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44 th LNF Scientific Committee, Frascati, 4-5 June 2012

DA F NE Status Catia Milardi (on behalf of the DA F NE Team). 44 th LNF Scientific Committee, Frascati, 4-5 June 2012. OUTLINE. Luminosity results & Background Collider uptime technical faults consolidation activities Ring optics developments Beam Dynamics Man power Future Plans

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44 th LNF Scientific Committee, Frascati, 4-5 June 2012

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  1. DAFNE Status Catia Milardi (on behalf of the DAFNE Team) 44th LNF Scientific Committee, Frascati, 4-5 June 2012

  2. OUTLINE • Luminosity results & Background • Collider uptime • technical faults • consolidation activities • Ring optics developments • Beam Dynamics • Man power • Future Plans • Conclusions

  3. Maximum Peak Luminosity so far … • Same peak luminosity as in 2005, but • less bunches in collision (100) • lower currents

  4. Comparison among DAFNE best runs with and without Crab-Waist Luminosity [1028 cm-2 s-1] Luminosity [1028 cm-2 s-1] At low currents the highest Ls achieved exceeds by 2÷3 times the best value measured during the past KLOE runs

  5. Best hourly integrated luminosity L∫1 hour = 0.359 pb-1 L∫day = 8.62 pb-1

  6. Best day Sunday, May 6th 2012 ~ 80% uptime L∫day ~ 7 pb-1

  7. Luminosity History

  8. DAFNE operations • Since January 2012 DAFNE operations suffered for several problems: • Hardware faults • Cooling system • Power supplies • Control system • Injection kickers • Linac klystron discharge • Anti-solenoid power supply • Holes in the Wiggler coils • Beam pipe heating at IP1 • Non reproducibility of the beam parameters in the Main Rings • Slow drift of the beam trajectory in the Transfer Lines • Radioprotection alarm in the Control Room • Adverse meteorological conditions: • DAFNE activities stopped for 6 and half days in February • Several glitches in the electric network

  9. DAFNE fault occurrency

  10. Jan – March 2012 problems with the injection, radioprotection alarm, vacuum rise in MRe Jan – May 2012 supervisor of the Cooling System not running, power supply, KCKs faults Holes in the WGLEL101, WGLES101, water leakage from the WGLES201 spigots, sH2O restored Bellows degassed, e- KCK feed through replaced, water leakage MRs, sH2O restored Control system fault due to the CPUs controlling the KCKs in the MRs Exit end pole of the WGLEL101 replaced, severe water leakage from the fluid system main duct, sH2O restored Radioprotection measurements in the MRs hall, lead shields installation Control system fault due to the CPU controlling the KCKs in the MRp Entrance end pole of the WGLEL101 is first soldered than replaced Snow, glitches in the electric network, water leakage MRs, Radioprotection measurements in the MRs Anti-solenoid power supply fault in the MRp Hole in the WGLEL101 coil, sH2O restored Longitudinal measurement of the KlOE IR 2 new dc generator for the ICE installed Microswitch of the scrapers replaced Alignment measurements in TLe Solenoid power supply fault

  11. DAFNE uptime

  12. Electrical continuity in the IR On mid January a sudden rise occurred in the temperature of the beam pipes inside the KLOE detector due to the leak of electrical continuity in the bellows at both ends of the section common to the two beams. Restoring electrical continuity Temperature Celsius degrees BEFORE AFTER

  13. Vacuum spikes in the MRe • Spikes in the vacuum pressure are observed, close by the first injection kicker, when storing the beam after a stop. • The bellows after the feedthroughs of the injection kicker, in the electron ring, have been all replaced (Jan 2012). • Possible explanation: • Dynamic vacuum still need to be improved • Small discharge in the injection kicker

  14. Wiggler faults in the Mre (March 25th 2012) Three out of four wigglers installed in the e- ring got seriously damaged due to a long term water leakage not detected due to a concomitant fault in the power supply board supervising the ground fault occurrence. …. discharge between the coils and the vacuum chamber … holes in the coils (6 mm wide) … calcareous concretions

  15. The Wiggler faults have been recovered in two and half days and ….. March 29th 2012 Lpeak = 1.33 cm-2s-1 L∫1 hour = 0.324 pb-1

  16. Main Rings optics • Relying on linear optics measurements (b1, b2, n1, n2, hx, hx,xx, xy) the Main Rings optics has been rematched (March) in order to restore: • the required betatron function at the IP as well as at the CW sextupoles • The proper phase advance between the injection kickers • Symmetry in the short sections • As a consequence of the beam rematch: • smoother injection with higher efficiency and lower radiation level • Reduced beam blow-up with the main and the opposite beam current

  17. Luminosity comparison Before optics rematch March 2012 After optics rematch March 2012

  18. Luminosity comparison After optics rematch March 2012 December 2011

  19. Background comparison After optics rematch March 2012 Before optics rematch March 2012

  20. Background comparison After optics rematch March 2012 December 2011

  21. Clearing electrodes for e-cloud suppression • Clearing electrodes are operative and produce the expected effect on the positron beam paremeters in terms of: • Transvese beam size • Horizontal tune-shift • Horizontal instability growth rates

  22. Horizontal Instability Growth Rate Measurements Using Bunch-by-Bunch Feedback Applied voltages: 0 V, 70 V and 140 V Mode 0 -1 Mode = -1 is unstable

  23. Tune Spread Measurements DAFNE e+ beam: 100 bunches, spaced by 2.7 ns with 20 buckets gapTurning some electrodes off(4 in the wigglers and 2 in the dipoles ) horizontal tune spread is almost halved Horizontal OFF Dnx1-100 ~ 0.006 (off) Dnx1-100 ~ 0.003 (on) <Dnx> ~ 0.0065 (on/off) OFF ON Measured by using the front end of the Bunch-by-Bunch feedback systems designed to damp the coupling instabilities. ON

  24. .. electrodes are effective in reducing the tune spread also in the vertical plane... ON Dny1-10 ~ 0.002 (on/off) OFF

  25. Vacuum Chamber HOM Shifts: results • Preliminary data analysis outlined the following points: • all modes have a positive frequency shiftas a function of the positron beam current. At I+~800 mA, it is between 100 and 400 kHz depending on the modes under consideration • switching on the electrodes the frequency shift can be partially cancel for almost all modes • quality factor of the modes decreases with positron current; • for some modes the frequency shift does not depend on the electron voltage. It might be due to the fact that those modes are localized in different places of the arcor in regions not covered by electrodes. • Frequency shifts can be used toevaluate the e-cloud density(see the theory given given in [J. Sikora et al., MOPPR074, IPAC12] • Identification of resonant mode location is still in progress, it is not trivial due to the complex 3D geometry of the arc chamber

  26. Current delivered by voltage generators The voltage generators connected to the electrodes absorbs the photo-electrons. In the present configuration each voltage generator is connected to three electrodes of one arc (i.e. one wiggler and two dipoles). The current delivered by the generator has been measured as a function of the generator voltage and for different beam currents. Possible explanation??? Current supplied by the generator IVDCne- e-cloud density ne-IB-VDC. Combining the two previous relations we obtain that IVDCIB-V2DC, The e-cloud is completely absorbed when I0. In all other situations there is still an e-cloud density. Fitting these curves and scaling their behaviour up to currents >1A, one discover that a voltage of the order of 250 V is no longer adequate to completely absorb the e-cloud when IB>1A. So the applied voltage has to be increased.

  27. Bunch Length Measurements (May 2012) ---- e+ May 2012 (VRF= 180 kV scrapers in) ---- e- May 2012 (VRF= 180 kV scrapers in)

  28. Comparison between e- bunch length measurement ---- e- May 2012 (VRF= 180 kV scrapers in) ---- e- Jan 2011 (VRF= 180 kV scrapers in)

  29. Comparison between e- (2011) and e+ (2012) bunch length measurement ---- e- Jan 2011 (VRF= 180 kV scrapers in) ---- e+ May 2012 (VRF= 180 kV scrapers in) Impedance (at least its inductive part) seems to be higher in the electron ring than in the positron one despite the e-cloud clearing electrodes

  30. Dynamic Vacuum trend in MRp

  31. Highest currents stored by now

  32. DAFNE manpower Run Coordinators Since December 2011 the DAFNE Run Coordinators decreased by 5 units.

  33. DAFNE Technical support

  34. DAFNE plans Jun 1st – July 15th machine and luminosity studies Jul 15th – Aug 27th shut down for ordinary maintenance Sep 3rd – Oct 31st machine and luminosity studies Oct 31st shut-down for KLOE inner tracker installation and DAFNE consolidation

  35. Some crucial points • The peak luminosity is now comparable with the maximum achieved at the end of the KLOE run in 2005 • Luminosity at low currents letting in collision 10 bunches is quite promising • At low currents the highest Ls achieved exceeds by 3 times the best value measured during the past KLOE runs • Luminosity achieved in December is reproducible regardless the IR heating problem • Maximum currents stored so far in collision are: • I- ~ 1.3 A • I+ ~ 0.9 A • Clearing electrodes are effective in keeping under control the e-cloud driven instabilities in the positron ring. An even better effect is expected after replacing the electrodes power supplies. • The uptime of the Linac subsystem, after a careful maintenance plan is now ~ 75% • DAFNE while working for the KLOE-2 experiment is also providing beam to the BTF and synchrotron radiation to the LNF beam lines

  36. Conclusions • Presently DAFNE, assuming 280 days of run and 80% uptime, might provide a yearly integrated luminosity in the range 2÷2.5 fb-1 • Relying on preliminary measurements and on the past experience it seems reasonable to increase the yearly integrated luminosity up to 3÷3.5 fb-1 • DAFNE is a collider of unequalled complexity (compact rings with no symmetry, collision at low energy with high currents) • The KLOE-2 IR is based on innovative concepts never tested before • Pushing the DAFNE luminosity, in the KLOE-2 configuration, at the same levels achieved during the test of the Crab-Waist collision scheme requires a remarkable efforts and expert man power (linear and non-linear optics, beam dynamics, beam-beam interaction, mechanical engineering) • The DAFNE accelerator complex is in operation from more than 13 years, as such it requires extraordinary and expensive maintenance in order to guarantee a 80% uptime • Testing the Crab-Waist collision with a large detector is a relevant issue for other projects

  37. Thank you for your attention

  38. SPARE SLIDES

  39. 10 bunches Luminosity 10 consecutive bunches • Beam-beam is not a limiting factor • Crab-Waist sextupoles work • This result can be improved by: • Vacuum conditioning • Scrabbing in the MRp • Optimizing multibunch and high current operations

  40. Vertical orbit oscillation(updated from Scient. Comm. June2011) Nov11 Apr11 Turn by turn e+/e- beam position measured at two monitors (symmetrical with respect to the IP) Beam oscillation reduction in the lower bandwidth due to activities carried on to damp residual mechanical vibration of the IP region Fixed ripples of a few corrector magnets power supply at 50Hz and 100Hz Typical harmonic components of the positron beam vertical oscillation

  41. Turning off the electrodes the transverse vertical beam dimension enlarges s+y (mm) s+x (mm) However the power supplies of the clearing electrodes must be replaced cause their load impedance changes with the beam current

  42. Specific Luminosity (December 2011) N1: n+x = 0.1100 n+y = 0.1810 nominal tunes n-x = 0.0955 n-y = 0.1615 N2: betratron coupling optimized N3: n+x = 0.1020 n+y = 0.1690 e+ tunes lower n-x = 0.096 n-y = 0.1605 N4: n+x = 0.1020 n+y = 0.1690 e+ e- tunes lower n-x = 0.094 n-y = 0.1560 At low currents Ls exceeds by 3 times the best value measured during the past KLOE runs.

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