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

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 of the OPCPA OPCPA system generates trains of picosecond or femtosecond pulses  = 150 fs.. 20 ps (FWHM)OPCPA system generates trains of picosecond or femtosecond pulses  = 150 fs.. 20 ps (FWHM) pulse energy: E micro = 50…100  J E train = up to 80 mJpulse energy: E micro = 50…100  J E train = up to 80 mJ Available wavelength:Available wavelength: = 790…830 nm = 790…830 nm up to 900 us 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  J pulse length: ~ 2 ns # pulses/train: 2820 Intensity jitter: < 5 % (rms) pulse spacing: 337 ns rep. rate: 5 Hz wavelength: nm DC gun: 120 keV HV Room temperature linac: Allows external focusing by solenoids Same 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 – 250GeV & Transfer Paths Primary e - source e - DR 5 – 100 GeV e - Bypass line 2 nd 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 GeV150 GeV Helical Undulator Photon Target IP250 GeV Positron Linac Beam Delivery System D Scott, Daresbury Undulator Based Source Many options for undulator placement etc

Undulator Prototypes D Scott, Daresbury 14mm SC, Rutherford Lab 10mm 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 %±10-20% Number of positrons agrees with expected Positron Polarisation = 95 %±30% Simulated 84% A Mikhailichenko, Cornell

Electron storage ring laser pulse stacking cavities positron stacking in main DR Compton Scheme to main linac Compton ring T Omori, KEK

Proof of Principle at KEK T Omori, KEK

Summary of Experiment 1) 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 trn5th bnch on 5th trn 100 bnchs on 18820th trn 10th bnch on 10th trn before 11th bnch on 941st trn 11th bnch on 942nd trn15th bnch on 946th trn 20th bnch on 951st trn before 21st bnch on 1882nd trn 100th bnch on 8479th trn 100 bnchs on 9410th trn ~110  sec ~10 msec ~10 msec  sec ~20 msec ~100 msec  sec ~110 msec~200 msec T= Longitudinal Pos. (m)  Energy/Energy i-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