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History of Electron Accelerators: Livingston Plot Rasmus Ischebeck 5

Applications of Accelerators Rasmus Ischebeck

How to Accelerate Charged Particles Assume: an ultrarelativistic particle of charge e moving along the z axis accelerated by a plane electromagnetic wave that propagates at an angle ϑ to the z axis k ϑ e- λ Rasmus Ischebeck

How to Accelerate Charged Particles Then: Position of the electron k ϑ e- λ Electric field Energy gradient Rasmus Ischebeck

Lawson Woodward Theorem Every wave in far field can be written as a superposition of plane waves The Lawson-Woodward Theorem states: the total acceleration of ultrarelativistic particles by far-field electromagnetic waves is zero Need near-field structures electron Woodward, J. IEE 93 (1947) Lawson, IEEE Trans. Nucl. Sci. 26 (1979) Palmer, Part. Accel. 11 (1980) electromagnetic wave Rasmus Ischebeck

RF Acceleration RF Acceleration electrical field Cu Using a resonant cavity at radio frequencies (RF) (∼GHz) Electromagnetic field provided by external source (e.g. klystron) electron Resonating RF Cavity Travelling Wave Structure 11.4 GHz 2π/3 Mode Eacc ≥ 50 MV/m Rasmus Ischebeck

Limits to the Accelerating Field Normal-conducting accelerators Breakdown on the surface Superconducting accelerators Critical magnetic field http://hyperphysics.phy-astr.gsu.edu/hbase/solids/scbc.html Rasmus Ischebeck

Possibilities for Accelerating Structures max. Field (V/m) Structure Power Sources electron beams: klystrons electron beams: klystrons or integrated structure Superconducting 5·107 solid state Metallic 2·108 solid state Dielectric 109 laser electron beams Plasma ≥1011 laser electron beams Plus: Inverse FEL, disposable structures, excited atoms, muon colliders Rasmus Ischebeck

> Transformation of far-field into accelerating field Metallic Structures > Transformation of far-field into accelerating field Rasmus Ischebeck

Laser-Based Acceleration Rasmus Ischebeck Laser-Based Acceleration

Laser Acceleration (1961) Koichi Shimoda, Applied Optics 1 (1), 33 (1961) Rasmus Ischebeck 15

Laser as a source of electromagnetic fields 1.  Smaller/less expensive than RF. 2.  Energy efficient (near 50%). 3.  High repetition rate (1 to 100 MHz). 4.  Large electric fields (GV/m). Solid-state laser RF Klystron Rasmus Ischebeck Bob Byer 16

Dielectric Accelerator Structures > Using much higher frequencies: THz to optical > Using dielectrics (e.g. SiO2) > Advantages: higher damage threshold Higher accelerating fields, up to ~GV/m > Generate the electromagnetic field > Cherenkov radiation from an electron beam > Laser > Confine the field > Photonic band gap 8 Rasmus Ischebeck 17

Planar Structures Elliptical Pillars Rectangular Pillars Laser Rectangular Pillars Laser Double Slab Grating Laser e- e- e- Laser Laser Buried Grating Laser Asymmetric Grating Reverse Slab Grating Laser e- e- e- Laser Laser Laser Rasmus Ischebeck Ken Leedle 18

Planar Structures: Measurements Rasmus Ischebeck Joel England 19

Circular Structures > Experiment at MIT Franz Kärtner Rasmus Ischebeck Franz Kärtner

> Structure geometry: Circular Structures > Structure geometry: electron beam E metal dielectric d a Rasmus Ischebeck Franz Kärtner

Circular Structures: Modeling > Analytical solution for the electromagnetic fields: 8 > 1 0 1 E J (r r)e i(kz-!t) , r < a < > E = ✓ ◆ z > J (r b) : > ei(kz-!t), E J0(r2r) - 0 2 Y0(r2r) a < r < b 2 Y0(r2b) 8 > > k i E J (r r)e i(kz-!t) , r < a > > < r 1 1 1 Er = > ✓ ◆ > > k J (r b) > i E J (r r) - : 0 2 Y (r r) e i(kz-!t) , a < r < b r2 2 2 Y0(r2b) 2 8 ! >i > E J (r r)e i(kz-!t) , r < a > < r c 2 1 1 1 B< = ✓ ◆ > > > ! J (r b) : i ✏ E J (r r) - 0 2 Y (r r) e i(kz-!t) , a < r < b r2c2 r 2 2 Y0(r2b) 2 Rasmus Ischebeck Max Kellermeier

Tool to Calculate Beam Propagation Rasmus Ischebeck Max Kellermeier

Circular Structures: Measurements 1 Measured Modeled Measured Modeled 0.8 Counts (Arb.) 0.6 0.4 0.2 45 50 55 60 65 70 Energy (keV) (a) 45 50 55 60 65 Energy (keV) (b) 70 75 Figure 4: Measured (black) and modeled (red) energy spec- trum with THz (a) off and (b) on at a gun voltage of 59 kV. Rasmus Ischebeck Nanni et al., Proceedings of IPAC 2014 24

Towards 3-Dimensional Structures: Photonic Crystals periodic electromagnetic media 1887 1987 1-D 2-D 3-D periodic in one direction periodic in two directions periodic in three directions (need a more complex with photonic band gaps: “optical insulators” topology) Steven G. Johnson 9 Rasmus Ischebeck 25

Photonic Band Gap Structures 12 Rasmus Ischebeck Chris Sramek 26

Installation of a Test Chamber in SwissFEL Rasmus Ischebeck

Planned Experimental Setup in SwissFEL > Goal: Acceleration by 1 MeV Laser Profile monitor Quadrupole magnets Electron beam from SwissFEL Accelerating structure Magnetic spectrometer Paraboloid mirror Rasmus Ischebeck

Focusing of the Electron Beam 90 80 70 60 50 40 30 20 10 x y β-function (m) 2 4 6 8 10 s [m] 12 14 16 18 2 4 6 8 10 12 14 16 18 Rasmus Ischebeck Eduard Prat 29

Design of Interaction Chamber > Design in progress… Rasmus Ischebeck Adriano Zandonella, Goran Kotrle, Eugenio Ferrari 30

Plasma Wakefield Acceleration

> Linear plasma wake: Plasma Wakes - Theory > Unlike electromagnetic waves in vacuum, plasma wakes can have a longitudinal electric field – – + – – + + + – + + + + + – + + – – + – – – + – – + – – + + – – – – + + + – – – + – + – + – – + + > – Tajima & Dawson, PRL, 43, 267(1979) – + – – + + – – – + – + + + – – – + – + – + + – + – + – – + + – – + – + + + + + – + – – – + + + – –– – + + + + – + – + – – E E E E E E > Linear plasma wake: > Limit: Rasmus Ischebeck 32

> Above this limit: non-linear wakes, “Blow-out regime” Plasma Wakes - Theory > Above this limit: non-linear wakes, “Blow-out regime” > Fields can be calculated only with numerical methods > Typical wavelength: 50 µm > Accelerating fields up to 50 GV/m Rasmus Ischebeck Miaomiao Zhou 33

Plasma Wakes - Reality Rasmus Ischebeck 34

> Incoming energy: 42 GeV > Peak energy: 85±7 GeV Energy Doubling > Plasma length: 85 cm > Density: 2.7•1023 m−3 > Incoming energy: 42 GeV > Peak energy: 85±7 GeV Rasmus Ischebeck 35

Measurement of Electromagnetic Fields Rasmus Ischebeck

Measured Electromagnetic Fields Rasmus Ischebeck

Recent Experiments at PSI Rasmus Ischebeck

Generation of a Density Ramp Blade 1.1mm Rasmus Ischebeck

Charge Measurement Rasmus Ischebeck Andreas Adelmann, Nick Sauerwein, Benedikt Herrmann 40

Livingston Plot 44 Rasmus Ischebeck 41

An Unfair Comparison 44 Rasmus Ischebeck 42

From Accelerating Fields to Accelerators There is More to Accelerating Structures than the Accelerating Field >Power sources >Beam loading >Emittance preservation > Non-linear transverse forces > Wakefields There is Much More to an Accelerator than Accelerating Structures >Particle sources (injectors) >Bend magnets for storage rings >Focusing, beam dynamics >Detectors Rasmus Ischebeck 43

Instrumentation and Acceleration Research at PSI > Special Thanks to: Adriano Zandonella Andreas Adelmann Benedikt Herrmann Bob Byer Chris Sramek Eduard Prat Eugenio Ferrari Franz Kärtner Goran Kotrle Joel England Ken Leedle Malte Kaluza Max Kellermeier Miaomiao Zhou Nick Sauerwein > This presentation is available at http://ischebeck.net © 2017 Paul Scherrer Institut Rasmus Ischebeck 44