PROBE PROTON BOOSTING EXTENSION FOR IMAGING AND THERAPY

PROBE: PROTON BOOSTING EXTENSION FOR IMAGING AND THERAPY Sam Pitman Dr Graeme Burt Dr Hywel Owen Dr Robert Apsimon

FUN FACT! First X-Ray image published in 1896. Wilhelm Röntgen took it of his wife Anna Bertha Ludwig. First patient to be treated with a linear accelerator was only 2 years old! In 1957. He survived into adulthood with normal vision.

PROTON THERAPY Maximum energy is deposited within the tumour site with minimal energy deposited in healthy tissue. Treatment currently limited by range verification. Margin around tumour site is limited in treatment planning to account for uncertainties in dose delivery. Image from: Ladra, M. and Yock, T, Cancers 2014, 6, 112 -127; doi: 10. 3390/cancers 6010112

PROTON TOMOGRAPHY PRa. VDA Technology Several modalities can aid range verification. CT currently used for treatment planning – conversion from Hounsfield units produces error. Proton imaging measures proton stopping power. 250 Me. V sufficient to image children and heads. Need 350 Me. V protons to image through anybody, Bragg peak must not occur inside patient. Second Proximal Proton Tracker First Distal Proton Tracker International Patent: WO 2015/189603 Residual Energy Detector (Range Telescope) Second Distal Proton Tracker 100 – 300 Me. V protons Energy. Absorbed = Energy. Beam - Energy. Residual ∝ Range Energy. Beam . . 24 layers of strip sensors or CMOS imagers Entry position Exit position Energy. Absorbed } Repeat millions of times!

PROTON STOPPING POWER PCT Prompt Gamma Better accuracy than X-Ray imaging and lower dose. Prompt Gamma ray emission occurs within nanoseconds of interaction. Imparts a small additional dose to the patient as opposed to prompt gamma which does not add to therapy dose. Independent of treatment – can be used for treatment planning Large equipment cost Each element emits characteristic gamma-rays with different energies i. e ‘real-time’ signal – patient must receive dose to be imaged. Gamma rays only emitted where proton beam interacts in the patient (i. e where dose is deposited)

PRODUCING 350 MEV PROTONS Cyclotrons High dose rate possible PSI cyclotron 590 Me. V High cost for proton therapy centres Synchrotrons Can produce 350 Me. V protons no degrader needed Large space requirement More complex

PRODUCING 350 MEV PROTONS Pro. BE NORMA Normal-Conducting Racetrack Medical FFAG Accelerator Large footprint. Not demonstrated. TERA and CERN have developed high TERA gradient linacs for proton therapy. We propose a pulsed linac upgrade. 3 m of available space in existing proton therapy facility. Cyclotron produces 250 Me. V protons for therapy, then Pro. BE linac accelerates to 350 Me. V for imaging. TERA & PSI – IMPULSE Cyclinac 7 m – 25 MV/m TERA b. TW achieved 50 MV/m at 3 GHz. 2. 5 mm aperture radius is too small Cyclotron 250 Me. V for cyclotron. Pro. BE Linac

SMALL APERTURE HIGH GRADIENT SCHEME A=1. 75 mm X-Band S-Band # cells 40 10 Coupling 12% 2% Septum 1 mm 2. 6 mm Epeak 167 MV/m 555 MV/m Hpeak 585 k. A/m 300 k. A/m Rs/L 72. 4 MΩ/m 96. 8 MΩ/m Gradient 50 MV/m ↑ single cell pillbox data with scaled septums. High coupling requirement for x-band degrades septum. high shunt impedance advantage. High Epeak needs to be optimised. High magnetic fields result from magnetic Aperture can be opened up without degrading coupling. Rs. 68 MV/m

TRACKING SIMULATIONS RF bucket is approximately 3 times synchronous phase for phases <80°. Estimated the longitudinal transmission then scanned the aperture to determine necessary aperture size.

STRUCTURES INVESTIGATED

FINAL STRUCTURE

TUNING STUDS Anticipated tuning from manufacturing tolerances ~3 MHz Maximum deformation of tuning stud 2 mm is +6 MHz/-4 MHz

POWER Average power limited to 2. 3 k. W by heat transfer through thin iris. Temperature gradient across the structure causes operational detuning. 18° between cooling and iris anticipated detuning of 180 k. Hz but this needs to be tested. 12. 8 MW at 4. 5µs long pulse. Rep rate 40 Hz = 2. 3 k. W Average power. Imaging current = 2% =3. 2 p. A.

ORIGINAL DISK Cut Septum

• Coupling slot must be manufactured to high accuracy. • Magnetic peak field here. • The slot geometry and the radius around are crucial to RF performance. • Cant access the slot with • Opposite side of disk. • Positioning of the capacitive region of the side coupled cell obstructs access to coupling slot with machining tools.

RF CHECK BONDING BRAZING

TESTING Experimentally verify gradient of prototype cavity S-Box 3 GHz testing facility at CERN Currently testing KT structure.

PROBE Operational location of linac R 3 2 1 Stage 1 • Develop prototype linac • S-Box • High gradient test at CERN Stage 2 • Research Beamline • 4 th room at Christie Stage 3 • Linac moved back into beamline • Superconducting Gantry

Thanks for listening! Questions?

RESEARCH BEAM LINE £ 4. 5 M funding from The Christie Charity only funds room & magnets so far. Other charitable and research funding being sought. Test linac with a relevant energy beam. 2 cavities and spectrometer to measure the energy spectrum of the beam after acceleration. Looking to borrow a klystron and modulator.

GANTRIES AND ENERGY SELECTION ‘A compact superconducting 330 Me. V proton gantry for radiotherapy and computed tomography’ In Proc. International Particle Accelerator Conference IPAC 14, 2014. Normal conducting (c. 1. 8 T) Superconducting (c. 2. 8 T) 350 Me. V beam rigidity is larger – superconducting magnets. Booster can either go in the Beam Transport System or mount onto gantry. Energy selection incorporated into optics – neutrons from collimation do not reach patient. Gantry optics underway