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EBIS Project and EBIS as an ionizer for polarized He-3 ?

EBIS Project and EBIS as an ionizer for polarized He-3 ?. Jim Alessi. Work of E. Beebe, A. Pikin, A. Zelenski, A. Kponou, … (BNL) R. Milner, F. Simon, … (MIT Bates) E. Hughes (Columbia), C. O’Connell (Caltech). 12. Advantages of the new preinjector: Simple, modern, low maintenance

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EBIS Project and EBIS as an ionizer for polarized He-3 ?

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  1. EBIS Projectand EBIS as an ionizer for polarized He-3 ? Jim Alessi Work of E. Beebe, A. Pikin, A. Zelenski, A. Kponou, … (BNL) R. Milner, F. Simon, … (MIT Bates) E. Hughes (Columbia), C. O’Connell (Caltech)

  2. 12 • Advantages of the new preinjector: • Simple, modern, low maintenance • Lower operating cost • Can produce any ions (noble gases, U, He3) • Higher Au injection energy into Booster • Fast switching between species, without • constraints on beam rigidity • Short transfer line to Booster (30 m) • Few-turn injection • No stripping needed before the Booster, • resulting in more stable beams • Expect future improvements to lead to • higher intensities Stripper

  3. Placement of EBIS Preinjector in lower equipment bay of 200 MeV Linac Booster Linac RFQ EBIS Beam port 17 keV/u 300 keV/u 2 MeV/u 100 MHz

  4. Principle of EBIS Operation • Radial trapping of ions by the space charge of the electron beam. • Axial trapping by applied electrostatic potentials on electrode at ends of trap. • The total charge of ions extracted per pulse is ~ (0.5 – 0.8) x ( # electrons in the trap) • Ion output per pulse is proportional to the trap length and electron current. • Ion charge state increases with increasing confinement time. • Charge per pulse (or electrical current) ~ independent of species or charge state!

  5. Axial magnetic field and electron beam radius along the Test EBIS axis

  6. Ion Injection and Extraction from the RHIC EBIS • External ion injection provides the ion species; the EBIS acts purely as a charge breeder. • Advantages: • One can easily change species and charge state on a pulse to pulse basis • There is virtually no contamination or memory effect • Several relatively low cost external sources can be connected and maintained independently of the EBIS. • However, gas injection is also commonly used in EBIS. This is proposed for He-3.

  7. Test EBIS presently operating on 100 kV platform Will inject ions into an RFQ, which arrives in the spring of 2008. E(out) = 300 keV/amu

  8. Performance Requirements of the Ion Source

  9. Key hardware features of the BNL Test EBIS

  10. EBIS Results and RHIC Design Parameters

  11. EBIS Assembly Electron Collector Superconducting Solenoid (6 T) Drift Tube Structure E-Gun (10 A) Acceleration Tube

  12. LEBT/Ion Source Region

  13. Schedule Procurements have been placed for the RFQ, Linac, EBIS solenoid, rf amplifiers, etc. EBIS components are being fabricated. Summer, 2008 – EBIS testing starts Spring, 2009 – EBIS/RFQ testing starts Fall, 2009 – full system tests

  14. EBIS ionizer for polarized 3He gas (proposal). • Polarized 3He gas is produced by a “metastability exchange” technique. P ~ 70-80% (pressure ~ 1 torr). • 3He gas is injected in the EBIS ionizer. • The ionization in EBIS is produced in a 50 kG field. • This field will greatly suppress the depolarization in the intermediate He+ single charge state, Bc(He+) = 3.1 kG • The charge ratio He++/He+>> 1. • The number of He++ ions is limited to the maximum charge which can be confined in EBIS (about 2.5 ·1011 of 3He++/store). • It is sufficient to obtain ~1011 He++/bunch in RHIC. (Zelenski)

  15. Estimate for 3He flow rate With P~10-8 in the trap, it should take ~20 ms to neutralize the e-beam with He (i.e. reach the trap capacity). If 10-8 in DT region, and with 50 l/s pumping speed from center of bore out (both ends)  need ~ 5 x 10-7 T-l/s gas flow. 5 x 10-7 T-l/s x 3.6e19 atoms/T-l = 2 x 1013 atoms/s, polarized 3He flow in needed to get P=10-8 in the bore.

  16. What intensity expected? Capacity will be 1012 charges/pulse  ~ 2-3 x 10113He++ ions per pulse ? Estimate of wall bounces : With feeding of gas into the center of the trap, we roughly estimate that an atom will undergo ~ 300-400 wall bounces before being pumped away. Depolarization?

  17. Polarized 3He gas injection into the EBIS-ionizer. • Polarized 3He gas can be transported without depolarization through glass and coated metal tubes. • There is a limitation due to the magnetic field gradient from the strong EBIS field in the transport line. Calculations show that there is no significant depolarization with the real magnetic field of the EBIS superconducting solenoid. A. Kocoloski (MIT) (Zelenski)

  18. Summary An EBIS-based preinjector is being built to deliver heavy ions for RHIC and NSRL. Ionization by an electron beam in a 6 T field may be well suited for ionization of polarized He-3 gas. Experiments could be done on the Test EBIS to study methods for injection of polarized gas in to the EBIS trap, possible depolarization, etc. These experiments will require a low energy polarimeter (≤ 200 keV 3He++, or 900 keV for a short period) (C. O’Connell talk)

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