1 / 17

Overview of 2012 MIB in ALICE

Overview of 2012 MIB in ALICE. A. Alici (INFN), A. Di Mauro (CERN) LBS #43, 28/01/2013. Introduction.

coty
Download Presentation

Overview of 2012 MIB in ALICE

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Overview of 2012 MIB in ALICE A. Alici (INFN), A. Di Mauro (CERN) LBS #43, 28/01/2013

  2. Introduction • As already reported in previous LBS meetings (#35, #37 and #40), vacuum conditions in LSS2 limited significantly ALICE running and data taking in 2012. In particular, probably due to a not perfect bake out at the end of the intervention during the 2011/12 winter stop, the TDI has shown a vacuum performance worst than 2011 (contrarily to LHCb TDI). • ALICE cannot ramp up most of gaseous detectors when the total LSS2P is larger than ~ 3E-8 mbar, corresponding to bkgd contamination up to 50%; ideal operating conditions would be P < 7E-9 mbar • Some basic observations: • The pressure in the TDI increases during injection when the jaws are closed and when the total beam charge is larger than 1.4E11 p, the longer this condition is kept the larger the pressure increase • At the end of injection when the TDI jaws are opened the pressure decreases slowly, the larger the starting value the longer the recovery time; if the starting value is larger than ~3E-8 mbar the decrease is followed by a bump of several hours which further delay the vacuum recovery • After our proposal (LPC, 03/09/12) the injection procedure has been modified since Sept 4 in order to minimize the time spent with closed jaws with circulating Beam 1: B1 is injected first, then TDI jaws are opened and finally B2 is injected. However, the TDI (and Left LSS2) pressure during a given fill is affected also by total beam intensity and condition at the beginning of the fill (cumulative effect if short delay between consecutive fills) . LBS#43

  3. ALICEvsLHCbTDI With proper conditioning/bakeout acceptable behaviour, good hopes for post LS1… LBS#43

  4. Left LSS2 P overview 08-12/2012 TDI p generally > 10E-8 mbar TDI ID800 VGPB.123 LBS#43

  5. ID800 recombination chambers ALICE magnets polarity reversal LBS#43

  6. FILL 2997 (Bad) LBS#43

  7. FILL 2997 (Bad) Example of large P bump, no data taking in ALICE (bkgd rate >200 KHz during all fill) LBS#43

  8. FILL 3027 (OK) First FILL with modified injection LBS#43

  9. FILL 3027 (OK) Start data taking at SB declaration LBS#43

  10. Bkgd rate measurements Correlation between Left bkgd rate measured by V0 trigger detector and product of beam intensity times sum of LSS2 pressure. KHz FILL 2858 LBS#43

  11. Outlook • Beam-gas simulation results were performed with R. Appleby’s and D. Brett’s help using a simplified FLUKA model of LSS2 for fill 2117 (2011) vacuum, results were presented in LBS#32. • In 2nd half of 2012 a new detailed model of LSS2 has been created by A. Lechner (EN/STI) and E. Leogrande (ALICE) • 2 M “20 m scoring planes” containing secondaries from beam-gas interactions in LSS2 for FILL 2736 vacuum have been generated during last weeks and will be used to produce events inside ALICE and x-check measured bkgd LBS#43

  12. BACKUP SLIDES LBS#43

  13. FILL 2736 LBS#43

  14. ALICE vacuum layout A C A side 70 m 69.7 m VGPB.623.4L2 VGI.500.4L2 120m C side 70 m 69.7 m VGPB.623.4R2 VGI.500.4R2 120m LBS#43 14

  15. ALICE layout Beam 1 BCM-A 8 sensors z = + 6 m, r = 10 cm Beam 2 BCM C 7 sensors z = -18.5 m, r=10 cm LBS#43 15

  16. The V0 detector ITS V0A rin=8 cm rout=100 cm V0C rin=8 cm rout= 76 cm SPD V0C V0A 340 cm 90 cm Two arrays of scintillator counters (V0A and V0C). Time spectra allow beam-gas events rejection LBS#43 16

  17. V0 timing properties V0A V0C IP beam2 beam1 340cm ~11.3ns 90cm ~3ns V0A+V0C ≈ 14.3ns V0A-V0C ≈ 8.3ns collisions IP beam1 Beam background from beam2 ~-11.3ns ~3ns V0A+V0C ≈ -8.3ns V0A-V0C ≈ -14.3ns Bkgd1 (BGA) Beam background from beam1 IP satellites beam2 ~11.3ns ~-3ns V0A+V0C ≈ 8.3ns V0A-V0C ≈ 14.3ns Bkgd2 (BGC) LBS#43

More Related