Table of contents
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Overview of the pumping system
Default setup of the pumping system
MEC's pumping system is comprised of 2 multi-stage dry vacuum pumps (Ebara A70) located on the mezzanine above the hutch, and 2 turbo pumps (Varian TV-2KG) backed with a scroll pump (Edwards xds35i). The following sketch shows the vacuum system as displayed in the controls window.
MEC vacuum system control diagram
The dark grey rectangle in the center symbolizes the target chamber and displays the readout values of different vacuum gauges measuring the in-chamber pressure (top: cold-cathode, bottom-left: pirani, right: capacitance). Let's note that the capacitance gauge is out of order and displays incorrect values.
The top right side of the window details the primary pump subsystem. The ends of this branch lead to the 2 Ebara pumps. Controllable gate-valves are positioned at the target chamber entrance to isolate the primary pump subsystem, at the inlet of each independent Ebara pump, and along the line to allow for venting of the subsystem. Pirani gauges are also used to monitor the pressure along the subsystem pumping line and at the inlet of both Ebara pumps.
The bottom side of the window details the secondary pump subsystem. It comprises 3 branches: 2 of them are identical and symmetric on the sketch, and 1 of them (left-most), the shortest one with only 3 symbols in a straight one, is obsolete. The 2 indentical branches each contain a Varian turbo pump and a scroll pump. The chamber is isolated from these subsystems by a gate-valve, a second gate-valve is used to isolate the turbo from the scroll when the system is shut down. A pirani gauge monitors the quality of the backup pressure provided by the scroll pump.
Finally, the top left side of the windows helps control the venting valves. There are 2 independent venting valves: one supplies compressed dry air (CDA) to initiate the venting procedure, the second one simply opens the chamber to the ambiant atmospheric air (Atm).
Current modifications in the pumping system
MEC has recently experienced a turbo pump failure. As a consequence, we are operating the pumping system with the following structural modifications. The primary vacuum subsystem and the venting valves are unchanged. The modifications are at the bottom side of the window with the failed turbo pump in a "Disabled" status and a backup turbo pump (Maglev) positioned in the formerly obsolete left-most branch.
MEC vacuum system control diagram with the current temporary modifications
The target chamber is in a secondary vacuum state on this sketch. The primary subsystem is vented and the maglev (gate-valve TC1-VGC-01 open/green) is pumping the chamber which reached 2.0e-04 torr on the cold-cathode gauge (the pirani gauge reached its lower readout limit). The Varian turbo branch (gate-valve TC1-VGC-02 closed/red) is not activated yet, but the turbo is accelerating after startup as shown by the yellow circle.
The procedure presented on this page will explain how to operate the primary vacuum subsystem and a branch of the secondary vacuum subsystem when running with a Varian turbo pump. The Maglev pump is a temporary solution for experiments needing high-quality vacuum, most of our beamtimes run with only one Varian.
Nomenclature of the vacuum system components
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Multi-stage dry pump (pre-pump)
RUN and STP buttons are used
to operate the pump
status: OFF mode
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Gate-valve
status: closed, not allowed to open
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Multi-stage dry pump (pre-pump)
status: MAIN mode
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Gate-valve
status: closed, allowed to open
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Multi-stage dry pump (pre-pump)
status: BOOSTER mode
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Gate-valve
status: open, allowed to open
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Gate-valve
status: open, not allowed to open
→ may have been forced open
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Turbo pump
status: OFF mode
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Pressure gauge
green: reading
red: out of range
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Turbo pump
status: Accelerating
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Pressure interlock display
red: condition not met
green: condition met
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Turbo pump
status: Full Speed
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Cold-cathode status display
circle: status display
ENA and DIS buttons are used
to force start or stop the gauge
Tools necessary for operation
It is necessary to open a couple of windows to be ready to operate the vacuum system. You must be operating from one of the hutch computer (mec-daq, mec-monitor, mec-console, mec-laser, mec-hutch01, mec-laptop08), or you can ssh to these computers.
mechome
In a terminal, type mechome to open the above window. It is the start point of many processes in the MEC system.
MEC Vacuum
In mechome, in the top left part of the window, press the "Vacuum" button to unfold the menu, then select MEC Vacuum to open the above window. It will be used to operate the pumping system components: pumps, gate-valves, etc
tc_vacuum
In a terminal logged as mecopr, type tc_vacuum to open the above window. Often called "striptool", this type of window can display the time evolution of some environmental parameters. Here it shows 4 curves monitoring the pressure value read by 4 different gauges. You can reshape the window and change the time axis range to monitor pressure values over a long time span (~ 1 hour). The curves correspond to the following gauges:
MEC:TC1:GPI:01:PMON → target chamber Pirani gauge
MEC:TC1:GCC:01:PMON → target chamber Cold-cathode gauge
MEC:SEW:GPI:03:PMON → scroll pump Pirani gauge (Maglev roughing)
MEC:SEW:GPI:04:PMON → scroll pump Pirani gauge (Varian turbo roughing)
Venting
Prerequisites
- If ending operation with the x-ray beamline, make sure that the pulse picker is closed, stopper S6 is inserted, hutch search is broken and glass window inserted.
- Stand next to the chamber during the procedure to be ready to react once the chamber is vented and avoid over-pressurization.
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