Present and possible future schemes for hadron therapy linacs Alberto Degiovanni for the ADAM team HG2017 Workshop , Valencia

Outline Present status of LIGHT Layout First results New developments Possible new schemes Discussion

LIGHT (Linac for Image Guided Hadron Therapy) Overview Proton Source Modulator-klystron systems Radio Frequency Quadrupole (RFQ) Side Coupled Drift Tube Linac (SCDTL) Coupled Cavity Linac (CCL)

LIGHT Main Parameters Parameter Value Unit Length ~25 m Max. Energy 230 MeV Output Peak Current (at the end) 0.3 - 90 μA Pulse Length 0.5-5 μs RF Frequency 2997.92 MHz Max. Repetition Rate 200 Hz Peak RF Power ~60 MW

LIGHT (Linac for Image Guided Hadron Therapy) @point 2 5 MeV 37.5 MeV 70-90 MeV 0.04 MeV

Proton Source Quantity Value Unit Output Energy 40 ± 0.4 keV Output pulsed Current Range: [1-300] ± 2% µA Current ripple during flattop ± 1 % Pulse to pulse current reproducibility ± 2-3 Repetition rate Range: [5-200] Hz Beam pulse width Range: [0.5-5] µs

Proton source test results Example of emittance measurements and corresponding rms emittances (white) with the representation of the RFQ acceptance ellipse (red).

The Radio Frequency Quadrupole (RFQ) High frequency RFQ designed by CERN 4 vanes type 750 MHz 4 modules - 2 m 5 MeV energy gain Section RFQ RF frequency [GHz] 0.749 Energy [MeV] 0.04-5 Length [m] 2 Foto piu’ recente

RFQ test results 5 MeV Results from the RFQ commissioning with beam Profile and energy measurements Comparison of measured and expected beam profiles at the spectrometer profile monitor calculated average beam energy from the spectrometer measurement is 5.07 MeV (expected energy 5.0 MeV) Energy spread: measured rms energy spread is 7.0 keV (expected value is 7.5 keV) Emittance The expected rms emittance is 0.33 p.mm.mrad in both planes 5 MeV

The Side Coupled Drift Tube Linac (SCDTL) Designed in collaboration with ENEA (Frascati, I) Manufactured at TSC/VDL Section SCDTL RF frequency [GHz] 2.998 Energy [MeV] 5-37.5 Length [m] 6.2

The Coupled Cavity Linac (CCL) Section CCL RF frequency [GHz] 2.998 Energy [MeV] 37.5-230 Length [m] 15.5 Designed by ADAM Manufactured by VDL 4 modules already conditioned

SCDTL and CCL E-field measurements

Fields in the CCL accelerating cells

Experience with conditioning and operation

Filling times module Q0 Qloaded τ [ns] CCL1 7320 3660 389 CCL2 7820 3910 415 CCL3 8200 4100 435 CCL4 8620 4310 458 CCL5 8940 4470 475 CCL6 9000 4500 478 CCL7 9800 4900 520 CCL8 10100 5050 536 CCL9 10400 5200 552 CCL10 10600 5300 563 CCL11 10820 5410 574 CCL12 11200 5600 595 CCL13 11520 5760 612   1.5 1.0 0 2.5 us

Some RF gymnastics – reducing the filling time

Energy and Intensity modulations pulsed source Einj active energy variation 70 <E < 230 MeV Klystron RF pulse RF power into the tanks Proton pulses from source 5.0 μs Active energy modulation Rep rate 200 HZ ~ 5 ms Active intensity modulation time I P The cyclinac concept, proposed by TERA Foundation foresees the use of a LINAC booster combined with a 25-30 MeV cyclotron as injector. The use of linacs for protontherapy is very well suited for 3D spot scanning. Protons are provided by an external pulsed source and pre-accelerated by the cyclotron. The extracted protons are then boosted by the linac, that is divided in a certain number of modules each one powered by a compact modulator-klystron system with a typical peak power in the order of 10 MW with a repetition rate up to 200 Hz. The modularity of the linac allows to achieve the active beam energy modulation. By switching ON and OFF the linac modules, and by reducing the power of the last active one, one can vary the energy of the beam from pulse to pulse by electronic means and without the need of absorbers. The beam intensity can also be varied by changing the current from the pulsed source.

A modular approach towards industrialization Unit Systems Accelerating System Control System Cooling System Focusing System RF Network System RF Power System Support System Vacuum System Accelerating System Control System Cooling System Focusing System RF Network System RF Power System Support System Vacuum System

Transverse beam optics A FODO lattice is used to keep the beam focused along the linac Small aperture Permanent Magnet Quadrupole (PMQ): + no power consumption ! + strong gradient possible + reduced size and cost ! - Precision alignement needed ! BJA Magnetics

Energy modulation

Accelerating gradient and real estate gradient Presence of electric field free spaces (for PMQ and flanges!) reduces real estate gradient! Typical filling factor is ~ 70-75%

TW first proposal in X-band X-band travelling wave structure design for TERA (A.Grudiev, 10/12/2008) https://indico.cern.ch/event/47627/contributions/1154791/attachments/955050/1355306/TERA_B05_TWS.pdf Reducing the space for focusing element along the beam path! Strong magnetic field needed!

Conservative/safety aspect in LIGHT 1 Power from klystron: 7.5 MW P_loss wg network: ~ 15% Power available per unit: ~ 6.4 MW Max power used: ~5 MW Power safety/operational margin: ~ 28% RF network includes Isolator for protection of the klystron from reflected power. Part of RF network under SF6 ! LIGHT: 70-230 MeV Peak power [Mw] 48 Total length [m] 12.3 Active length [m] 9.5 Fill factor 0.77 Number of kl. 8

Accelerator shielding Example of shielding impact on the foot-print (only accelerator is considered, since treatment room will be all the same independent of accelerator)

TULIP all-linac with new btw structures BTW – MB klystrons Btw: 70-230 MeV Peak power [Mw] 108 Total length [m] 7.7 Active length [m] 4.4 Fill factor 0.57 Number of kl. 18 SCDTL RFQ

Peak surface fields RFQ IH-750 DTL-3000 BTW-3000 Frequency [MHz] 750 Avg gradient E0 [MV/m] - 5.7 16 50 Peak Es [MV/m] ~ 50 150 200 Peak Sc [MW/mm2] 0.036 0.5 0.75

CABOTO: CArbon BOoster for Therapy in Oncology

Shorter linac = higher power ! Gradient vs Power L = n*lc Shorter linac = higher power !

Conclusion First prototype of LIGHT is under construction and being installed and tested with beam at CERN P2 Conservative design for version 1 – (length vs power) New developments are ongoing in the field, collaboration TERA-CLIC New TULIP and CABOTO designs takes advantages of novel TW structures and future spread of High Efficiency MB klystrons!

¡ MUCHAS GRACIAS !

EXTRA

Typical beam spot at the output of the linac <1mm <1mm <1mm