Presentation on theme: "H-Jet polarimeter status report Yousef Makdisi RSC 09/29/06 BNL: A. Bravar, G. Bunce, R. Gill, Z. Li. A. Khodinov, A. Kponou, Y. Makdisi, W. Meng, A. Nass,"— Presentation transcript:
H-Jet polarimeter status report Yousef Makdisi RSC 09/29/06 BNL: A. Bravar, G. Bunce, R. Gill, Z. Li. A. Khodinov, A. Kponou, Y. Makdisi, W. Meng, A. Nass, S. Resica, A. Zelenski, V. Zubets WISCONSIN: T. Wise, M.A. Chapman, W. Haeberli Kyoto: H. Okada, N. Saito ITEP-Moscow: I. Alekseev, D. Svirida IUCF: E. Stephenson Rikkyo U.: K. Kurita Data analysis: H.Okada, O. Eyser, K. Boyle
Atomic beam intensity and density measurements in the collision region H-beam intensity and density vs. H2 flow in dissociator.
Jet Operating Parameters Stable behavior over the `04, `05 runs, `06 run is similar `06 we ran typically with 55 cfm H 2,.25 cfm O 2 P + = 0.957±0.001 and Pˉ = -0.959±0.001 Intensity 12.4 x10 16 Atoms/sec Thickness along the beam1.3±0.2 x 10 12 Atoms/cm 2 After cleaning the nozzle, the intensity starts at 0.5-.6 of maximum, rises to maximum in about 1 day, flat for 12 days, and decreases slowly to blockage in 2 weeks. This year for the first time we observed the silicon oxide powder that is responsible for the blockage. Changed the beam beta* from 5 to 10 meters in an attempt to reduce background.
H 2 and H 2 O dilution Sample Jet with 600 eV Electron Beam Extract Ions and Momentum analyze Correct for cross-section H 2 dilution is (2.3±1.2)% during normal running conditions H 2 O dilution is small but measurable: (0.15±0.05)% Mass 1 Mass 2
Total target polarization ATOMS ARE DILUTED BY: (2.3±1.2)% H 2 and (0.15±0.05)% H 2 O P + JET = 0.933±0.013 P - JET = 0.935±0.013 Assume only the H in H2O contributes because of Fermi motion of oxygen nuclei Instability and problems determining the proper cross sections Thus still use the QMA results.
Mirror Box Primary Lens Upper Box RHIC Jet Beam Profile Imaging System S. Bellavia, D. Gasner, D. Trbojevic, T. Tsang, A Zelenski Camera Filter Wheel Secondary Lens Doublet Motion Stage Mirror box If successful, could provide in situ H and H 2 monitoring
Beam in the Cage Camera Focus on Near Wires Camera Focus on Far Wires Camera Focus on Beam
FWHM (y) = 1.9 mm FWHM (x) = 4.5 mm σ(y) = 0.8 mm σ(x) = 1.91 mm FWHM (x) = 6.4 mm σ(x) = 2.7 mm 486 nm filter: H-β line gives similar result Expect to see molecular hydrogen in a broad band around 350 nm. A 320 nm filter shows no jet image. Tsang: May need a camera sensitive to far IR to detect this! } H-jet Width RHIC beam } RHIC Yellow beam profile after 656 nm red filter Data of Feb 28, 2006
Depolarizing Resonance Scan with 112 bunches At Spin 2004 Nass reported no depolarizing resonance effects on the Jet polarization with 60 bunches in the RHIC beam. In 2006 RHIC ran in a 120 bunch pattern with much higher intensities: We conducted a resonance scan using the "flip in" method. Conditions: ABS SF transition ON BRP WF transition ON Beam intensity total ~120x10 11 protons, or ~1.1x10 11 /bunch The scan took about 1 hour and during that time blue beam decayed to ~103x10 11 protons. Scanned the Inner and Outer holding field coil currents from 319.8 inner/252.0 outer to 356.6/281.0 amps respectively in 69 steps. This range guarantees at least one 1-2 resonance but most likely two 1- 2 resonances (harmonic numbers 59 and 60) We observe no resonances across the entire scan at a level 1x10 -3 The JET required a field uniformity over 3 cm gap of 6ּ10 -3 what was achieved is 5ּ10 -3
Jet operations in `06 New code to readout the full waveform along with a new versatile monitoring program. (Alekseev and Svirida) Daily PC and DAQ technical support and monitoring (Gill) Daily jet oversight and maintenance (Zelenski and Makdisi) The SFT RF acted up (Wise: rescue increase gain) Replaced the dissociator nozzle midway. MCR Operators took full responsibility and saw to it that data were collected in each fill. Attempted to collect data with both beams vertically separated failed due to loss of acceptance. This would represent the greatest benefit if it can be done. Horizontally separated beams is not acceptable as the beams have to cross and exacerbate the beam-beam problem.
Waveforms (new H-Jet data format this year) Fit Half maximum Baseline = 8
Snap shot of online Monitoring Yellow Beam hitting the jet Blue Beam background
Click on Info to get statistics With 112 bunch fills and high intensities per bunch on average the jet collects enough statistics (online) to measure the beam to jet polarization ratio to better than 10% per 7-8 hour fill. Offline analysis is required to see how much data are lost to attain The signal to background ratio.
Data Collected @ 100 GeV FillsDatesBeamEvents 7630-76523/18-25B2.5M 7662-76973/26-4/4Y2.8M 7718-77454/4-11B1.6M 4/11 Lost Si detector # 3 7780-78024/12-5/2Y3.8M 7810-78585/3-15B4.2M 7887-79465/19-6/1Y2.5M 6/2 Si detector #1 acted up: reduced the bias from 200 – 175 V. 7949-80026/3-5B2.0M
Data Collected at 31.2 GeV FillsDatesBeamEvents 8005-80546/9-17B3.6M 8055-80616/18-20Y2.6M The Fills were relatively shorter durations. The statistics will allow a good calibration of the p-CNI polarimeters near injection.
Data Analysis The 2004 100 GeV data A N and A NN were published (Hiromi Okada’s thesis). The 2004, 24 GeV analysis (15 hours) A N and A NN is complete (Hiromi Okada). The `05 data is complete (Oleg Eyser). The 31.2 GeV data a good statistical sample taken in conjunction with the polarimeters (Oleg Eyser). The 100 GeV `06 to be analyzed (Kieran Boyle). The Jet has met its goal to provide the necessary polarimeter calibration to the desired level of 3% A remaining issue is the ability to process the data off line on a timely basis.
What is next? Determine the cause of the silicon failure. Replaced the failed detectors with existing spares. We are experiencing high currents in the new detectors. Placed an order with Hamamatsu for 12 new detectors. procure spare 25 Wave Form Digitizer units for jet and polarimeters. Look into increasing the acceptance to be able to measure both beams simultaneously (not so easy) As and R&D effort, Wisconsin is building two RF cavities to allow a polarized deuteron jet beam.
Setup of the JET Atomic beam produced by expansion of a dissociated H beam through a cold nozzle into vacuum chamber Nuclear polarization achieved by HFT’s (SFT, WFT) after focusing with sextupole magnets After passing RHIC beam BRP sextupoles focus the atomic beam into the detector Determination of the efficiencies of these HFT’s and the polarization of the beam by comparing the detector signals while running different HFT’s, e.g.: ABS SFT ABS WFT ABS SFT + ABS WFT BRP HFT’s for calibration
Depolarizing Effects Beam induced depolarization due to bunched structure of p-beam transient magnetic fields transverse to the beam direction Closely spaced depolarizing resonances in the usable range of the surrounding target holding field High uniformity of the target holding field necessary Required at JET: B/B=6 ּ10 -3 achieved 5ּ10 -3 No depolarization with 60 bunches in RHIC Toms theoretical values to be added
Operational issues Nozzle blockage frequency: every two weeks. It takes 3 hours to warm up, ½ hour beam down, and two hours to cool down and back online. Slower intensity ramp up than before. 3-4 days to reach full intensity, plateau for a few days and then a slow decrease to blockage. Midway replaced the nozzle which improved matters somewhat. The SFT phase became unstable for a period. Fixed by T. Wise by increasing the gain. Lost some precious time due to memory full condition. Lost one silicon detector, and another acted up.
Operations continued Failed to take data with two beams at the same time: a)Requirement that the two beams be separated by 4-6 mm. b)The vertical collimation occluded the silicon acceptance. Determined no polarization loss with 112 bunch operation and 1.10 11 p/bunch implying the holding field uniformity is adequate. Installed a CCD camera to look at light emitted as the beam hits the jet. This serves as another vertical beam emittance device. Our interest is to measure the molecular hydrogen contamination. No pump failure this run.
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