1 / 19

Accelerators (<1 MeV/n) for Low-Energy Measurements Workshop on Underground Accelerators for

Accelerators (<1 MeV/n) for Low-Energy Measurements Workshop on Underground Accelerators for Nuclear Astrophysics October 27-28, 2003 Jose Alonso, Rick Gough Lawrence Berkeley National Laboratory. Outline.

maxim
Download Presentation

Accelerators (<1 MeV/n) for Low-Energy Measurements Workshop on Underground Accelerators for

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. Accelerators (<1 MeV/n) for Low-Energy Measurements Workshop on Underground Accelerators for Nuclear Astrophysics October 27-28, 2003 Jose Alonso, Rick Gough Lawrence Berkeley National Laboratory

  2. Outline • Types of accelerators suitable for low-energy nuclear astrophysics applications • Other system components • Existing and possible new configurations • Important questions to be addressed • REQUIREMENTS

  3. Types of Accelerators • For low energy, linacs are generally considered more “straight forward” than circular machines • There are various schemes to apply kinetic energy:- radio frequency (rf), induction, or static potential drop • A dc electrostatic accelerator is a potential-drop type of linac with typical voltages up to several MV • Offers easy and continuous energy variation • Superior energy dispersion: DE/E ~10-4 compared to room temp. rf linacs or RFQs (~10 -2 ), SCRF linacs (<10-3), or cyclotrons (>10 -3 ) • Energy dispersion determined by dc power supply voltage regulation

  4. Power Supply Types for DC Accelerators • Van de Graaff (including pelletron) – low current but capable of reaching terminal potentials > 10 MV • Cockcroft-Walton – uses a ladder network to build voltage up to ~1 MV • Dynamitron – a “shunt-fed” type Cockcroft-Walton that has higher current capability and provides voltages to a few MV • External transformer – high current capability but high voltage limited by breakdown between windings • Coaxial transformer – a high current (50 mA) and high voltage (2.5 MV) design under development

  5. Tandem Configuration • Higher beam energies • Ion source at ground • Requires negative ion source which limits current and ion species +V • Strip to q+ in high voltage dome • E/A = V  (q+1)/A but

  6. Van de Graaff / Pelletron S-Series NEC Pelletron (1 - 5 MV) National Electrostatics Corporation Open air systems for lower beam energies (1 - 500 keV) Pelletron charging principle

  7. Ultra high precision energy… TUNL, ca 1980??

  8. Traditional Linac Injectors • Open air electrostatic systems used as traditional linac injectors – require lots of space, largely being replaced by RFQs • RFQs are compact and efficient – tunability and low DE/E problematic for this application 500 kV open-air injector at Livermore 2.5 MeV H– RFQ built by LBNL for SNS

  9. Dynamitrons • Dynamitron from Boeing Radiation Effects Lab shown w/cover removed • used to produce x-rays, protons, electrons, and low-Z ions for TREE & space radiation effects • pulsed or dc operation • energies from 0.2 - 2.8 MeV • < 10 mA of electrons • hundreds of microAmps of positive ions • Require high pressure gas ( SF6 ) • Dynamitron was used as HILAC injector and is in use at Argonne for radioactive beam studies

  10. High Current Accelerator Development at LBNL 2 MV pulsed ESQ accelerator for fusion energy (base program) 0.6A K+ 2.5 MV CW ESQ accelerator for BNCT (spin-off application)  25 mA protons coaxial transformer power supply

  11. Then there’s always…

  12. Types of Beam Focusing Electric field lens • Aperture lens – strength decreases with beam energy • Electrostatic quadrupole (ESQ) – strength increases with beam energy Magnetic field lens (best at high beam energy) • Magnetic solenoid lens • Magnetic quadrupoles

  13. ElectroStatic Quadrupole (ESQ) Focusing Basic ESQ module • Provides strong focusing for high beam current • Suppresses secondary electrons • Reduces longitudinal average voltage gradient to accommodate insulators ESQ module for 4 parallel beams

  14. LUNA: Pace-setter in the field LUNA Collaboration, INFN, Gran Sasso

  15. Surface Laboratories • LENA - TUNL • Bochum • Notre Dame • ISAC, TRIUMF • … others? • ~1 MeV electrostatic • Spectrometers • Careful attention to unavoidable backgrounds

  16. Possible HI Solution for Underground Lab Requirement: 50 eµA up to 0.5 MeV/nucleon protons to argon • Low power, permanent magnet ECR ion source mounted on the terminal of a 2.5 MV Van de Graaff could provide cw ion beams from hydrogen to argon at 0.5 MeV/nucleon • Demonstrated performance: commercial permanent magnet ECR ion sources can produce Ar9+ at greater than 100 eµA • Utilize lower charge states for lower energy ranges • Beams from gaseous elements straightforward; beams from solids more challenging but possible • Integration of ECR and Van deGraaff technologies has been demonstrated, but not available as commercial off-the-shelf item E / A = 9 / 40 x 2.5 = 0.56 MeV / amu

  17. ECR in Electrostatic Accelerators ISL Hahn-Meitner Institute Berlin ECR Ion Source in HV terminal JAERI Tandem Tokai Research Establishment, Japan Ar8+ 2eµA at 112 MeV

  18. Important Questions for Accelerator Design - I • Maximum beam energies?(rest-frame, to determine accel. potential) • Range of energies needed?(tunability, energy precision) • Short / long term energy stability(high voltage control, ripple) • Energy spread?(ion source temperature or RF accelerator design) • Ion species needed? • Purity of ion species? – heavy ions with q/A = 0.5 likely to have contaminants – molecular, charge-state ambiguities • What beam currents are required? • What are the beam current stability requirements?

  19. Important Questions for Accelerator Design-II • Beam-on-target requirements?(spot size…) • Duty factor(CW or pulsed? Is RF structure OK?) • Noise constraints? – could x-rays beyond some energy interfere w/ exp. signals? – are accelerator-produced neutrons a background problem? • Site constraints? – space, access, power, utilities, special safety issues... • Configuration flexibility? – may be necessary to have more than one accelerator system to meet all requirements

More Related