1 / 21

H  Transport and Stripping

H  Transport and Stripping. Weiren Chou March 15 , 2005. Outline. Introduction Mini-workshop on H  transport and stripping 8 GeV H  stripping losses during transport Magnetic field Blackbody radiation Residual gas Foil stripping of 8 GeV H  at injection Conclusions.

salvador-hoover
Download Presentation

H  Transport and Stripping

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. H Transport and Stripping Weiren Chou March 15 , 2005 W. Chou - Proton Driver Director's Review

  2. Outline • Introduction • Mini-workshop on H transport and stripping • 8 GeV H stripping losses during transport • Magnetic field • Blackbody radiation • Residual gas • Foil stripping of 8 GeV H at injection • Conclusions Reference: Fermilab-TM-2285 W. Chou - Proton Driver Director's Review

  3. Introduction • Transport and stripping of 8 GeV H ions is a major technical issue concerning an SCRF linac proton driver. • Today’s highest H beam energy is 800 MeV at LANL, an order of magnitude lower than 8 GeV. • H has two electrons, one tightly bound (13.6 eV), another loosely bound (0.75 eV). • Problems when H energy goes higher: • Easier to lose the 2nd electron during transport (by blackbody radiation or magnetic field) • But harder to strip both electrons by a foil at injection Both are not what we want and have to be addressed seriously • Higher energy also means more difficult to correct energy and phase jitters of the linac beam prior to injection W. Chou - Proton Driver Director's Review

  4. Mini-Workshop on H Transport and Stripping • Dec 9-10, 2005 at Fermilab. Ten physicists from other labs and a dozen from Fermilab attended. • ANL: P. Ostroumov, L. Teng • BNL: J. Wei, YY Lee, D. Raparia • LANL: R. Macek, T. Spickermann, A. Jason • U. New Mexico: H. Bryant • ORNL: R. Shaw • Fermilab: D. Bogert, B. Brown, A. Drozhdin, B. Foster, G. Jackson (consultant), C. Hill, S. Holmes, M. Kostin, J. Lackey, F. Ostiguy, Z. Tang, W. Chou, etc. • Purpose: Feasibility of transporting and stripping 8 GeV H ions • Three topics: • Stripping losses of 8 GeV H ions • Stripping foil • Jitter correction of 8 GeV H beam W. Chou - Proton Driver Director's Review

  5. Magnetic Field Stripping Scherk’s formula Can J. Phys. v. 57, p. 558 (1979):  = a/E  exp (b/E) E = 3.197 p(GeV/c) B 500 G  Hloss rate = 109 m1 W. Chou - Proton Driver Director's Review

  6. Blackbody Radiation Stripping • A newly discovered loss mechanism, dominant for 8 GeV H • First pointed out and calculated by H. Bryant, also independently analyzed by C. Hill. Results in agreement. • Illustration of how this becomes a problem: photon distribution cross section 0.75 eV W. Chou - Proton Driver Director's Review

  7. Blackbody Radiation Stripping (cont…) Energy Dependence Temperature Dependence At 305 K (90 F) and 8 GeV, Hloss rate = 0.8  106 m1 W. Chou - Proton Driver Director's Review

  8. Residual Gas Stripping Energy dependence of total electron loss cross section for H incident on atoms W. Chou - Proton Driver Director's Review

  9. Residual Gas Stripping (cont…) Total electron loss cross section for H (unit 1018 cm2) H2 Measurement of A150 line vacuum by T. Anderson (similar to PD line) N2 Ar O2 Hloss rate = 0.1  106 m1 He W. Chou - Proton Driver Director's Review

  10. Summary of H Stripping Losses • Transport line ~ 1 km Loss on the beam line ~ 103 • H Beam intensity = 1  1014 s1 Loss rate ~108m1s1 • At 8 GeV  0.13 W/m • When MI operates at lower energy E with same beam power, loss will increase: W. Chou - Proton Driver Director's Review

  11. Discussion of H Stripping Losses • 1999 ICFA mini-workshop at Lake Como, Wisconsin, established the allowable loss for hands-on maintenance at 1 W/m • But this criterion assumes the losses are distributed unevenly around the machine and mostly shielded by the magnet • This does not apply to our case, where the losses are continuous along the whole beam line • MARS shows high dose on the beam pipe between two magnets • Observations on the MI pipe hot spots support this calculation • Possible solutions to suppress BR: • H0 intercepts (jaws) inside magnets (under investigation) • Cryogenic beam screen at 77 K 1000 mR/h (no jaw) 100 mR/h (w/ jaw) W. Chou - Proton Driver Director's Review

  12. Carbon Foil Stripping Efficiency Webber & Hojvat, 1979 Fermilab linac, 200 MeV Gulley et al., 1996 LANL linac, 800 MeV H+ H+ H- H- 11.2% H0 H0 0.4% H0 H0 W. Chou - Proton Driver Director's Review

  13. Electron Loss Cross Section Scaling (unit 10-18 cm2) 800 MeV 200 MeV 400 MeV 8 GeV (, 0) 0.676±0.009 1.49 0.942 0.484 (1.56±0.14) (0, +) 0.264±0.005 0.584 0.368 0.189 (0.60±0.10) (, +) 0.012±0.006 0.026 0.0167 0.0086 (0.08 ±0.13) scaling blue: measured red: scaled W. Chou - Proton Driver Director's Review

  14. Energy Dependence of H(0) Yield W. Chou - Proton Driver Director's Review

  15. Energy Dependence of H(0) Yield W. Chou - Proton Driver Director's Review

  16. Energy Dependence of H(0) Yield W. Chou - Proton Driver Director's Review

  17. Energy Dependence of H(0) Yield W. Chou - Proton Driver Director's Review

  18. Energy Dependence of H(0) Yield 8 GeV, 0.5% H0 W. Chou - Proton Driver Director's Review

  19. Lifetime of Stark States • In an electric field, each energy level n of H0 split into n(n+1)/2 Stark states • Lifetime formula given by R.J. Damburg and V.V. Kolosov in 1983 • Calculation for 8 GeV H0 in a magnetic field • Gap between n = 3 & 4 or n = 4 & 5 can be used for H0 loss control W. Chou - Proton Driver Director's Review

  20. Discussion of Stripping Foil • Total thickness 600 g/cm2 • Use two foils, each 300 g/cm2 • Carbon foil o.k. for 1 ms beam pulse • Diamond foil needed for 3 ms beam pulse • Issues concerning thick foils: • Multiple Coulomb scattering • Large angle Coulomb scattering • Energy straggling • Heating • Stress and buckling • Lifetime • Radiation • More to be presented by Lackey, Drozhdin and Kostin in breakout session 3 • Note added: TRIUMF 500 MeV Hfoil stripping efficiency data (G. Mackenzie) shows anomalous behavior. Reason unknown. W. Chou - Proton Driver Director's Review

  21. Conclusions • To go from 800 MeV (today’s highest energy of H ) to 8 GeV is a big leap forward • There are a number of technical challenges to transport and strip 8 GeV H ions • An intensive study in the past months gave us the basic understanding of the problems, including some new phenomena (e.g., blackbody radiation loss) • The bottom line is: To every problem we can find a solution • We found no show stoppers – which was also the conclusion of the Dec 2005 Fermilab mini-workshop W. Chou - Proton Driver Director's Review

More Related