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Heat stress to IP chamber

Heat stress to IP chamber. 11 November 2002 Toru Tsuboyama (KEK). Cracks in the IP Berryllium chamber （ discovered on 8 November ）. Crac ks like structure were found here. Beryllium and aluminum parts are welded. 200 m m thick gold plate (where dark spots were found).

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Heat stress to IP chamber

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  1. Heat stress to IP chamber 11 November 2002 Toru Tsuboyama (KEK)

  2. Cracks in the IP Berryllium chamber （discovered on 8 November） • Cracks like structure were found here. • Beryllium and aluminum parts are welded. • 200 mm thick gold plate (where dark spots were found)

  3. The temperature history of the IP chamber • The temperature of the inner beryllium part can not be measured. We only know • T0, the temperatures of the aluminum part cooled by water. • T1, the outer cylinder of the beryllium part cooled by Helium gas. • The heat and mechanical stress simulation tells T1-T0 should be kept less than 5 degrees. • 5 November 2000, fill pattern study. • A 2.5 bunch spacing hit the resonance of he IP chamber. • Two accidents in the helium circulation system. • September 30 6:10 • October 16 12:50 T1 T0

  4. 2000 autumn – 2002 autumn • Due to large amount of data, ~10 minutes average values are plotted and peaks in data are smeared out in this page • Beam current • LER+HER(black) • LER(red) • HER(blue) • Beam current was gradually increased according to the length of solenoid coils around the vacuum chambers. • T1-T0 vs LER+HER • 2000 fall- blue • 2001 fall – red • 2002 fall -- black T1 T0 T1-T0

  5. January-June 2002 • In spring, KEKB run in pure 4 bucket spacing since luminosity in semi 4-bucket spacing mode was lower than pure 4-bucket spacing mode. • T1-T0>2.0oC when LER+HER>1.9A.

  6. 2002 September-October • Increase of current. • High current runs are done in semi 4-bucket fill pattern. • Semi 4-bucket spacing fill pattern yielded lower heat to IP. • T1-T0~2.5oC when a run starts LER+HER=2.5A.

  7. 5 November 2000: Bunch pattern study • 2.5-bunch spacing caused high temperature. • T1-T0 was about 5oC at LER =600mA. • MAFIA code showed a resonance frequency of ~1/5 of the acceleration RF(508MHz). • Even the aluminum part was heated. (T0) • No detail data is left. T1 T0 T1-T0

  8. 30 Septemebr, 6:10. Circulation system stopped. • Beam current ~1.9A • Beam abort request • The hardware abort from the circulation system. • 30 seconds after the system stops. • Temperature interlock did not fire • Condition: One of the temperature sensors shows 3 degree higher temperature than that in the usual operation. T1 T0 T1-T0

  9. Close up • Horizontal axis shows minutes. • Max (T1-T0) ~5.5 oC • (T1-T0) < 0 oC region at minute > 10 is due to the absence of the helium flow. T1 T0 T1-T0

  10. 16 October 12:50 The second accident • Beam current~1.5A • Beam abort • Abort from the circulation system • No temperature increase. • No temperature beam abort. • After the first accident I asked the company to shorten the delay of the circulation hardware abort. (I should confirm the modification) T1 T0 T1-T0

  11. 30 October LER high current study • No particular increase of the temperature. T1 T0 T1-T0

  12. 30 October 2:30 AM. Vacuum leak • No particular increase of the temperatures T1 T0 T1-T0

  13. 1 November: Scrubbing • No particular temperature increase was found T1 T0 T1-T0

  14. 6 November: Scrubbing • NO particular temperature increase was found T1 T0 T1-T0

  15. Fill number (Spring-summer 2002) • Total 2200 fills • In most fills T1-T0 >~ 2.0oC • Among them, in about 500 fills, T1-T0 >~ 2.5oC

  16. Fill number (2002 fall) • Since –60 days from today, T1-T0 is more than 2.5oC. Corresponding fills are 10400-9600=800 runs.

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