PAIR SPECTROMETERPAIR SPECTROMETERDEVELOPMENT IN HALL D DEVELOPMENT IN HALL D

PAWEL AMBROZEWICZPAWEL AMBROZEWICZNC A&TNC A&T

OUTLINEOUTLINE::• PS GoalsPS Goals• PrimEx ExperiencePrimEx Experience• Design DetailsDesign Details• ResponsibilitiesResponsibilities• MilestonesMilestones

Hall D Pair Spectrometer GoalsHall D Pair Spectrometer Goals

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Continuously measure photon spectrum as function of energy in 6-12 Continuously measure photon spectrum as function of energy in 6-12 GeV rangeGeV range

The PrimEx collaboration has an extensive experience in The PrimEx collaboration has an extensive experience in handling these tasks in Hall Bhandling these tasks in Hall B

Determine the photon beam linear polarization (Determine the photon beam linear polarization (δδP<0.03)P<0.03)

Monitor the relative tagging efficiencyMonitor the relative tagging efficiency

Control the absolute photon flux at 1% level normalized to total Control the absolute photon flux at 1% level normalized to total absorption counterabsorption counter Provide an independent tagger energy calibrationProvide an independent tagger energy calibration

PrimEx Pair Spectrometer in Hall BPrimEx Pair Spectrometer in Hall B

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Measured in experiment: Measured in experiment: absolute tagging ratios:absolute tagging ratios:

TAC measurements at low TAC measurements at low intensitiesintensities

Uncertainty in photon flux at Uncertainty in photon flux at the level ofthe level of 1% has been 1% has been reachedreached

relative tagging ratios:relative tagging ratios: pair spectrometer at low and highpair spectrometer at low and high intensities (concurrent with data intensities (concurrent with data taking)taking)

PrimEx PS PrimEx PS was awas acombination of: combination of: 1.6 T-m dipole magnet1.6 T-m dipole magnet 2 telescopes of 2x8 2 telescopes of 2x8 scintillating detectorsscintillating detectors

PrimEx PS Field MappingPrimEx PS Field Mapping

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Field MapperField Mapper: : 2 stepper motors allowed precise 2 stepper motors allowed precise measurements in x and z directionsmeasurements in x and z directions ~1in steps in homogenous part of the field~1in steps in homogenous part of the field ~5mm steps in the fringe area~5mm steps in the fringe area Hall probe measured field valueHall probe measured field value NMR monitored field value at the centerNMR monitored field value at the center

Field Mapping ResultsField Mapping Results

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Dipole Field Map Dipole Field Map Measurements spannedMeasurements spanned:: 3 different y positions:3 different y positions: - top- top - center- center - bottom- bottom entire magnetic field rangeentire magnetic field range

Verification Of Absolute Verification Of Absolute NormalizationNormalization

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The data for the following 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 productione+e- Pair production Compton scatteringCompton scattering

Cross sections for both processes Cross sections for both processes were determined with precision at 2% were determined with precision at 2% level level

Current Design Of Hall D PSCurrent Design Of Hall D PS

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Wide Spaced Forward Wide Spaced Forward hodoscope (WSF):hodoscope (WSF): 6 narrow counters spaced 6 narrow counters spaced 1 GeV 1 GeV apartapart

Wide Spaced Backward Wide Spaced Backward hodoscope (WSB)hodoscope (WSB) 6 narrow counters 6 narrow counters

Fine Spaced Forward Fine Spaced Forward hodoscope (FSF)hodoscope (FSF) 24 narrow close packed counters covering 24 narrow close packed counters covering 3-4 GeV3-4 GeV Fine Spaced Backward Fine Spaced Backward hodoscope (FSB)hodoscope (FSB) 4 counters which cover the FSF4 counters which cover the FSF

7Front hodoscopes are Front hodoscopes are

used to used to

measure the momentummeasure the momentum

Back hodoscopes are Back hodoscopes are used to used to

trigger the readouttrigger the readout

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30D72 Magnet30D72 Magnet

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The BNL 30D72 Magnet Characteristics

Maximum Field 20.0 KGVoltage 150 VCurrent 2500 AmpsMean Effective Length ~79.0 INGap Width 30 INGap Height 6 INGross Weight 64 TONSWater Consumption 34 GPMP 160 PSIT 75 FResistance 0.6 Ω

Can measure momentum above ~2.8 GeV Can measure momentum above ~2.8 GeV Will instrument measurements 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

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FSF Hodoscope ArrayFSF Hodoscope Array

FSF Hodoscope

3 GeV 4 GeV

24 counters cover 3 and 4 GeV range24 counters cover 3 and 4 GeV range Each count covers the same momentum rangeEach count covers the same momentum range

ppmaxmax-p-pminmin=1 GeV/24=42 MeV=1 GeV/24=42 MeV All counters measure with 12 MeV uncertaintyAll counters measure with 12 MeV uncertainty

p/p = 42 MeV/p/p = 42 MeV/√√1212 = 12 MeV= 12 MeV Counter range from 6.1mm wide @ 4 GeV to 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 thickand are 5 mm thick

6 counters at 3.25, 4.25, 5.25, 6.25, 7.25 ,and 8.25 GeV.6 counters at 3.25, 4.25, 5.25, 6.25, 7.25 ,and 8.25 GeV. Each count covers a momentum rangeEach count covers a momentum range

o ppmaxmax-p-pminmin= 60 MeV= 60 MeV All counters measure with 17 MeV uncertaintyAll counters measure with 17 MeV uncertainty Counter range from 1.8mm to 13.1 mm wide and are 5 mm Counter range from 1.8mm to 13.1 mm wide and are 5 mm

thickthick

beam

FSF

8.25 GeV

7.25 GeV

6.25 GeV

5.25 GeV

4.25 GeV

3.25 GeV

e-

e+

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WSF WSF HodoscopesHodoscopes

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Current Design Open IssuesCurrent Design Open Issues

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Energy resolution:Energy resolution: - - effects of beam spot size with effects of beam spot size with

both 3.4mm and 5mm collimationboth 3.4mm and 5mm collimation - effects of converter thickness - effects of converter thickness

AcceptanceAcceptance Rates at both high and low intensity runsRates at both high and low intensity runs Rate for PrimEx for this design is few HzRate for PrimEx for this design is few Hz

UNCW Responsibilities UNCW Responsibilities

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collaborate with BNL to bring a 30D72 magnet on loan 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 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. conduct Monte Carlo simulation for the spectrometer design. develop and construct Pair Spectrometer detectors. develop and construct Pair Spectrometer detectors. collaborate with NC A&T University group to map the collaborate with NC A&T University group to map the

magnetic field of the spectrometer magnetmagnetic field of the spectrometer magnet participate in the Pair Spectrometer detector testing, participate in the Pair Spectrometer detector testing,

installation, commissioning, calibration and maintenance. installation, commissioning, calibration and maintenance.

NC A&T Responsibilities NC A&T Responsibilities

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participate development, construction and maintenance of Hall D PSparticipate development, construction and maintenance of Hall D PS

conduct Monte Carlo simulations to optimize the gap size of the magnet 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 constructionand the size and the shape of the vacuum box, and participate in construction

cooperate with the Hall D engineering group to develop, design and constructcooperate with the Hall D engineering group to develop, design and construct a field mapping device for the Pair Spectrometer dipole magneta field mapping device for the Pair Spectrometer dipole magnet

develop and provide the control software package for the 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 targetparticipate in design and construction of the converter target

develop the Pair Spectrometer energy calibration method, including softwaredevelop the Pair Spectrometer energy calibration method, including software

develop photon beam flux monitoring procedure, including softwaredevelop photon beam flux monitoring procedure, including software

cooperate and assist the UNCW group in every stage of the projectcooperate and assist the UNCW group in every stage of the project

NCAT group is open to take part in other beamline projectsNCAT group is open to take part in other beamline projects

ManpowerManpower

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NAME POSITION FTE(2010)

FTE(2011)

FTE(2012)

FTE(2013)

Ashot Gasparian Professor 0.3 0.3 0.3 0.3

Ron Pedroni Associate Professor 0.1 0.1 0.1 0.1

Pawel Ambrozewicz Postdoctoral research associate

0.5 0.3 0.25 0.5

Graduate student 0.5 1.0 1.0 1.0

Undergraduate student

0.25 0.25 0.25 0.25

NAME POSITION FTE(2010)

FTE(2011)

FTE(2012)

FTE(2013)

Liping Gan Associate Professor 0.3 0.3 0.3 0.3

Tim Black Associate Professor 0.2 0.2 0.2 0.2

Undergraduates 0.5 0.5 0.5 0.5

Postdoc 0 1.0 1.0 1.0

NC

A&

TN

C A

&T

UN

CW

UN

CW

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DatesDates MilestonesMilestones

Fall 2010Fall 2010 Pair Spectrometer magnet arrives in Pair Spectrometer magnet arrives in Jlab.Jlab.

Spring 2011Spring 2011 Finalize the design of detector array.Finalize the design of detector array.

Summer 2011Summer 2011 Purchase material for constructing the Purchase material for constructing the detectors and electronics system.detectors and electronics system.

Fall 2011Fall 2011 Magnet installed in the hall.Magnet installed in the hall.

Spring 2012Spring 2012 Purchase of magnet power supply and Purchase of magnet power supply and field mappingfield mapping

Fall 2012Fall 2012 Detector array and electronic systems Detector array and electronic systems installationinstallation..

20132013 Testing and commissioning.Testing and commissioning.

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