ERLP Overview

Hywel Owen

ASTeC Daresbury Laboratory

Light Source Hierarchy

First generation - parasitic SR beamlines on high-energy physics accelerators; e.g. the SRF on NINA.

Second generation - dedicated particle accelerators providing synchrotron radiation from bending (dipole) magnets.

Third generation - dedicated particle accelerators providing synchrotron radiation from special magnets (insertion devices) placed between the dipole magnets.

Fourth generation - FEL-based (could be linac, storage ring)

The Solution - a Linac-Based Light Source

Linac can deliver a very high quality electron beam (now) Electrons are required only once then dumped. Temporal pulse pattern flexibility.

Features: High average brightness gun. Normal or superconducting linear accelerator. One or more FELs. Energy Recovery required for economy

(55 MW power in 4GLS CW branch).

ERLP - A Prototype Accelerator for 4GLS

EMMAFor more information, and Conceptual Report,See www.4gls.ac.uk

electrons

electrons

anode

ERLP DC Electron Gun

Electrons

XHV

CeramicCathode SF6Vessel removed

Cathode ball

Stem

laser

Anode Plate

• Text

Glassman PK500N008GD5

Voltage -500 kV

Current 8 mA

Cockcroft-Walton based multiplier

Delivered December 2003

Gun Power Supply

Superconducting Modules

Delivery April/July 2006

JLab HOM coupler design adopted for the LINAC module

2 x Stanford/Rossendorf cryomodules – 1 Booster and 1 Main LINAC.

Booster module: 4 MV/m gradient 32 kW RF power

Main LINAC module: 14 MV/m gradient 16 kW RF power

ERLP Cavity Test Results

Booster Cavity1 Linac Cavity1

Booster Cavity2 Linac Cavity2

Specification of > 15MV/m at Qo > 5 x 109

Goal Goal

Goal

Goal

ERLP as an Injector for EMMA

2 x 1.3 GHz Superconducting Modules

ERLP Parameters

Parameter Value

Nominal Gun Energy 350 keV

Max. Booster Volts 8 MV

TL 2 Energy 8.33 MeV

Max. Linac Volts 26.67 MV

Max. Energy 35 MeV

Linac RF Frequency 1.300 GHz (+/- 1 MHz)

Bunch Repetition Rate 81.25 MHz

Bunch Spacing 12.3 ns

Max Bunch Charge 80 pC (risk variable)

Particles per Bunch 5 x 108

Bunches per

Extraction Energy 10 to 20 MeV (need to check lower limit)

Extraction Emittance 5-20 mm mrad (various issues)

ERLP Operating as an Injector for EMMA

8.00 MV (2x4 MV)(standard)

8.35 MeV(standard)

0.35 MeV(fixed)

10-20 MeV(variable)

1.65-11.65 MV(variable)

Later we will need to consider adapted injector (post-4GLS construction)

Bunch Shapes in ERLP (B.Muratori presentation)

Sextupoles also needed in return arc Optimise energy spread after deceleration Allow clean extraction of beam to dump

ERLP Laser Paths – Injector, FEL, THz, EO

ERLP Photoinjector and Laser

LASER ROOM

ACCELERATORHALL

Shield wall

Optical Table

DC GunBased on

Jlab design

Commercial 500kV(350kV)8mA DC Power Supply(Glassman Europe)Power supply and gun enveloped by 0.8 Bar SF6 environment

Booster Cavity

Laser Beam Transport System

ERLP Laser Pulse Output Characteristics

Cathode material Cs:GaAs

Electron bunch charge 80 pC

Bunch length 20 ps

Bunch repetition rate 81.25 MHz

Pulse train length 1 bunch and 20-100 s

Pulse train repetition rate Single shot and 1-20 Hz

Cathode efficiency 1 %

Laser wavelength 532 nm

Laser pulse energy at cathode 20 nJ

Average power at cathode <4 mW

Pulse length <20 ps

Beam diameter at cathode 2-6 mm (FWHM)

Nd:Vanadate Laser material

- -

- -

81.25 MHz Pulse repetition rate

- -

Cw mode-locked Pulse train rep. rate

- -

1064 / 532 nm Laser wavelength

61.5 nJ

532nm output energy per pulse

5 W Average power

7 ps Pulse length (FWHM)

0.6 mmBeam diameter output

The commercial solutionRequirements

ERLP Laser

ChopperChopper• To generate 60-140 s long trains of pulses

with 100 Hz repetition rate• To decrease the thermal load on the electro-optic

modulator (Pockels cell)

Mechanical shutterMechanical shutter• To select pulsetrains with 1-20 Hz• To decrease the thermal load on the Pockels cell

PockelsPockels cellcell•To clean up the rising and falling edges•To select down to single pulse

Injection and Extraction Timing Structure

Standard ERLP injector 12.3 ns bunch spacing Up to ~160 pC per bunch Up to 2 bunches Total charge <0.32 nC Spec is 1 bunch, 80 pC

Pulse-stacking (adapted injector) Down to 0.77 ns spacing Up to ~80 pC per bunch Up to 18 bunches Total charge? Costs more!

Revolution time 55 ns (16.5 m)

risetime

falltimeInjection flat-top time

(top is not really flat)

12.3 ns (81.25 MHz)

~15 ns

~20 ns

Revolution time 55 ns (16.5 m)

0.77 ns (1.3 GHz)max. 18 bunches

RF frequency in injector can be changed by ~1 MHz – not enough!

~20 ns

risetime

falltimeInjection flat-top time

~15 ns

~20 ns ~20 ns

Faro Laser Tracker

Repeatability 1m +1 m /m

Accuracy 10 m + 0.8 m /m

Uncertainty ≈ 10 m /m

Portable

Robust

Spatial Analyzer Metrology Software

Error Simulations

Multiple instruments/types

Automation

ERLP and EMMA Survey – see talk by John Strachan

Simulation of reference grid in SA

76 Grid reference points

40 Instrument positions

Each point measured by a minimum of 3 instrument locations

Faro Tracker

Grid reference points

ERLP Hall Survey and Alignment

Installation Progress

Photoinjector laser operating since April ’06 Gun installed with a dedicated gun diagnostic beamline Both superconducting modules delivered from Accel Cryosystem installed and used to cool accelerating modules down to 2K All beam transport modules now installed – one area under vacuum Most hardware components now installed

Performance Achieved So Far

Gun operating voltage 350 kV (spec value)

Output bunch charge 5 pC (target 80 pC)

Cathode quantum efficiency In gun: 0.4% In the lab: 3.5% (spec is ~few percent)

Bunch train length 100 µs (spec value)

Train repetition rate 20 Hz (spec value)

Parameter Value Nominal Gun Energy 350 keV Max. Booster Volts 8 MV TL 2 Energy 8.33 MeV Max. Linac Volts 26.67 MV Max. Energy 35 MeV Linac RF Frequency 1.300 GHz Bunch Repetition Rate 81.25 MHz Bunch Spacing 12.3 ns Max Bunch Charge 80 pC Particles per Bunch 5 x 10^8 Bunches per Extraction Energy 10 to 20 MeV Extraction Emittance 5-20 mm

mrad

350 keVTest line screen

Ongoing Work

Cleaning and re-assembly of the gun Understanding and testing the cryogenic system Installation and testing of all RF systems Commissioning of the booster and linac modules BTS Installation/Commissioning Laser room modification to accept the terawatt laser

2007 Schedule

Gun & diag line studies finished 3rd April Re-configure booster 16th April Full BTS Pumpdown 25th April RF Systems ready 25th May Beam through Module 1 (8.35 MeV) June Beam through Module 2 (35 MeV) June onwards Energy recovery demonstrated October

Install wiggler Energy recovery from FEL-disrupted beam Produce output from the FEL