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PAIR SPECTROMETER DEVELOPMENT IN HALL D

PAIR SPECTROMETER DEVELOPMENT IN HALL D. PAWEL AMBROZEWICZ NC A&T. OUTLINE : PS Goals PrimEx Experience Design Details Responsibilities Milestones. Hall D Pair Spectrometer Goals. Continuously measure photon spectrum as function of energy in 6-12 GeV range.

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PAIR SPECTROMETER DEVELOPMENT IN HALL D

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  1. PAIR SPECTROMETERDEVELOPMENT IN HALL D PAWEL AMBROZEWICZ NC A&T • OUTLINE: • PS Goals • PrimEx Experience • Design Details • Responsibilities • Milestones

  2. Hall D Pair Spectrometer Goals • Continuously measure photon spectrum as function of energy in 6-12 GeV range • Determine the photon beam linear polarization (δP<0.03) • Monitor the relative tagging efficiency • Control the absolute photon flux at 1% level normalized to total absorption counter • Provide an independent tagger energy calibration The PrimEx collaboration has an extensive experience in handling these tasks in Hall B GlueX Collaboration Meeting

  3. PrimEx Pair Spectrometer in Hall B PrimEx PS was a combination of: • 1.6 T-m dipole magnet • 2 telescopes of 2x8 scintillating detectors Measured in experiment: • absolute tagging ratios: • TAC measurements at low intensities • relative tagging ratios: • pair spectrometer at low and high intensities (concurrent with data taking) • Uncertainty in photon flux at the level of1% has been reached GlueX Collaboration Meeting

  4. PrimEx PS Field Mapping Field Mapper: • 2 stepper motors allowed precise • measurements in x and z directions • ~1in steps in homogenous part of the field • ~5mm steps in the fringe area • Hall probe measured field value • NMR monitored field value at the center GlueX Collaboration Meeting

  5. Field Mapping Results Dipole Field Map Measurements spanned: • 3 different y positions: • - top • - center • - bottom • entire magnetic field range GlueX Collaboration Meeting

  6. Verification Of Absolute Normalization • The data for the following • QED processes had been taken • periodically in this experiment: • e+e- Pair production • Compton scattering • Cross sections for both processes • were determined with precision at 2% level GlueX Collaboration Meeting

  7. Current Design Of Hall D PS 7 • Fine Spaced Forward hodoscope(FSF) • 24 narrow close packed counters covering 3-4 GeV • Fine Spaced Backward hodoscope (FSB) • 4 counters which cover the FSF Front hodoscopes are used to measure the momentum Back hodoscopes are used to trigger the readout • Wide Spaced Forward • hodoscope (WSF): • 6 narrow counters spaced • 1 GeVapart • Wide Spaced Backward • hodoscope (WSB) • 6 narrow counters GlueX Collaboration Meeting

  8. 30D72 Magnet • Can measure momentum above ~2.8 GeV • Will instrument measurements between 3 and 8.28 GeV • Reduce the gap from 6” to 3” • Will reduce the power by 4 • Less cooling requirements GlueX Collaboration Meeting

  9. FSF Hodoscope Array • 24 counters cover 3 and 4 GeV range • Each count covers the same momentum range • pmax-pmin=1 GeV/24=42 MeV • All counters measure with 12 MeV uncertainty • Dp/p = 42 MeV/√12= 12 MeV • Counter range from 6.1mm wide @ 4 GeV to 11.1 m wide @ 3 GeV and are 5 mm thick 3 GeV 4 GeV FSF Hodoscope GlueX Collaboration Meeting

  10. WSF Hodoscopes FSF e- 3.25GeV • 6 counters at 3.25, 4.25, 5.25, 6.25, 7.25 ,and 8.25 GeV. • Each count covers a momentum range • pmax-pmin= 60 MeV • All counters measure with 17 MeV uncertainty • Counter range from 1.8mm to 13.1 mm wide and are 5 mm thick 4.25 GeV 5.25 GeV 6.25 GeV 7.25 GeV 8.25 GeV g beam e+ GlueX Collaboration Meeting

  11. Current Design Open Issues • Energy resolution: - effects of beam spot size with both 3.4mm and 5mm collimation - effects of converter thickness • Acceptance • Rates at both high and low intensity runs • Rate for PrimEx for this design is few Hz GlueX Collaboration Meeting

  12. UNCW Responsibilities • collaborate with BNL to bring a 30D72 magnet on loan from BNL to Jlab. • coordinate an engineering effort to modify the gap size of the magnet in order to fit the experimental configuration. • conduct Monte Carlo simulation for the spectrometer design. • develop and construct Pair Spectrometer detectors. • collaborate with NC A&T University group to map the magnetic field of the spectrometer magnet • participate in the Pair Spectrometer detector testing, installation, commissioning, calibration and maintenance. GlueX Collaboration Meeting

  13. NC A&T Responsibilities • participate development, construction and maintenance of Hall D PS • conduct Monte Carlo simulations to optimize the gap size of the magnet • and the size and the shape of the vacuum box, and participate in construction • cooperate with the Hall D engineering group to develop, design and construct • a field mapping device for the Pair Spectrometer dipole magnet • develop and provide the control software package for the • mapper and conduct the actual field mapping measurements. • participate in design and construction of the converter target • develop the Pair Spectrometer energy calibration method, including software • develop photon beam flux monitoring procedure, including software • cooperate and assist the UNCW group in every stage of the project • NCAT group is open to take part in other beamline projects GlueX Collaboration Meeting

  14. Manpower NC A&T UNCW GlueX Collaboration Meeting

  15. GlueX Collaboration Meeting

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