PSI Leadership in high power cyclotrons development and

PSI Leadership in high power cyclotrons, development and synergy with TRIUMF Symposium in Honour of Gerardo Dutto (1938 - 2020) TRIUMF 22. January 2021 Werner Joho PSI

• The PSI/SIN Cyclotron • Connections with TRIUMF • the personality of Gerardo

The race for a Mesonfactory started in 1962 like a friendly Pokergame LAMPF at Los Alamos (800 Me. V Linac) had the best hand with a Full House: 99. 9% extraction TRIUMF in Vancouver had three Queens 98% extraction (with H- - stripping) SIN (PSI) in Villigen, Switzerland had only two Pairs 95% extraction (previous record for cyclotrons was 70%)

TRIUMF Cyclotron SIN Cyclotron

Ring Cyclotron 1974 590 Me. V Protons 8 Magnets 4 RF-Cavities 15 m Diameter Concept: Hans Willax Director: J. P. Blaser

first Sectormagnet 5 pieces à 50 tons (crane!) coils small magnetgap 100 mm at injection 50 mm at extraction

Advantages of a Ring Cyclotron (Hans Willax 1963) Magnet and RF system are decoupled many high voltage cavities good turn separation small magnet gap flattop cavity single turn extraction easy injection and extraction strong vertical focusing low extraction losses => high straight sections intensity low power consumption space for diagnostics + correction elements requires powerful injector!

First 590 Me. V protons on meson-targets 24. 2. 1974 Thomas Werner Stammbach Joho Urs Hans Willax Schryber Francesco Resmini Jean-Pierre Blaser Courtesy M. Olivo

Ring Cyclotron 590 Me. V Protons 2. 4 m. A, 1. 4 MW average Beam Power (World Record!) most intensive Spallation-Neutron- Muon Beams Source 1014 n/s 5· 108 µ+/s , 108 µ-/s equivalent to medium Flux Reactor (but without Uranium!)

Flattop Voltage gives minimum energy spread => separated turns Flattop RF-Voltage with addition of a 3. harmonic (150 MHz) Voltage no flattop: V 1 = cos F 1, 0 0, 8 ideal flattop: V=V 1+V 3 0, 6 0, 4 0, 2 3. harmonic: V 3 = - 0. 115 cos 3 F 0, 0 -90 -0, 2 -60 -30 0 30 60 Phase Φ (deg) 90

Ring Cyclotron (1980) 315 separate turns due to Flattop Cavity Extraction

Injector II 72 Me. V protons Injection Line 870 ke. V Extraction Line Resonator 50 MHz

Current Limit in Ring Cyclotron 2. 4 m. A Longitudinal space charge forces 2009 increase the energy spread 2000 => higher extraction losses Remedy: high voltage V on the RF cavities => low turn number n (V·n = const. ) current limit ~ V 3 ~1/n 3 => new cavities ! Design current W. Joho, 9 th Int. Cyclotron conference CAEN (1981)

New Copper Cavity 50 MHz, 5. 6 m long Voltage limit 1 MV operation at 850 k. V: 60% of the RF power goes to the beam => 1. 4 MW beampower only 40% losses in cavity good for electricity bill !

High Currents in Ringcyclotron 0. 1 to 2. 4 m. A => opportunity for Neutron Source New cavities 1 -4 new RFAmplifiers 4 new targets new Targets Design Goal Injector II 0. 1 m. A Flattop Courtesy M. Seidel

Ringcyclotron: the last 9 of 188 turns eccentric injection, turn separation: 6 => 17 mm => deep valley at extraction septum! Intensity [a. u. ] turns Septum Simulation with Program OPAL (A. Adelman, Y. J. Bi et al) measurement at 2 m. A current limit with losses at Septum of 2 x 10 -4 Factor 1’ 000 in Intensity

Reduction of Extraction losses Current [µA] Losses [%] 100 5 5 2’ 400 0. 02 0. 5 Design Values achieved (2009) Losses [µA] Present Interlock limit of 0. 5 µA allows "hands on" maintenance loss reduction by a factor of Beam Quality Injector II Flattop Cavity eccentric Injection Cavity Voltage (V 3 Law) Total 3 3 5 5 ≈ 250

PSI Experimental Hall Neutronsource SINQ cold Neutrons Injector I => China Pions Muons Injector II Ringcyclotron ultra cold Neutrons Medical Annex (3 Gantries)

PSI has 4 Top-Accelerators Ring-Cyclotron 590 Me. V Protons Swiss Light Source SLS 2. 4 Ge. V Electron Storage Ring, X-rays COMET SC-Cyclotron Protons 250 Me. V, Tumour Therapy Swiss. FEL 6 Ge. V Electrons, X-ray Flashes

PSI East Swiss. FEL => Aare psi Forum Auditorium Exp. Hall Neutron Source Ringcyclotron Medical Annex PSI West SLS

3 complementary Probes for Material Research Muons (m. SR) Neutrons X-rays (SINQ) (SLS, Swiss. FEL) internal magnetic fields in Solids Atomic Nuclei Electron Cloud => only available at PSI and Rutherford Lab

Connections of PSI with TRIUMF => people! many reciprocal visits on cyclotron topics: mostly RF-systems, beam dynamics TRIUMF: Karl Erdman, Milos Zach, Ken Fong, Corrie Kost (created his computer library), SIN/PSI: Paul Lanz, Peter Sigg, Miguel Olivo, Werner Joho (chairman of TRIUMF Accelerator Planning Committee) Many additional exchanges on experiments, theory Hardware: Superconducting muon channel SIN => TRIUMF

The influence of Gerardo Dutto at TRIUMF Gerardo’s first important contribution was to the injection region: he moved the injection point to the correct position! energy gain at first gap: e·V on successive Dee crossings: e· 2 V Þ same beam center for different RF-phases, gives big improvement in beam quality

Another important contribution of Gerardo: Vertical Deflection Plates to compensate misalignments of the large "air plane wings" of the RF-System his top priority as leader of the TRIUMF Cyclotron group: => reliable operation with stable beams for the experimtal groups! But most important: Gerardo was a passionate patron. He cared for his people, like an Italian father and was fighting hard for them! Gerardo initiated good relations with industry (medical cyclotrons), other Institutes and invited many specialists from all over the world (Europe, Russia, China) to TRIUMF => see the talks by Bruce Milton, Tianjue Zhang, Franco Mammarella

Bob Jameson (LAMPF) Ewart Blackmore (TRIUMF) Werner Joho (PSI) Representing the three poker participants! PAC Conference Vancouver 1997 J. Martin T. Stammbach G. Ryckewaert Y. Jongen G. Tagliaferri Gerado Dutto Karl Erdmann Werner Joho Int. Cyclotron Conference Zurich 1975 Werner playing for the TRIUMF Soccer Team

TRIUMF Specialties - great skills of their experts: beam quality, RF-system, controls. . . - simultaneous beams of variable energy - with 300µA: surpassing the design goal of 100µA by a big margin! I enjoyed the company of many good friends: Mike Craddock, Corrie Kost, Dave Gurd, Don Dohan, Karl Erdman, George Mackenzie, Volker Rödel, Bruno Duelli, Larry Root, Paul Schmor, Ewart Blackmore, Rick Baartman, Bob Laxdal, … I am sure a forgot a few! And I had a very good relationship with the first three directors: John Warren, Reg Richardson, Erich Vogt (with ancestors from Villigen!)

a wonderful compliment from Mike Craddock in his talk, celebrating 40 years of he Ring cyclotron in 2014

But very special was my close relationship with Gerardo and his family Marie-Paule George Mackenzie Gerardo 1971 Zurich 1975 Ludka Beijing 2007

Thanks to TRIUMF and to many good friends for two wonderful years in Vancouver (1971 -1973), for many more visits and an everlasting memory Very special thanks to a great friend: mille grazie Gerardo