General Meeting Summary 11/16/17

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NPS Collaboration Meeting set for Tuesday, 23 January 2018, following the Hall C meeting


  • Discussion about an update from Mike Fowler on design status and plans
  • idea is to complete the general design drawings based on HyCal with all pieces fitted together and then send them to IPNO for fabrication design drawing
  • crystal length is 20cm, the detector box on order 1m to provide enough space to work
  • connectors will be on top
  • box includes Cu plates (shown in orange) from sides only - this will give a temperature gradient
  • hinged doors for access from all sides during installation
  • option for ventilation in box would be good
  • largest tolerable vertical offset expected on order 1cm
  • rail design similar to DVCS
  • Discussion about prototype design and what parts might be adaptable for full frame design
    • prototype consists of a copper box, a "Front Plate" and a "Back Plate" made by 3D printing technology from some plastic (could also be a mesh box such as using for bottles transportation from carbon-fiber),
  • Tests show that such a design for a 9x9 crystal matrix can hold 10 kg vertical pressure with 50 mkm deformation
  • prototype assembling procedure:
  • clean PbWO crystals after testing and selection, wrap with Teflon and Tedlar paper and keep in clean room (ready for stacking)
  • Mount "Front Plate" (see picture links in Agenda) inside of Cu Box
  • Stack all Crystals; fix their positions relative the side walls.
  • Mount "Backplate" and will check that positions of crystals-and holes for PMTs are OK.
  • Mount PMTs with tensioning rod and pushed towards crystal. For crystal-PMT optical contact use optical grease (Saint Gobain, organic scintillator, Bicron630).
  • Monitoring can be done from the front side using ~100 mkm diameter quartz fibers. For the full detector, a set of LED could be located on the back of the calorimeter and below beam level (to minimize radiation damage). For the prototype, this procedure was tested in Hall A.
  • For curing system, prototype uses "UV curing", a separate frame holds high intensity Lamps (as for BigCal) and

curing would be done in a beam off period

  • Discussion about full detector frame design
  • Design geometry optimization ongoing at IPNO - finalization anticipated beginning of 2018
  • Current design has two sets of LEDs from back for curing and monitoring - tests of curing efficiency, also including fibers to deliver light to specific locations, ongoing


  • Main coil construction is on schedule, pictures of preliminary assembly shown, company still needs to perform final checks
  • Iron cut pictures for the yoke are shown - looks like ready to ship
  • First task when pieces arrive is to test iron - this can be done before the main coil arrives


  • Visual inspection identified two boxes of crystals (20/100) that seem not new (traces of old labels, chemical film)
  • After consulting with material science, best course of action for these would be to send back to company
  • Optical measurements and microscopy of identify individual crystals out of a set of 100 with major flaws like bubbles and deep pits in the bulk
  • Mechanical measurement tool has arrived, accuracy is 1um.
  • still need a granite table to optimize the setup
  • Measurement of PMT mechanical properties shows that:
  • diameters are consistent with specifications
  • diameters are consistent from PMT-to-PMT
  • DAQ system in clean room needs to be setup for PMT (relative quantum efficiency) and prototype tests
  • These tests could be and some are already done in collaboration with Hall D
  • A. Somov mentions that he has many components for setting up a DAQ