FCC Kicker Systems M.J. Barnes, T. Kramer CERN TE-ABT 02/12/2016 - ETHZ visit

Outline of Presentation CERN Accelerator Complex Beam Transfer – Kicker Magnets Kicker Magnets – brief description Pulse generators typically used for kicker systems The need for new developments FCC extraction (dump) kicker system FCC dilutor kicker system M.J. Barnes & T. Kramer 02/12/2016 - ETHZ visit

CERN’s particle accelerators The Large Hadron Collider (LHC): Two beams of >1014 of protons each circulating around a 27 km ring at close to the speed of light, in opposite directions; Made to collide in 4 detectors (ALICE, ATLAS, CMS, LHCb); ~90 µs per rotation; At 7 TeV each proton has ~7500 times the mass of a stationary proton. 25 ns Bunch: presently up to 1.16x1011 protons per bunch. Up to 2808 bunches circulating per beam LHC Beam: Awake LHC 450+450GeV to 7+7TEV; SPS 25Gev to 450GeV PS 1.4GeV to 25GeV PSB to 50MeV to 1.4GeV Note: relative circumference of the rings…. Many different detectors have to be used, each providing a different piece of information to physicists. To understand such a complex system, one needs to observe the phenomenon from different points of view, using different instruments at the same time. LHC experiments ATLAS A Toroidal LHC Apparatus, general-purpose detector. 46 metres long, 25 metres in diameter, and weighs about 7,000 tonnes; CMS Compact Muon Solenoid, general-purpose detector. The complete detector is 21 metres long, 15 metres wide and 15 metres high. 4T magnetic field LHCb LHC-beauty. A specialized b-physics experiment, that is measuring the parameters of CP violation in the interactions of b-hadrons (heavy particles containing a bottom quark) ALICE A Large Ion Collider Experiment: optimized to study heavy-ion collisions. TOTEM Total Cross Section, Elastic Scattering and Diffraction Dissociation. The detector aims at measurement of total cross section, elastic scattering, and diffractive processes. LHCf LHC-forward, is intended to measure the energy and numbers of neutral pions (π0) produced by the collider. This will hopefully help explain the origin of ultra-high-energy cosmic rays. MoEDAL Monopole and Exotics Detector At the LHC LHC preaccelerators Linear accelerators for protons (Linac 2) and Lead (Linac 3) PS Proton Synchrotron SPS Super Proton Synchrotron Animation courtesy of Lorena Vega Cid M.J. Barnes & T. Kramer 02/12/2016 - ETHZ visit

Beam transfer between accelerators time kicker field intensity injected beam ‘boxcar’ stacking “n” Septum magnet Kicker magnet (installed in circulating beam) Focusing-quad Injected beam Circulating beam Defocusing-quad Field “free” region Thin septum blade Homogeneous field in septum Kicker field: fast rise/fall, good flat-top, high precision timing Beam injection, extraction, dump: M.J. Barnes & T. Kramer 02/12/2016 - ETHZ visit

LHC Injection Kicker Magnets LHC Transmission Line Kicker Magnet Ferrite yoke Magnet, in vacuum tank, with ceramic tube Ceramic tube Kicker Magnet Screen conductor in slot “Ground” on one end of outside of ceramic tube Ceramic capacitor LHC Injection Kicker Magnets Baked out to 325°C to be compatible with ultra-high vacuum (~10-11 mbar in tank); 2.7m long magnet; ~3m long ceramic tube with 42 mm inside diameter, in 54 x 54 mm aperture of kicker. Ceramic tube is a “carrier” for conductors – to screen the ferrite yoke from the high intensity LHC beam; One end of each screen conductors is connected to ground, the other is capacitively coupled to ground; High vacuum pressure can result in electrical breakdown. M.J. Barnes & T. Kramer 02/12/2016 - ETHZ visit

Pulse Generators PFL and PFN based Generators Very fast systems (30ns rise time) are mostly using PFL’s and thyratron switches (di/dt): in general deuterium thyratrons are used as the power switch for kicker systems. “Slower” systems (0.2-3µs) are based on PFN and GTO, IGBT or MOSFET technology (stacked). M.J. Barnes & T. Kramer 02/12/2016 - ETHZ visit

The need for new developments Pulse Forming Line: PFL has limitations: it should be matched to the load impedance, but coaxial transmission lines are commercially available only with certain impedances; It is increasingly difficult to source coaxial transmission line for the highest voltage (~80 kV) kicker systems. Suitable semiconductor switch topologies can help to solve the above problems. ~340mm Thyratrons: +ve: Three-gap thyratrons can hold-off 80 kV and switch 6 kA of current with a 30 ns rise-time (10% to 90%) [~150 kA/μs]. -ve: pre-fire (self turn-on without a trigger signal) is a concern for systems requiring very high reliability; -ve: is only a closing switch  need for PFN/PFL for energy storage. M.J. Barnes & T. Kramer 02/12/2016 - ETHZ visit

Inductive Adder R&D Traditional topology: Inductive adder topology: n x low voltage layers ON/OFF by MOSFETs or IGBTs Magnetic coupling Impedance Z PCB Courtesy Patrick Faure: Magnetic core Capacitor Secondary M.J. Barnes & T. Kramer 02/12/2016 - ETHZ visit

FCC Extraction Kicker System MKD QF QD MSD MKBH MKBV TCDS Dump Block TCDQ Part of a safety critical system: Up to 8.5 GJ to be safely extracted and dumped. Extraction Kickers & Generators (MKD) Horizontal Dilution Kickers & Generators (MKBH) Vertical Dilution Kickers & Generators (MKBV Septum Initially challenging requirements. BT-Optics team developed very beneficial layout! Started with ultra high current considerations (tr=10µs). Evolved to a fast but segmented system for machine protection and feasibility reasons. Unit Extraction Dilution Kinetic Energy TeV 3.3 to 50 Available length m 130 150 Deflection angle mrad 0.13 0.21 Field rise time (0.5-90%) µs 1 Field flattop duration ≥ 333 ~350 Magnet current kA 0.5 to 8 11 Output voltage range kV ~10 ~20 M.J. Barnes & T. Kramer 02/12/2016 - ETHZ visit

Extraction Kicker Magnet Preliminary Design Concept : Based on (robust) LHC MKD design. Outside vacuum (ceramic chamber). Segmented system (300 units per beam): Allows low inductance and hence fast rise time Impact of one unit on beam <1σ 10 “hot spares” included (increases system availability) With the help of the developed beam optics we succeed to achieve reasonable design values! Parameters (per module) B.dl [T.m] 0.076 k [µrad] 0.517 B [T] 0.25 Length [mm] 300 Inductance [µH] 0.38 Current [kA] To 8 Voltage [kV] 10 * Aperture (h/v) [mm] 36/36 * assuming additional circuit inductance (1µH) M.J. Barnes & T. Kramer 02/12/2016 - ETHZ visit

Extraction Kicker Generator One generator per Magnet (10 kV / 8 kA) System rise time of 1 µs. Challenge: Compensation stage to be designed for 330 µs: Long flat top needs some thought (compensation circuits). Possibly using GTO switch technology. long “on” state duration (330 µs) – segmented system (lower current helps a lot versus very high current concept) Promising developments within the “wide band gap” sector. Direct laser triggering being investigated. Again reasonable basic design values achieved but: Reliability will be extremely important! Possible radiation effects will be a serious issue which needs to be addressed. M.J. Barnes & T. Kramer 02/12/2016 - ETHZ visit

Dilution Kicker System Dump pattern crucial for survival of dump block! Dense collaboration with FLUKA studies on dump devices. No crossing, 1.8 mm minimum bunch separation. Spiral seems to be the only good solution. Painting inwards to ease hardware design. Resulting dump radius in the region of 600 mm! Same radiation concerns as for MKD! Horizontal and vertical system could use the same generator design. Vertical generators would be triggered at 90 degree of horizontal sine wave (= 5µs @ 50kHz). No issue during normal operation but for asynchronous beam dumps only the horizontal dilution is available immediately. First 5 µs of beam would be painted on a horizontal line before the spiral starts. Impact to be checked. M.J. Barnes & T. Kramer 02/12/2016 - ETHZ visit

Dilution Kicker Magnets A very challenging system! Highest B.dl to deliver and aperture of the vertical system increases with length. Introduced 2 vertical magnet types. Quadrupole after MKBH for “over focusing” in horizontal plane under study. Short magnets to allow for 3-turn coil and higher dilution frequency. Higher number of magnets: Impact of missing (or misbehaving) unit lower (to be optimized). Unit Value B.dl Tm 35 Lever arm m 2800 Angle mrad 0.21 Max. deflection 0.588 Design frequency kHz 50 MKBH Unit MKBV1 MKBV2 max. B-field T 0.85 0.5 0.4 magnetic length m 0.9 horizontal aperture mm 62 81 104 vertical aperture 40 58 Total length ~150m MKBH MKBV2 MKBV1 39 48 43 m 54 m M.J. Barnes & T. Kramer 02/12/2016 - ETHZ visit

Dilution Kicker Generators Magnet Inductance [µH]* I [kA]* U [kV] ** MKBH 5 9 22 MKBV1 4.8 10.8 20.5 MKBV2 4.4 11 19 * For magnet with three turn coil. ** 1µH considered for additional circuit Inductance. Reasonable main capacitance: 1.8 µF Amplitude decay needs to be improved to avoid getting higher density towards the centre. M.J. Barnes & T. Kramer 02/12/2016 - ETHZ visit