1. September 13, 2007 J. Alessi 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)

2. September 13, 2007 J. Alessi Advantages of the new preinjector: Simple, modern, low maintenance Lower operating cost Can produce any ions (noble gases, U, He 3  ) 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 12 Stripper

3. September 13, 2007 J. Alessi Placement of EBIS Preinjector in lower equipment bay of 200 MeV Linac Beam port Booster Linac RFQ EBIS 17 keV/u 300 keV/u 2 MeV/u 100 MHz Ion He - U Q/m≥1/6 Current> 1.5 emA (for 1 turn inj) Pulse Length 10  s Rep. Rate5 Hz Time to switch species 1 second

4. September 13, 2007 J. Alessi 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! Principle of EBIS Operation

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

6. September 13, 2007 J. Alessi Ion Injection and Extraction from the RHIC EBIS External ion injection provides the ion species; the EBIS acts purely as a charge breeder. Advantages: 1.One can easily change species and charge state on a pulse to pulse basis 2.There is virtually no contamination or memory effect 3.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. September 13, 2007 J. Alessi 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. September 13, 2007 J. Alessi Performance Requirements of the Ion Source SpeciesHe to U Output (single charge state)≥1.1 x 10 11 charges / pulse Intensity (examples)3.4 x 10 9 Au 32+ / pulse (1.7 mA) 5 x 10 9 Fe 20+ / pulse (1.6 mA) > 10 11 He 2+ / pulse (> 3.0 mA) Q/m≥ 0.16, depending on ion species Repetition rate5 Hz Pulse width10 - 40 µs Switching time between species1 second Output emittance (Au 32+ ) < 0.18  mm mrad,norm,rms Output energy17 keV/amu

9. September 13, 2007 J. Alessi Superconducting solenoid: Length1 meter Maximum field5 Tesla Bore155 mm diameter, warm Helium consumption0.12 l/hr Drift tubes: No. of electrodes12 Bore diameter31 mm Trap length0.7 m Electron gun cathodeLaB 6, 8.3 mm diameter (upgraded to IrCe) Electron collector power50 kW Vacuum1 x 10 -9 to 4 x10 -10 Torr in most regions (most sections bakeable to 200C, central DT’s to 450 C) Diagnostics: Toroid current monitor0.5 m from ion extractor Emittance1.0 m from ion extractor Faraday cup1.5 m from ion extractor Time-of-flightMamyrin-type, 2 m from ion extractor Key hardware features of the BNL Test EBIS

10. September 13, 2007 J. Alessi EBIS Results and RHIC Design Parameters

11. September 13, 2007 J. Alessi EBIS Assembly E-Gun (10 A) Drift Tube Structure Electron Collector Superconducting Solenoid (6 T) Acceleration Tube

12. September 13, 2007 J. Alessi LEBT/Ion Source Region

13. September 13, 2007 J. Alessi 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 3 He gas (proposal). Polarized 3 He gas is produced by a “metastability exchange” technique. P ~ 70-80% (pressure ~ 1 torr). 3 He 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, B c (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 ·10 11 of 3 He ++ /store). It is sufficient to obtain ~10 11 He ++ /bunch in RHIC. (Zelenski)

15. September 13, 2007 J. Alessi Estimate for 3 He 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 10 13 atoms/s, polarized 3 He flow in needed to get P=10 -8 in the bore.

16. September 13, 2007 J. Alessi What intensity expected? Capacity will be 10 12 charges/pulse  ~ 2-3 x 10 11 3 He ++ 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 3 He gas injection into the EBIS-ionizer. Polarized 3 He 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. September 13, 2007 J. Alessi

19. September 13, 2007 J. Alessi

20. September 13, 2007 J. Alessi 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 3 He++, or 900 keV for a short period) (C. O’Connell talk)