1. Operation of the ATLAS Superconducting Accelerator for Heavy Ions Matthew Hendricks ATLAS Operations Supervisor October 27, 2014

2. 2 Outline  Overview the ATLAS accelerator  Staffing and beam scheduling  Accelerator startup  Accelerator configuration logging and mass to charge scaling  Tuning below ammeter detectable currents and associated diagnostics  Maintenance  Problems/Troubleshooting  Summary Workshop on Accelerator Operations - Mainz, Germany Oct. 27, 2014 M. Hendricks

3. 3 Overview  ATLAS is world’s first superconducting (SC) heavy-ion accelerator  It is the designated stable-beam national user facility for low-energy nuclear physics research in the U.S.  Made up of 3 distinct accelerator sections, totaling 45 SC RF resonators providing an effective total voltage of 52MV, coupled with 26 SC solenoids  Stable ion species provided by ATLAS range from protons through uranium For FY2012 ATLAS delivered 40 unique ion species, 7 of those were radioactive ion beams  21.6% of beam time is devoted to radioactive ion beams, either from CARIBU or “in- flight” Workshop on Accelerator Operations - Mainz, Germany Oct. 27, 2014 M. Hendricks ATLAS Beams for FY2012  Typical beam currents are in the range of 5 to 500 electrical nanoamps, however demonstrated 35 electrical microamps through PII  Radiation hazard mitigated by the ATLAS Radiation Interlock System (ARIS)  ATLAS Operations budget is ~$10M/year

4. 4 Floor Plan and Location Oct. 27, 2014 M. Hendricks Workshop on Accelerator Operations - Mainz, Germany A rgonne T andem L inear A ccelerating S ystem Total accelerator length is ~120 meters

5. 5 ATLAS Staffing and Operator Training Workshop on Accelerator Operations - Mainz, Germany Oct. 27, 2014 M. Hendricks  21 Full time employees, 2 part time employees, & 2 students –Divisional Groups: Physicists (2), Operations (8), Ion Source(2), Control System (2), Cryogenic (2), Mechanical (2), Electronic (3)  7 qualified operators keep the accelerator running 24 hours a day, 7 days a week  Almost 50% of shifts are staffed by 2 operators, 1 operator is the chief shift operator, the other is safety watch.  Every operator is required to work each shift at least once per 6 months  When only one operator is on shift the safety watch is fulfilled by the experimenter  On average 40 safety classes must be kept up to date for each operator  New operator qualification consists of 6-8 “classroom session”, the rest is on the job  Operator qualification typically takes 6 months, made up of 2 exams and 1 practical 0000-0800 0800-1600 1600-2400 0000-0800 0800-1600 1600-2400 0000-0800 0800-1600 1600-2400 Shift Times ShiftMon.Tues.Wed.Thur.Fri.Sat.Sun. 0000-0800 0800-1600 1600-2400 BB NP TR GD BB RB NP TR SB GD BB RB NP TR SB GD BB RB NP TR SB GD RB SB GD RB SB BB NP TR 0000-0800 0800-1600 1600-2400 BB NP TR GD BB RB NP TR SB GD BB RB NP TR SB GD BB RB NP TR SB GD RB SB GD RB SB BB NP TR

6. 6 ATLAS Scheduling Oct. 27, 2014 M. Hendricks Workshop on Accelerator Operations - Mainz, Germany  Scientific Director proposes beam schedule based on approved experiments from the Program Advisory Committee (PAC)  Operations and ion source personnel then provide input concerning conflicts/abilities  Average at least 1 startup day per week  24 hours schedule for startup, only 12-16 hours needed on average  Typical experiments 4-10 days  Radioactive ion beams require additional support from beamline physicist  Due to heavy demand approximately half of proposed beam time is approved; ATLAS is significantly and consistently over- subscribed.

7. 7  “Authorization to Operate” form insures experiment is reviewed and authorized prior to delivering beam to the user.  Reconfigure all elements of the accelerator for each experiment  Two options for accelerator startup  Use a previous accelerator configuration from a computerized library Useful for either exact configuration or scaled configuration Saves time  Establish a new accelerator configuration Time consuming New Experiment Startup and Beam Tuning Oct. 27, 2014 M. Hendricks Workshop on Accelerator Operations - Mainz, Germany

8. 8 Accelerator Logging and Scaling  Offline computer (Paradox) records entire accelerator configuration, creating a library of old accelerator configurations based on mass to charge ratio  Paradox allows mass to charge scaling of entire accelerator –Scaling is limited to ±15% of saved configuration’s mass to charge –Scaling also limited by resonator amplitudes Oct. 27, 2014 M. Hendricks Workshop on Accelerator Operations - Mainz, Germany

9. 9 Accelerator Modifications – Since 2009 Oct. 27, 2014 M. Hendricks Workshop on Accelerator Operations - Mainz, Germany  Pioneered heavy ion accelerator technology in 1978, averaged 0.75MV accelerating voltage per resonator  World record high 2.0MV accelerating voltage average per resonator  Separate cavity and cryostat vacuum  No degradation of quality or gradients since July 2009  Only continuous wave room temperature RFQ in regular operation in the world  Operates with greater than 90% reliability  Bunches, focuses, and accelerates at the same time  World record 2.5MV accelerating voltage average per resonator  Only 5W of power into 4.5K liquid helium system for entire cryostat during operation

10. 10 CARIBU Radioactive Beam Tuning  Initial tuning with “guide beam” with similar mass to charge ratio  Scale entire accelerator for mass to charge ratio difference  Use Beta Detectors and rate meter for final fine tuning Stable beams intensities are 10 9 particles/second, use of standard Faraday cups and nano-ammeter for tuning Radioactive beams intensities are 10 5 particles/second, use of specialized detectors and electronics necessary Oct. 27, 2014 M. Hendricks Workshop on Accelerator Operations - Mainz, Germany 36 Ar 7+ 72 Ge 14+ 180 Hf 35+ 144 Ba 28+ 108 Cd 21+ CARIBU ON CARIBU OFF

11. 11 Maintenance  One major planned maintenance period per year (~4 weeks in length) Address annual safety testing and inspections Cryostat repairs Cryogenic system repairs Any other major repairs  Run to failure philosophy  Minor maintenance work handled during startup day  ATLAS has been averaging 91.9% reliability over the last 6 years  Recent upgrades to the accelerator have made reliability better, but those upgrades require more and diverse expertise to achieve. Oct. 27, 2014 M. Hendricks Workshop on Accelerator Operations - Mainz, Germany

12. 12 Troubleshooting - Problems  Operators expected to handle (at least diagnose) almost any problem Examples: resonator problems, He compressor trips, power supply exchange, water/air leaks/blockage, vacuum problems Ask for assistance if the problem lasts longer than one hour  Heavy reliance on system experts All system experts are on call at all times  Recent LHe plumbing failure inside a cryostat Resulted in ~4 hours of downtime before beam delivery resumed Loss of ~3MV from entire accelerator 15-35% transmission loss through affected cryostat until repaired Demonstrates nimble abilities of small knowledgeable workforce Oct. 27, 2014 M. Hendricks Workshop on Accelerator Operations - Mainz, Germany Staffed hours for 2014

13. 13 Summary  Heavy demand for beamtime, over-subscribed  21 full time employees to operate and maintain the accelerator  Only 7 operators for accelerator operation 24 hours, 7 days a week  Operators perform maintenance tasks as well as tuning beam  Accelerator configuration library and scaling saves time  Radioactive beam tuning becoming standard, significantly complicates operation  3 major improvement projects in last 5 years  One scheduled 4 week maintenance period per year, run to failure philosophy, perform repairs as needed Workshop on Accelerator Operations - Mainz, Germany Oct. 27, 2014 M. Hendricks