NPS Frame and Infrastructure Meeting (JLab, 6/25-6/26 2019)

DISCUSSION MATERIAL

[ PMT module prototype photos]

ACTION ITEMS

• PMT module assembly: design a special tool to pull out the PMT?

• Some concern about what to pull out (initial thought by hand/finger and sturdy enough for that) - after settling perhaps parts are more stuck together, would connector or base come off?

• Calorimeter: consider including a special transportation frame when entire assembly may be tilted, e.g. during tranportation down truck ramp to experimental hall

• Fiber side PCB: Question: if fiber in place and remove crystal, can crystal move and break fiber?

• Detector box:

• exchanging PMTs on sides: no line of sight, unscrew by feel good enough?
• bottom of box: leg room? Have only about 18inches, box sits on a platform, bottom plate removable; how to get more space? - modified platform? region between rails with more room? Needs to be checked

• Chiller for cooling crystals: where to put chiller? - length of cooling lines? size of box? - needs to move with and be protected from radiation - send specifications to S. Lassiter, M. Fowler, P. Medeiro

• Assembly space - check with Walt Akers: requirements: space with crane acces, electrical power, high voltage, DAQ, table space, quasi clean room/tent, quiet, temperature controlled (AC), how long? summer 2020 (June?) start, ask NPS collaborators to come Sept 2020 for assembly tasks

SUMMARY NOTES

• Presentation mechanical design

• new system for fibers
• no change to cables
• PMT assembly: design final, one long captive screw, some modifications for support of fiber - metal support

• Wrapping: horizontal thickness (260um (2x70 + 2x60)), assume no air between crystal and reflective sheet, vertical: 260um (), front face: reflector on plastic frame/connector

• Pitch aveoli: gap aveoli and crystal, assume 260um +50um wrap, SICCAS: 20.85, CRYTUR: 20.77, so pitch 21mm inner - gap between two crytals 1 mm, gap 0.15mm (SICCAS), 0.23mm (CRYTUR)

• Shearing on one tower with no gap underneath:

• simulation assuming ~0.7kg/crystal, 1.4MPa/each stage, shear resistance carbon plate 90MPa, security coeff 64 - very safe
• simulation (ANSYS) assuming all load supported at bottom plate: 125N down, 36P/2, Max stress 48MPa, Shear res 90MPa, security coeff 2 ->safe but not secure -> need to reduce gap under vertical plates
• tests in lab:

• load on tower from top on 3x3 prototype with crystals in it, 76kg (3 columns weight), gap under vertical carbon plates -> no damage
• alveoli deformation with one crystal: simulation (ANSYS), 4 measurement points, no significant deformation
• buckling: 1.35 (>1, so ok)
• remove lower row of crystals -> not a good idea, get shearing since load is not perfectly vertical from top - note in actual, full design crystals share the load - fine in principle since not concentrated load, but distributed (also note HYcal had no problems with stacking)

• Fiber side crystal: metal ferrule screwed on alumin support at PMT/crystal junction joined to silicon fiber sleeve for fiber, fiber: quartz (stiff)

• Fiber side PCB: between 2 Al plates, protected with plastic tube, inserted NOT glued in plastic ferrule, plastic to not damage fiber, fiber length: 51cm; fibers can be dismounted, PCB can be dismounted if necessary

• Interface PCB: have 40 PCBs, cables now routed along top rather than side as before; have done mock up with real dimensions, PCB shifted 15cm vertical of PMT column

• Electronics input/output:

• Cooling: crystals, external, heating zones; use chiller + two fans (top/bottom like CCal)

• Discussion of tasks list:

• Orsay: provides components and assemblies, e.g. cutting reflective sheets, prefolding, wrapping plastic front part, glue mu metal with plastic support, block PMT assembly; cutting/polishing fibers vs purchase (~21eu/meter) - use bundle of ~100, cut in insert tube then polish all same time
• JLab/NPS collaboration: assemble remaining components, e.g. wrapping crystals (initial estimate 12min/crystal -> 216 hrs, can likely be reduced), insert column PMT assembly and PCB; Mounting: insert cooling, finalize mounting, mounting (Hall C techs); Cabling: Brad, J. Beaufait et al.