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Photon Tagged Beamline at the DESY II Test Beam FacilityKatherine Dunne, Jan Dreyling-Eschweiler, Marcel Stanitzki
7th Beam Telescopes and Testbeams Workshop, January 2019
● Motivation● Simulation● Testbeam● Results● Summary
Outline
K. Dunne | Photon Tagged Beamline | 7th Beam Telescopes and Testbeams Workshop 2
MotivationInvestigate feasibility of photon tagging in the DESY II test beam areas:● Requested by users ● Useful for calorimeter tests● Summer student project provides proof of concept● Informs what rates we can get for different photon energies
DESY Test Beam Users Workshop ‘17
K. Dunne | Photon Tagged Beamline | 7th Beam Telescopes and Testbeams Workshop 3
Photon Tagging
e- e-
𝛾
3mm Copper target
0.18T Magnetic Field
Detector
Scintillatorsfor trigger
● 5 GeV electron beam in TB21 ● Install 3mm copper target in test beam area to create
bremsstrahlung photons● Big Red Magnet fans out electrons by momentum ● Lead-glass detector measures energy of photons● Pair of scintilators trigger Lead-glass detector
K. Dunne | Photon Tagged Beamline | 7th Beam Telescopes and Testbeams Workshop 4
● Motivation● Simulation● Testbeam● Results● Summary
Outline
K. Dunne | Photon Tagged Beamline | 7th Beam Telescopes and Testbeams Workshop 5
Simulation● SLIC (Geant4 based simulation tool for linear colliders)● Useful info for test beam plan:
○ Electrons won’t be measured in photon detector area (deflected 5cm)
Simulation Image
Photons Deflected Electrons
Endpoint X [mm]
Endp
oint
Y [m
m]
1.4 GeV5 GeV 3.6 GeV 2.4 GeV
K. Dunne | Photon Tagged Beamline | 7th Beam Telescopes and Testbeams Workshop 6
Simulation● SLIC (Geant4 based simulation tool for linear colliders)● Useful info for test beam plan:
○ Electrons won’t be measured in photon detector area (deflected 5cm) ○ Deflection positions found for each trigger position
Simulation Image
Photons Deflected Electrons
Endpoint X [mm]
Endp
oint
Y [m
m]
1.4 GeV5 GeV 3.6 GeV 2.4 GeV
K. Dunne | Photon Tagged Beamline | 7th Beam Telescopes and Testbeams Workshop 7
Simulation● SLIC (Geant4 based simulation tool for linear colliders)● Useful info for test beam plan:
○ Electrons won’t be measured in photon detector area (deflected 5cm) ○ Deflection positions found for each trigger position○ Bremsstrahlung photon distribution contained within lead glass area
Simulation Image
Photons Deflected Electrons
Endpoint X [mm]
Endp
oint
Y [m
m]
1.4 GeV5 GeV 3.6 GeV 2.4 GeV
K. Dunne | Photon Tagged Beamline | 7th Beam Telescopes and Testbeams Workshop 8
Simulation● SLIC (Geant4 based simulation tool for linear colliders)● Useful info for test beam plan:
○ Electrons won’t be measured in photon detector area (deflected 5cm) ○ Deflection positions found for each trigger position○ Bremsstrahlung photon distribution contained within lead glass area○ Synchrotron photons found in lead-glass area
Simulation Image
Photons Deflected Electrons
Endpoint X [mm]
Endp
oint
Y [m
m]
1.4 GeV5 GeV 3.6 GeV 2.4 GeV
K. Dunne | Photon Tagged Beamline | 7th Beam Telescopes and Testbeams Workshop 9
● Motivation● Simulation● Testbeam● Results● Summary
Outline
K. Dunne | Photon Tagged Beamline | 7th Beam Telescopes and Testbeams Workshop 10
Detector Setup
Lead-Glass Detector● Used for energy measurements ● Pulse shape proportional to incident energy
2 Scintillators● 1cm x 2cm arranged in
cross● Trigger for lead-glass ● Moveable remotely via
horizontal stage
e- e-
𝛾
Counting Room
K. Dunne | Photon Tagged Beamline | 7th Beam Telescopes and Testbeams Workshop 11
Calibrate energy to pulse height
● Magnet off● Vary electron momentum● Measure lead-glass pulse
height on scope● Record histogram ~30k events
e-
Histogram mean 1.18 V
Pulse from lead-glass detector
K. Dunne | Photon Tagged Beamline | 7th Beam Telescopes and Testbeams Workshop 12
B = 0
Detector calibration with electrons
𝜎 0.24% 𝜎 6.5% 𝜎 7.1% 𝜎 9.0% 𝜎 10.0% 𝜎 13.8%
K. Dunne | Photon Tagged Beamline | 7th Beam Telescopes and Testbeams Workshop 13
Deflection Position
● Vary electron momentum● Magnetic field applied● Measure deflection position:
○ Simulation guides first measurement position
○ Count rate measured in mm increments around first position
○ Highest count rate: deflection position
DeflectionPosition
Moveable Stage
K. Dunne | Photon Tagged Beamline | 7th Beam Telescopes and Testbeams Workshop 14
Deflection Position
DeflectionPosition
K. Dunne | Photon Tagged Beamline | 7th Beam Telescopes and Testbeams Workshop 15
Photon Energy Measurements
● 5 GeV electron momentum● Trigger on photons arriving at
lead glass: Bremsstrahlung spectrum
converter target
5 GeV e-
K. Dunne | Photon Tagged Beamline | 7th Beam Telescopes and Testbeams Workshop 16
Photon Energy Measurements
converter target
● 5 GeV electron momentum● Trigger on electron
momentum (via scintillator position)
● Measure corresponding photon energy
1.4 GeV e-
3.6 GeV 𝜸5 GeV e-
Peak at 3.6 GeV
K. Dunne | Photon Tagged Beamline | 7th Beam Telescopes and Testbeams Workshop 17
● Motivation● Simulation● Testbeam● Results● Summary
Outline
K. Dunne | Photon Tagged Beamline | 7th Beam Telescopes and Testbeams Workshop 18
Photon Energy Results1.0 GeV 1.6 GeV 2.0 GeV
Photon Measurement
ElectronCalibration
K. Dunne | Photon Tagged Beamline | 7th Beam Telescopes and Testbeams Workshop 19
Photon Energy Results2.6 GeV 3.0 GeV 3.6 GeV
Photon Measurement
ElectronCalibration
K. Dunne | Photon Tagged Beamline | 7th Beam Telescopes and Testbeams Workshop 20
Photon Rate Results
Count rate: coincidence signal between scintillators + lead-glass
K. Dunne | Photon Tagged Beamline | 7th Beam Telescopes and Testbeams Workshop 21
Photon Rate Results
Endpoint X [mm]
1.4 GeV electrons● Wide distribution:
multiple scattering● Triggering on 1x2 cm
slice
Simulation
K. Dunne | Photon Tagged Beamline | 7th Beam Telescopes and Testbeams Workshop 22
● Motivation● Simulation● Testbeam● Results● Summary
K. Dunne | Photon Tagged Beamline | 7th Beam Telescopes and Testbeams Workshop 23
Summary
● 1st photon tagging experiment done in DESY II test beam facility
● Proof of concept for measuring photon energies with oscilloscope pulse height
● Rates of photon production for this setuporder of 10 --100 Hz
To Look Into● Background of low energy particles● Triggering on low energy electrons
affected by multiple scattering
K. Dunne | Photon Tagged Beamline | 7th Beam Telescopes and Testbeams Workshop 24
DESY II Test Beam
DESY IIMagnetic field fans out particles by their momentum
Carbon fiber target creates photons Collimator selects
particle momentum for test beam
Converter target creates e+/e- pairs
DESY II Circumference: ~292 m
K. Dunne | Photon Tagged Beamline | 7th Beam Telescopes and Testbeams Workshop 26
Synchrotron photons No converter
Magnet on
Vary electron energy
K. Dunne | Photon Tagged Beamline | 7th Beam Telescopes and Testbeams Workshop 27
Converter Target
3mm copper target between collimator and magnetic field
Converter target
e-e-
K. Dunne | Photon Tagged Beamline | 7th Beam Telescopes and Testbeams Workshop 28