1 / 25

Present Status of feasibility study on Polarized 3 He Ion Source

3He : 80 % polarization. 3He++ : ? % polarization. ECR Ionizer. Optical Pumping. To Injector (AVF Cyclotron). Polarized 3 He Atoms. Polarized 3 He 2+ Ions. 3 He Atoms. Present Status of feasibility study on Polarized 3 He Ion Source. Yasuhiro Sakemi : 2003-October-20.

baylee
Download Presentation

Present Status of feasibility study on Polarized 3 He Ion Source

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. 3He : 80 % polarization 3He++ : ? % polarization ECR Ionizer Optical Pumping To Injector (AVF Cyclotron) Polarized 3He Atoms Polarized 3He2+Ions 3He Atoms Present Status of feasibility study on Polarized 3He Ion Source Yasuhiro Sakemi : 2003-October-20 • 3He polarizer + ECR ionizer • 3He+ Ion Polarizer + Ionizer (alternative design)

  2. 3He Polarizer ECR Ionizer Mirror Coil Sextupole magnet electron Plasma Sextupole magnet 3He* 3He+* 3He 3He 3He+ 3He++ IonizationProcess Residence Time in ECR chamber ~ 100 ms Confinement Time in ECR plasma ~ 1 ms Depolarization in ECR Ionizer P~10-5 torr Hz~0.5 T dHx/dx/Hz~ P~1 torr Hz~1 mT dHx/dx/Hz~10-4

  3. Depolarization 1 : Depolarization due to inhomogeneous magnetic field ECR chamber Cell volume : V ρp F atoms/s Polarized 3He atoms : ρi Polarized 3He++ Ions Extraction Polarized 3He Atoms Residence Time ~ Relaxation Time Conductance : C1 F atoms/s Conductance : C2 Vacuum Pump ρ0 Residence Time : tr ~ depend on ECR chamber size, vacuum system, pressure, conductance, flow rate … ECR chamber size : 13 φ, 42 cm , a= 1φ, L=50 cm Residence Time ~ 100 ms order, but depend on ECR chamber spec.

  4. B B Relaxation Time in inhomogeneous magnetic field Behavior of relaxation time : T1 ~ depend on the ratio of diffusion time :τd and precession time : τl Relaxation time : T1 depend on field gradient • ECR chamber : dHx/dx ~ 0.1-0.3 T/cm , H0~0.5 T : field gradient ~ 20 – 30 m-1 : T1 ~ 100 ms • Pumping cell@HERMES : dHx/dx ~ 0.001 mT/cm, H0~1 mT : field gradient ~ 0.1 m-1 : T1 ~ 300 s • Mainz 3He polarizer : field gradient ~ 0.001 m-1 : T1 ~ 1 hour

  5. ECR chamber design • Depolarization due to relaxation ~ should be careful • ECR design : • Relaxation time : T1 > Residence time : Tr • Depolarization due to relaxation can be solved by : • Field gradient ~ small : Mirror field , Multipole field • Chamber size, Conductance, Vacuum system : optimize • Others …

  6. I J B Depolarization 2 : Depolarization in the ionization process Depolarization due to : Electron Spin Resonance Hyperfine Interaction in magnetic field De-Ionization Process Electron De-ionization Time B1 He ion • Ion Confinement Time • ~ enough to ionize, • but should be not too long • Inelastic Scattering • Neutral Density ECR Plasma electron Micro Wave For Electron heating Ion Strong Field Micro Wave Power High frequency ECR Ionizer 1.Adjustable Mirror Ratio High frequency region ~ depolarization due to De-ionization process ~ dominant 2.Inelastic Scattering 3.Neutral Density ~ Vacuum

  7. Obtained Polarization Calculation with Tanaka-Model • Polarization ~ 30 % will be achieved with Polarized 3He gas : 50 % input • Ion Confinement Time : 1.5 msec input • Depolarization due to ionization, de-ionization effects : included • Depolarization due to ESR effects ~ not included for the reason described later slide • Others …

  8. Additional Information If we apply nice Mainz 3He polarizer, High polarized 3He gas : 80 % is obtained ! (Ion Confinement Time =1.5 msec) ESR effects ~ what should be checked: Can be neglected or should be included ? (Ion Confinement Time = 1.5 msec)

  9. Polarization including all effects (inelastic scattering) • Ionization rate (3He+ ⇒ 3He++) • ~ 2.3×10-9 cm3/s • Inelastic scattering rate (3He+⇒3He+*) • ~ 2.5×10-8 cm3/s • 3He gas polarization ~ 80% • Inelastic scattering included • 3He++ ~ 25% polarization • Depolarization due to • Inelastic scattering ~ dominant • ESR effects ~ small effect • at high frequency region • Others..

  10. Conclusion at present • Depolarization due de-ionization process (inelastic scattering) ~ dominant process • Neutral density in ECR chamber ~ large effect to depolarization • Depolarization due to ESR effects ~ at high frequency region, other effects large • Relaxation time ~ Residence time : should be careful in the design of ECR ionizer • ECR ionizer ~ modify to dedicate for the 2 electrons stripping / Not highly charged ions • Mirror Ratio , Micro-Wave power adjustment • Expected polarization : 20 % ~ 30 % @ 80 % 3He atoms polarization at present • Experimental depolarization study ~ necessary • Further feasibility study • ECR Ionizer is Good or Bad for polarized ion source ~ should be concluded soon… • What should be checked further : • Vacuum (Neutral Density) in ECR chamber • De-ionization process ~ depolarization process • Required polarization and intensity for Physics goal

  11. 3He* 3He+* 3He+* Alternative (Ideal) method : 3He+ Ion polarizer + Charge breeder 3He+ 3He++ 3He+ 3He 3He 3He++ 3He+ Homogeneous Magnetic Field IonizationProcess Alternative (Ideal) method of Polarized 3He Ion Source 3He polarizer + ECR IonizationProcess Residence Time in ECR chamber ~ 100 ms Confinement Time in ECR plasma ~ 1 ms • Depolarization due to • Ionization process ⇒ 3He+ polarize + 1 electron strip in ionizer • ESR (u-wave) ⇒ decrease the strip electron number • Relaxation ⇒ homogeneous magnetic field Residence Time < Relaxation Time Confinement Time ~ short

  12. 3He+ Ion Polarizer + Ionizer Possible configuration • Meta-Stability Exchange • Spin Exchange • Electron Pumping • Others … • ECR charge breeder • EBIS ~ pulse beam, low intensity .. • Acceleration and Strip with foil etc. • Others …

  13. 3He Polarizer ECR charge breeder Mirror Coil Sextupole magnet electron Plasma Sextupole magnet 3He+ ion polarizer + ECR charge breeder Based on the work at Rice Univ. ~ Phys. Rev. Lett. 20 (1968) 738 3He+ ion beam ~ Polarization : 5 %, Intensity : 4 uA RF discharge 3He++ 3He+ P~1 torr Hz~1 mT dHx/dx/Hz~10-4 P~10-5 torr Hz~0.5 T dHx/dx/Hz~ 3He, 3He*, 3He+ one electron ~ strip in ECR Similar to RF Ion Source

  14. 3He* 3He Nuclear Spin : conserved Meta-stable orientation : transferred 3He* Polarized 3He Optically pumped Polarized Meta-stable 3He 3He polarization with direct optical pumping • Polarization production process : • Produce meta-stable 3He atoms with RF discharge • 3Heg.s. ⇒ 3He (23S1) • Coupling to the radiation field with optical pumping • 3He* (23S1) ⇔ 3He (23P0) ~ atom polarization • Transfer of polarization to the nucleus with hyperfine coupling • Meta-stability exchange collisions • ⇒ transfer of nuclear polarization to the ground state • 3Heg.s.(11S0 , mF=-1/2) + 3He*(23S1 , m’F) • ⇔ 3He*(23S1, m’F-1) + 3Heg.s.(11S0 , mF=1/2) • Others Ionization 23P 2. Optical pumping with laser at 1083 nm 3He* : Meta-stable state 4. Meta-stability exchange collision 23S1 1. Meta-stable state of 8000 s, populated by RF discharge 3He : ground state 11S0

  15. Pumping Cell 3He, 3He*, 3He+ 1 Torr 3He+ Ion Production in pumping cell 1. Direct Ionization 2. Cumulative Ionization 3.Meta-stable collisions σ ~ 10-18 Meta-stable collision cross section : σ~ 10-14 cm2 : large

  16. Meta-stability exchange collision σ ~ 7×10-16 cm2 Laser Pumping τpump ~ 10-7 s Electron transfer reaction ~ large σ ~ 10-15 cm2 3He* 3S1 mF=-3/2,-1/2 mF=3/2,1/2 τex~10-6s Discharge Tex~(N3He/N3He*)τex~1 s 3He 1S0 mF=-1/2 mF=1/2 Relaxation time : T1~100 s τex+(g.s.⇒1+)~10-6s 3He+ Ion Tex+(g.s.⇒1+)~(N3He+/N3He)τex(g.s.⇒1+)~10-6s Polarized 3He+ Ion Production Hierarchy of time constants : τpump <<τex<<Tex<<T1>>τex+~Tex+

  17. 3He+(Ion) P+ / N+ (cm-3) Tr+ 3He(G.S. atom) P / N (cm-3) Tr 3He*(Meta-stable) P* / n (cm-3) τr Pumping Polarization of 3He+ ions Pumping Degradation of polarization • Pumping term >> Degradation term ⇒ • T2/Tr << 1 ~ experimentally OK • T2/T3 <<1 or Tr+/T3+ >>1 • ⇒ relaxation time : Tr+ >> T3+ P3He atom ~ P+ Polarization of 3He+ ions (relaxation time 3He ion) should be checked experimentally

  18. 3He+* 3He+ 3He++ 3He+ Homogeneous Magnetic Field IonizationProcess Expected Polarization of extracted 3He++ ion beam • 3He+ ion polarization ~ 80 % • Simple ionization process • Only rough estimation !! • 3He++ ~ 50 % polarization • Depolarization due to • inelastic scattering ~ large contribution • Detailed MC study ~ necessary • Depolarization mechanism • due to inelastic scattering • Others Not Final Result

  19. What should be checked • Polarization of 3He+ ion in the pumping cell • Relaxation time of polarized 3He+ ions in the pumping cell • Density of 3He+ ions in the cell • Depolarization of 3He+ ions in ECR charge breeder • Beam intensity

  20. Prof. Tanaka-san’s method スピン交換型偏極３Heイオン源 断面積　＞　10-14ｃｍ２

  21. Prof. Tanaka-san’s method 特長：１）大電流　　I(3He+) ～１ｍA以上 　　　２） 3He+核偏極度　８０％以上 　　　３)６Li＋偏極にも用いられる。 　　　　（スピン交換断面積は3He+より大きい？ ）

  22. Estimated Polarization and Intensity at present

  23. Summary • Feasibility study ~ continue • Monte-Carlo simulation for feasibility study and design work • Design of 3He polarizer + dedicated Ionizer • Experimental feasibility check : Unknown number • Confinement Time in ECR : 6Li development ~ RIKEN experiment ~ 2003 • Depolarization due to ECR ionizer : detailed plan ~ until next meeting ~ 2004 • Ionization efficiency ~μwave power : RCNP ~ 2003/2004 • ESR effects ~ μ wave power : HIPIS@RCNP ~ 2003/2004 • Polarization of 3He+ ions : discussion with ENS/Mainz group • Feedback everything into LOI/TDR • Schedule • P-PAC on Nov-10 ~ Polarized 6Li ion source , depolarization study of 3He • 2003 – 2004 ~ feasibility check, design work • P-PAC in 2004 ~ LOI , judgment which method is best for polarized 3He ion source • Budget in 2004 ~ 科研費等、外部資金 • Construction ~ start in 2004 or 2005 if P-PAC, budget ~ approved • Time line ~ 2006

  24. Feasibility check experiment ECR ionizer : Ionization ~ complicated multi-step Polarized 3He atoms Polarized 3He2+ ion Polarimeter NMR ( Polarization: Pi, Intensity: Ii ) ( Polarization: Pf, Intensity: If ) Theoretical / Simulation evaluation Experimental Feasibility Check • What should be checked experimentally and with simulation (if possible) • Depolarization in the ionizer : inject polarized 3He gas supplied by (1) Polarized Target at RCNP or (2) LKB, Paris • Ionization efficiency : inject 4He gas / detect 2+ ions • Detailed study of ionization mechanism • Delivered from Mainz to Sheffield in 2001 • magnetized spin box • Housing a glass vessel • Relaxation time ~ 50 hours (reproducibly ?)

  25. Present Status of Polarized Nuclear Beam • Polarized 3He ion source ~ feasibility study : still continued, in progress • Independent feasibility study (Sakemi / Prof. Tanaka) • Prof. Tanaka ~ publication NIM ~ discuss the difficulty of this method • Still no consensus in the collaboration • Nice idea for high polarization ~ needed ! ~ alternative method • Polarized 6Li ion source (Dr.Tamii) ~ feasibility check : in progress / almost completed • Detailed study ~ reported in the previous meeting , 6Li polarization ~ 70~80 % • Physics ~ workshop on 0- states in Aug. • LOI writing ~ in progress / PPAC on 10-Nov / Budget • Construction in part ~ will be started after the discussion at P-PAC • Others

More Related