How To Use “The Facility Which Must Not Be Named” To Optimize CEBAF Performance (Energy Reach, Availability, and Weeks-Of-Operation) S. Benson, D. Douglas (scribe, reporter, and sacrificial lamb…), K. Jordan, R. Legg, T. Powers, M. Spata, and C. Tennant

Machine Layout

Motivation Unique facility world record beam (ERL) and light (FEL) powers two distinct accelerators – the only ERLs (with IR Demo) to exceed RF drive breakeven same technology/hardware base as CEBAF 120M$ investment of taxpayer dollars – mostly from DoD (ONR) and Commonwealth of Virginia – almost completely unutilized Low operational costs beam time cost/hour << (<<<<…) CEBAF Can run intermittently with reliable startup and recovery key point: when its on the air, keep it on the air very robust over short time scales: when run on a regular basis, can shut down and turn back on very quickly ~5 min to high power beam & light from controlled access

What It Can’t (Yet – or Maybe Ever…?) Do Long term stability and reliability not spec’d to do this; it’s a “tune as you go” machine; it will drift and things will break and I dare you to fix this… ;) Recover quickly/reliably after long shutdown it gets lonely, wakes up slowly, and will be cranky until fully awake. And it will be mad that you stole its toys (even if you put them back) Be described by “conventional” models over entire parameter space inherently non-conservative (though it can be run without significant radiative loss) linear optics sometimes fails (CSR from [parasitic] compressions) Multi-pass acceleration with energy recovery it can do multi-pass acceleration (and has been encouraged to do so for years by Roger Carlini…), but can’t recover afterwards right now beam dumps onto chamber in 1st arc dipole => pulsed/low current could add line to extract “energy doubled” beam, (re)install dump…

Delivers beam to open area Provides appropriate beam/lattice properties for tuning/control extraction transport can be configured to cross over above cryo transfer line at west end of building

JLab FEL Accelerator Capabilities External target Internal Target Near Term Capability, Dec. 2013 Full Capability E (MeV) 80-320 80-610 80-165 80-310 Pmax (kW) 100 300 1650 3100 I (mA) 1.25-0.31 (100 kW/E) 3.75-0.5 (300 kW/E) 10 fbunch (MHz) 750/75 Qbunch (pC) 1.67-0.4/16.7-4 (I/fbunch) 5-0.67/50-6.7 (I/fbunch) 13.5/135 etransverse (mm-mrad) ~1/~3 ~2/~5 ~3/~10 elongitudinal (keV-psec) ~5/~15 ~10/~25 ~15/~50 Polarization No 500 mA @ 600 MeV (300 kW) up to 10 mA (or source limit) 750 MHz drive laser; single F100 12 GeV RF drive; three F100s

Vision: Meet Multiple Needs At Very Low Cost Technology test-bed hardware/software tests cost less & frees CEBAF beam up for users extremely flexible platform: system is easy – and designed – to modify to off-normal operation and recover/restore quickly; inexpensive to operate “extreme beam” – high power, bunch charge, etc Training tool Process validation procedure tests recovery/reliability tests (I dare you to make it long-term stable and reliable…!) in situ benchmarks and measurements: rapid system access/recovery “I want to run downstairs for 15 minutes and change ‘whatever’, and then run for another 2 hours” is okay! Leverage short term robustness to support invasive activities; use long-term sensitivity as opportunity for reliability studies

Arne Suggestions Tool development: qsUtility with viewer driven data, bringing Raytrace to completion Training operators scientists technicians RF stuff F100 microphonic analysis and suppression develop multi-cavity PZT algorithms liquid He levels and gradient

Committee (Collusion?) Brainstorming Diagnostic testing Development of new diagnostics Prototyping and tests with beam: diagnostics, cavities, magnets… Any main injector experiments (including at higher energy… can go to 175ish MeV) e.g. bubble chamber or any other low energy physics experiment optics modeling tests nonlinear compensation, non- conservative (non-Hamiltonian) modeling algorithm validation debugging RF testing microphonics beam loading collaboration with ODU – beam dynamics, RF testing, cavity testing (pull zone 3 and put in test cavities) test/commission refurbished modules catch rebuild issues before affecting CEBAF operations/availability cryo load balancing: FEL01-04 provide “ballast”…

Whimsical, Reach, and Somewhat Off-Topic/Off-Color Suggestions Isotope production: offload from CEBAF injector JLEIC R&D magnetized beam tests collimation tests halo characterization high current beam tests weird-ass cavity tests kicker cavities at high current CSR Shielding tests Testbed for positron production THz experiments – can make kW of THz… if there is an application LCLS-II cryomodule testing module and vertical slice test – offload from CMTF can test with 1 MHz beam… Lab leadership foul weather parking Lab leadership foul weather “shelter in place”...? Student (or CASA) bohemian district in labs/trailers…? Service to a broad range of uses/initiatives that have indirect benefit to CEBAF operations and/or institutional mission off-load demands from CEBAF and CEBAF-critical-path facility access free up CEBAF beam for users reduce demands on CMFT, test lab,… leverage lower cost/beam hour These include: Facility/beam time support for SBIR, Stewardship, Early Career,… programs

Summary Basic concept: use the “cheap system” to off-load beam time demands from the “expensive system” “Pre-release” tests for potentially invasive changes Test hardware, provide beam time, at low cost If it can be done in CEBAF using individual sub-systems and/or beam up to ~200 (400…) MeV, it can be done in the facility which must not be named

Summary - continued Can do the things that can be done on the ERLs more cheaply on them than in CEBAF The facility was *designed* for invasive operation: turn on, turn off, access, recover it was *not* designed for long-term stability operation, or to be shut down for long periods of time, or to change in an uncontrolled manner (undocumented part-swapping is problematic) Obvious applications: hardware testing software validation process development training

Issues, Open Questions, and Acknowledgments Startup overhead: machine has been off the air for some time and there will be a price to pay Knowledge base is diffusing away Configuration control: keeping people out of the “spare parts bin” We thank the organizers for the opportunity to discuss this topic, and Joe Gubeli, Todd Satogata, Jay Benesch and Yves Roblin for useful input/review