Gamma Beam Systems a simple introduction

Purpose of the machine Deliver a high performance photon beam: Variable energy Highly polarized High intensity Low bandwidth

Where photons come from? Scattering of photons on high energy electrons. What is the photon energy after scattering?

Where photons come from? Scattering of photons on high energy electrons. What is the photon energy after scattering?

Example

High correlation: photon energy and photon direction Scattering in the direction of the electron

Purpose of the machine Deliver a high performance photon beam: Variable energy: variable energy of the electron beam Highly polarized High intensity Low bandwidth

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

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

Purpose of the machine Deliver a high performance photon beam: Variable energy Highly polarized High intensity: from intense photon and electron beams Low bandwidth

electrons laser High intensity photon beam Many photons -> High intensity laser Many electrons ->High charge electron bunches Large overlap between photons and electrons

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

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

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)

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

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

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

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

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 < 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