1. 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

2. Machine Layout

3. 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

4. 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…

5. 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

6. 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)
(100 kW/E)
(300 kW/E) 10
fbunch (MHz)
750/75
Qbunch (pC)
/ (I/fbunch)
5-0.67/ (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
MeV
(300 kW)
up to 10 mA
(or source limit)
750 MHz drive laser; single F100
12 GeV RF drive; three F100s

7. 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

8. 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

9. 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”…

10. 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

11. 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

12. 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

13. 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