Linac Beams for Fixed Target Experiments Presentation by Roger Erickson SLAC Operations Review SLAC, June 15-16, 2004

06/16/04 Accelerator Operations Review Outline  Linac and sources  Interleaved beams  A-Line and End Station A (ESA)  Final Focus Test Beam (FFTB)  Secondary Test Beams  Summary

06/16/04 Accelerator Operations Review Linac Beam Lines LCLS will add an electron injector downstream of the positron source. Fixed target experiments can be carried out in End Station A (ESA) or the Final Focus Test Beam (FFTB) facility.

06/16/04 Accelerator Operations Review The Two-mile Linac  50 GeV Linac with multiple pulsed extraction points.  120 pulses per second max; now running 30.  Up to 6e11 electrons per pulse.  Polarized electrons available up to full intensity.  4e10 positrons per pulse, interleaved with electron pulses.  Long pulses (undamped) or short pulses (damped).  Typically running two programs simultaneously: PEP-II Fixed target in ESA or FFTB  Flexibility for interleaved beams: e+, e-, damped and undamped, different energies, intensities and rates.

06/16/04 Accelerator Operations Review Typical (Recent) Running Mode Linac runs well at 30 pulses/sec (half the ac line frequency).  9 GeV electrons to HER: on demand for trickling, up to 10 Hz.  3.1 GeV positrons to LER: on demand for trickling, up to 10 Hz.  28.5 GeV “scavenger” electrons to Sector 19 (to make more positrons for the next cycle).  28.5 GeV electrons to FFTB: 10 Hz for fixed target programs (interleaved with PEP injection pulses). At the push of a button,  Electrons and Positrons to PEP-II for rapid filling at 15 Hz each (with no rate to FFTB).

06/16/04 Accelerator Operations Review Research Yard Experimental Facilities ESA FFTB

06/16/04 Accelerator Operations Review A-Line to ESA  SLAC’s original experimental hall, site of parton discovery and parity violation in eP scattering.  Recent E-158 success: first observation of parity violation in polarized e-e- Moller scattering. E-158 had three production runs at 120 Hz in ; once with PEP-II and twice alone.  High power (500 kW) beam capability.  ESA is convenient for staging fixed target experiments Large, massively shielded building. Power, LCW, and cryogenic facilities. Easy truck access. Crane coverage. Counting house with DAQ facilities.  Strong bends and weak focusing preclude “FFTB beams” with small emittance and compressed bunch length.

06/16/04 Accelerator Operations Review Energy dithering region  BPM ~2 microns  energy ~1 MeV Agreement (MeV) BPM24 X (MeV) BPM12 X (MeV)  toroid ~30 ppm A-Line Beam Monitoring Devices

06/16/04 Accelerator Operations Review ParameterE-158NLC-500 Charge/Train5 x x Repetition Rate120 Hz Energy45 GeV250 GeV e - Polarization85% Train Length270ns267ns Microbunch spacing0.3ns1.4ns Beam Loading13%22% Energy Spread0.15%0.16% E-158 Beam Comparison with 500 GeV Linear Collider Design.

06/16/04 Accelerator Operations Review End Station A Photo Shows E-158 Spectrometer Magnets.

06/16/04 Accelerator Operations Review Pending Programs in ESA Calibration of GLAST detector components with secondary hadrons (to be scheduled to accommodate GLAST requirements). A Letter of Intent submitted to the EPAC: Beam Instrumentation Tests for the Linear Collider using the SLAC A-Line and End Station A

06/16/04 Accelerator Operations Review Final Focus Test Beam  The FFTB was originally built to demonstrate technology for focusing and measuring sub-micron electron beams suitable for a future linear collider. Recent on-going programs include:  Plasma Wakefield Acceleration – a series of experiments that have recently demonstrated high-gradient acceleration in a lithium plasma.  SPPS – A new facility that uses compressed electron bunches to generate intense x-ray pulses. Technology applicable to the LCLS:  Extreme bunch compression.  Beam control and feedback for stability.  Instrumentation for characterizing extremely short x-ray pulses.

06/16/04 Accelerator Operations Review FFTB Experimental Area

06/16/04 Accelerator Operations Review RTL DAMPING RING SLAC LINAC 9 ps0.4 ps 50 ps 1 GeV28.5 GeV 14-meter chicane compressor in linac at 1/3 point (9 GeV) CHICANE BENDING MAGNETS LONGER PATH TAKEN BY HEAD OF THE BUNCH Energy e- Energy Time ELECTRON BUNCH WITH HIGHER ENERGY TAIL TAIL BEGINS TO CATCH UP FULLY COMPRESSED FFTB Short Bunches in FFTB

06/16/04 Accelerator Operations Review Plasma Wakefield Acceleration e-e- N=1.8   z =20-12µm E=28.5 GeV Optical Transition Radiators Li Plasma Gas Cell: H 2, Xe, NO n e ≈ cm -3 L≈ cm Plasma light X-Ray Diagnostic, e-/e + Production Cherenkov Radiator Dump ∫Cdt Imaging Spectrometer Energy Spectrum “X-ray” 25m Coherent Transition Radiation and Interferometer n e =2.5x10 17 No Plasma Gain Loss GeV ≈3 GeV! n e =2.5x Pyro= GeV n e =3.5x10 17 No Plasma Min. Gain Min. Loss Relative Energy (GeV)

06/16/04 Accelerator Operations Review SPPS in FFTB

06/16/04 Accelerator Operations Review Photon beam line Electron beam line Experimental Area Beam dump FFTB Dump Line Experimental Area

06/16/04 Accelerator Operations Review Pending Programs in FFTB SPPS Ongoing program of technology development involving extremely short x- ray pulses. Plasma Wakefield Acceleration Ongoing program to develop exotic new methods for achieving very high accelerating gradients, strong plasma focusing, and related technology. Experiment E-165 Flourescence in Air from Showers (FLASH) A continuing program to quantitatively understand the production of light by cosmic rays in the upper amosphere, using controlled laboratory conditions. Experiment E166 A Proposal to Test Production of Polarized Positrons with the SLAC 50-GeV Beam in the FFTB An undulator-based technique applicable to a future linear collider.

06/16/04 Accelerator Operations Review Test Beam Facilities  Primary electron or positron beams to ESA or FFTB.  Secondary electron or positron beams to ESA or FFTB. Produced by double conversion (e- to gammas to e+ or e-). One or a few particles/pulse. Energy easily selectable with transport line magnets.  Secondary hadron beam to ESA. Primary electrons to beryllium target near end of linac. Secondary particles scattered at 0.5 deg into A-Line. Positrons, pions, kaons, and protons tagged with time-of-flight and Cerenkov detectors. One tagged particle/pulse was delivered to GLAST detector development test.

06/16/04 Accelerator Operations Review Test Beam Scheduling  The approval and scheduling process is designed to minimize effort for outside users and minimize cost and impact for SLAC.  Proposals are submitted to Experimental Facilities Department. EFD staff provide technical and administrative support for users.  “Test Request” summary is circulated to: Radiation physicist Chairman, Safety Oversight Committee FFTB (or ESA) Area Manager Accelerator Department physicist Research Division Program Coordinator  Test Request is submitted to Accelerator Department Operations Section for scheduling.  Beam Authorization Sheet is prepared by Radiation Physics Department.  Most test beam experiments are carried out with no significant adverse impact on other programs. Many are done in 1 to 3 days.

06/16/04 Accelerator Operations Review Test Beam Experiments in FFTB T-447Single Pulse Damage in Materials (Sept 2000) T-448Magnified Optical Transition Radiation Test (Oct 2000) T-450Damage Test in Diamond for LCLS (Oct 2000) T-451High Energy Neutron Spectra Measurement (March 2001) T-452STAR Endcap Calorimeter Detector Prototype Test (Jan 2001) T-453Radiation Damage in Diamond for LCLS (April 2001) T-454Measurement of Neutron Spectra (June 2001) T-455Measurement of the Calorimeter for the Local Polarimeter at Phenix/RHIC (Aug 2001) T-456Magnetization Dynamics in Magnetic Films (Sept 2001) T-457Measurement of Neutron Energy Spectra Using Bonner Multi-Sphere Spectrometer (June 2002) T-460Characterization of Askaryan Effect in Rock Salt (June 2002) T-461 High Atmosphere Air Fluorescence (June 2002) T-462 Magnetization Dynamics of Soft-Magnetic Films (June 2002) T-464 Correlation of Linac Transverse Deflection Cavity with FFTB Streak Camera (June 2002) T-465 Magnetization Dynamics in the Sub-picosecond Time Scale (May 2003) T-466 UCLA Electromagnetic Calorimeter (EMC) Prototype (May 2003) T-467Measurement of FFTB Backgrounds for E166 (Jan 2004) T-468Diamond Detector Response (July 2003) Experiments not yet run: T-469DIRC R&D Program T-470DASH: Diamond Detectors for FLASH T-471Incoherent Radio Emission from Showers

06/16/04 Accelerator Operations Review Conclusions  Extra linac pulses, not needed for PEP-II injection, can be delivered to End Station A or the FFTB facility for use by fixed target or “test beam” experiments.  We have seen a constant demand for these beams from a wide variety of users.  Small experiments can be set up and run with no adverse impact on the PEP-II program and with very little additional cost to SLAC.  Significant new physics results have been achieved, and a large number of detector technology development tests have been carried out.  The FFTB will be dismantled in 2006 to make room for the Linac Coherent Light Source (LCLS). We are exploring possible replacement options.  The requests for test beams keep coming!