Maurizio Vretenar Linac4 Project Leader EuCARD-2 Coordinator

Transcription

1 Maurizio Vretenar Linac4 Project Leader EuCARD-2 Coordinator

2 Every accelerator needs a linac as injector to pass the region where the velocity of the particles increases with energy. At high energies (relativity) the velocity saturates at the speed of light and it is less expensive to use circular accelerators. In addition, linear accelerators for electrons are used up to very high energy because in a linear path particles do not lose energy for synchrotron radiation. linacs Linac2 (50 MeV) PS Booster (1.4 GeV) PS (25 GeV) SPS (450 GeV) LHC Stand-alone linacs are low-energy accelerators with many applications in medecine and industry (more than linacs in the world mainly for X-ray therapy) The LHC Injection chain 2

3 A linear accelerator is required as injector to any accelerator chain to cover the range where particle velocity increases with energy. At high energy where b ~ const. a synchrotron is economically more convenient. accelerating gaps d d=bl/2=variable d d bc 2 f bl 2 accelerating gap d=2pr=constant Linear accelerator: Circular accelerator: Particles accelerated by a sequence of gaps (all at the same RF phase). Distance between gaps increases proportionally to the particle velocity, to keep synchronicity. Used in the range where b increases. Newton machine Particles accelerated by one (or more) gaps at given positions in the ring. Distance between gaps is fixed. Synchronicity only for b~const, or varying (in a limited range!) the RF frequency. Used in the range where b is nearly constant. Einstein machine

4 100m One of the options for the future of CERN after the LHC: Compact LInear Collider Study supported by a large international collaboration for a 3 TeV electron collider of 48 km length Advanced R&D phase: 12 GHz, 100 MV/m Normal-conducting e+ INJECTION DESCENT TUNNEL e- INJECTION DESCENT TUNNEL COMBINER RINGS DRIVE BEAM INJECTOR BYPASS TUNNEL DRIVE BEAM LOOPS DAMPING RINGS INTERACTION REGION MAIN BEAM INJECTOR 1km DRIVE BEAM DUMPS TURN AROUND Limestones Moraines Molasse Sands and gravels INJECTION TUNNEL CLIC SCHEMATIC (not to scale) e- SIDE LHC e+ SIDE 4 FRANCE SWITZERLAND

5 In final construction phase 160 MeV proton (H-) linac, 100 m Will contribute to increasing the number of protons in the LHC Visit this afternoon at 16:00 No superconductivity (not economically justified in this range of b and duty cycles); Single RF frequency 352 MHz PIMS CCDTL Energy [MeV] DTL Length [m] RFQ DTL CCDTL PIMS chopper line RF Power [MW] RFQ 160 MeV 104 MeV 50 MeV 3 MeV 86 m 5

6 Main oscillator RF feedback system HV AC/DC power converter High power RF amplifier (tube or klystron) AC to DC conversion efficiency ~90% DC to RF conversion efficiency ~50% RF to beam voltage conversion efficiency particle beam, energy W particle beam, energy W+DW magnet powering system vacuum system water cooling system LINAC STRUCTURE accelerating gaps + focusing magnets designed for a given ion, energy range, energy gain Goal: high accelerating gradients (e-field), high frequency Technological challenges: 1. High precision machining and joining of copper parts 2. High-efficiency generation of high Radio-Frequency power

7 Mechanics (Copper!) 1. High RF frequencies small structures, more compact and with higher power efficiency tighter tolerances to achieve the required precision in the electric field (field error ~ tolerances / wavelength) few microns 2. Joining the parts: excellent RF conductance, good vacuum, keep tolerances. Radio-Frequency: 1. Generation of peak power of >100 kw (but for low duty cycle, usually <5%) at frequencies in the range 350 MHz (Linac4) 12 GHz (CLIC). 2. Achieve DC to RF conversion efficiency > 60%. 7

8 TD26 CC SiC Assembly - Diffusion bonding of high precision disk at about 1035 C - Vacuum brazing of bonded disk stack, assembled cooling blocks, couplers, beam pipes and tuning studs at about 1020 C - TIG welding of vacuum flanges

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10 PIMS (PI-Mode Structure) 12 RF cavities of length 1.5m Tolerances ~ 10 mm Built in collaboration with Poland RFQ (Radio-Frequency Quadrupole) 3 meter length, Tolerances ~ 5 mm Built at CERN

11 Tolerances: ±10 µm for the cavity and ±5 µm for the electrodes

12 - High powers (>100 kw) are produced with klystrons, only 3 companies on the market worldwide. Space for companies producing lower power (<100 kw) solidstate units and associated components (couplers, loads, specialised connectors, etc.). New high-power transistors can open new perspectives bringing the cost/w down

13 Under developement within the new CERN program for medical applications Mini-RFQ at 750 MHz 4 Solid-state RF amplifiers, 100 kw each Compact light-weight system for production of radioisotopes in hospitals: single doses of 18F for PET tomography, short-living isotopes for new imaging techniques. Made of 2 RFQs in cascade reaching 8 MeV energy in a length of 3.2 m. Peak current 1 ma, duty cycle 5%, average current 50 ma. Small size, minimum weight, minimum shielding, high reliability, low electricity consumption in operation and in stand-by.