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Chicane and Bunch Spacing Scans

Chicane and Bunch Spacing Scans. Joe Calvey 6/17/09. Chicane Scans. We have chicane scan data at: 2 and 5 GeV 4ns and 8ns 4 ns plots for a train of 45 positron bunches, .75 mA/bunch 8 ns plots for a train of 45 positron bunches, 1 mA/bunch

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Chicane and Bunch Spacing Scans

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  1. Chicane and Bunch Spacing Scans • Joe Calvey • 6/17/09

  2. Chicane Scans • We have chicane scan data at: • 2 and 5 GeV • 4ns and 8ns • 4 ns plots for a train of 45 positron bunches, .75 mA/bunch • 8 ns plots for a train of 45 positron bunches, 1 mA/bunch • Plots show collector 1 (edge) and collector 9 (center)‏

  3. 4ns, 2 GeV TiN, Collector 1 TiN, Collector 9 Al, Collector 1 Al, Collector 9

  4. 4ns, 5 GeV TiN, Collector 1 TiN, Collector 9 Al, Collector 1 Al, Collector 9

  5. 8ns, 2 GeV TiN, Collector 1 TiN, Collector 9 Al, Collector 1 Al, Collector 9

  6. 8ns, 2 GeV, detail TiN, Collector 1 TiN, Collector 9 Al, Collector 1 Al, Collector 9

  7. TiN TiN, Detail Al Al, Detail

  8. 8ns, 5 GeV TiN, Collector 1 TiN, Collector 9 Al, Collector 1 Al, Collector 9

  9. Chicane Scan Observations • 8 ns data has huge enhancement at n=20 resonance • n = 21 also big, but not much • Note: TiN RFA 3 (next to Al chamber) also sees some extra current there but TiN RFA 2 (not shown) does not • Electrons leaking from RFA 4? • 5 GeV data has spike at low current • RFA efficiency issue? • Density higher in drift?

  10. Large Bunch Spacing Energy Scans • Dominated by primary photoelectrons • 43 bunches, 56ns separation, .8mA/bunch • 2 GeV shown (we also have 5 GeV)‏ • Data taken with all (22!) RFAs around ring • Chicane field = 860 Gauss

  11. Cu Wiggler, Pole Center TiN Wiggler, Pole Center Drift (downstream of wigglers)‏ Drift (upstream of wigglers)‏

  12. Dipole 13W Chicane RFA2 (TiN)‏ Chicane RFA3 (TiN)‏ Chicane RFA4 (Al)‏

  13. Energy Scans with Varying Bunch Spacing • We have data from all RFAs at 4, 8, 12, 16, and 20ns bunch spacing • In general bunch spacing does not seem to have a huge effect on RFA response • We have not examined this thoroughly • It does have an interesting effect on the center pole wiggler RFAs • Becomes more prominent with higher bunch currents • “Trampoline” effect? • Data shown is for a 45 bunch positron beam at 1.25 mA/bunch, 5 GeV • Wiggler pole center RFA, center collector

  14. “Trampoline” Effect? 4ns 8ns 12 ns 20 ns

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