Contributions to ELI-NP on RF accelerator activities Andrea Mostacci Università di Roma, Sapienza The joint Sapienza/INFN-LNF group is active in the field of S-band, C-band, X- band accelerator devices design and construction. The group is interested both in designing beam generation and manipulation devices as well as the technological issues related to the construction of devices standing the high RF power needed in modern accelerators. Through numerical simulation, we study and optimize the electron beam dynamics in a single device as well as in the whole machine. Moreover we are commissioning the LNF photo- injector (SPARC), the first S-band/C-band high brilliance linear accelerator. As a university based group, we have also experience in training students in their first steps in the accelerator physics and technology.

Contributions to ELI-NP on RF accelerator activities ELI-NP: the way ahead Bucharest, March 2011 Outline GoalShow our experience and ongoing activities on RF issues of accelerator physics which can be useful for ELI-NP Group M. Ferrario, B. Spataro, L. Serafini (INFN/LNF) and researchers from INFN/LNF accelerator division R&D activities on RF issues X-band devices: beam manipulation devices (e.g. harmonic cavities) and beam generation devices (hybrid SW/TW gun). C-band devices: high gradient accelerating sections and RF guns, installation and commissioning. Beam dynamics studies and optimisation (S-band, C-band, X-band and mixed solutions). High brightness photo-injector (SPARC) commissioning. Training and educational experience. Contribution to ELI-NP. L. Palumbo (Sapienza) and its group S-band devices: installation and operation of S-band accelerator and in-house RF gun construction.

Contributions to ELI-NP on RF accelerator activities ELI-NP: the way ahead Bucharest, March 2011 Commissioning of SPARC S-band Gun Velocity Bunching Long Solenoids Diagnostic and Matching Seeding THz Source 150 MeV S-band linac 10 m Undulators u = 2.8 cm K max = 2.2 r = 500 nm 15 m High Brilliance photo-injector

Contributions to ELI-NP on RF accelerator activities ELI-NP: the way ahead Bucharest, March 2011 S-band devices (~ 3 GHz) We presently are runnig a S-band linear accelerator producing high brightness 180 MeV electorons. A novel improved RF gun is at the executive design stage (design scalable to higher frequencies). We design, built and operate RF deflectors for beam length measurement. Our device, first tested at SPARC, has been rebilt and installed in PSI SWISS-FEL and FERMI FEL injectors. SPARC RF DeflectorRF gun Beam

Contributions to ELI-NP on RF accelerator activities ELI-NP: the way ahead Bucharest, March 2011 C-band devices (~ 6 GHz) For SPARC energy upgrade ( 180  250 MeV ), we will install and operate in- house built TW sections. (>35 MV/m accelerating field) Symmetric input coupler Output couplers S-band injector in a C-band linac will be tested next SPARC and it is the solution adopted by PSI. After the succesful Spring 8 FEL, the C-band seems a mature and reliable technology. We are investigating a fully C-band linac design, including C-band RF gun. For a given bunch charge, wake fields and beam loading are relaxed with respect to higher frequency solutions. The same arguments holds for timing, synchronization and jitters issues. Beam RF power 48 MV/m Power KEK

Contributions to ELI-NP on RF accelerator activities ELI-NP: the way ahead Bucharest, March 2011 X-band devices: design & production X-band ( GHz) harmonic cavities for longitudinal phase space compensation in high brilliance photo-injectors Technological issues (high power SLAC), novel materials Low power test and multi-cell cavity tuning z axis (cm) Accelerating cells TUNERTUNER Coupling cells Cu Mo RF power Beam RF CAD design

Contributions to ELI-NP on RF accelerator activities ELI-NP: the way ahead Bucharest, March 2011 X-band devices: design & production Technological issues (high power SLAC), novel materials Low power test and multi-cell cavity tuning z axis (cm) ~ 17 cm 9 cells Accelerating cells TUNERTUNER Coupling cells Cu Mo RF power Beam X-band ( GHz) harmonic cavities for longitudinal phase space compensation in high brilliance photo-injectors

Contributions to ELI-NP on RF accelerator activities ELI-NP: the way ahead Bucharest, March 2011 X-band devices: R&D on manufacturing Photographs of three manufactured X band cavities: (a) Cu brazed; (b) Mo brazed; (c) Cu electroformed. B. Spataro, invited contribution to X-Band Structures, Beam Dynamics and Sources, December 2010 V. Dolgachev, SLAC We join the world wide effort to avoid hot brazing to

Contributions to ELI-NP on RF accelerator activities ELI-NP: the way ahead Bucharest, March 2011 X-band hybrid gun (Sapienza/INFN/UCLA) The S-band version will be commissioned in UCLA (J. Rosenzweig) Device under study Emittance- Compensating Solenoids Photo- cathode RF input Laser (266 nm) Electrons RF Input coupler TW structure (lower field) 1.6 SW structure (higher field) SW RF gun section fed on-axis from coupling cell that also feeds (the majority of the power) to a lower gradient downstream TW section (no circulators needed). The gun strongly longitudinally focuses, from velocity bunching due to 90° phase shift between SW cell and input coupler. Next steps: RF design optimisation (with beam dynamics), hot tests … The hybrid gun is part of the CRISP proposal. 2.5 SW structure TW structure RF input coupler RF output coupler RF power

Contributions to ELI-NP on RF accelerator activities ELI-NP: the way ahead Bucharest, March 2011 Beam dynamics studies Simulations of particle beam evolution in linear and circular accelerators based on macro-particle models. Study of collective effect due the particle wake fields. Micro-bunching instability due to coherent synchrotron radiation (CSR) and space charge in linear or in circular machines (e.g. RF and/or magnetic compressors). Beam dynamics optimization of accelerator devices (e.g. hybrid gun). Beam optimisation in S-band, C-band, X-band linac and for mixed frequency machines (SPARC is the first linac operating at two frequencies) CSR in a ring Bunch Length in hybrid gun time energy 1 O C temperature shift

Contributions to ELI-NP on RF accelerator activities ELI-NP: the way ahead Bucharest, March 2011 Beam dynamics studies for SPARX SPARX is a mixed frequency machine (S-band/C-band) to be commissioned before 2015 (C-band gun is under investigation). SPARX has a nominal energy of 750 MeV (FEL operation) to 900 MeV (on crest operation, corresponding to 18 MeV Compton photons). C-band has been chosen for reliability consideration (as PSI). Thermal emittance 0.6 um/mm, minimum emittance (Ferrario) working point. Q (pC) ε (μm) E peak (MV/m) Brightness (A/m 2 ) Q/ε 2 (pC/μm 2 ) S-band (90 A)1000 S-band (70 A)1720 S-band (40 A)2770 C-band (92 A)2080 C-band (scaled) (73 A)1830 X-band (90 A)3400 X-band (58 A)3400 X-band (Hyb. gun) (90 A)1050 Luminosity/spectral density Parmela/Astra simulation + scaling laws

Contributions to ELI-NP on RF accelerator activities ELI-NP: the way ahead Bucharest, March 2011 Educational and training experience All the previous activities are pursued with the aid of students, either master thesis or PhD level, that every year get their diploma at Sapienza (Faculty of Engineering). We give lectures in international accelerator schools, such as Joint Universities Accelerator School (JUAS) or Cern Accelerator School (CAS). We give also a course on Physics and Technology of Accelerators at the University of Rome, Faculty of Engineering and Faculty of Physics. In the framework of our long standing collaboration with INFN/LNF accelerator physics division, we can also profit of the experience gained at SPARC (an accelerator physics research machine) where many talented PhD students from our university have been trained. At the moment we have PhD and master students working on accelerator physics topics. The core topics where most of the students have been trained range from beam dynamics in linear and circular machines (including collective effects) to design methodology and bench measurements of RF devices in particle accelerators at frequencies from S-band (3 GHz) to X-band (12 GHz).

Contributions to ELI-NP on RF accelerator activities ELI-NP: the way ahead Bucharest, March 2011 Conclusions Ongoing collaborations: We design and construct RF devices for beam generation (photo-gun) and beam manipulation (IV harm. cavity, RF deflectors, …) in the 3-12 GHz frequency range. We have experience in beam dynamics optimisation of linear/circular machines We take part to commissioning of High Brilliance photo-injector SPARC We train PhDs and technical engineers in accelerator physics INFN (other labs/sections), UCLA, CERN, LULI, ELI, EuroFEL (IRUVX FEL), SLAC, KEK We are interested in sharing our experience in design and the realization of RF devices for the ELI- NP accelerator We are interested in contributing to the setting up of accelerator physics expertise in ELI-NP We are interested in contributing to beam dynamics studies and commissioning of the accelerator in ELI-NP

Contributions to ELI-NP on RF accelerator activities ELI-NP: the way ahead Bucharest, March 2011 Additional material

Contributions to ELI-NP on RF accelerator activities ELI-NP: the way ahead Bucharest, March 2011 The S-band version will be commissioned in UCLA (J. Rosenzweig) Device under study Emittance- Compensating Solenoids Photo- cathode RF input Laser Electrons RF Input coupler TW structure (lower field) 1.6 SW structure (higher field) SW RF gun section fed on-axis from coupling cell that also feeds (the majority of the power) to a lower gradient downstream TW section (no circulators needed). The gun strongly longitudinally focuses, from velocity bunching due to 90° phase shift between SW cell and input coupler. Next steps: RF design optimisation (with beam dynamics), hot tests … The hybrid gun is part of the CRISP proposal. 2.5 SW structure TW structure RF input coupler RF output coupler RF power X-band hybrid gun (Sapienza/INFN/UCLA)

Contributions to ELI-NP on RF accelerator activities ELI-NP: the way ahead Bucharest, March 2011 The S-band version will be commissioned in UCLA Device under study Emittance- Compensating Solenoids Photo- cathode RF input Laser Electrons RF Input coupler TW structure (lower field) 1.6 SW structure (higher field) SW RF gun section fed on-axis from coupling cell that also feeds (the majority of the power) to a lower gradient downstream TW section (no circulators needed). The gun strongly longitudinally focuses, from velocity bunching due to 90° phase shift between SW cell and input coupler. Next steps: RF design optimisation (with beam dynamics), hot tests … The hybrid gun is part of the CRISP proposal. 2.5 SW structure TW structure RF input coupler X-band hybrid gun (Sapienza/INFN/UCLA) Temperature sensitivity 200 kHz/ o C

Contributions to ELI-NP on RF accelerator activities ELI-NP: the way ahead Bucharest, March 2011 The S-band version will be commissioned in UCLA Device under study Emittance- Compensating Solenoids Photo- cathode RF input Laser Electrons RF Input coupler TW structure (lower field) 1.6 SW structure (higher field) SW RF gun section fed on-axis from coupling cell that also feeds (the majority of the power) to a lower gradient downstream TW section (no circulators needed). The gun strongly longitudinally focuses, from velocity bunching due to 90° phase shift between SW cell and input coupler. Next steps: RF design optimisation (with beam dynamics), hot tests … The hybrid gun is part of the CRISP σ z < 10  m (90 A) ε n,x < 0.08 mm-mrad σ x < 80  m 6.7 pC Brilliance= A/m 2 X-band hybrid gun (Sapienza/INFN/UCLA) 6 kG