield cyclotron (1948-1999).

10 MeV p, 40 MeV α.

Construction started 1937: copy of Lawrence’s 60” cyclotron.

Operated 51 years.

Yoke etc. still in place.

2015



1 GeV proton synchrotron(1953-1967).

Mark Oliphant had idea for proton synchrotron.

Birmingham machine overtaken during construction by Brookhaven Cosmotron.



Radial Ridge cylotron(1960-2002).

(Axially injected polarised beams)12 MeV d, 24 MeV α,33 MeV 3He.

Completely decommissioned after 2002: yoke now in Nuffield vault.


Safety

Decontamination area – wipes, eyewash etc.Soon to be

added, alarm to attract attention.

Lockable physical barrier.

Lockable door motor controls.


Safety

Ozone monitor.

Dose monitor data logger

and interlock.


Safety

Health and Safety Executive (HSE) visit in April 2016.

Improvements made:● Continuous training of operators (annually) and focused on

unexpected scenarios – contingency planning.● Personal Electronic Dosimeters (PEDs) for all classified

workers.● Berthold dose monitor (10µSv/h-10Sv/h) installed inside the

cyclotron vault with display and logger outside area.● Interlock above 200 µSv/hr controlled by monitor.● Ozone monitor.

● Physical barriers to prevent casual access – lockable cover over door motor controls and metal barrier to demark supervised area.

the birmingham experience; problem solving at the birmingham … wheldon_copenhagen_2017... ·...

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