LIU-PSB Meeting 224 (New wire scanner commissioning + EVM report)

864/2-B14 - SALLE J.B.ADAMS (CERN)

864/2-B14 - SALLE J.B.ADAMS


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Gian Piero Di Giovanni (CERN)

Participants: Fanouria Antoniou, Gian Piero Di Giovanni, Jonathan Emery, Alessandro Floriduz, Eve Fortescue-Beck, Aurelie Noelle Goldblatt, Matthias Haase, David Hay, Bettina Mikulec, Gabor Petrika, Serge Pittet, Sylvie Prodon, Federico Roncarolo, Andrea Santamaria Garcia, Jose Luis Sirvent, Raymond Veness.

Approval of minutes

The minutes of the LIU-PSB WG #223 meeting were approved.



  • The LIU event will probably be held from the 13th to the 15th of February, 2018. It will last two nights and will take place in Montreux.

LIU-PT Meeting

  • Most of the meeting was dedicated to the aftermath of the LS2 Day held during week 41. A follow-up of few actions was presented by F. Baltasar Dos Santos Pedrosa at the LIU-PT meeting.
  • The installation readiness dates and the planning will be confirmed by the groups in November 2018.
  • The LBE run of Linac4 has been delayed to September 2019. The Open Days will take place from the 14th to the 15th of September 2019 and will need to be taken into account in the schedule, since no activities can take place during that week. In particular, the individual equipment tests will need to be carried out after the Open Days. There is a push to shorten the LBE run to eight weeks so B. Mikulec and A. Lombardi have asked for the daily planning of the run. On the same topic, it has been confirmed by TE-EPC that the power converters can run without cooling support.
  • Six weeks will be allocated in the master schedule for the individual equipment tests. The hardware commissioning coordinators will need to contact the hardware owners.
  • Differential drawings are still missing for many of the LS2 installation activities. It has been agreed with the integration team that they will generate the drawings according to the installation date of the equipment.
  • S. Mataguez has been officially appointed activity technical coordinator for the Linac4 connection from December 2018 to September 2019.

Follow-up of open actions

M. Buzio (2018-10-23): Investigate and report the options for implementing an online field measurement in the switching dipole BT.BHZ10.

  • The prototype is being installed on the test bench in building 311. After the standard acceptance tests they will begin the tests for the online system. They will issue a first statement concerning cost and accuracy by the end of January 2019.
  • Action postponed to 2019-01-31.

T. Dobers (2018-10-23): Produce the tilt measurement tool and perform measurements on spare / future magnets.

  • The tilt meter has been produced and it will be tested on a spare magnet in building 867 very soon.
  • Action postponed to 2018-10-27.

F. Roncarolo (2018-10-23):  Report on the status of the design of the SEM grid monitors in the L4T and LBE lines.

  • Action postponed to 2019-01-15. There will be a talk on the topic in January 2019.

Commissioning of the new PSB wire scanner (J. L. Sirvent Blasco)

LIU–Beam wire scanners architecture and design

  • All mobile parts of the wire scanner are in vacuum, so there are no bellows.
  • Concerning the control and acquisition electronics, an intelligent drive takes care of the power management of the motor. There is a VFC card for the digitalisations of the optical position sensors and four photomultipliers that digitalise the signal in parallel with a factor 10 attenuation filter in each of them. HV controls the high voltage of the photomultiplier set-up. Currently the acquisitions are beam scoped-based instead of using the cards.
  • The beam profile determination devices are a passive optical position sensor (the fibre optics focus the light into the light sensors) and a secondary particle detector system (shielded scintillator).

Calibration procedure and wire position incertitude

  • The calibration of the new wire scanner is more precise compared to the one of the current operational wire scanners, since the vibrations of the system have been minimized by changing the way the wire moves. The angular-to-projected motion is still subject to assembly tolerances.
  • Three parameters are used to fit the calibration: angular position at the laser crossing, the laser position, and the wire position. The precision of the wire position determination is of ~11um at a speed of 20 m/s.
  • Some fatigue tests were performed in 2017, where 52900 scans were made. The behaviour of the wire was consistent for a given speed.

LIU-BWS on the PSB

  • Four different MDs were carried out at the PSB during 2017 and 2018. During the first two MDs the glass disk of the prototype was sliding, so it was changed to a metallic one. The carbon wire broke during the third MD.
  • The geometry of the scintillators was changed from cylindrical to square.
  • During the shutdown eight new wire scanners will be installed in the PSB: the horizontal ones in section 4L1 and the vertical ones in 11L1. The scanners will sit on drawers for easy access. The vacuum tanks were delayed due to a problem with a supplier. The supporting structures are under production. The assembly and acceptance tests of the kinematic units will take place in November-December 2018 and the final assembly tests in February-March 2019.

PSB Beam test results

  • A study comparing the precision of the new prototype and the operational wire scanners was carried out. Both prototypes showed an RMS error of ~1.6 % while one would have expected better performance in the new prototype. After the change of type of disk, the RMS error given by the new prototype went down to 1.07 %.
  • Concerning the metallic disk motion reproducibility studies, the jitter in flight time was measured to be 0.7 ms for the in scan and 1.73 ms for the out scan. The speed of the wire at the time of the beam crossing was not 20 m/s but 18 m/s. Additionally, they can measure and correct for the eccentricity thanks to two optical sensors 180 degrees apart.

Sneak peek to some CPS BWS results

  • The activities in CPS complex during the run in 2018 included tests with different beams, studies with systematics, measurements in the bumps at injection energy, and tests with TOF and SFTPRO beam types.
  • There were tests where the beam centroid was displaced and measured with the wire scanner. Preliminary results show good agreement in the in and out measurements with the prototype, much closer than with the operational ones.


  • F. Roncarolo asked if the time jitters of around 1 ms are tolerable in operation. B. Mikulec said that for certain studies, beyond 2 ms might be too much.
  • R. Veness asked about the origin of the time jitter. J. L. Sirvent Blasco answered that it depends on the initial angle at which the motion starts, which in turn depends on the resolution of the resolver. A second thing to consider is that the friction might not be uniform and the way the control loop is done. J. Emery commented that currently they have values below 1 ms in the PS. There is a correlation between time of flight and starting angle, given by the feedback. Given the friction, the more difficult it is to estimate the position, but it can be compensated. B. Mikulec commented that this might be important in comparative measurements due to the spread.
  • G. P. Di Giovanni commented that sigma should be fitted to a parabolic function since it is the emittance the parameter that varies linearly with intensity. F. Roncarolo commented that the shot by shot variation is in any case small, below the level of 1%.
  • G. P. Di Giovanni asked if the baseline is still to use the optical disk. R. Veness answered that the baseline is now to use the metallic disk. The manufacturer changed the laser from a picosecond laser to a nanosecond laser without communicating it because of a production problem.
  • B. Mikulec asked if the wire breakage occurred at the beginning of the year was understood. R. Veness answered that the kapton wires were not completely fixed into the hook, so they got loose and may have cut the wire. The kapton wire fixing procedure has been now improved to make sure that a similar issue becomes highly unlikely.
  • B. Mikulec asked if the electronics of the tunnel are radiation hard. J. L. Sirvent Blasco answered that the passive electronics have a well known radiation tolerance. Concerning the active electronics, such as the amplifiers, they are the same as the ones used in the LHC and the SPS and had no issues with radiation during operation. J. L. Sirvent Blasco also remarked that the design of the PCB where the photomultipliers sit allows to easily change configuration and not use these amplifiers, so there is the possibility to have or not active electronic parts in radiation. 
  • B. Mikulec asked is the FESA class is different between the prototype and the operational wire scanner. F. Roncarolo answered that there is no FESA class for the current prototype. The results so far are based on scopes and there is no alternative to provide digitalised data for the time being. B. Mikulec asked about the availability of the final working system to allow working on the operational application, e.g. compatibility with the PS. J. Emery commented that a prototype can be provided next year in April.
  • B. Mikulec suggested to include J. F. Comblin in the discussion before having a final version of the FESA class to give some input. R. Veness suggested to set some milestones for the next six months.
  • B. Mikulec asked if they found the optimal scintillator positions. J. L. Sirvent Blasco answered that they figured out the range for the detector, given the constraints of the space. In the PSB they need to be straight on the flange. This will be integrated soon.
  • B. Mikulec asked if the old wire scanners will be taken out and re-calibrated. F. Roncarolo confirmed that all the current wire scanners will be taken out and re-calibrated.


EVM report (S. Prodon)

  • The cost variance is positive and the project is two months and a half behind the cost and schedule review baseline, which is probably due to lack of reporting during the summer holidays and it is still there. Small schedule variances are observed in almost all the groups. A larger fluctuation was observed in TE-EPC, but it could easily be explained by lack or reporting in activities like the POPS-B.
  • Regarding the CERN Expenditure Tracking for the LIU-PSB project, there is currently 68% of charges and 107% of commitment versus the 64% of charges and 91% commitment standard averages at the end of October.
  • Data extraction will be done for the Council paper. The reporting needs to be done by the 15th November 2019.

Next LIU-PSB meeting: 6th of November 2018 on the Work Package Analysis and PSB master schedule by David Hay.

There are minutes attached to this event. Show them.
    • 4:00 PM 4:05 PM
      Approval of Minutes 5m
      Speaker: Gian Piero Di Giovanni (CERN)
    • 4:05 PM 4:10 PM
      Communications 5m
      Speaker: Gian Piero Di Giovanni (CERN)
    • 4:10 PM 4:15 PM
      Follow-up of Open Actions 5m
      Speaker: Gian Piero Di Giovanni (CERN)
    • 4:15 PM 4:30 PM
      Commissioning of the new PSB wire scanner 15m
      Speaker: Jose Luis Sirvent Blasco (CERN)
    • 4:30 PM 4:35 PM
      AOB 5m