Injection system of the 4GLS light source B.L. Militsyn on behalf of 4GLS team ASTeC STFC Daresbury...

Injection system of the 4GLS light source

B.L. Militsynon behalf of 4GLS team

ASTeC

STFC Daresbury Laboratory

ERL’07 Workshop, Daresbury, 21.05.2007-25.05.2007

2/

Outline

Introduction4GLS light sourceInjection system of 4GLS

•XUV-FEL normal conductive RF photoinjector•VUV-FEL High Average Current DC NEA photocathodes based injector•4GLS laser system•IR-FEL thermionic injector

Status and perspectivesConclusion

B.L. Militsyn, ERL’07 Workshop, Daresbury, 21.05.2007-25.05.2007

3/

4GLS Layout


4/

XUV-FEL branch of 4GLS


Photon energy range, eV 8-4035-100

Peak power, GW 3-51-3

Photon pulse length, fs 22Repetition rate, kHz 1

Beam energy 750 MeV

5/

XUV-FEL injector


Beam parameters at the entrance of main linac

Bunch charge, nC 1.0Bunch repetition rate, kHz 1.0Beam energy, MeV 210Normalised emittance, π·mm·mrad <2Uncorrelated energy spread, % <0.05RMS bunch length (σ ), ps ~2

6/

Normal conductive 1.5-cell RF photocathode gun


0

400

800

1200

1600

2000

2400

0 0.2 0.4 0.6 0.8 1

Longitudinal position, m.

Ma

gn

eti

c f

ield

, a

.u.

-60.0

-40.0

-20.0

0.0

20.0

40.0

60.0

Ele

ctr

ic f

ield

, a

.u.

Focusing magnetic field

Accelerating electric field

Distribution of accelerating RF and focusing magnetic field in the gun

7/

ASTRA simulation of the RF gun


0 0.5 1 1.5 2 2.5 330

1

2

3

4

5

Horizontal position, m

RM

S t

rans

vers

e be

am s

ize,

mm

Simulation parameters

Laser spot diameter, mm 4Spatial laser spot distribution UniformTemporal laser pulse shape Flat-topLaser pulse length, ps 20Rise time, ps 2Initial rms beam energy spread, V 0.4Maximum RF accelerating field, MV/m 40

8/

ASTRA simulation of the XUV-FEL injector


9/

ASTRA simulation of the XUV-FEL injector


10/

Laser for the XUV-FEL injector

[%]][

1241

eQnm

nCqJE


Required energy of laser pulse is given by:

For an CsTe2 photocathode Qe=1% at =262 nm :

Wavelength, nm 262Repetition rate, kHz 1.0Pulse shape Flat topMaximum rise time, ps 2Pulse length, ps 10Laser pulse energy, µJ 1

11/

VUV-FEL branch of 4GLS


Photon energy range, eV 3-10Peak power, MW 350Photon pulse length, fs 64Repetition rate, MHz n*4.33

Beam energy 550 MeV

Maximum photon energy, eV 80Average flux, 1/s/0.1% bp 1.0*1015

Repetition rate, GHz 1.3

12/

VUV-FEL injector


Beam parameters at the entrance of main linac

Bunch charge, pC 77Bunch repetition rate, GHz 1.3Operation mode CWBeam energy, MeV 10Normalised beam emittance, π·mm·mrad < 2Uncorrelated energy spread, % < 0.1Bunch length, ps 5

13/

High voltage DC photocathode gun


Parameter of the photocathode gun

Gun voltage, kV 500Average beam current, mA 100Bunch repetition rate, GHz 1.3RMS laser pulse length, ps 20Laser pulse shape GaussianEstimated operational lifetime, hours 27Estimated rms transverse emittance, π·mm·mrad 2.8Estimated rms bunch Length, ps 30

14/

Photocathode preparation set-up


Required photocathodes:

•NEA III/V semiconductor•Transmission mode•High quantum efficiency•Fast response•High emission current density

15/

Photoemission from “thick” NEA photocathodes


Photoemission from “thick” NEA photocathodes illuminated by

green light

by the courtesy of A.S. Terekhov

Energy distribution of electrons emitted from bulk GaAs photocathodes according to

measurements made at Max Planck Institut für Kernphysik (MPI-K), Heidelberg, Germany.

16/

Photoemission from “thin” NEA photocathodes


100 nm

1000 nm

2.3 ps

30 ps

Data from Mainz: experiment, diffusion model

if d≤L - thermalization length “hot” photo-electrons increase transverse energy spread

17/

Beam dynamics in the VUV-FEL injector


18/

Laser for VUV-FEL injector


For GaAs photocathodes <850 nm, for =520 nm

Wavelength, nm 520Repetition rate, GHz 1.3RMS pulse with, ps 10Average laser power for Qe=10%, W 2.3Average laser power for Qe=1%, W 23Average laser power for Qe=1%,=0.7, W 33Timing jitter, fs 100

19/

Time structure of the beam in the main linac


20/

4GLS laser system


by the courtesy of G. Hirst

21/

IR-FEL branch of 4GLS


Wavelength, m 2.5-2520-200

Repetition rate, MHz 13Peak power, MW 3-20Photon pulse length, ps 0.8-2.4Switch yard frequency, Hz 100

Beam energy 25-60 MeV

22/

IR-FEL injector


Bunch charge, pC 200Bunch repetition rate, MHz 13Peak current, A 8 to 80Energy, MeV 25 to 60Normalised emittance, π·mm·mrad < 10RMS energy spread, % < 0.1RMS bunch length, ps 1 - 10

23/

Thermionic emitter


-2

-1

0

1

2

0 0.5 1 1.5 2

RF phase, p .

Gri

d v

olt

age,

a.u

.

Grid modulated 6 mm LaB6 emitter Formation of the grid voltage

24/

ASTRA simulation of a 400 kV thermionic gun


25/

Beam in the transverse and longitudinal phase spaces


26/

Status and perspectives


XUV-FEL injector R&DVUV-FEL injector

•Photocathode gun Drawing room•Preparation facility Drawing room•Photocathodes R&D•Laser system R&D•High voltage power supply R&D•Test beam line ERLP test beam line

IR-FEL injector R&D

27/

Conclusion


Injection system of 4GLS requires state of the art and beyond electron sources, laser and synchronisation devicesThough requirements for injector for XUV-FEL very close to the parameters of BESSY-PITZ project some research are required in thew derection of

High power gun cavityHigh repetition rate low jitter laser system

Injector for VUV-FEL requires additional research in the direction ofPhotocathode developmentPhotocathode preparation and manipulation techniqueVery high voltage photocathode gun designHigh frequency high power laser system

IR-FEL injector may be build on the bases of well known grid modulated thermionic gun

Injection system of the 4GLS light source B.L. Militsyn on behalf of 4GLS team ASTeC STFC Daresbury...

Documents

Transcript of Injection system of the 4GLS light source B.L. Militsyn on behalf of 4GLS team ASTeC STFC Daresbury...