10/10/2008 Mitglied der Helmholtz-Gemeinschaft First Experiments with the Polarized Internal Gas Target (PIT) at ANKE/COSY Ralf Engels for the ANKE collaboration JCHP / Institut für Kernphysik, FZ Jülich

R. Engels for the ANKE collaboration 10/02/08Folie 2 internal experiments – with the circulating beam external experiments – with the extracted beam p, p, d, d with momenta up to 3.7 GeV/c COSY – COoler SYnchrotron see talk by A. Kacharava (ANKE) / F. Rathmann and A. Nass (PAX)

R. Engels for the ANKE collaboration 10/02/08Folie 3 ANKE at COSY Targets Solid strip Cluster jet Polarized internal target PIT ( storage cell or jet ) Magnets D2 – spectrometer magnet D1, D3 – beam bending magnets Detector systems Positive & Negative Forward & Backward Spectator Detectors Spectrometer ANKE

R. Engels for the ANKE collaboration 10/02/08Folie 4 PIT at ANKE 3D CAD drawing of PIT at ANKE Storage cell Polarimeter ABS Technical constraints Target exchange within a maintenance week New support bridge, following the movement of D2 magnet Magnetic shielding of components of the Atomic Beam Source (ABS) (D2 Magnet: 1.6 Tesla)

R. Engels for the ANKE collaboration 10/02/08Folie 5 Polarized Internal Gas Target Main parts of a PIT: Atomic Beam Source Target gas hydrogen or deuterium H beam intensity (2 hyperfine states) ~ atoms / s Beam size at the interaction point σ = 2.85 ± 0.42 mm Polarization for hydrogen atoms P Z = 0.89 ± 0.01 P Z = ± 0.01 Lamb-Shift Polarimeter Target chamber with Storage Cell ABS and LSP at the laboratory

R. Engels for the ANKE collaboration 10/02/08Folie 6 The Lamb-shift Polarimeter

R. Engels for the ANKE collaboration 10/02/08Folie 7 ABS and LSP in the COSY hall December 2004 – transfer to COSY hall (outside of the COSY tunnel) May 2005 – tests after reassembling Setup in the COSY hall Supports representing D1 and D2 New support bridge Platform for all electronic and supply components Heat exchanger with closed cooling-water circuit June 2005 – setup ready for installation at ANKE

R. Engels for the ANKE collaboration 10/02/08Folie 8 PIT installation at ANKE Platform transportation ABS transportation

R. Engels for the ANKE collaboration 10/02/08Folie 9 PIT at ANKE

R. Engels for the ANKE collaboration 10/02/08Folie 10 Magnetic stray field of D2 PIT setup with shielded components at ANKE x y z calculated field strength (G) measured field strength (G) permissible field strength for the device given by the producer (G)

R. Engels for the ANKE collaboration 10/02/08Folie 11 Test of the medium-field rf transition unit no ABS beam MFT off (HFS 1 and 2) MFT on (HFS 1 only)

R. Engels for the ANKE collaboration 10/02/08Folie 12 Tuning of the Transition Units Supporting bridge Additional shielding from the spectrometer magnet stray fields Cryopump at the target chamber LSP ionizer below the target chamber Atomic Beam Source Target chamber with cell Lamb-shift polarimeter

R. Engels for the ANKE collaboration 10/02/08Folie 13 First Polarization Measurement with the LSP Problems: - The magnetic stray field of the D2 magnet deflected the produced protons. - The quantization axis was rotated by the stray field and the LSP measures only the projection on the horizontal beam line. Next time: More shielding and a rotatable Wien filter to compensate the misalignment of the polarization axis! WFT was tuned online at the ANKE target position near the D2 magnet. The measured asymmetry was stable during the beam time. Transition unit ON : Q = ± Transition unit OFF : Q = ± 0.008

R. Engels for the ANKE collaboration 10/02/08Folie · ·10 -9 With catcher 3.0· ·10 -9 Without catcher With ABS jet Without ABS jet ABS beam catcher ~13cm Measured pressures in the target chamber, mbar ABS-jet density, cm -3 integral thickness ~ cm -2 ABS jet COSY Beam The ABS jet target

R. Engels for the ANKE collaboration 10/02/08Folie 15 Storage cell setup COSY beam XY-tableFrame with storage cell and aperture Target chamber Feeding tube: l = 120 mm, Ø = 10 mm Extraction tube: l = 230 mm, Ø = 10 mm Beam tube : l = 400 mm, 20x20 mm 2 400mm

R. Engels for the ANKE collaboration 10/02/08 Measurement procedure 1. Beam in the center of the diaphragm 50 mm 2. Diaphragm moves to the right until intensity drops +5 mm 3. Diaphragm moves to the left until intensity drops 11 mm Distance 3 Distance 2 Minimum cell size = Diaphragm inner width - ( Distance 2 + Distance 3 ) Beam intensity is maximumBeam intensity starts to decrease Distance 2 Beam intensity starts to decrease

R. Engels for the ANKE collaboration 10/02/08 Measurement results Square root of the COSY beam lifetime as function of the diaphragm shift 2-D reconstructed COSY beam profile  the storage cell should have a 15mm ver ×20 mm hor cross section  openable cell will increase the luminosity NIM A (submitted); arXiv: At injection energy 45 MeV After acceleration to 2.65 GeV

R. Engels for the ANKE collaboration 10/02/08Folie 18 Storage cell: Final setup for the 1. Experiment  Tools for the experiment New storage cell & support ( mm 3 ) >high target density >unpolarized gas feeding system LSP below the target chamber >online measurement of the ABS beam polarization Silicon Tracking Telescope (STT) >measurement of spectator protons nearby the storage cell center

R. Engels for the ANKE collaboration 10/02/08Folie 19 Cooler stacking with the storage cell 28 stacks followed by 2s electron cooling after 58s acceleration toT p =600 MeV Cooler Stacking allows for higher polarized beam intensities with cell. Without storage cell 2.5·10 10 ions were reached. (With cell: 6·10 9 ions )

R. Engels for the ANKE collaboration 10/02/08Folie 20 Storage cell and stochastically cooled beam Cooling off Cooling on T p = 831 MeV

R. Engels for the ANKE collaboration 10/02/08Folie 21 First Beam Time Stacking injection 120 injections with 10 s e-cooling Time, min Acceleration without gas in the storage cell Switching on the gas to feed the storage cell Flat top 30 min, to have about 2/3 duty time ~7 · 10 9 polarized deuterons!!!

R. Engels for the ANKE collaboration 10/02/08Folie 22 T d =1.2 GeV, target H ( N 2 ) gas dp→dp dp, → → First Double Polarized Experiment: d p →→

R. Engels for the ANKE collaboration 10/02/08Folie 23 T d =1.2 GeV, target H ( N 2 ) gas dp→(dp sp ) π o quasi-free np→d π o (High & Low branch) High branch Low branch dp, → → First Double Polarized Experiment: d p →→

R. Engels for the ANKE collaboration 10/02/08Folie 24 First Polarization Measurement of the Target ANKE preliminary dp, T d =1.2 GeV, polarized H gas quasi-free np→d π o (High & Low branch) = 0.75 ± 0.06 θ d = θ d = θ d = θ d = θ d = θ d = θ d = → quasi-free np → dπ 0 (High and low branch) = 0.75 ± 0.06

R. Engels for the ANKE collaboration 10/02/08Folie 25 Summary of commissioning and first experiment 1. Cell-target thickness for H (hyperfine state 1) ~ 2 · cm ABS jet-target thickness ~ 1.5 · cm -2 Tests at ANKE with ABS and storage cell with stacking injection and stochastic cooling 2. A verage luminosity for the storage-cell test ~ 2 · cm -2 s Hydrogen polarization in the cell ~ / (deuteron beam: p z =0.64 ± 0.05) First experiment dp→ppn Clear Particle Identification →→

R. Engels for the ANKE collaboration 10/02/08Folie 26 Plans for the future March '09 – PIT reinstallation: With rotatable Wien filter and better shielding of the LSP March/April ’ 09 – Next beam time: d p→ (pp)n at – 3.7 GeV/c (5 Weeks) May ’09 – PIT deinstallation ABS and LSP can be used for other experiments: - Nuclear Polarization in H 2 /D 2 Molecules - Direct Measurements of the Hyperfine Splitting of Hydrogen (Deuterium) or the Lambshift (see talk yesterday) 2009/10 – openable cell To increase the target density up to cm -2 →

R. Engels for the ANKE collaboration 10/02/08Folie 27 The COSY beam size at injection with an accelerated beam no target with cluster target (density ~ at/cm 2 ) 9x12 mm 16x15 mm 36x16 mm 15 x 15 mm 2

R. Engels for the ANKE collaboration 10/02/08Folie 28 Results of the cell tests single injection3.557empty cell 26no cell 80 stacking + electron cooling flattop (600 MeV) after cooling injection empty cell no cell target 9.2º 0º0º Θ ANKE 30 stacking + electron cooling 83 number of stored protons * stacking + electron cooling 1421single injection injection type 30 stacking + electron cooling 9.2º cell with H gas from ABS empty cell