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

2. Hall D Pair Spectrometer Goals 9/10/2009 2 GlueX Collaboration Meeting Continuously measure photon spectrum as function of energy in 6-12 GeV range  Continuously measure photon spectrum as function of energy in 6-12 GeV range The PrimEx collaboration has an extensive experience in handling these tasks in Hall B Determine the photon beam linear polarization (δP<0.03)  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

3. PrimEx Pair Spectrometer in Hall B 9/10/2009 GlueX Collaboration Meeting 3 Measured in experiment:  absolute tagging ratios:  TAC measurements at low intensities  Uncertainty in photon flux at the level of 1% has been reached the level of 1% has been reached  relative tagging ratios:  pair spectrometer at low and high intensities (concurrent with data taking) intensities (concurrent with data taking) PrimEx PS was a combination of:  1.6 T-m dipole magnet  2 telescopes of 2x8 scintillating detectors scintillating detectors

4. PrimEx PS Field Mapping 9/10/2009 GlueX Collaboration Meeting 4 Field Mapper:  2 stepper motors allowed precise measurements in x and z directions 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

5. Field Mapping Results 9/10/2009 GlueX Collaboration Meeting 5 Dipole Field Map Measurements spanned:  3 different y positions: - top - top - center - center - bottom - bottom  entire magnetic field range

6. Verification Of Absolute Normalization 9/10/2009 GlueX Collaboration Meeting 6  The data for the following QED processes had been taken QED processes had been taken periodically in this experiment: periodically in this experiment:  e+e- Pair production  Compton scattering  Cross sections for both processes were determined with precision at 2% level were determined with precision at 2% level

7. Current Design Of Hall D PS 9/10/2009 GlueX Collaboration Meeting Wide Spaced Forward  Wide Spaced Forward hodoscope (WSF): hodoscope (WSF): 6 narrow counters spaced 6 narrow counters spaced 1 GeV apart 1 GeV apart  Wide Spaced Backward hodoscope (WSB) hodoscope (WSB) 6 narrow counters 6 narrow counters Fine Spaced Forward hodoscope (FSF)  Fine Spaced Forward hodoscope (FSF) 24 narrow close packed counters covering 3-4 GeV 24 narrow close packed counters covering 3-4 GeV  Fine Spaced Backward hodoscope (FSB) 4 counters which cover the FSF 4 counters which cover the FSF 7 Front hodoscopes are used to measure the momentum Back hodoscopes are used to trigger the readout 7

8. 30D72 Magnet 9/10/2009 GlueX Collaboration Meeting 8 The BNL 30D72 Magnet Characteristics Maximum Field20.0 KG Voltage 150 V Current2500 Amps Mean Effective Length~79.0 IN Gap Width30 IN Gap Height6 IN Gross Weight64 TONS Water Consumption34 GPM PP 160 PSI TT 75◦ F Resistance0.6 Ω  Can measure momentum above ~2.8 GeV  Will instrument measurements between 3 and 8.28 GeV between 3 and 8.28 GeV Reduce the gap from 6” to 3” Will reduce the power by 4 Less cooling requirements

9. 9/10/2009 GlueX Collaboration Meeting 9 FSF Hodoscope Array FSF Hodoscope 3 GeV 4 GeV  24 counters cover 3 and 4 GeV range  Each count covers the same momentum range  p max -p min =1 GeV/24=42 MeV  All counters measure with 12 MeV uncertainty   p/p = 42 MeV/ √ 12 = 12 MeV  Counter range from 6.1mm wide @ 4 GeV to 11.1 m wide @ 3 GeV 11.1 m wide @ 3 GeV and are 5 mm thick and are 5 mm thick

10.  6 counters at 3.25, 4.25, 5.25, 6.25, 7.25,and 8.25 GeV.  Each count covers a momentum range o p max -p min = 60 MeV  All counters measure with 17 MeV uncertainty  Counter range from 1.8mm to 13.1 mm wide and are 5 mm thick  beam FSF 8.25 GeV 7.25 GeV 6.25 GeV 5.25 GeV 4.25 GeV 3.25 GeV e-e- e+ 10 WSF Hodoscopes WSF Hodoscopes 9/10/2009 GlueX Collaboration Meeting

11. Current Design Open Issues 9/10/2009 GlueX Collaboration Meeting 11  Energy resolution: - effects of beam spot size with both 3.4mm and 5mm collimation - effects of converter thickness 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

12. UNCW Responsibilities 9/10/2009 GlueX Collaboration Meeting 12  collaborate with BNL to bring a 30D72 magnet on loan from BNL to Jlab. from BNL to Jlab.  coordinate an engineering effort to modify the gap size of the magnet in order to fit the experimental configuration. 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.

13. NC A&T Responsibilities 9/10/2009 GlueX Collaboration Meeting 13  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 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 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. 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

14. Manpower 9/10/2009 GlueX Collaboration Meeting 14 NAMEPOSITIONFTE (2010) FTE (2011) FTE (2012) FTE (2013) Ashot GasparianProfessor0.3 Ron PedroniAssociate Professor0.1 Pawel AmbrozewiczPostdoctoral research associate 0.50.30.250.5 Graduate student0.51.0 Undergraduate student0.25 NAMEPOSITIONFTE (2010) FTE (2011) FTE (2012) FTE (2013) Liping GanAssociate Professor0.3 Tim BlackAssociate Professor0.2 Undergraduates0.5 Postdoc01.0 NC A&T UNCW

15. 9/10/2009 GlueX Collaboration Meeting DatesMilestones Fall 2010 Pair Spectrometer magnet arrives in Jlab. Spring 2011 Finalize the design of detector array. Summer 2011 Purchase material for constructing the detectors and electronics system. Fall 2011 Magnet installed in the hall. Spring 2012 Purchase of magnet power supply and field mapping Fall 2012 Detector array and electronic systems installation. 2013 Testing and commissioning. 15