The development of ultra bright electron sources: An overview B.L. Militsyn Accelerator Science and Technology Centre Science & Technology Facility Council, UK

Production of ultra bright electron beams. Outline of problems. Emission of fs electron bunches Time structure definition and synchronisation Acceleration with the preservation of bunch length and emittance Bunch compression Transportation and manipulation Characterisation 29/6/2011 B.L. Militsyn, Ultra bright electron sources workshop, 29 June – 1July 2011, Daresbury, UK 2/15

Emission of fs-scale electron beams Thermal emission –Medium brightness –High repetition rate –Poor controllability Photoemission from metal photocathodes –Medium brightness –Medium repetition rate –Good controllability –Generation of high power fs-scale laser pulses is required Field emission –High brightness, –Low repetition rate –Poor controllability Non-traditional electron emitters –Plasma emitters –... 29/6/2011 B.L. Militsyn, Ultra bright electron sources workshop, 29 June – 1July 2011, Daresbury, UK 3/15

Emission. Photoemitters. Metal photocathodes B.L. Militsyn, Ultra bright electron sources workshop, 29 June – 1July 2011, Daresbury, UK 29/6/20114/15 F. Le Pimpec et al., Workshop on Photocathodes for RF Guns, 1-2 March 2011, Lecce, Italy Very fast – few fs response time Relatively high QE – – Very robust at a vacuum of mbar

Emission of high brightness beam. Demands to the cathode field. 29/6/2011 B.L. Militsyn, Ultra bright electron sources workshop, 29 June – 1July 2011, Daresbury, UK Field strength Technology0.01 nC0.1 nC1.0 nC 10 MV/mDC gun MV/mVHF gun MV/mL-band gun MV/mS-band gun /15

Acceleration technologies DC gun –Low field –Highly stability –Acceptable environment for photocathodes –Unlimited repetition rate (limited by the laser repetition rate and photocathode thermal load) NC RF guns –High field –Medium stability –Relative low repetition rate SRF guns –Medium field –High repetition rate (limited by the RF frequency) Non-traditional accelerator schemes –Plasma wake-field acceleration 29/6/2011 B.L. Militsyn, Ultra bright electron sources workshop, 29 June – 1July 2011, Daresbury, UK 6/15

Acceleration. PITZ/FLASH L-band NCRF photocathode gun 29/6/2011 B.L. Militsyn, Ultra bright electron sources workshop, 29 June – 1July 2011, Daresbury, UK 7/15 Distribution of accelerating RF and focusing magnetic field in the gun

Transportation and manipulation Emittance preservation –Emittance compensation –Transportation –Precise beam optical system Velocity bunching –Require relative low energy –Linearity –High demands to phase stability of the bunching cavity Magnetic compression –High energy –CSR at high bunch charge –Physical length of the chicane 29/6/2011 B.L. Militsyn, Ultra bright electron sources workshop, 29 June – 1July 2011, Daresbury, UK 8/15

Transportation and manipulation. MAX-IV high brightness injector. B.L. Militsyn, Ultra bright electron sources workshop, 29 June – 1July 2011, Daresbury, UK Periodic section State 156 cells Output coupling cell Input coupling cell 1.5-cell FERMI type S-band gun with Cu photocathode 5 m long S-band 2π/3 travelling wave linac 29/6/20119/15

MAX-IV high brightness injector. Emittance compensation scheme optimisation results B.L. Militsyn, Ultra bright electron sources workshop, 29 June – 1July 2011, Daresbury, UK 29/6/201110/15

Beam characterisation Emittance –Projection and slice emittance <0.1 mm · mrad at a bunch charge of 1-10 pC Bunch length –Bunch length fs Energy spread –Less than Arrival time –Precision of 10’s fs Slice parameters 29/6/2011 B.L. Militsyn, Ultra bright electron sources workshop, 29 June – 1July 2011, Daresbury, UK 11/15

Beam characterisation. PITZ diagnostic beam line 29/6/2011 B.L. Militsyn, Ultra bright electron sources workshop, 29 June – 1July 2011, Daresbury, UK 12/15 J. W. Bähr et al., Recent upgrade of the PITZ facility, 2010 Beam Instrumentation Workshop

Time structure definition and synchronisation Laser system –Laser pulse duration –Laser pulse repetition rate –Laser pulse stability –Temporal pulses structure –Spatial laser pulse structure –Laser pulse temporal stability relative to the master oscillator RF system –Amplitude stability –Phase stability relative to the master oscillator Synchronisation system –Temporal stability –Thermal stability –Etc. 29/6/2011 B.L. Militsyn, Ultra bright electron sources workshop, 29 June – 1July 2011, Daresbury, UK 13/15

Time structure definition and synchronisation. The LCLS laser system 29/6/2011 B.L. Militsyn, Ultra bright electron sources workshop, 29 June – 1July 2011, Daresbury, UK 14/15

Where we are? We can deliver electron pulses from RF guns with –A pulse duration of 300 fs and less –A bunch charge of 100 pC and more –Relative emittance of up to 0.4 mm  mrad/mm We can generate UV laser pulses with –An energy of several mJ –Pulse duration of 10’s fs scale –Temporal stability of fs We can compress the high energy bunches to a 10’s fs scale We can accelerate and transport beams with emittance of 1 mm  mrad scale We can measure –Emittance in 0.1 mm  mrad range –Bunch length with a precision of 100’s fs We begin to develop non-traditional electron sources We still have order(s) of magnitude to go! 29/6/2011 B.L. Militsyn, Ultra bright electron sources workshop, 29 June – 1July 2011, Daresbury, UK 15/15

Welcome to discussion! 29/6/2011 B.L. Militsyn, Ultra bright electron sources workshop, 29 June – 1July 2011, Daresbury, UK 16/15