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Vacuum Pressure Calculations

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Vaccalc

• The program vaccalc was used for all calculations.

• The program required three pieces of information for each chamber: pumping, conductance, and outgassing.

• Using the given information, the program calculates the pressure at any point along the entire tube.

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Chamber Design

HER downstream

LER upstream

LER downstream

HER upstream

Support chamber

Q5 NEG

Q5 NEG

66.114 m

69.33 m

ST plot

plot

plot

plot

plot

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4

5 6

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Assumptions

• Bertollini’s numbers on outgassing were true.

• 2000 (l/s)/m pumping for all NEG pumps with B or C screens.

• 1000 (l/s)/m pumping for all NEG pumps with A or D screens

• 1000 (l/s)/m pumping for all ion pumps (150 l/s pump over 0.15 m)

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Data

• Conductance remains a constant throughout the LER tubes.

• Lengths were taken from drawings and tables.

• This is a work in progress, making it difficult to draw final conclusions from the plots.

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Cases

• Baseline Design– No Radial Pumps

• No C Pumps– No Upstream Q4 Pump

No Q4 pump with Ion pump LER Q5 not pumping LER Q5 outgassingNo Q4 pump with Ion pump and frangible

pump LER Q5 not pumping with Frangible Link

Pump LER Q5 outgassing with Frangible Link

Pump

• No C Pumps – Q4 and Q5 outgassing– No Q4 and Q5 outgassing

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Baseline Design (Support Tube)

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Upstream HER

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Upstream LER

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Downstream HER

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Downstream LER

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No radial pumps

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No C Pumps Upstream (support tube)

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Upstream LER

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No Upstream Q4 Pump (support tube)

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Upstream LER

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No Q4 pump with ion pump

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Q5 not pumping

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Q5 Outgassing

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No Q4 pump with ion and frangible pump

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Q5 not pumping with Frangible Link Pump

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Q5 outgassing with Frangible Link Pump

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No C Pumps Upstream (support tube)

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Upstream LER

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Q4 and HER Q5 outgassing (support tube)

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Upstream HER

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Upstream LER

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No Q4 and HER Q5 outgassing (support tube)

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Upstream HER

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Upstream LER

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Next Steps

• Test other possible combinations

• Finish the HER– Upstream– Downstream

• Recalculate outgassing numbers

• Check pump speed numbers– screen conductances