COBRA Magnet Status

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COBRA Magnet Status

• W. Ootani
• MEG collaboration meeting, Feb. 8th, 2007

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COBRA in Run 2006

• COBRA was pretty stable except for two
  incidents...
• Field stability 0.05(FWHM)

Monitored field
BTS OFF
BTS ON

• We had two unexpected quenches during one week
  running.
• Dec.16th, 2130 COBRA ON
• Dec.19th, 1905 First quench (cooling water
  problem?)
• Dec.21st, 1200 Second quench
• Dec.22nd, 700 COBRA OFF

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Quench Problem

• We had two quenches during the beam time in last
  December.
• No (fake) quench for 8 months before December
  since fixing the previous noise problem...
• External noise was observed again in the quench
  detector signal line.
• Much faster than the previous one
• New noise source? inside the MEG system?
• What measures can be taken?
• Look for the noise source
• Modify shielding and grounding scheme
• Different method to detect quench? SQD?
• A few good things to know...
• Nothing was damaged by the quench.
• Quick recovery (2.5hrs) thanks to newly
  installed TMP

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Schedule

• Feb.13 Refrigerator maintenance
• Feb.23 COBRA will be cold.
• - mid-Apr. Investigate quench problem
• Look for noise source
• Improve shielding and grounding