AWAKE Electron Spectrometer

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AWAKE Electron Spectrometer Simon Jolly 6 th December 2013

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AWAKE Electron Spectrometer. Simon Jolly 6 th December 2013. Spectrometer Specifications. Wakefield accelerated electrons ejected collinear with proton beam: need to separate the 2 and measure energy of electron beam only. - PowerPoint PPT Presentation

Transcript of AWAKE Electron Spectrometer

AWAKE Electron Spectrometer

Simon Jolly6th December 2013

Spectrometer Specifications

• Wakefield accelerated electrons ejected collinear with proton beam: need to separate the 2 and measure energy of electron beam only.

• Must be able to resolve energy spread as well as energy: spectrometer must accept a range of energies, probably 0-5 GeV.

• Current conceptual layout:– Dipole mounted ~2 m downstream of plasma exit

induces dispersion in electron beam.– Scintillator screen 1 m downstream of dipole

intercepts electron beam ONLY.– Dispersion gives energy-dependent position spread

on screen.– Scintillator imaged by intensified CCD camera

viewing upstream face of scintillator screen.

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2 GeV Beam, 1.86 T Field

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2 GeV Beam, 1.86 T Field

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2 GeV Beam, 1.86 T Field

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2 GeV Beam, 1.86 T Field

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2 GeV Beam, 1.86 T Field

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2 GeV Beam, 1.86 T Field

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AWAKE Spectrometer Area

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Spectrometer Layout

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Camera

Scintillator Screen

CERN MBPS dipole

Protons

Electrons + Protons

Current Progress

• Reconstruction software shows we can resolve energy spread in electron beam given reasonable intensity pattern on screen.

• Current work progressing on several fronts:– Scintillator screen light output.– Vacuum layout (protons inside, DAQ

outside).– Optimum experimental geometry.– Alternative screen technologies.

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Scintillator Screen• Default scintillator choice is Lanex:

• Manufactured by Kodak.• Used in Medical Physics as X-ray phosphor for imaging.• Gd2O2S:Tb – Gadolinium sensitiser, Terbium dopant

activator/wavelength shifter.• Phosphor grains on reflective backing.• Properties don’t seem to be well documented/studied…

• Need to simulate light production (photons per MeV conversion efficiency) to ensure we have enough photons emitted in direction of camera.

• Is this the correct scintillator for our purposes?

• We care about:• Light output.• Resolution• Radiation hardness.• Area.

• We don’t care about:• Speed.

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GadOx: Geant4 Photons (J. Goodhand)

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And Now:A Scintillator

Interlude.

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A Scinterludeyoutu.be/gaI6kBVyu00

MBPS Magnet

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MBPS Magnet: Good Field Region?

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300 mm 1000 mm

Spectrometer Layout

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Spectrometer + Beam Dump

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Beam Dump

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AWAKE Spectrometer Area (1)

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AWAKE Spectrometer Area (2)

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AWAKE Spectrometer Area (3)

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Spectrometer Camera View (1)

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Spectrometer Camera View (2)

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Spectrometer Camera View (3)

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No Vacuum

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Vacuum Vessel (1)

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Vacuum Vessel (2)

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Vacuum Window

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Vacuum Window: Fresnel Lens

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No Vacuum

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Windowed Beampipe (1)

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Windowed Beampipe (2)

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Reverse Geometry

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Reverse Geometry: Beam Dump

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Reverse Geometry: Camera Position

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Reverse Geometry: Vacuum Vessel

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Light Tight Vessel

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Off-Axis Camera + Focussing Mirror

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Off-Axis Camera: CNGS Tunnel

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Spectrometer Status

• Preliminary Geant4 scintillator results encouraging:– ~100,000 photons into camera without additional

optics.– Some results need more investigation…

• Work ongoing to optimise experimental layout:– We need a vacuum vessel for protons, but what

about electrons?– Is screen compatible with vacuum?

• Open questions:– Good field region within dipole.– Optimum camera distance from beamline to

minimise damage but maximise light.– Electron/photon transition from vacuum to

atmosphere (light tight).– Fresnel lens/Herschelian Telescope optics.– “Modifications” to CNGS tunnel…

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