2011 Hall B FCAL Beam Test

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2011 Hall B FCAL Beam Test

Test out 25 FCAL modules using Hall B electron beam.

  • HBList Task list for Hall B to coordinate work in the hall with the work coordinator, Doug Tilles (unaccessible from offsite)
  • HDFCALEST electronic log book (from on-site)
  • HDFCALTEST electronic log book (from off-site)




2.2 Gev through ~March

Electron running Mid February

5.5 GeV after ~March


  • Target date to finish construction - 11/02/2011 (Wed)
  • Drive from IU to JLab for installation - 11/08/2011 (Tue)~


Pictures of setup to hold detector and trigger scintillators. Built by John Frye and the machine shop at IU, and shown here:

FCAL Beamtest Setup Pictures

Outside view of detector housing 25 modules.

See also Matt's Flickr page


  • Have put together NIM modules at IU, no need to borrow any NIM modules
  • Have tested inputs/outputs, all units working
  • Output widths of all NIM modules with adjustable widths set to 50 ns. As long as the rate of electrons coming in is less than 20 MHz, we should be fine (the total rate on the CLAS tagger should be on this order).
  • All thresholds on discriminators have been adjusted to 50 mV.
  • List of electronics are shown here:

List of FCAL Beamtest Electronics


Visit the special page on Mini-FCAL Beam Test Software


The geometry for the Hall B tagger and our detector setup is shown in

FCAL Beamtest Geometry

Hall B Geometry

Beam Rates

Rates measured on floor with scintillators
Rates measured on floor with scintillating fibres

  • The difference between the two figures seems to stem from the scintillating fibres having

directional dependence on the incoming electrons. Without any veto on the incoming electron direction, it seems we will be saturated with scattered electrons.

  • Also note that these measurements were done near the end of the beam, where there is

lots of scattering as the main beam exits the vacuum.


Each of the PMT/base combinations for the

  • 25 detector modules
  • 10 trigger scintillator modules
  • There are 3 remote trigger paddles, all with different dimensions. Below the width * thickness of each paddle is given, where width determines the energy fraction that the intersects the electron trajectories, and thickness is how much material the electrons will transverse.
    • Thick - 1.760" * 0.98"
    • Medium - 0.880" * 0.109"
    • Thin - 0.500" * 0.120"

have been tested in tandem for gain adjustments. The position, base ID, PMT ID, and cable number are listed here:

List of FCAL Beamtest Component IDs

Gain Adjustments

Gains for each PMT/base combination have been tested. We placed two trigger paddles on top of each other, and varied the HV on the one we are testing, while keeping the other held at 1700 V. The coincidence rates for cosmic rays were taken, and plotted against HV. The figures are here:Gain Adjustments, with a table of HV values.

Gains for ID:0x72360e


Personnel Available for Datataking

  • IU
    • Kei Moriya (time centered around November 7th not available due to birth of child)
  • Regina

Operating Safety Procedure

OSP can be found at PHY-11-040-0SP

Links to EHS&Q manual:

How to run DAQ

You can find some instructions on how to run DAQ in the HDFCALEST electronic log book or in the trigger page.