Axel Brachmann, John Sheppard, Vinod Bharadwaj SLAC Particle Sources Efforts Review/Status and Plans SLAC HEP Program Review June 13 th, 2007

International Linear Collider – Americas 2/24 Gun Laser Injector specific RF structures Photo cathodes Electron Source Systems

International Linear Collider – Americas 3/24 Positron Source Systems

International Linear Collider – Americas 4/24 e+/e- Institutions in the US –SLAC Overall coordination & leadership Define parameters Polarized e - Source Laser System Photocathode Development Target hall, remote handling, activation Beamline optics and tracking NC L-Band accelerator structures and RF systems Experiments – E166, FLUKA validation experiment –LLNL Target simulations Target design Pulsed OMD design –ANL Optics Tracking OMD studies Eddy current calculations –Jlab Polarized gun development –Cornell Undulator design, alternative target concepts

International Linear Collider – Americas 5/24 Collaborating non-US Institutions Institutions doing substantial work on ILC baseline e+ development –CCLRC-Daresbury undulator design and prototyping beam degradation calculations –CCLRC-RAL (?) remote handling eddy current calculations target hall activation –Cockcroft and Liverpool University target design and prototyping –DESY-Zeuthen target hall activation spin preservation photon collimation E166

International Linear Collider – Americas 6/24 Electron Source Technical Milestones 1.Demonstrate Source Laser System. 2.DC Gun Development (HV design). 3.Advance Polarized Photocathode Technology. 4.Bunching system design. 5.Beam Dynamics. 6.Demonstrate polarized electron bunch train with ILC parameters.

International Linear Collider – Americas 7/24 Source Laser System

International Linear Collider – Americas 8/24 Source Laser System Source laser development has started at SLAC’s ILC Injector Development Facility. Laser system pushes the state of the art in laser technology. Collaboration with Kapteyn-Murnane Labs through SBIR phase II (pending approval) aids in laser development. Facility allows use of SLC 120 kV DC gun in combination with laser system to generate polarized ILC electron bunch train. Goal is to demonstrate the operating laser system by the end of FY 09.

International Linear Collider – Americas 9/24 DC Gun Development Project will start in FY 08 at Jlab. 140 kV minimum operating voltage  200 kV design. Combine features of SLAC’s 120 kV SLC gun and Jlab’s 100 kV gun. HV design (power supply). Optimize electrodes (material and design) for ILC conditions. Load lock is essential for high reliability. Goal is to test the gun with laser system developed at SLAC.

International Linear Collider – Americas 10/24 Photocathode R&D Program Supported by ILC (mostly FTE’s, small M&S contribution) Several SBIR’s/STTR’s in FY07 (all Phase I): –Activation Layer Stabilization of High Polarization Photocathodes in Sub-Optimal RF Gun Environments. –High Polarization and High Peak Current Compositionally Graded AlGaAs/GaAs Superlattice Photocathodes for RF Gun Applications. –High Polarization and High Robustness Antimonide Based Superlattice Photocathodes for RF Gun Applications.  All applicable to DC guns as well Collaboration with University of St. Petersburg (Russia): –Study of AlInGaAs/AlGaAs cathodes Baseline Design Strained GaAs/GaAsP R&D goals: Improve robustness and lifetime Investigate alternative materials with increased polarization and QE Maintain and build expertise

International Linear Collider – Americas 11/24 Photocathode R&D Program Faraday rotation experiment Measures Depolarization Dynamics Depolarization occurs during transport through cathode material Interband absorption smearing due to bandedge fluctuations Hole scattering between the HH and LH states causes a broadening of the LH band Spin precession due to an effective magnetic field generated by the lack of crystal inversion symmetry and spin orbit coupling Electron hole scattering Less polarization selectivity in the BBR Scattering and trapping of electrons in the BBR SLAC-Pub Understanding depolarization allows design of optimized photocathodes

International Linear Collider – Americas 12/24 ILC Sources Optics and beam line design Example: Electron Source Optics Positron beam line geometry

International Linear Collider – Americas 13/24 ILC Polarized Positron System Technical Milestones 1. Demonstrate undulator parameters. 2. Demonstrate NC SW structure high power rf performance. 3. Spinning target pre-prototype demonstration. 3. Eddy current measurements on spinning target. 4. Selection and Technical design of Optical Matching Device. 5. System engineering for e+ source remote handling. 6. System engineering for photon dump. 7. System design compatibility with ILC upgrade scenarios: polarization and energy.

International Linear Collider – Americas 14/24 Undulator Challenges High fields –Pushing the limits of technology Short Periods –Shorter periods imply higher fields Narrow apertures –Very tight tolerances - Alignment critical Cold bore (4K surface) –Cannot tolerate more than few W of heating per module Minimizing impact on electron beam –Must not degrade electron beam properties but have to remove energy from electrons Creating a vacuum –Impossible to use conventional pumps, need other solution Minimizing cost –Minimize total length, value engineering

International Linear Collider – Americas 15/24 UK 4m Prototype Module Stainless steel vacuum vessel with Central turret 50K Al Alloy Thermal shield. Supported from He bath Stainless Steel He bath filled with liquid Helium. Magnet support provided by a stiff U Beam U beam Support rod Superconducting Magnet cooled to 4.2K Beam Tube Construction has started, will be complete by Autumn 07

International Linear Collider – Americas 16/24 Undulator Magnet Design Concept Steel Yoke. Provides 10% increase in field and mechanical support for former PC board for S/C ribbon connections Winding pins Steel yoke Cu beam pipe, with conductor wound on to tube OD 2 start helical groove machined in steel former

International Linear Collider – Americas 17/24 Baseline Target Design Wheel rim speed (100m/s) fixed by thermal load (~8% of photon beam power) Rotation reduces pulse energy density from ~900J/g to ~24J/g Cooled by internal water-cooling channel Wheel diameter (~1m) fixed by radiation damage and capture optics Materials fixed by thermal and mechanical properties and pair- production cross-section (Ti6%Al4%V) Wheel geometry (~30mm radial width) constrained by eddy currents. 20cm between target and rf cavity. T. Piggott, LLNL

International Linear Collider – Americas 18/24 Activation Simulations New target geometry (mostly) migrated to FLUKA Simulations will begin at DL shortly as well as DESY/Z NC rf cavity motor assembly target wheel (including water channel) L. Fernandez-Hernando, DL

International Linear Collider – Americas 19/24 Experiments at SLAC E166 – proof of principle: Undulator based polarized positron production –Publication is pending (NIM, PRL) Validation of FLUKA activation calculations –SLAC/CERN Collaboration (RP groups) 100 W 30 GeV electron beam in ESA at SLAC Cylindrical copper dump Samples around the dump (including a Ti-4V- 6Al) Look mr/hour and gamma spectrum from irradiated samples –Data taken, analysis in progress – 489http://www-group.slac.stanford.edu/esh/rp/rpg/T- 489

International Linear Collider – Americas 20/24 Target Remote Handling (conceptual)

International Linear Collider – Americas 21/24 Optical Matching Device –factor of 2 in positron yield (3 if immersed target) –DC solenoid before target or pulsed flux concentrator after target –Pulsed device is the baseline design Target spins in the magnetic field of the OMD –Eddy currents in the target – need to calculate power –Magnetic field is modified by the eddy currents – effect on yield?? Eddy current mitigation –Reduce amount of spinning metal –Do experiment to validate eddy current calculations –Look for low electrical / high thermal conductivity Ti-alloys –Other materials such as ceramics –No OMD Use focusing solenoidal lens (1/4 wave) – lower fields OMD is upgrade to polarization!!!!!

International Linear Collider – Americas 22/24 Eddy Current Experiment Eddy current calculation mesh - S. Antipov, W. Liu, W. Gai - ANL Proposed experiment Layout at Cockcroft Institute/Daresbury (this summer)

International Linear Collider – Americas 23/24 Prototype Positron Capture Section Design and Prototype High Power Test using L-band station in SLAC’s Endstation B

International Linear Collider – Americas 24/24 Outlook – EDR phase for e-/e+ Need Systems Engineering in FY08 Dec 07: EDR Scope definition: design depth and breadth, cost, schedule, staff Dec 09: Freeze layout, full component and civil specifications Jan 09: EDR detailed component inventory May 09: First cost review Dec 09: Deliver EDR and preconstruction work plan