Tuning Techniques And Operator Diagnostics for FACET at SLAC National Accelerator Laboratory Chris Melton SLAC Accelerator Operations

2 FACET Tuning And Diagnostics What is FACET? FACET Performance Challenges Operations Solutions FACET Future WAO 2012 / Chris Melton

3 What is FACET? Design Criteria Facility overview Scientific mission WAO 2012 / Chris Melton Facility for Advanced Accelerator Experimental Tests

4 FACET Beamline Overview WAO 2012 / Chris Melton

5 FACET “W Chicane” Beamline WAO 2012 / Chris Melton e- from Linac Beam to User Experiments

6 FACET Experiment Beamline WAO 2012 / Chris Melton e- from W chicane

7 e- from W chicane FACET User Experiment Facilities WAO 2012 / Chris Melton

8 FACET Design Criteria 23 GeV e- and e+ beams 30Hz pulses 3.2nC bunches 20 kA peak currents (I pk ) 20  m bunch length (  z ) 20  m x 20  m spot size (  x,y ) WAO 2012 / Chris Melton The “Ideal Beam” FACET is designed to deliver high energy, high peak current, short bunch length electrons and positrons with low transverse emittance to user experiments.

9 FACET Scientific Mission New research frontiers require larger, more expensive accelerators New accelerating methods can reach higher energies in shorter distances These methods leverage plasma wakes in dielectric & metallic structures FACET was an ideal test facility for these new techniques due to –The high charge of SLAC Linac beams –The high compression made possible by SLAC beamlines –High historical demand for electron / positron beams from the SLAC Linac –Success of the SLAC Final Focus Test Beam (FFTB) plasma experiments WAO 2012 / Chris Melton FACET will serve the scientific community as a high energy physics user facility for the exploration of novel methods of beam acceleration, related beam physics, and development of related diagnostics, with specific applications to materials, biological, energy, and plasma sciences.

10 FACET Science WAO 2012 / Chris Melton Plasma Wakefield Acceleration How FACET generates high gradient acceleration with low energy spread: Send a bunch of electrons through Lithium (2011) or Rubidium (2012) plasma This drive bunch creates a ~ 50GeV/m acceleration gradient in the plasma A witness bunch then travels through the plasma and is accelerated

11 FACET Performance WAO 2012 / Chris Melton First beam to FACET dump on June 23, 2011

12 What To Characterize and Tune? How? WAO 2012 / Chris Melton Primary beam properties of interest Charge Position Transverse Beam Size Transverse Emittance Longitudinal Beam Size Tools for measurement Toroid Charge Monitors Beam Position Monitors Profile Monitors (YAG, OTR) Wire Scanners Transition Radiation Monitors If it were only that simple…

13 Diagnostic Challenges - Linac WAO 2012 / Chris Melton Few measurements of bunch length (  z ). Accuracy? Emittance (  x,y ) and beam size (  x,y ) measurements slow Lack of efficient and robust beta matching tools No dispersion characterization tools until end of 2012 run zz  x,y  x,y E zz

14 Diagnostic Challenges – Chicane & IP WAO 2012 / Chris Melton  x,y  x,y zz Densely installed magnets and experiment stations - little room for BPMs, Wires, and Profile Monitors Few robust and convenient beam diagnostics after Linac Vertical ‘W’ Chicane dispersion not yet understood Beam Based Alignment very difficult (sextupole movers) Optical Transition Radiation damage at peak compression Beam waist location often unknown E

15 SLAC Operations Finding What Works SLAC Operators start building software early Proficiency in Matlab and EPICS is encouraged Collaborative environment encourages revisions Google Model: Build often; Failure is ok! Operators have standardized a display format –High contrast allows readability from across the room –Summary displays for subsystems by geography –Graphic overlays draw eye toward meaningful data –Information density balanced against interactivity WAO 2012 / Chris Melton

16 SLAC Main Control Room Can we do better?

17 Yes! WAO 2012 / Chris Melton

18 Including Klystron Displays WAO 2012 / Chris Melton

19 Console Tuning and Diagnostics WAO 2012 / Chris Melton FACET uses a hybrid control system: OpenVMS and EPICS

20 Console Tuning and Diagnostics WAO 2012 / Chris Melton Example: Investigating a Beam Containment System (BCS) Alarm

21 Console Tuning and Diagnostics WAO 2012 / Chris Melton Example: Investigating a Beam Containment System (BCS) Alarm

22 Console Tuning and Diagnostics WAO 2012 / Chris Melton Console driven high level tuning and diagnostic information

23 Console Tuning and Diagnostics WAO 2012 / Chris Melton Example: Measuring transverse beam size

24 Console Tuning and Diagnostics WAO 2012 / Chris Melton Example: Measuring transverse beam size

25 New Tools For Better Performance WAO 2012 / Chris Melton

26 What’s Next For FACET? X-band Transverse Deflection Cavity –Better bunch length diagnostics –Commissioning started end of 2012 run –Testing will continue during 2013 run WAO 2012 / Chris Melton

27 What’s Next For FACET? WAO 2012 / Chris Melton FACET-II would be an R&D accelerator using the first 1/3 of the Linac Early FACET-II would be about January 2018 including construction Upstream of LCLS-II, which poses diagnostic constraints - Final focus energy feedbacks will need different BPMs - Space and budget constraints restrict profile monitors and wire scans - FACET-II ?

28 Questions? WAO 2012 / Chris Melton