Tim Whitlatch OLAV Workshop 2005 - CERN

Thomas Jefferson National Accelerator Facility

Operated by the Southeastern Universities Research Association for the U.S. Department of Energy

Jefferson Lab’s CEBAF (Continuous Electron Beam Accelerator Facility) Vacuum System Overview, Concerns and Diagnostic Tools

Tim Whitlatch

OLAV Workshop 2005 - CERN



What is CEBAF?

A user facility for scientists worldwide, its primary mission is to conduct basic research of the atom’s nucleus at the quark level.

Uses Superconducting Radio Frequency (SRF) technology for accelerating the electron beam



Continuous Electron Beam Accelerator Facility

Injector

North LINAC

East Arc

South LINAC

Experimental Halls

West Arc



Cryomodule / LINAC



ARC Beamline Components



Cryomodule Cutaway



Vacuum Operating Range

• LINACs 1.0E-10 – 1.0E-9 Torr (As measured in warm girder adjacent to cold cavities)

• Arcs and Transport 1.0E-7 Torr

• Insulating Vacuum 1.0E-6 Torr

• Waveguide Vacuum 5.0 E-10 – 1.0E-8 Torr



Quantities of Vacuum Equipment

• Over 5 km of Beam Line under vacuum• (450+) 11/20 l/s Ion Pumps (PE-Gamma)• (80+) 35/40 l/s Ion Pumps (PE-Gamma)• (45+) Convectron Gages (Granville)• (40+) Pirani Gages (HPS)• (40+) Cold Cathode Gages (Troy-Onics)• (40+) TC gauges (DV6)(Teledyne Hastings)• (160+) Valves (3.8 cm) (VAT)• (10+) Fast Valves (VAT)• (10+) Turbo pump stations (insulating and waveguide vacuum)• (8) Differential Pump Stations (NEGs and Ion Pumps)



Vacuum Protection

• Fast Shut Down System (FSD) (To interrupt the beam)• DP Stations ( to protect SRF cavities)• Ion Pumps (SRF Cavity protection force valves to close at set

point)• Pirani Gages For SRF Region

—100 to 10-4 Torr (will not allow Ion pumps to turn)• Convectron Gages for NON SRF Regions

—Atm down to 10-3 Torr (valves close at min detectable range)—Millisec response time

• Fast Valves to Protect Superconducting Cavities (<10 msec closing time)

• UHV valves (.4 second closing time)



Differential Pump Station



Diagnostic and Monitoring Tools (Non Invasive)

1. MEDM (Bar charts with color changes)

2. Archive Viewer (XARR)

3. Strip Tool



MEDM Screen



SRF MEDM Screen



Archive Viewer (vacuum)



Strip Tool



Special Considerations/Concerns

• Protection of SRF Cavity Vacuum and Performance— Insulating Vacuum – minimize Cryogenic load

• Additional Pumping—Superfluid Helium leaks into beam line

• Cryocycles to remove He

• Age of Components (10 – 15 yrs)— Ion Pumps—Cold Cathode Gages

• Radiation Damage—Viton seals (leaky Valves)—Electronics

• Beam Strikes

Tim Whitlatch OLAV Workshop 2005 - CERN

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