Spin Filtering at COSY - First Results

Size: px

Start display at page:

Download "Spin Filtering at COSY - First Results"

Clement Anthony
5 years ago
Views:

1 Mitglied der Helmholtz-Gemeinschaft Spin Filtering at COSY - First Results Dieter Oellers University of Ferrara, INFN Ferrara STORI11, Frascati

2 PAX-Collaboration Goal: Produce a beam of polarized antiprotons Method: Spin-filtering of a stored beam Ongoing: Commission and establish this technique with protons at COSY Future: Establish this method with antiprotons at AD Folie 2

3 Outline Spin Filtering Experimental Setup Online Results Outlook (see H. Stroeher on Friday) Folie 3

et al., PRL 71, 1379 (1993) COSY-Experiment 199.2 08.

4 Spin Filtering Spin-dependent attenuation Tested with protons (FILTEX) Picture by H-O. Meyer F. Rathmann. et al., PRL 71, 1379 (1993) COSY-Experiment MD end of August August data taking Folie 4

5 Spin filtering cross section σ to t = σ 0 + σ 1 ( S Q) + σ 2 ( S kˆ)(q kˆ) Accessible region with E-Cooling T = 49.3 MeV known Ay in pd elastic COSY Folie 5

6 Outline Spin Filtering Experimental Setup Online Results Outlook (see H. Stroeher on Friday) Folie 6

7 Spin Flipper RF Solenoid Schematic overview stored protons at T > 45 MeV polarized internal H-target electron cooler to reduce beam losses analyser reaction + detector to measure beam polarization spin flipper to reduce systematic effects Folie 7

8 Beam lifetime: low-β-section Target position Beam lifetime τ: small β residual gas & target has small impact on beam lifetime Goal: low pressure high target density low pressure

9 Polarized H target H flux: 3*1016 H1/s storage cell: Ø = 9.6 mm L = 400 mm dt = 5.5 * 1013H/cm2 P = 0.75

10 Holding field and storage cell ABS Beam To BRP Beam through storage cell Pictures of target cell in beam direction. Left: Closed cell Right: Opened cell Holding field coils (dark brown) compensation coils (light brown) Folie 10

11 Vacuum system at PAX-IP ABS-flux: 3*1016 H/s requirements: 1. high pumping speed in target chamber > l/s Mounted at the target chamber Folie 11

12 Vacuum system at PAX-IP ABS-flux: 3*1016 H/s requirements: 1. high pumping speed in target chamber 2. low residual gas flow into adjacent sections Flow limiter tubes: Ø = 19 mm L = 80 mm Folie 12

13 Vacuum system at PAX-IP ABS-flux: 3*1016 H/s requirements: 1. high pumping speed in target chamber 2. low residual gas flow into adjacent sections 3. high pumping speed in adjacent sections Flow limiter tubes: Ø = 19 mm L = 80 mm 2xTS Fast Shutters NEG 5000 l/s NEG 5000 l/s BPM IG 100 l/s BPM IG 100 l/s BPM IG 100 l/s IG 100 l/s Target chamber is installed in this position Folie 13

14 Detection system 2 times 3 layers of double sided silicon strip detectors p D2 Folie 14

15 Outline Spin Filtering Experimental Setup Online Results Outlook (see H. Stroeher on Friday) Folie 15

16 Beam development The machine has to be optimized for long beam lifetimes and high intensities with low-β section switched on at at experiment energy and at injection energy: 1. flat orbit 2. optimal tunes 3. E-Cooler 4. Stacking injection τ = 8000 s Folie 16

17 Spin Filtering Cycle Folie 17

18 Expected build-up rate Input parameters: target density: ~ 5.5 * 1013/cm2 target polarization: ~ 0.75 cross section: σ1 = mb (at T=49.3MeV, Θacc = 7mrad) ΔPexpected ~ 0.002/h Long filtering time necessary high beam lifetime highest possible target density best possible vacuum

19 d stopped in 3rd layer ( ) p stopped in 3rd layer ( ) FOM d stopped in 2nd layer ( ) Polarimetry Proton beam D2 Cluster Target d p d p Folie 19

20 Double ratio luminosity cancels geometrical acceptance & detector efficiency cancel under the assumption, that they don't change between the P and P sample controll ratio must be CONSTANT in time spin flipper both polarization states in one cycle detector stability only during each cycle Folie 20

Pressure at filter target mbar Pressure at deuterium

21 Cycle Structure Pictures from data Total trigger rate 2 Spin Flips DAQ stopped Target off Beam intensity Pressure at filter target mbar Pressure at deuterium target 16000s of spin-filtering 2500s of polarisation measurement

22 Correlations in pd elastic (online) Deuteron in left detector & any track in right detector Δφ-correlation Deuteron in left detector & any track in right detector θ-correlation clear recontructed pd elastic events (background < 0.5% after cuts) Folie 22

23 Polarization lifetime (online) 2 Periods of Measurement: 100s at beginning 300s at end 5000s gap (to prolongate cycle) Result: τ = 200,000 s ± 50,000 s ~ 5% polarization loss Folie 23

24 Spin flip efficiency (online) 2 Periods of Measurement: 50s at beginning 60s at end 100s gap (with 99 Spin Flips) Result: ε = s ± ~2% polarization loss Folie 24

25 X / mm Beam target overlap (online) Runnumber Beam target overlap and thus geometrical acceptance is stable within 10 μm over all runs and better than 5 μm with each spin flip Folie 25

26 Next steps in Analysis optimize energy calibration analyse and handle dead time check and correct any time dependence calibrate analysis using data with unpolarized beam run analysis on data with high polarized beam blind analysis of spin filtering data Folie 26

27 Summary successfully set up COSY for spin filtering successfully performed a spin filtering experiment necessary subsystems work as expected or even better (eg the vacuum system resulting in very long beam lifetimes) sufficient data for statistical significant result collected data to gain experience in high precission experiments... Folie 27

28 Summary successfully set up COSY for spin filtering successfully performed a spin filtering experiment necessary subsystems work as expected or even better (eg the vacuum system resulting in very long beam lifetimes) sufficient data for statistical significant result collected data to gain experience in high precission experiments... Thank you! Folie 28

29 Title:PAXframesassembly.fig Creator:fig2dev Version 3.2 Patchlevel 5 CreationDate:Fri May 6 08:21:50 LanguageLevel:2 Lifetime /s Determination of machine acceptance using the frame system x / mm Measure beam lifetime at different positions of frame system. Curvature at left and right edge due to beam emittance (out of fit) Fit measurement with trapezodial shape. Ax(π mm mrad) Ay(π mm mrad) Θx (mrad) Θy (mrad) Θacc (mrad) 20.4 ± ± ± ± ± 0.2 Folie 29

30 Beam development procedure 1. Injection of unpolarized (polarized) protons and acceleration to T = 49.3MeV 2. Adjustment of E-Cooler 1 week 3. Beam on ANKE-Cluster-Target 4. Orbit Correction in x- and y-direction 5. Optimize E-Cooler (tilting angle, feedback etc.) Switching to PAX-Optics 1 week 12. Orbit Correction in x- and y-direction 13. Vacuum break: Install moveable frame system (at PAX) and detection system (at ANKE) 17. Measure acceptance angle and beam position at PAX 1 week 18. Vacuum break: Install openable target cell 19. Calibrate Spin Flipper 20. Prepare three cycles (Filtering, Spin Flip Efficiency, Polarization Lifetime) Folie 30

31 Polarization build-up cross section For the determination of the polarization build-up cross section several parameters have to be measured. Here is a list of the most important ones: Acceptance angle at polarized H-Target (PAX-IP) Target density Target polarization Beam polarization after filtering Filtering time Folie 31

32 Control signals Voltage of pickup coil at RF-solenoid magnet to detect each spin flip individually Target density Baratron to measure pressure in storage cell & Schottky method Control signal for storage cell position opened / closed Currents of holding field coils Beam polarization bits Beam current Target polarization from BRP and ABS status Folie 32

33 FILTEX at TSR (1992) Observed polarization build-up: dp/dt = ± (1.24 ± 0.06) x 10-2 h-1 P(t)=tanh(t/ 1) 1/ 1=σ1 Q dt frev σ1 = 72.5 ± 5.8 mb F. Rathmann. et al., PRL 71, 1379 (1993) Spin filtering works! But how? Motivation Folie 33

34 Mitglied der Helmholtz-Gemeinschaft Spin Filtering at COSY - First Results Double ratio FILTEX at TSR (1992)

Spin-Filtering Studies at COSY

Mitglied der Helmholtz-Gemeinschaft Spin-Filtering Studies at COSY Proposal and beam request #199 PAX collaboration 6. September 2009 Mikhail Nekipelov Outline Spin-filtering. Polarisation buildup at COSY.