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Performance Comparison of Luminosity and Beam Current: June 5-6 vs December 23, 2003

This report presents a comparative analysis of luminosity performance and beam current dependence between two data sets collected on June 5-6 and December 23, 2003. Key findings include differences in peak bunch currents, specific luminosity, and spot sizes for the Low Energy Ring (LER) and High Energy Ring (HER). The June data showed slightly higher peak bunch currents and more favorable spot sizes compared to December, which exhibited lower currents and variations in beam parameters. The analysis indicates the need for further optimization in achieving higher luminosity levels.

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Performance Comparison of Luminosity and Beam Current: June 5-6 vs December 23, 2003

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  1. Luminosity performance comparison: 5-6 Jun vs. 23 Dec 03 • Compare beam-current dependence of • (specific) luminosity • spot sizes • Data sets • 5-6 Jun: stable running , after a few rounds of optimization • LEB: restored to 3 May config + new tune spot • HEB: restored to 3 May config + 20 (addt’l) % of beta*y knob + better tune • by-3 pattern, 934 bunches, coasting • CRR data file: PHYSICS3_DATA:[pep2.ip.witold.spr03]lumb_t_2_5Jun • 23 Dec: stable running, then MD pushing currents • by-2 pattern, 1319 bunches, LER trickle • CRR data file: PHYSICS3_DATA:[pep2.ip.witold.win04]lumb_t_1_23Dec

  2. Beam currents & Luminosity: 23 Dec 03 LER current (23 Dec) L (23 Dec) HER current (23 Dec) Lsp (23 Dec)

  3. Beam currents & Luminosity: 5 Jun 03 LER current (5 Jun) L (5 Jun) HER current (5 Jun) Lsp (5 Jun)

  4. Bunch currents & L/bunch: 5 Jun vs. 23 Dec LER vs. HER bunch currents (5 Jun) LER vs. HER bunch currents (23 Dec) L/bunch (5 Jun) L/bunch (23 Dec) -12 % -22 %

  5. Specific luminosity: 5 Jun vs. 23 Dec Lsp (5 Jun) Lsp (23 Dec) -20 -25 % Lsp (5 Jun) Lsp (23 Dec) -12 %

  6. LER beam sizes: 5 Jun vs. 23 Dec LER x-size (23 Dec) LER x-size (5 Jun) +6 % LER y-size (5 Jun) LER y-size (23 Dec)

  7. HER beam sizes: 5 Jun vs. 23 Dec HER x-size (5 Jun) HER x-size (23 Dec) +5-10 % HER y-size (5 Jun) HER y-size (23 Dec)

  8. Summary • Compared to the 5-6 June data set, the 23 Dec data set exhibits • in the LER • peak bunch current now ~ 10% lower • x- spot size* + 6% (at the same Ib-), with comparable HER-current dependence • y-spot size* comparable (at the same Ib-) • both x & y spot sizes increase with increasing HER current • in the HER • peak bunch current now ~ 20% lower • x- spot size* +5 - 10 %, increases with HER current (??) • y- spot size* comparable, decreases with HER current (trickle + beam-beam) • Luminosity • achieved a peak luminosity of 7.2 E33 by pushing currents (mainly HER) • luminosity curves show only moderate saturation: we need more current! • at the same bunch-current product, the L/bunch is ~ 12% smaller • the peak L/bunch is 22% lower because (i) • the Lsp is smaller, and • (ii) the peak bunch currents are lower (for both rings, but mainly in the HER) • because of the different running mode (coast vs. trickle) and diferent bunch-current regime, hard to tell which beam is ‘weaker’.

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