Birmingham MC40 – technical report - Rigshospitalet mc40_wheldon_lund_small.pdf · MC40 cyclotron – uses Hot filament ion source Also 46 MeV 14N4+ and 70 MeV 14N5+ for nuclear

August 2019 Lund, Scanditronix meeting 1

Birmingham MC40 – technical report

Carl WheldonCarl Wheldon


Overview

● Operation and uses

● Technical issues

● changes/improvements


Orientation


Background of accelerators at Birmingham

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


Background of accelerators at Birmingham

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


MC40 cyclotron – uses

Hot filament ion sourceAlso 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 (hands-on experiment

course).

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 Research Council (MRC) Cyclotron Unit (Hammersmith Hospital, London):● Irradiate target containing 82Kr gas (6 bar pressure) with 27 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.


Rubidium/krypton production

Rubidium statistics: since 2006 made rubidium for 37390 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:– 2018 (to Apr) 94.1%. Main issue was August break down (loose magnetic channel).

Overall since 2006, success rate 96.1%.


Issues/changes since May 2018

● New, regular (fortnightly) Cu-64 production for St Thomas’s hospital, London

● New laboratory refurbished for activation studies and PET/PEPT testing and detector construction.

● Switch to O-18 water for some F-18 production (previously only He-3+O-16).

● Regular trips on the new DanPhysik main magnet power. Eventually tracked to a loose connection to the holding circuit contactor (factory issue).

● Cooling fan replaced on heat exchanger for anode power supply.

● Ion source water leak fixed (symptom was filaments lasting only hours as oppose to weeks) – filaments now lasting well. Still a problem with limit switch and sluice – cyclotron vacuum lost on removal – hard to reach o-ring in need of replacement (moved or damaged). Needs entire centre tube removing – awaiting suitable free day for this maintenance.

● Flap drive threads stripped due to failed limit switch. Workshop made new parts.



● Köln Faraday cup from Uppsala (thanks Holger and Joachim). This affected beam tuning on beam line 6 (the ATLAS beam line). Old FC has a leak in the bellows. NO SPARE…may ask workshop to try fabricating.

● Investigating Berthold stack monitor for positron emitting isotopes – will check flow and level with scintillator detector. Discussion around this would be useful, as we have no way of identifying isotopes with such a monitor.

● Our big re-occurring issue has been failure of our Havar windows on the krypton targets. Two separate causes - failure of our steering/beam scanning power supplies and contamination of our helium cooling system with water (and all the rubbish (Cu sludge) the water flushed out). As a result this has been a poor year for production (



● RF issues – leak around insulator. Also occasional braid burn-up and a water leak in one of the cavities.

● Chiller issues on hot (relative to normal UK temperatures) days with incoming cooling water being very warm. Issue still not clear.

● Broken compressed airline valves not operating – pressure switch added.

● He compressor repaired – replacement being sought. Any suggestions.

● Recently implemented regular maintenance days – every second Friday – as oppose to one large maintenance period. The cyclotron has been busier than ever this year and a large backlog of repairs was acruing.


Shielding – additional wax-filled door in front of vault for high intensity running


Longer term

● As our decommissioning plan states there is 10-15 years of the cyclotron’s lifetime remaining we have been asked to seek agreement in principle from the low-level waste depository for the relevant cyclotron waste.

The Drigg site inNorth West England


Background of accelerators at Birmingham – Dynamitron

RDI 3MV Dynamitron(1970 – v. soon )3 MeV (1-2 mA) of protons on natLi (B’ham developed target).Neutron source >1x1012 n/s @1 mA at 2.8 MeV. Peak epithermal fluence ~2x108 n/cm2/sThis machine will retire in 2 years.

Current bid for replacement (high on the NNUF priority list) neutron irradiation machine using protons or deuterons.


Future accelerator-driven neutron facility

Easily achievable levels - Standard HyperionDynamitron at 30 mA protons specified

Neutron Therapeutics target – fast neutrons at 1.8 x 1011 n/cm2/s.

Thermal neutrons at 6.6 x 109 n/cm2/s(200 x more intense than available at NPL)

Hyperion: A single-ended electrostatic accelerator, 50 mA+ capability

Now sold by Neutron Therapeutics as part of accelerator BNCT facilities, including a developed high power Li target.


Future accelerator-driven neutron facility

Phase 1 (years 1 and 2)Building alteration and hardware procurementAccelerator delivery and installationWork-up to 30 mA protonsFast neutron fluence rate of 2 x 1011n/cm2/sThermal fluence rate of 6 x 109 n/cm2/s.

Phase 2 (years 3-4) Develop suitable ECR deuteron ion sourceModel and test improved solid Li targetNegotiate access to compact liquid Li target if required.

Phase 3(year 5) (separate funding)Implement capability for approaching ~0.5 x 1013 n/cm2/s.Aiming to be the most intense such facility worldwide.

Fig 1. Neutron production cross sections as a function of energy, from [1].


Building overview

Building offers opportunities for expanding the basement (MC40 cyclotron) level.

Dual beam facility possible to study He embrittlement.


Summary and perspectives

FutureIncreased use needs to be managed. Ultimately may need to move to a 7-day running schedule if demand continues to grow. Managing regular maintenance essential.

Main magnet power supply to be scrappedOnly two previous owners….going, going, gone.If any one wants the whole or parts, please let us know this week it will be stripped down and scrapped soon.No warranty to worry about!

Thanks to Prof. David Parker and Ben Phoenix for providing some of the information shown in this presentation.


Thanks for your attention.Thanks for your attention.


Birmingham in the sunshine

The tallest free-standingclock tower in the world.


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.


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.


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.

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Documents

Birmingham MC40 – technical report - Rigshospitalet mc40_wheldon_lund_small.pdf · MC40 cyclotron – uses Hot filament ion source Also 46 MeV 14N4+ and 70 MeV 14N5+ for nuclear