WG3a Sources Summary

Jim Clarke

on behalf of

John Sheppard, Masao Kuriki, Philippe Piot and all the contributors to WG3a

Goals for WG3a• Review ILC electron and positron source requirements. • Review proposed source designs. • Make recommendation for the baseline reference

design. • Develop list of R&D tasks. • Discuss design options. • Propose a timeline for the development of the ILC

sources which includes criteria and milestones for technology selection.

• Make a list of current activities; make a list of institutional interest in future development activities.

ILC Source Requirements

Parameter Symbol Value Units Particles per bunch

bn 102 10x ( 101 10x )† e- or e+

Bunches per pulse bN 2820 (5600) † number

Bunch Spacing Tb ~300 ns Pulse Repetition Rate

repf 5 Hz

Energy E0 5 GeV DR Transverse Acceptance A=2J 0.04 m-rad DR Energy Acceptance E/E 1 %,FW Overhead Factor Fc 1.5 number Electron Polarization Pe >80 % Positron Polarization (option) Pp ~60 %

Electron source

• 2 sessions dedicated to electrons

• 7 presentations

• Type of gun– DC or RF– What DC voltage to use– What RF scheme to use

• Photocathodes

• Lasers

N Yamamoto, Nagoya

OPCPA system for generation of trains

of femtosecond pulses with ~800 nm wavelength

Output pulse train Output pulse train of the OPCPAof the OPCPA

• OPCPA system generates trains of OPCPA system generates trains of picosecond or femtosecond pulses picosecond or femtosecond pulses

= 150 fs .. 20 ps (FWHM) = 150 fs .. 20 ps (FWHM)• pulse energy: pulse energy:

EEmicromicro = 50…100 = 50…100 JJEEtraintrain = up to 80 mJ = up to 80 mJ

• Available wavelength: Available wavelength: = 790…830 nm= 790…830 nm

up to 900 us

= 12 ps(FWHM)

= 523 nm

synchronizedNd:YLF Burst-Mode laser

pumping the OPA

= 150 fs (FWHM)Emicro = 50...100 J

@ f= 1 MHz

picosecond-pulseoutput channel:

pulse trains, 800 s long

= 15 ps 100 fs

G > 5 000primary

synchronization loop

master clockf = 1.3 GHz

mixer1.3 GHz

photodiode

Piezo

three-crystalOPA

outputpulse trains800 s long, = 790 ...

830 nm

gratingcompressorgrating stretcherTi:Sa oscillator

G ~ 20

I. Will, H. Redlin, MBI Berlin

K Floettmann, DESY

Easily stretched

Far more energy than needed

room-temperature accelerating sect.

diagnostics section

standard ILC SCRF modules

DC gun(s)

sub-harmonic bunchers + solenoids

laser

ILC polarized electron source, Baseline Recommendation!

Laser requirements:pulse energy: ~ 2 Jpulse length: ~ 2 ns# pulses/train: 2820Intensity jitter: < 5 % (rms)pulse spacing: 337 nsrep. rate: 5 Hzwavelength: 750-850 nm

DC gun:120 keV HV

Room temperature linac:Allows external focusing by solenoidsSame as e+ capture linac

photocathodes:GaAs/GaAsP

Positron Source

• 4 sessions dedicated to positrons

• 13 presentations

• 3 alternative schemes were considered in detail

• Lively discussion on pros and cons of each scheme !!

“Conventional” Scheme

Conventional Target

W Stein, LLNL

Target material WRe

56kW absorbed

Target rotates at 360m/s

Operates at fatigue stress of material

Positron Yield

W Gei, ANL

Positron yield is defined as the ratio of the number of captured positrons to that of incoming electrons striking the conversion target.

Specification is 1.5

no safety margin

Schematic Layout – Undulator @ 250GeV & Transfer Paths

Primary e-

source

e-

DR

5 – 100 GeV e- Bypass line

2nd e- Source

150 – 250 GeV e- Transfer Line

Target e- Dump

Photon Beam Dump

e+

DR

Auxiliary e- Source

Photon Collimators

Adiabatic Matching

Device

e+ pre-accelerator

~5GeV

Electron Linacs

100 GeV 150 GeV

HelicalUndulator

PhotonTarget

IP 250 GeV

Positron Linac

BeamDeliverySystem

D Scott, Daresbury

Undulator Based SourceMany options for undulator placement etc

Undulator Prototypes

D Scott, Daresbury

14mm SC, Rutherford Lab10mm SC, Cornell

14mm PM, Daresbury

Target and Yield

• Target– Material is Ti– 18kW absorbed– Rotates at 100 m/s– Factor of 2 safety margin in fatigue stress

• The value of positron capture for undulator-based source is 3-4 larger than that of electron-based source because of better positron beam emittance after target. (Y Batygin, SLAC)

E-166 Experiment

E-166 is a demonstration of undulator-based production of (polarized) positrons for linear colliders:

- Photons are produced ~in the same energy range and polarization characteristics as for ILC;

-The same target thickness and material are used as in the linear collider;

-The polarization of the produced positrons is the same as in a linear collider.

-The simulation tools are the same as those being used to design the polarized positron system for a linear collider.

- Number of gammas per electron is lower ~210 times, however: (150/1)(2.54/10)(0.4/0.17)2.

A Mikhailichenko, Cornell

E-166 at SLAC

Undulator table

Positron table

Gamma table

Vertical soft bend

Undulator table

Positron table

Gamma table

Vertical soft bend

A Mikhailichenko, Cornell

E166 Undulator Area

A Mikhailichenko, Cornell

E-166 Results

• Number of photons agrees with expected

• Gamma polarisation agrees with theory 82-99.3 %±10-20%

• Number of positrons agrees with expected

• Positron Polarisation = 95 %±30%

• Simulated 84%A Mikhailichenko, Cornell

Electron storage ring

laser pulse stacking cavities

po

sitron

stacking

in m

ain D

RCompton Scheme

to main linac

Compton ring

T Omori, KEK

Proof of Principle at KEK

T Omori, KEK

Summary of Experiment1) The experiment was successful. High intensity short pulse polarized e+ beam was firstly produced. Pol. ~ 80%

3) We established polarimetry of short pulse & high intensity -rays, positrons, and electrons.

2) We confirmed propagation of the polarization from laser photons -> -rays -> and pair created e+s & e-s.

T Omori, KEK

Compton Scheme for ILC

• Electron storage ring

• Laser pulse stacking

• Positron stacking ring

• Two versions, based on either CO2 or YAG laser

• Expect 60% polarisation

Schematic View of Whole System (CO2)

~2.5A average current

One laser feeds 30 cavities in daisy chain

T Omori, KEK

e+ stacking in Damping Ring (simulation)1st bnch on 1st trn 5th bnch on 5th trn

100 bnchs on 18820th trn

10th bnch on 10th trn

before 11th bnch on 941st trn

11th bnch on 942nd trn 15th bnch on 946th trn

20th bnch on 951st trn before 21st bnch on1882nd trn

100th bnch on 8479th trn

100 bnchs on 9410th trn

~110 sec

~10 msec

~10 msec + 110 sec ~20 msec ~100 msec + 110 sec

~110 msec ~200 msec

T=0

-0.4 0.4Longitudinal Pos. (m)

-0.0

3

0.

03E

ner

gy/E

ner

gyi-th bunch on

j-th DR turn

Time

e+ in a bucket

stacking loss = 18% in total

T Omori, KEK

Open Issues for Positron Sources• L-band warm structure 1ms operation : U , LC and Cv.

• Target damage : Cv.• Radiation damage on target : U,LC• Thermal load of the capture section: Cv. • Damage by the operation failure : U (MPS)• Damage or failure by the instabilities : U• Degrade the electron beam quality: U• Positron Stacking in DR : LC• e beam stability in Compton Ring: LC

• Vacuum pumping : U• Stability of integration of optical cavity : LC• Radiation loss, heat load in DR : LC• Fast Kicker operation with large kick angle for DR injection : U, LC and

Cv (DR problem)• Mechanical failure on the rotation target: Cv and U

Cv: Conventional U: Undulator LC: Laser Compton

Baseline

• Baseline not yet agreed

• A number of issues for each scheme will be examined in detail (next week)

• Need some interaction with other groups (eg Damping Ring)

• Generate Performance & Issues List

• Aim to make recommendation for baseline (and alternative) next week