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Published byLorena Reed Modified over 9 years ago
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Gamma Beam Systems a simple introduction
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Purpose of the machine Deliver a high performance photon beam: Variable energy Highly polarized High intensity Low bandwidth
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Where photons come from? Scattering of photons on high energy electrons. What is the photon energy after scattering?
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Where photons come from? Scattering of photons on high energy electrons. What is the photon energy after scattering?
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Example
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High correlation: photon energy and photon direction Scattering in the direction of the electron
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Purpose of the machine Deliver a high performance photon beam: Variable energy: variable energy of the electron beam Highly polarized High intensity Low bandwidth
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Purpose of the machine Deliver a high performance photon beam: Variable energy: variable energy of the electron beam – Large energy range - > magnetic machine Highly polarized High intensity Low bandwidth
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Purpose of the machine Deliver a high performance photon beam: Variable energy: variable energy of the electron beam Highly polarized: Compton scattering retains the polarization of the laser photon High intensity Low bandwidth
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Purpose of the machine Deliver a high performance photon beam: Variable energy Highly polarized High intensity: from intense photon and electron beams Low bandwidth
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electrons laser High intensity photon beam Many photons -> High intensity laser Many electrons ->High charge electron bunches Large overlap between photons and electrons
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Purpose of the machine Deliver a high performance photon beam: Variable energy Highly polarized High intensity: from intense photon and electron beams Low bandwidth: from collimation of photons – We retain 0.1% of the photons after collimation
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Principle of operation of GBS 1.Electron bunches generated at photocathode 2.Electron bunches transported to Interaction Point – acceleration – focusing 3.Laser transported to interaction point 4.Electron-Photon interaction 5.Collimation of photons 6.Experiments
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Why is it a complicated machine? Interaction laser – High intensity = low repetition rate (100 Hz) -> recirculator to artificially increase the frequency Recirculator: gives the time structure of the beam (1ns = 30 cm)
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Why is it a complicated machine? High charge electron bunches(250 pC): – High space charge effects leads to high emittance (size of beam) - - - - - - - - - Low bandwidth needs very low emittance: size of beam at interaction point direction of photon given by direction of electron
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Why is it a complicated machine? Beam time structure: – Complex recirculator – Complex cathode laser – Complex synchronisation – Wakefields in RF cavities – Complicated electron beam diagnostics – Complicated photon beam diagnostics
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Gamma Beam System – Layout e – RF LINAC Low Energy 300 MeV Interaction Laser Low Energy Photo–drive Laser e – source Interaction Point Low Energy Photogunmultibunch e – beam dump beam coll&diag e – beam dump Low Energy Stage Gamma rays up to 3.5 MeV ControlRoom RacksRoom RacksRoom
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Gamma Beam System – Layout e – RF LINAC High Energy 720 MeV Interaction Laser High Energy Interaction Laser Low Energy Photo–drive Laser e – source Interaction Point High Energy Photogunmultibunch e – beam dump beam coll&diag e – beam dump High Energy Stage Gamma rays up to 19.5 MeV ControlRoom RacksRoom RacksRoom
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Gamma Beam System – Layout e – RF LINAC Low Energy 300 MeV Interaction Laser High Energy Interaction Laser Low Energy Photo–drive Laser e – source Master clock synchronization @ < 0.5 ps Interaction Point High Energy Interaction Point Low Energy Photogunmultibunch e – beam dump dump beam coll&diag coll&diag e – beam dump ControlRoom RacksRoom RacksRoom e – RF LINAC High Energy 720 MeV
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