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LHCb VELO Upgrade


The upgraded LHCb VELO silicon vertex detector is a lightweight hybrid pixel detector capable of 40 MHz readout at a luminosity of 2 x 1033 cm-2 s-1. The track reconstruction speed and precision is enhanced relative to the current VELO detector even at the high occupancy conditions of the upgrade, due to the pixel geometry and a closest distance of approach to the LHC beams of just 5.1 mm for the first sensitive pixel.

Cooling is provided by evaporative CO2 circulating microchannel cooling substrates. The detector contains 41 million 55 μm × 55 μm pixels, read out by the custom developed VeloPix front end ASIC.

The detector will start operation together with the rest of the upgraded LHCb experiment after the LHC LS2 shutdown, currently scheduled to end in 2019.

The VELO upgrade has been described in the Technical Design Report External link mark, submitted in November 2013 which lays out the planned construction and installation, and gives an overview of the expected detector performance. Some key figures and diagrams related to the VELO Upgrade can be found on our collection at Material for Presentations.


The Velo Upgrade Project operates under the responsibility of the VELO Project leader Paula Collinsand deputy project leader Kazu AkibaSome practical links are given in the table below. The project is organised into workpackages which are given in the list below.

The VELO Upgrade work packages:


Upgrade Software




DAQ Integration





Module Cooling 

  • Malcolm John, Workpackage webpage here
  • Velo Upgrade cooling meetings are held weekly at 10 am Monday CET and can be searched in indico under "Velo Upgrade Cooling". In addition the "LHCb CO2 Cooling meetings" discuss the general status of the joint cooling plant development for the UT and Velo Upgrade.


  • Girish Patel, here
  • The responsibility for this workpackage after the retirement of Girish Patel is taken over by Kurt Rinnert and Themis Bowcock pending the appointment of the new workpackage coordinator, expected for Q2 2016

RF boxes


Sensor activity

The VELO upgrade baseline option is for planar sensors, approximately 200 um thick. In the past, 3d and diamond sensors have been considered.  



The VELO upgrade testbeam programme is very active, coordinated by Kazu Akiba and Martin van Beuzekom

Please find the twiki page here


Upgrade commissioning


Microchannel Cooled Hybrid Pixels for LHCb

The decision to replace the Phase I VELO Strip detector with pixels was adopted in 2013 at a dedicated technology review held at Nikhef, Amsterdam. Some workpackages were dedicated to the concept development and R&D for this review, and have now been completed. This includes the workpackage setting in place the Strawman Defintion workpackage and the investigations of alternative pixel sensor technologies incuding 3D (Presentation by Chris Parkes on 3D detectors External link mark) and diamond sensors which were not in the end adopted for the Upgrade. Considerable work was put into the development of a strip option, which is described at the technology review links given above. The initial descriptions of the development of hybrid pixel modules, based on the electronics chip "VeloPix" derived from Timepix2, as a baseline option was described in our LOI External link mark and developed in the Framework TDR External link mark. The VELO Institutes committed to involvement in various aspects of the VELO Upgrade activities by completing a survey velo_expression_of_interest_4.xlsx and some technical information about the simulation studies can be found here.The old R&D pages can be found here.


Other Interesting Links and Reference Documents

LHCb Upgrade Expression of Interest External link mark




Material for presentations

* Material for Presentations

Documents currently in preparation


  • Plan of activities in the pit:
  • P8Activities.mpp: Plan of activities in the pit (Microsoft project source file)
Topic attachments
I Attachment Action Size Date Who Comment
JPEGjpg 081118PB185135.jpg manage 1282.8 K 2009-02-06 - 10:39 PaulaCollins Photo of Hera B feedthroughs
Microsoft Excel Spreadsheetxls Currents-Power-Charge-Engineering.xls manage 66.0 K 2009-02-06 - 13:38 PaulaCollins Calculations of CCE and currents expected at LHCb upgrade irradiation levels from Tony Affolder
Microsoft Word filedoc LHCbUpgrade_-_vespa-official.doc manage 1113.0 K 2008-07-11 - 13:47 MarinaArtuso velo upgrade plans document
Unknown file formatdocx LHCb_front-end.docx manage 643.0 K 2009-04-20 - 15:18 PaulaCollins Document describing a study of modifications of the Medipix for LHCb RICH
PDFpdf Maenpaa_2008_Nuclear-Instruments-and-Methods-in-Physics-Research-Section-A-Accelerators-Spectrometers-Detectors-and-Associated-Equipment.pdf manage 668.0 K 2009-03-16 - 13:05 PaulaCollins CMS telescope
PDFpdf Medipix2_testbeam.pdf manage 894.5 K 2009-03-30 - 11:30 PaulaCollins Muon imaging with medipix
PDFpdf Medipix3DTestbeamJSR_v2.pdf manage 1255.4 K 2009-03-30 - 08:10 PaulaCollins Medipix testbeam at Diamond facility
PDFpdf NikhefVUTCPreference.130617.pdf manage 151.7 K 2013-06-19 - 12:23 PaulaCollins  
Unknown file formatPNG P8Activities.PNG manage 365.9 K 2021-11-22 - 09:44 MarkoMilovanovic  
Unknown file formatmpp P8Activities.mpp manage 496.0 K 2021-11-22 - 09:44 MarkoMilovanovic  
Unknown file formatxlsx PixelModule0_v0.0.xlsx manage 60.2 K 2012-09-19 - 11:19 StefanoDeCapua  
PDFpdf Review_preliminary_14062013.pdf manage 65.6 K 2013-06-19 - 12:21 PaulaCollins  
PDFpdf SALT_DSP.pdf manage 186.7 K 2013-05-16 - 08:18 TomaszSzumlak Current Digital Processing Chain for the SALT chip
PDFpdf SLAT_DSP.pdf manage 186.7 K 2013-05-16 - 08:08 TomaszSzumlak Current Digital Processing Chain for the SALT chip
Unknown file formatdocx VELO__Issues_Critical_to_Upgrade.docx manage 14.4 K 2009-02-06 - 10:29 PaulaCollins Document prepared by Themis Bowcock describing critical issues for VELO upgrade
GIFgif VeloLogo.gif manage 1652.4 K 2014-10-12 - 05:14 PaulaCollins  
PDFpdf Vertex202007_039.pdf manage 320.2 K 2008-07-11 - 13:34 MarinaArtuso Paper on LHCb upgrade written by Marina Artuso for the Vertex 2007 proceedings
PDFpdf artuso-wang-2000.pdf manage 160.9 K 2008-09-24 - 06:39 MarinaArtuso pixel simulation artuso-wang
PDFpdf cern_overview.pdf manage 62.5 K 2013-06-19 - 12:22 PaulaCollins  
PDFpdf cms-fpix.pdf manage 1210.9 K 2009-02-06 - 10:16 PaulaCollins Measurement of CMS Hybrid Pixels up to 45 MRad
PDFpdf final_paper.pdf manage 693.5 K 2009-05-30 - 11:00 PaulaCollins DEPFET telescope performance
PDFpdf fpix2.pdf manage 460.1 K 2009-02-11 - 19:57 MarinaArtuso radiation studies on fpix2 prototypes
PDFpdf gl_consensus_final.pdf manage 110.1 K 2013-06-19 - 12:30 PaulaCollins  
PDFpdf nobu.pdf manage 1501.2 K 2010-10-04 - 09:15 PaulaCollins p-spray and p-stop rad hard silicon design
PDFpdf oct_7_2010_thesis_tuomas_poikela_FINAL.pdf manage 2352.9 K 2010-10-11 - 13:41 PaulaCollins Tuomas Poikela Master Thesis on VeloPix architecture
PDFpdf pixel2013-rev2.pdf manage 372.2 K 2008-12-19 - 11:48 MarinaArtuso First draft of rationale for pixel option and R&D plans
PowerPointppt poster_VELOpgrade_twepp09_2.ppt manage 1000.5 K 2010-10-03 - 12:41 PaulaCollins Jan Buytaert - TWEPP 2009 poster
PowerPointppt poster_pixel2010.ppt manage 7379.0 K 2010-10-03 - 09:06 PaulaCollins Richard Plackett - LHCb VELO Upgrade Pixel 2010
PDFpdf poster_pixel2012_pc.pdf manage 2032.7 K 2012-10-15 - 20:51 PaulaCollins pixel 2012 gdm poster
PDFpdf referee_guide_vutr_may18_2013.pdf manage 11005.6 K 2013-05-18 - 12:29 PaulaCollins  
PDFpdf referee_guide_vutr_may20_2013.pdf manage 12313.3 K 2013-05-20 - 14:47 PaulaCollins  
PDFpdf timep-x_nim.pdf manage 1690.0 K 2009-02-06 - 10:33 PaulaCollins Timepix NIM paper, general description II
PDFpdf timepix_nim_coor.pdf manage 1201.3 K 2009-02-06 - 10:33 PaulaCollins Time Pix NIM publication, general description
PowerPointppt upgrade.ppt manage 955.5 K 2009-02-06 - 10:28 PaulaCollins Presentation to Upgrade WG 20 January 2009
Unknown file formatxlsx velo_expression_of_interest_4.xlsx manage 13.1 K 2012-07-23 - 08:55 PaulaCollins  
PDFpdf vutr_june14.pdf manage 15159.3 K 2013-06-19 - 12:21 PaulaCollins  
Topic revision: r81 - 2021-11-22 - MarkoMilovanovic

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