1 / 113

PHY862 Accelerator Systems Hadron linacs (protons, H-minus, ions)

PHY862 Accelerator Systems Hadron linacs (protons, H-minus, ions). Peter N. Ostroumov Professor of Physics Michigan State University. Content. LINAC layout, LINAC systems Pulsed and CW linacs Linacs for light ions (protons, H-minus, deuterons) Linacs for heavy ions up to uranium

sunee
Télécharger la présentation

PHY862 Accelerator Systems Hadron linacs (protons, H-minus, ions)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. PHY862 Accelerator SystemsHadron linacs (protons, H-minus, ions) Peter N. OstroumovProfessor of Physics Michigan State University

  2. Content • LINAC layout, LINAC systems • Pulsed and CW linacs • Linacs for light ions (protons, H-minus, deuterons) • Linacs for heavy ions up to uranium • Proton/H-minus linacs • RF system • Focusing • Accelerating structures • RFQ • RF resonators • Beam dynamics • Heavy ion linacs • Multi-charge acceleration • Literature: https://lib.msu.edu/searchresults/?Ntt=RF+Linear+Accelerators+Wangler P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  3. Conditions for RF acceleration • Two conditions for RF acceleration should be fulfilled: • The wave has electric field component in the direction of particle motion • The wave phase velocity is equal to the particle velocity: synchronism • Two periodic systems can be used for the RF acceleration • Periodically loaded waveguides: acceleration by a traveling wave. Periodic reflections from the conducting walls reduces phase velocity of the wave below the speed of light • So far traveling wave structures are use in electron linacs only • Periodic coupled resonator structure: acceleration by a standing wave. Standing wave is composed of a sum of two traveling waves prorogating in opposite directions • Room temperature linacs • Single resonators structures • Mainly superconducting cavities P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  4. Transit time factor • Electric field distribution in the accelerating gap in resonator • Note: sometimes q is the charge and sometimes q is a number of electrons removed from an atom General expression for the energy gain P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  5. Energy Gain •  is the synchronous phase • Note : q or qe in ion accelerator • Transit time factor ( T or TTF) • In linear hadron accelerators the phase is referenced to the crest P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  6. Transit time factor for even function Ez • If the electrical center coincides with geometrical center • If the velocity change in the gap is small P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  7. Transit time factor in Drift Tube Linac (DTL) gap, simplified • Some approximations • TTF for multi-cell cavity: Lecture 8, p.14 g Ez -g/2 z g/2 P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  8. Transit time factor for a multi-gap SC resonators Ez is the odd function Ez is the even function P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  9. Hadron RF Linac Layout Typical RF Linac structure Medium-energy section Front end High-energy section Drift Tube Linac (DTL) Separated DTL (SDTL) IH-structure SC cavities Ion source Radio Frequency Quadrupole Coupled Cavity Linac (Side coupled structure Disk-and Washer Structure Annular Coupled Structure) SC Cavities (Elliptical Spoke-loaded TEM-class) Frequency jump Lattice transition P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  10. Hadron Linear Accelerator Systems • Ion source • Accelerating structures • Standing wave structures (resonators) • To reduce the cost of the linac, radio frequency can change as velocity increases • Focusing structure • Pulsed or DC power supplies • RF power amplifiers • Based on vacuum tubes, klystrons, solid state • HV modulators, cooling system • Beam diagnostics • Sensors and electronics • Control system • Cryogenic system • Vacuum system • Provide residual pressure below 10-7Torr • In SC resonators, vacuum is ~10-9Torr P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  11. RF linacs ATLAS ISAC-II INFN ReA3 SARAF ADS-IMP FRIB ADS front end SPIRAL-2 PIP-II EURISOL ISAC-I (RFQ, IH) RIKEN inj. SARAF RFQ ANL RFQ FRIB RFQ RISP RFQ GANIL RFQ LANSCE Synchrotron Injectors (FNAL,KEK, CERN, IHEP….) MMF (Moscow) SNS CSNS SNS ESS CSNS CERN SPL *Low-energy, several MeV/u Heavy-ions P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  12. Typical parameters of hadron linacs • Normal conducting (usually pulsed machines due to limitations of thermal issues ) • Beam current: up to 200 mA • Beam energy: up to1 GeVfor protons or H-minus • Uranium (UNILAC - GSI): up to 11 MeV/u • Duty cycle up to 12% (LANSCE) • Superconducting ion accelerators (CW) • ATLAS • 50 SC cavities, ~70 MV total voltage • 238U up to 10 MeV/u • PIAVE-ALPI (INFN, Legnaro, Italy) • 40 SC cavities, ~50 MV total voltage • 132Xe up to ~7 MeV/u • ISAC (TRIUMF) –about 40 MV total voltage • FRIB: 200 MeV/u Uranium, 400 MeV/u light ions, 400 kW beam power, CW • SNS (NC up to 187 MeV and SC from 187 MeV to 1 GeV) • 1.4 MW proton beam on target • Projects • FNAL PIP-II: 0.8 GeV, 1 mA CW • GANIL: 5 mA, 40 MeV, q/A=1/3 • SARAF: 5 mA 40 MeV, q/A=1/2 • IFMIF: 125 mA, 40 MeV deuterons • ESS: pulsed, 2 GeV, 5 MW • MYRRHA, CW, 600 MeV, 4mA P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  13. Standing wave structure: DTL (Alvarez)- drift tube linac • Long cylinder resonator • Loaded with drift tubes • Electromagnetic field is TM010 like (Lecture 6, p. 36) • Drift tubes are usually used to house focusing devices: magnetic quadrupoles • Traveling wave structures are not efficient for low velocities due to high RF losses (heat in the walls) • Proton and ion accelerators use standing wave structures Decrease d to reduce 0 P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  14. DTL • Protons, f=198.2 MHz, resonator diameter is ~1 meter • From 0.75 to 20 MeV from 90 MeV to 100 MeV P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  15. Drift Tube Linac (DTL) P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  16. Wideroe or interdigital structure Wideroe or Sloan–Lawrence coaxial-line structure in a π−3π configuration P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  17. IH and CH structures Focusing triplet P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  18. IH and CH structures • Very high shunt impedance up to  ~ 0.5 P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  19. JPARC H-minus linac P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  20. J-PARC Linac Layout DTLSDTL Drift-Tube LInacSeparated DTLAnnular-Ring Coupled Structure (ACS) P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  21. J-PARC DTL • F=325 MHz, H-minus, 3 MeV to 50 MeV • H-minus accelerators are popular as injectors to synchrotrons P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  22. Side coupled structure, LANSCE, SNS section • Energy range: 100- 800 MeV • High shunt impedance ~50 M/m • See Lecture 7-10, p. 108-110 • Room temperature • Known as CCL – coupled cavity linac • Lecture 7, p. 37-39 P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  23. Annular coupled structure at JPARC 972 MHz Axially symmetric coupling cell High shunt impedance P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  24. High power amplifiers for DTL P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  25. Klystron P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  26. 805 MHz Klystron • Klystron in its solenoid mounted on its pulse transformer P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  27. JPARC klystron gallery 2011.09 Klystron gallery of the J-PARC linac 972MHz 330m 324MHz P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems" P.N. Ostroumov Lecture 11 PHY862 "Aceclerator Systems"

  28. Fixed velocity and variable velocity accelerating structures Normal Conducting Beam β/2 Normal or Super Conducting Beam βOPT/2 P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems" P.N. Ostroumov Linac Overview - Introduction 28 June 15, 2014

  29. CW Linacs • 200 MeV/u FRIB linac P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  30. FRIB Linac configuration (see also Lecture 8, p 23-30) N= 12 100 72 148 P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  31. High power heavy ion linac is required for production of radioactive beams • Beam power is limited by available current from the ECR ECR LINAC Target St1 St1 St1 q is the ion charge state P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  32. Stripper effect on beam parameter • Stripping lowers intensity in each charge state • Main issue is the stripper damage due to • (a) heating • (b) radiation P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  33. Theory of multi-q beam acceleration Energy gain per nucleon q is the ion charge state, A is the mass number Fixed velocity profile. (RFQ, RT DTL), energy gain per nucleon will be the same for any q/A if Velocity is defined from energy gain per nucleon. Beam synchronous velocity is defined by the geometry of drift tubes and electric field Variable velocity profile (SC Linac) E0=const, Tune phases of individual cavities Multi-q heavy-ion beam Acceleration. The same synchronous velocity for different charge states P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  34. Synchronous phase as a function of uranium ion charge state. The designed synchronous phase is –30for q0 =75. P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  35. E (z) g 0.15 -0.15 -0.1 -0.05 0 0.05 0.1 Distance, m E 0 q=73 q=75 q=77 w t Later arrival Earlier arrival Synchronous phase of multi-q beam • Single accelerating gap S P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  36. Separatrix and small longitudinal oscillations (Lecture 5) P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  37. Uranium beam stripping and total voltage, 400 kW, 400 MeV/u Bunching efficiency =80% Multiple charge state acceleration P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  38. Effective shunt impedance of accelerating structure • V is the effective voltage which includes transit time factor, R is the shunt impedance of the cavity (see also Lecture 6, p.45) • In Linacs we also use effective shunt impedance per unit length, L is the length of the accelerating structure • The maximum accelerating field in resonators is limited with breakdown field EPEAK • Depending on specific type of the resonator,E0is lower than EPEAK by factor of 2-6 P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  39. Peak fields in accelerating cavities • Normal conducting structures made from copper • Kilpatrick limit was introduced in 1950s, it is an empirical formula • In modern structures, electric field exceeds Kilpatrick limit by a factor of 1.5 – 2.0 • Superconducting structures • Peak magnetic field is limited by quench, theoretical value is ~200 mT at 2K • Peak electric field is limited by the surface quality. ~120 MV/m can be achieved. Operational values are lower • Peak fields can not be measured • These ratios are known from the simulations of the resonator design • EACC can be obtained experimentally from the stored energy P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  40. Linac economics The linac cost is sum of capital and operation cost The capital cost is the cost of accelerating structure The operational cost is the electric bill and maintenance effort The cost of a linac depends from the choice of an average accelerating gradient • Total cost, L is the length of linac • Capital cost per meter CL • Capital cost per watt of power CP • Energy gain • Power loss in the resonators’ walls, E includes TTF • Beam power P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  41. Linac cost Accelerator cost as a function of the accelerating gradient • Total cost • Structure power cost • Beam power cost • Structure length cost Cost E (MV/m) Accelerating field can be limited by breakdowns in resonators P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  42. Continuous Wave Linac (100% duty cycle): NC or SC ? • Required wall plug power to create accelerating field where  is the efficiency of the RF generator • Typical example: 1 GeV CW linac • Superconducting CW linac is much more economic than NC • Both pulsed or CW SC linacs require NC front end for ~0.1 to 10 MeV/u depending on q/A and duty factor Transition energy is higher for pulsed linacs: SNS – 187 MeV ESS - 50 MeV P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  43. Notations P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  44. Radial dependence of the accelerating field • See Lectures 6, p 19,20 • The radial dependence of the accelerating field is notable only for hadron accelerating structures due to <c • The Bessel functions appear as a result of wave equation solution in axially-symmetric structures P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  45. Longitudinal motion In most of accelerators particles perform radial oscillation close to axis in the way that << 1 and the value of the modified Bessel function is close to 1. Compare to Lecture 5, now we have radial dependence of the accelerating field P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  46. Hamiltonian is generalized momentum which is canonically conjugate to the generalized motion coordinate  Hamiltonian describes particle oscillations around synchronous particle. If we assume that particle energy and velocity are changing slowly during particle oscillations then the Hamiltonian does not depend on time and it is a constant of motion.  P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  47. Phase space trajectories • Potential energy Phase trajectory equation for each value of H Separatrix extension in phase is ~3s Profile of the potential function and a family of phase trajectories 47 P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  48. Separatrix For stability condition, the synchronous phase must be negative The value of Hamiltonian, corresponding to separatrix, is New variable, more commonly used in Linacs Separatrix equation P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  49. Acceptance . P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

  50. Accelerating field and phase trajectories • This separatrix is plotted for a conservative approximation (“fish”) • These trajectories include acceleration, non-conservative approximation (“golf club” shape) 4. P.N. Ostroumov Lecture 11 PHY862 "Accelerator Systems"

More Related