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Investigation of 0.1s bunch gap

Investigation of 0.1s bunch gap. Earlier runs had shown large temperature losses in the hot zone after 0.1s, of the order of 60-80%. There was some uncertainty over these results because the time step between solutions was too large.

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Investigation of 0.1s bunch gap

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  1. Investigation of 0.1s bunch gap • Earlier runs had shown large temperature losses in the hot zone after 0.1s, of the order of 60-80%. • There was some uncertainty over these results because the time step between solutions was too large. • As the results are cumulative and depend on the result from the previous solution, the later results couldn’t be relied on even if they looked more even.

  2. Initial work • I used a small model (x=.5mm, y=.05mm, z=.5mm). With a 10mmx10mmx100mm mesh. • I used symmetric boundary conditions to allow me to reduce the model to ¼ of its normal size. • I took the input file supplied by Luis that gave the heat deposition from a 250GeV beam over a volume 1mm x .1mm x 30mm. • This allowed me to study time steps to find out over what gap was needed to remove the uncertainty. • I’ve taken the temperature of the hottest node and plotted it against time.

  3. 0<t<0.02s 100 sub-steps

  4. 0<t<.004s 40 sub-steps

  5. 0<t<.001s 40 sub-steps

  6. Combined results 0<t<.001s

  7. Combined results 0<t<.004s

  8. Initial findings • The best results were found with a 2.5x10-5s time interval. • Although when the time step is too large there is an uncertain region in the results, this doesn’t seem to affect the later results. • This is shown on slides 6 & 7. • 0.1s is enough time for the temperature to spread outside the boundaries of the volume modelled here. • But in this model the heat isn’t allowed to spread past the boundaries so the overall temperature may be higher than would be seen in reality.

  9. Later work • I used a larger model (x=.5mm, y=.05mm, z=5mm). With a 10mmx10mmx100mm mesh. • I used symmetric boundary conditions. • I took the input file supplied by Luis used previously. • I used a time gap of 2.5x10-5s, and studied the 0<t<.005s. • This was the region where most heat loss occurred, and where there was uncertainty over the results.

  10. Conclusions • With the limited time and space model used, I’ve found the hottest node has decreased from 253°C to 48°C after 0.005s. • If a larger volume could be modelled at times up to 0.1s, a greater temperature loss would be seen but isn’t calculable from these results.

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